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Centaur
2013-Feb-27, 01:18 AM
Hyperbolic Comet C/2013 A1 (Siding Spring) may be as wide as 50 km. There is a possibility of it crashing into Mars on 2014 OCT 19, according to Russian comet hunter Leonid Elenin in this article: http://spaceobs.org/en/news/

The comet will approach closest to Earth on 2014 SEP 05. Its maximum brilliance is expected on 2014 SEP 10 and is estimated at magnitude +7.7.

I’ve created a diagram with an “overhead” view of the comet, Mars, Earth and Sun. It’s for the months surrounding the comet’s encounter with Mars. It can be viewed from the bottom of my comets webpage: www.CurtRenz.com/comets

Bad Ronald
2013-Feb-27, 02:34 AM
That's very interesting news to hear. I hope it does crash into Mars.

Swift
2013-Feb-27, 03:09 AM
I wonder what the maximum brilliance on Mars will be, even if it doesn't hit? Will any of the rovers or the orbiters get a good look?

I found this story on discovery.com (http://news.discovery.com/space/astronomy/could-a-comet-hit-mars-in-2014-130225.htm)

According to calculations by NASA’s Jet Propulsion Laboratory (JPL), close approach data suggests the comet is most likely to make a close pass of 0.0007 AU (that’s approximately 63,000 miles from the Martian surface). However, there’s one huge caveat.

Due to uncertainties in the observations — the comet has only been observed for 74 days (so far), so it’s difficult for astronomers to forecast the comet’s precise location in 20 months time — comet C/2013 A1 may fly past at a very safe distance of 0.008 AU (650,000 miles). But to the other extreme, its orbital pass could put Mars directly in its path. At time of Mars close approach (or impact), the comet will be barreling along at a breakneck speed of 35 miles per second (126,000 miles per hour).

neilzero
2013-Feb-27, 03:38 AM
Is this the first medium size hyperbolic body confirmed inside our solar system, possibly not confirmed? My guess is 35 miles per second is right on the edge of hyperbolic for 63,000 miles from Mars, and slower than hyperbolic for 1000 kilometers from the surface of Mars. Neil

Centaur
2013-Feb-27, 04:59 AM
Is this the first medium size hyperbolic body confirmed inside our solar system, possibly not confirmed?

This comet's osculating orbit relative to the Sun for the given epoch has been calculated as hyperbolic. That's rather common. However, when comets' orbits are calculated relative to the solar system barycenter and at an epoch when they are far from major planets, their orbits turn out to be highly elliptical.

Don Alexander
2013-Feb-27, 07:25 PM
Leonid Elenin has obtained some new observations with the (now famous) ISON-NM telescope which show the comet will pass by Mars at an offset of just 37000 km:

http://spaceobs.org/en/tag/c2013-a1-siding-spring/

No errors are given, though, and I assume they are still so large that an actual collision is not ruled out.

JustAFriend
2013-Feb-27, 08:03 PM
I would hate to see our rovers get incapacitated, but in a way I truly hope it happens.

It would be a very sobering lesson for people to see what havoc a global disaster of this magnitude would create.

(the Shoemaker-Levy impact on Jupiter really didn't do this because Jupiter is just too vast for the average person
to comprehend and there were no craters and such.)

Romanus
2013-Feb-27, 11:14 PM
^
Ditto. The data haul would be (well, initially) enormous, and--IMO--well worth it even if it obliterated our probes in the process.

Even as is, this will basically be a "free" comet flyby mission.

Nick Theodorakis
2013-Feb-27, 11:26 PM
Wasn't one of the plot points of Larry Niven's novel Protector was that Brennan the protector flung a comet at Mars to kill all the (native) Martians? Hmmmm....

Nick

Concerned
2013-Feb-27, 11:28 PM
Hi, sorry to bother.

I am reading comments on other websites suggesting that the comet could produce debris that could reach earth and that Mars would be as bright as the sun at the time of the impact. Is any of this possible/true? Very worried.

schlaugh
2013-Feb-28, 02:41 AM
Sure, debris might reach Earth; Martian ejecta has been found on Earth from impacts long ago. Click here (http://upload.wikimedia.org/wikipedia/commons/thumb/2/27/EETA79001.jpg/280px-EETA79001.jpg) for an image of one such. But if the other posters mean that the Earth will be showered with debris and all life on Earth will end.....ah,...no. And no, Mars won't shine like the sun (but it will be a pretty large fireball if viewed with telescopes).

Don't worry. What happens on Mars, stays on Mars.

chornedsnorkack
2013-Feb-28, 07:12 AM
On which side of Mars shall Deimod be at the time of passage?

Tog
2013-Feb-28, 01:34 PM
Sure, debris might reach Earth; Martian ejecta has been found on Earth from impacts long ago.

Maybe Spirit will make it home after all.
Sad XKCD Spirit comic (http://xkcd.com/695/) for reference.

schlaugh
2013-Feb-28, 02:28 PM
On which side of Mars shall Deimod be at the time of passage?
The passage of the comet will last several days, at least. Deimos has an orbit of about 30 hours at an altitude of 23,460 km (14,580 mi). So Deimos will complete a number of orbits during the comet's transit near (or into) Mars.

ngc3314
2013-Feb-28, 05:12 PM
Doing a very quick check with the JPL Horizons ephemeris, the relative velocity will be about 55 km/s, so the comet would cross the orbit of Deimos in
about (gulp) 15 minutes. Retrograde near-hyperbolic orbits...

Trantor
2013-Feb-28, 05:22 PM
Assuming an impact on Mars, far away from Curiosity, I wonder what the odds of survival are? I would also assume that if an impact was confirmed in 2014, Curiosity's mission would go into overdrive.

Centaur
2013-Feb-28, 09:14 PM
I’ve been in contact with Aldo Vitagliano, the creator of the Solex astronomical numerical integration program. He developed 50,000 clones of the comet that fit within the possible error range of the still quite preliminary data. After running them through Solex he got 6 hits or 0.0012%. So a collision appears extremely unlikely, though still possible. Aldo hopes to know more tomorrow. If so, he’ll send me a file with a thousand clones including a few impactors to input into my copy of Solex. That may cause me to fine tune my chart: www.CurtRenz.com/comets

Buttercup
2013-Feb-28, 09:16 PM
I'll be following this. :) Yeah, it'd be cool if it hit Mars.

neilzero
2013-Feb-28, 09:50 PM
I suppose it is about a 20 times more probable that it will hit Mars than Deimos or the other moon of Mars with the present probable miss distance. Neil

Rhaedas
2013-Feb-28, 10:34 PM
I would think the odds would be a lot less for the moons, given their size. Plus Mars would affect a close pass much more with its gravity.

redshifter
2013-Feb-28, 11:11 PM
I can only imagine what the conspiracy theorists will come up with regarding this event/non-event. Might even have to start a 'best conspiracy theory' thread on the fun n games forum...

schlaugh
2013-Mar-01, 02:59 PM
This one might require its own forum in CT.

Concerned
2013-Mar-01, 07:24 PM
The JPL has updated its figures for the trajectory of the comet. Please see:-

http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad

It would appear that the nominal distance has been reduced, now showing 0.000702579318608323. The Maximum distance is standing at:- 0.00794058075188626.

I believe that this translates to a nominal distance of approximately 105104.3700553388 kilometers. Please correct me if incorrect.

Concerned
2013-Mar-01, 07:32 PM
Anybody else think that it is about time we started investing heavily in planetary defence. Strikes me that it would be an incredibly worthwhile industry, and anyhow, can we really afford not to?

Centaur
2013-Mar-02, 03:31 AM
The JPL has updated its figures for the trajectory of the comet.

Please understand that JPL is providing “osculating” orbital elements only accurate for the epoch 2013 JAN 11.0. While these may be fairly good for weeks or even months on either side of the epoch, they break down after longer periods or when a minor body passes near a major planet. The elements are based on a two-body Keplerian solution, i.e. the only bodies in the universe are assumed to be the comet and the Sun. Future perturbations from planets are not considered. Numerical integration is required for long term accuracy, but even that leads to doubtful predictions following a close passage.

Centaur
2013-Mar-02, 03:35 AM
Anybody else think that it is about time we started investing heavily in planetary defence. Strikes me that it would be an incredibly worthwhile industry, and anyhow, can we really afford not to?

Considering the federal spending sequester, it may have to be done privately. With that in mind, it's impressive how the private firm SpaceX encountered glitches in its launch to the ISS today and was able to repair them from the ground.

Concerned
2013-Mar-02, 11:22 AM
Please understand that JPL is providing “osculating” orbital elements only accurate for the epoch 2013 JAN 11.0. While these may be fairly good for weeks or even months on either side of the epoch, they break down after longer periods or when a minor body passes near a major planet. The elements are based on a two-body Keplerian solution, i.e. the only bodies in the universe are assumed to be the comet and the Sun. Future perturbations from planets are not considered. Numerical integration is required for long term accuracy, but even that leads to doubtful predictions following a close passage.

Does this mean that any data from the jpl is inherently untrustworthy at this time? I have read updates by elenin which place comets nominal trajectory closer to mars. Which source, therefore, has more value?

Concerned
2013-Mar-02, 11:35 AM
Updates from the kitt peak observatory has now increased the distance of closest approach to 70500 kilometers (43806 mi). Please see link http://spaceobs.org/en/2013/03/02/close-approach-to-mars-up-to-date-analysis/ for more info.

Concerned
2013-Mar-02, 12:26 PM
Considering the federal spending sequester, it may have to be done privately. With that in mind, it's impressive how the private firm SpaceX encountered glitches in its launch to the ISS today and was able to repair them from the ground.

It is very impressive, but, still more does need to be done. The problem with tackling such a problem, for private investors is the lack of obvious returns. SpaceX has the benefit of commercial contracts from NASA (at least for development), due to its previously successful transportation missions. Whereas where would the financial reward be for a company with the sole aim of manoeuvring/annihilating an asteroid. They might develop technologies that could be patented to their benefit, but, there would not be a direct financial gain. Such an endeavour literally requires someone/an agency/government willing to throw money at the problem, similarly to the original space program. Better to start now than later?

Maybe an economic model would be if we all paid an earth safety tax, to aid in funding the industry? :)

Centaur
2013-Mar-02, 03:32 PM
Does this mean that any data from the jpl is inherently untrustworthy at this time? I have read updates by elenin which place comets nominal trajectory closer to mars. Which source, therefore, has more value?

Neither one, and JPL concedes that. As I stated earlier, numerical integration is required in such a case rather than reliance on osculating orbital elements. Solex creator Aldo Vitagliano is working on that as he awaits more observational data. I'll let you know when I get an update from him.

Concerned
2013-Mar-02, 04:05 PM
Neither one, and JPL concedes that. As I stated earlier, numerical integration is required in such a case rather than reliance on osculating orbital elements. Solex creator Aldo Vitagliano is working on that as he awaits more observational data. I'll let you know when I get an update from him.

Thank you.

Concerned
2013-Mar-02, 04:18 PM
Neither one, and JPL concedes that. As I stated earlier, numerical integration is required in such a case rather than reliance on osculating orbital elements. Solex creator Aldo Vitagliano is working on that as he awaits more observational data. I'll let you know when I get an update from him.

Sorry, another response.

It's striking that with so much uncertainty as to the current data/observations that even a suggested conclusion of a mars impat could be drawn. How many days of observation might actually be required before the absolute trajectory of the comet can be determined? I understand now that there is approximately 80 days of observation. How many more might be required for this particular comet?

I understand that such observational requirement will vary on a case by case basis.

Once again, thank you for your previous comment. I will eagerly await your post.

Tog
2013-Mar-02, 09:12 PM
Think of it like this...

Say you have a jar of jelly beans and you want to know how many are in it. The average person might figure the height and diameter of the jar and the size of the average jelly bean, then take off a few for the wasted space between them. THey get about 18,000 beans.

Someone will better knowledge of such things might have a formula that gets much closer to the right answer because it has a much better model of how much wasted space there is between beans. They get 16,500 to 17,200

Someone else comes along with an even better models that takes into account the varying sizes of different beans and the fact that some will stick together into a much larger, oddly shaped bean. They get 16,825 to 17,100.

The estimates are all in the same range, and the right answer will be in there somewhere. Until someone actually takes the time to count the beans, then someone else verifies that count, we won't know for sure how many beans there are in the jar.

In the case of this comet, we have an irregularly shaped jar that has beans made in several different sizes, that we can't get close enough to to dump out and count. The only way we'll work it out is by taking careful measurements and narrowing the window between the high and the low.

Centaur
2013-Mar-02, 09:25 PM
Due to the latest (March 1) observational data for comet C/2013 A1 (Siding Spring), today Aldo Vitagliano provided me with initial conditions for 2000 clones to be entered into his Solex numerical integrator. The clones represent deviations from the nominal solution within the range of reasonable error. He has upgraded the probability of collision with Mars to 1 / 333 from his previous figure of 1 / 8333.

In response, I have updated my diagram illustrating an “overhead” (north of ecliptic) view of the encounter with output from what Aldo considers to be the nominal solution. Under the nominal solution during closest approach to Mars the comet’s heliocentric eccentricity switches from hyperbolic to elliptical. The closest approach between the centers of Mars and the comet utilizing the nominal solution is 50,586 km (81,410 mi) on 2014 OCT 19 at 19:21:24 UT. My diagram can be found at: www.CurtRenz.com/comets

ngc3314
2013-Mar-02, 10:13 PM
As I stated earlier, numerical integration is required in such a case rather than reliance on osculating orbital elements.

I have long had the impression that the JPL Horizons site does generate numerically integrated positions, since it provides a list of perturbing bodies included. Do you know whether this correct?

Concerned
2013-Mar-02, 10:27 PM
Due to the latest (March 1) observational data for comet C/2013 A1 (Siding Spring), today Aldo Vitagliano provided me with initial conditions for 2000 clones to be entered into his Solex numerical integrator. The clones represent deviations from the nominal solution within the range of reasonable error. He has upgraded the probability of collision with Mars to 1 / 333 from his previous figure of 1 / 8333.

In response, I have updated my diagram illustrating an “overhead” (north of ecliptic) view of the encounter with output from what Aldo considers to be the nominal solution. Under the nominal solution during closest approach to Mars the comet’s heliocentric eccentricity switches from hyperbolic to elliptical. The closest approach between the centers of Mars and the comet utilizing the nominal solution is 50,586 km (81,410 mi) on 2014 OCT 19 at 19:21:24 UT. My diagram can be found at: www.CurtRenz.com/comets

Wow, thank you for the post. The diagram looks great. Are you going to be providing further diagrams as observational data is updated?

Centaur
2013-Mar-02, 10:57 PM
I have long had the impression that the JPL Horizons site does generate numerically integrated positions, since it provides a list of perturbing bodies included. Do you know whether this correct?

JPL currently presents a table of osculating orbital elements for the epoch 2013 JAN 11.0. The epoch appears to be near the average of the dates for observational data. Regarding these elements, JPL states:

"Osculating orbital elements are often used in two-body propagation to estimate a body's state (position and velocity) at some time other than the epoch. It is important to realize that for some bodies, especially planetary satellites and comets, that such estimates may be grossly in error with respect to the actual orbit. In general, the farther away in time from the epoch, the greater the error."

However, it is the type of data most people input to their software. It's what I did until Aldo sent me his numerically integrated data. I now see that JPL indicates it uses a method other than osculation for its ephemerides. If that is numerical integration, I applaud them.

Centaur
2013-Mar-02, 11:06 PM
It's striking that with so much uncertainty as to the current data/observations that even a suggested conclusion of a mars impat could be drawn. How many days of observation might actually be required before the absolute trajectory of the comet can be determined? I understand now that there is approximately 80 days of observation. How many more might be required for this particular comet?

The fact that the comet is still 20 months away from its encounter with Mars enhances the uncertainty. In the case of comets, non-gravitational forces such as those due to random ejections of material further complicate the matter. All that can now be said is that a collision is possible but highly unlikely. We'll know better as time progresses and more observations are made.

Centaur
2013-Mar-03, 12:27 AM
Wow, thank you for the post. The diagram looks great. Are you going to be providing further diagrams as observational data is updated?

You're welcome. The answer is yes. I may not always provide alerts here, but occasionally check my comets webpage for updated graphics and data.

Concerned
2013-Mar-03, 01:21 AM
You're welcome. The answer is yes. I may not always provide alerts here, but occasionally check my comets webpage for updated graphics and data.

Hi centaur,

Thank you for responding. Yes, I understand more observation is very much required to reduce uncertainty and to determine the path of the comet. Personally, im hoping that it does not hit. I will also keep an eye on your web page. Thanks again.

Superluminal
2013-Mar-03, 02:14 AM
You're welcome. The answer is yes. I may not always provide alerts here, but occasionally check my comets webpage for updated graphics and data.

Mars should be inside the comet's coma and there may be a good chance of a really good meteor shower. Would the camera on Curiosity be able to pick up meteors?

Concerned
2013-Mar-03, 02:28 PM
Updates have been provided by astroblog and elenin. Further data has been collated from historical observations. A trajectory with closest approach of 58000 kilometers has been suggested. Please see http://spaceobs.org/en/2013/03/02/close-approach-to-mars-up-to-date-analysis/ and http://spaceobs.org/en/2013/03/02/close-approach-to-mars-up-to-date-analysis/ for further info, although I'm sure more observational data is required as indicated by Centaur.

Swift
2013-Mar-03, 04:07 PM
Mars should be inside the comet's coma and there may be a good chance of a really good meteor shower. Would the camera on Curiosity be able to pick up meteors?
Spirit seems to have, so I think it probable.

LINK (http://www.space.com/1155-shooting-star-mars.html)

NASA's Spirit rover photographed a streak of light that was likely part of a martian meteor shower, scientists announced today.

The picture is the first of a shooting star above Mars. Further, the flash has been traced back to its parent comet. And now astronomers figure they should be able to forecast martian meteor showers.

Concerned
2013-Mar-03, 05:07 PM
Spirit seems to have, so I think it probable.

LINK (http://www.space.com/1155-shooting-star-mars.html)


Wow, that's very cool.

Tuckerfan
2013-Mar-03, 07:50 PM
I wonder how stable this comet is. IIRC, some of them can fragment as they warm up. As others have said, I'd hate to lose the probes we've got on and around Mars, watching that sucker blow up would be all kinds of cool.

Romanus
2013-Mar-03, 08:25 PM
^
The complicating factor is that this comet's perihelion is fairly distant from the Sun, which will limit the kind of "explosive" activity that can break up comets with very close perihelia. If any breakup occurs, it may be due to Martian tidal forces, especially if this comet is as big as they think.

Concerned
2013-Mar-03, 09:05 PM
Once again, the JPL has updated the trajectory of the comet. Showing a nominal distance of 0.000357788824707267 au (53524.4463332426 kilometers), with a maximum distance of 0.0021188268623973 au (316971.9869775286 kilometers). Please be aware of Centaurs earlier comments regarding numerically integrated results. The data is available at:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad.

ngc3314
2013-Mar-03, 09:48 PM
To see the fully propagated JPL prediction (i.e. not simply propagating a current ephemeris), the JPL Horizons (http://ssd.jpl.nasa.gov/horizons.cgi) web service allows input of non-Terrestrial locations. Location 499 is the Martian center; *@499 gives a list of surface locations available (all landers are included). For quick reconnaissance, set elevation limit to -90 and turn off daylight suppression.

Currently, it shows nominal miss distance from the center of 0.00035787112 AU (53,680 km) or 50,285 from the surface (2014-Oct-19 19:28; I'm not completely sure whether that's Earth-received time or not). It's still too early to even be sure on which side of the planet it will pass, so concrete measures for orbiter safety and rover observations can't get underway until the orbit is better determined.

publiusr
2013-Mar-03, 10:26 PM
Some discussion here:
http://forum.nasaspaceflight.com/index.php?topic=31205.120

"Estimation by Jakub Černý is 2.7-5.4 km."

So less than 50km. Oh well.

Concerned
2013-Mar-03, 10:29 PM
Some discussion here:
http://forum.nasaspaceflight.com/index.php?topic=31205.120

"Estimation by Jakub Černý is 2.7-5.4 km."

So less than 50km. Oh well.

Thank goodness.

Rhaedas
2013-Mar-03, 10:48 PM
Some discussion here:
http://forum.nasaspaceflight.com/index.php?topic=31205.120

"Estimation by Jakub Černý is 2.7-5.4 km."

So less than 50km. Oh well.

Only about half the size of the Chicxulub impact object. Still quite a wallop, if it makes it, and with less gravity and atmosphere to break it up, plus it being retrograde so a high relative velocity to Mars, it won't be just another Sol on Mars.

Of course, given the comet's orbit, if it hits, wouldn't a major possibility be near the ice cap? Still could get a lot of stuff into the atmosphere.

Rhaedas
2013-Mar-03, 10:50 PM
Thank goodness.

Some of us want a bigger impact. For science. Because Shoemaker-Levy was too far away and too temporary to make a lasting point.

Better Mars than here.

Concerned
2013-Mar-03, 11:51 PM
Some of us want a bigger impact. For science. Because Shoemaker-Levy was too far away and too temporary to make a lasting point.

Better Mars than here.

Personally happy with no impact/ or a much much smaller impact. Why have all your Christmases at once? :)

Concerned
2013-Mar-04, 01:05 AM
Some of us want a bigger impact. For science. Because Shoemaker-Levy was too far away and too temporary to make a lasting point.

Better Mars than here.

In a way I can understand the scientific interest of such events, but, from an entirely human (selfish) perspective I would rather mars be the way it is, to enable us to explore it. The notion of manned trips to mars would be set back years if their was a massive mars impact. We need mars to be a target for human exploration, just as the moon before it. We could not visit a fireball. As long as mars is safe (ish) it will remain within the sight (within this generation if not the next) as a target for exploration. This is why Im hoping that the comet will miss. Believe it or not, we live in a solar system that has provided us with (I believe) the perfect beginning. Without the moon we would never have developed a space programme, where would we have gone (are goal was reachable). And noW we have mars, within reach within the coming decades. What' would be more important, a space rock hitting the planet, or the continued opportunity for mankind to continue to move forward now. Sorry, big off topic babble (would also like to point out that my belief that the notion of the solar system being perfect for the beginnings of human exploration is not a creationist theory - no intention of getting into that- only that the solar system has evolved in a way that strikes me personally as being fantastic for entreprid goals). :)

Tuckerfan
2013-Mar-04, 01:20 AM
Some of us want a bigger impact. For science. Because Shoemaker-Levy was too far away and too temporary to make a lasting point.

Better Mars than here.Given that there were conflicting accounts of the recent Russian meteor's size, and that was here on Earth, I imagine that it'll be quite some time before we're able to accurately pin down the size of this comet. And we may yet get "lucky." I wasn't able to find any recent figures in a quick Google flail, but it seems to me that there's been an increase in naked eye comets in the past 20 years. Its possible that we're just entering a period when large numbers of long period comets make their appearance, it's also possible that something passing by has shaken things loose in the Oort Cloud and we're in for some "interesting" times.

Rhaedas
2013-Mar-04, 01:41 AM
All the more reason to have something that shakes up the public's perception of the issue. Now we shouldn't go the extreme as the tabloids do, but at the very least we need to improve our ability to see what's out there, and having a nearby constant reminder of what ignoring the skies could do may help the budget needs of those trying to make a difference. Especially if your speculation of more activity to come is correct.

Jens
2013-Mar-04, 01:58 AM
Thank goodness.

I can't really see any reason to be grateful it won't strike Mars. For two reasons I'd look forward to it. One is that it would be great to have that data. The other other is that the news coverage might encourage people to take the idea of protective measures more seriously. Though I should add that protecting ourselves from those kinds of things is not very easy. It's definitely worth pursuing, but don't expect easy results.

Concerned
2013-Mar-04, 01:59 AM
Given that there were conflicting accounts of the recent Russian meteor's size, and that was here on Earth, I imagine that it'll be quite some time before we're able to accurately pin down the size of this comet. And we may yet get "lucky." I wasn't able to find any recent figures in a quick Google flail, but it seems to me that there's been an increase in naked eye comets in the past 20 years. Its possible that we're just entering a period when large numbers of long period comets make their appearance, it's also possible that something passing by has shaken things loose in the Oort Cloud and we're in for some "interesting" times.

Hi, the statement about more comets in the past twenty years, is there a study indicating this? Is it not possibe that are observations mean that we are seeing more. Quite simply, I imagine there to be more astronomers today than ever before.

Concerned
2013-Mar-04, 02:02 AM
I can't really see any reason to be grateful it won't strike Mars. For two reasons I'd look forward to it. One is that it would be great to have that data. The other other is that the news coverage might encourage people to take the idea of protective measures more seriously. Though I should add that protecting ourselves from those kinds of things is not very easy. It's definitely worth pursuing, but don't expect easy results.

Surely we can direct ourselves to protective measures without such a threat. Could not the Russian incident, not be all the warning that we need?

Concerned
2013-Mar-04, 02:04 AM
I can't really see any reason to be grateful it won't strike Mars. For two reasons I'd look forward to it. One is that it would be great to have that data. The other other is that the news coverage might encourage people to take the idea of protective measures more seriously. Though I should add that protecting ourselves from those kinds of things is not very easy. It's definitely worth pursuing, but don't expect easy results.

I imagine NASA would be grateful with the investment costs of curiosity..etc

Concerned
2013-Mar-04, 02:11 AM
I can't really see any reason to be grateful it won't strike Mars. For two reasons I'd look forward to it. One is that it would be great to have that data. The other other is that the news coverage might encourage people to take the idea of protective measures more seriously. Though I should add that protecting ourselves from those kinds of things is not very easy. It's definitely worth pursuing, but don't expect easy results.

How could we ever have manned missions to mars, if it were effectively turned into a dusty fireball?

Hornblower
2013-Mar-04, 03:24 AM
Given that there were conflicting accounts of the recent Russian meteor's size, and that was here on Earth, I imagine that it'll be quite some time before we're able to accurately pin down the size of this comet. And we may yet get "lucky." I wasn't able to find any recent figures in a quick Google flail, but it seems to me that there's been an increase in naked eye comets in the past 20 years. Its possible that we're just entering a period when large numbers of long period comets make their appearance, it's also possible that something passing by has shaken things loose in the Oort Cloud and we're in for some "interesting" times.

It also is possible that this was nothing more than the random clumping that sometimes happens with sporadic events.

Tuckerfan
2013-Mar-04, 03:58 AM
Hi, the statement about more comets in the past twenty years, is there a study indicating this? Is it not possibe that are observations mean that we are seeing more. Quite simply, I imagine there to be more astronomers today than ever before.That's why I said "naked eye comets." Lots of comets cycle through he solar system invisible to the naked eye, so an increase in the number of them is relatively meaningless, since its possible that they went through the solar system before, without being noticed. There's a much harder chance for a comet that's visible to the naked eye to get through the system without anyone seeing or commenting upon it. I'm sure that there's probably a study dealing with the subject, but I didn't find one in a quick search on Google that was more recent than the late 90s, and it wasn't very detailed, so I can only go off of my memories. I was born in '68, and the only comet I can remember hearing about as being possibly visible, prior to the late '90s, was Halley's, which was a dud for us in the Northern hemisphere. Since the late '90s, it seems like there's been a number of them that have been visible.

Human memory is fallible, so I might have forgotten hearing about them, and its possible that I didn't hear of the other comets, and we're seeing them at an average rate.


It also is possible that this was nothing more than the random clumping that sometimes happens with sporadic events.
True.

Centaur
2013-Mar-04, 06:07 AM
Hi, the statement about more comets in the past twenty years, is there a study indicating this? Is it not possibe that are observations mean that we are seeing more. Quite simply, I imagine there to be more astronomers today than ever before.

There may be something to Hornblower's suggestion regarding random clumping. But another factor is the systematic surveys in recent years done with telescopes guided by computers and the resulting digital photographs examined by computers. Many comets that would have gone unnoticed in the past are revealed nowadays.

Jens
2013-Mar-04, 08:11 AM
How could we ever have manned missions to mars, if it were effectively turned into a dusty fireball?

I could be wrong, but I don't think the effect of such a collision would last very long. Dust would be created by the impact, but Mars has fairly substantial gravity so I think it would settle back down pretty quickly. Of course there would be a big crater left behind.

Tog
2013-Mar-04, 08:41 AM
Remember too, Mars has global dust storms just about every Martian summer. They cover the planet but don't last long. The atmosphere isn't thick enough to hold it up.

baskerbosse
2013-Mar-04, 12:12 PM
Does anyone know what the probability is of the comet being ripped to bits by the gravity of Mars as it flies past?

Rhaedas
2013-Mar-04, 01:49 PM
Using a calculator and an average comet density of 0.6 g/cm^3, I show the Roche limit to be 15400 km. Less density increases that by a few thousand kms.

neilzero
2013-Mar-04, 03:04 PM
The high speed, plus up to 50 kilometer diameter could mean a million square kilometers of lava on the surface of Mars or destruction of one of the Moons of Mars, giving Mars a significant ring, something like Saturn. The much more probable hit on Mars could double the atmospheric pressure of Mars due to volatiles released from the large crater, the lava surface and volatiles in the comet, most of which would be retained by Mars for millions of years. How can we take advantage of the increased atmosphere and brief and small average temperature rise? Please correct, refute and/or comment

Concerned
2013-Mar-04, 07:10 PM
The high speed, plus up to 50 kilometer diameter could mean a million square kilometers of lava on the surface of Mars or destruction of one of the Moons of Mars, giving Mars a significant ring, something like Saturn. The much more probable hit on Mars could double the atmospheric pressure of Mars due to volatiles released from the large crater, the lava surface and volatiles in the comet, most of which would be retained by Mars for millions of years. How can we take advantage of the increased atmosphere and brief and small average temperature rise? Please correct, refute and/or comment

Any chance that a moon hit could be dangerous for earth, i.e the orbit of Mars is changed and or debris/the moon is knocked out of orbit and makes it way here?

Rhaedas
2013-Mar-04, 07:18 PM
Any chance that a moon hit could be dangerous for earth, i.e the orbit of Mars is changed and or debris/the moon is knocked out of orbit and makes it way here?

No. Mars is very far away, and space is very big. Plus a lot of other factors, but those are the main ones that make this a non-event for Earth itself.

Concerned
2013-Mar-04, 09:02 PM
No. Mars is very far away, and space is very big. Plus a lot of other factors, but those are the main ones that make this a non-event for Earth itself.

Thank you for the response.

Swift
2013-Mar-04, 09:21 PM
No. Mars is very far away, and space is very big.
I am, of course, reminded of what Douglas Adams had to say about this:

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.

Concerned
2013-Mar-04, 10:10 PM
I am, of course, reminded of what Douglas Adams had to say about this:

:)

baskerbosse
2013-Mar-05, 12:00 AM
Using a calculator and an average comet density of 0.6 g/cm^3, I show the Roche limit to be 15400 km. Less density increases that by a few thousand kms.

Ok, thanks.
With the nominal distance currently at 53600 km, I'll take that as not likely..

:-/

publiusr
2013-Mar-05, 12:19 AM
Now, if a big comet impacts Mars, would it deliver more volatiles than it blows off? I guess that depends on the size.

But if it were to thicken up the atmosphere, that would actually ease manned Mars missions in that it eases heat-shield requirements.

Then too, it it is too large, and too fast, and hits at a grazing angle, it may remove more than it deposits.

Maybe it is best for a fast object to be a bit smaller after all.

Centaur
2013-Mar-05, 12:33 AM
I’ve added an equatorial finder chart. It may give you a better idea regarding the relative movements of Mars and the comet: www.CurtRenz.com/comets

Tuckerfan
2013-Mar-05, 02:52 AM
There may be something to Hornblower's suggestion regarding random clumping. But another factor is the systematic surveys in recent years done with telescopes guided by computers and the resulting digital photographs examined by computers. Many comets that would have gone unnoticed in the past are revealed nowadays.
That would explain an increase in the overall number of known comets, but not an increase in those comets visible by the unaided eye.

ngc3314
2013-Mar-05, 04:30 AM
Using this table (http://www.icq.eps.harvard.edu/brightest.html) of naked-eye comets since 1935, I pulled out comets peaking brighter than visual magnitude 3.0 (as being fairly prominent) and sorted by listed date (usually discovery year, except for Holmes). There are some surprises in here - some of them peaked so close to the Sun that they could have been missed decades ago (such as SOHO discoveries). This graph shows the cumulative number since 1935 versus year, compared to the straight line which marks the average rate. There was either a notable deficit in the 1990s or has been a pickup just lately, but a Kolmogorov-Smirnov test shows that (loosely speaking, for those who know about details of what the KS test actually tells you) the deficit is not significant enough to reject the null hypothesis of constant rate at the 90% level or greater.

Since (with the notable exception of Kreutz sungrazers) these are on widely different orbits and have widely different periods with correspondingly different infall times from aphelion, this is not how a disturbance in the Oort cloud would manifest itself.

18281

Concerned
2013-Mar-05, 09:03 AM
I’ve added an equatorial finder chart. It may give you a better idea regarding the relative movements of Mars and the comet: www.CurtRenz.com/comets

Hi Centaur,

Thank you for this. It looks great, and is very clear.

Squink
2013-Mar-05, 06:25 PM
Earth and Mars crater size frequency distribution and impact rates: Theoretical and observational analysis (http://arxiv.org/abs/1212.3273)
for energies of one megaton or larger we find near one impact every three years for Mars, an interesting and concerning result for future Mars explorations. The corresponding calculations for our planet give a probability of one impact per 15 years, while for a Tunguska like event, of about E=10 megatons, an estimate of one per century is obtained for Earth. See also How often does Mars get whacked? (http://redplanet.asu.edu/?p=597)

This comet appears to have a once in several million years likelihood of hitting Mars.

Concerned
2013-Mar-05, 08:25 PM
Elenin has posted an amazing visualised video of what a close pass of mars might look like. It's very good. Available at:-

http://spaceobs.org/en/2013/03/05/vizualizaciya-sblizheniya-komety-c2013-a1-s-marsom/

neilzero
2013-Mar-05, 10:42 PM
Combining comet hits with asteroid hits, Mars gets hit about as often as Earth. Mars is a smaller target with a smaller gravity well, but it is closer to the main asteroid belt and lacks the protection that our massive moon gives Earth. Possibly Jupiter protects Earth by diverting orbits closer to Mars orbit. My guess is the smaller cross sectional area is by far the most important factor. If so, Earth gets hit about twice as often as Mars. Neil

Concerned
2013-Mar-05, 11:08 PM
The NASA jpl has Made a press release regarding the comet. It is hoped, that with future observations, it will be determined that the comet will safely pass mars. Please see link to jpl article http://www.jpl.nasa.gov/news/news.php?release=2013-081.

Rhaedas
2013-Mar-06, 12:27 AM
I think the only ones wanting a safe passage are martians, riders on the comet, and any Red Mars (http://en.wikipedia.org/wiki/Red_Mars) fanatics out there. A collision would be great science and great publicity for the cause.

Hornblower
2013-Mar-06, 02:40 AM
Combining comet hits with asteroid hits, Mars gets hit about as often as Earth. Mars is a smaller target with a smaller gravity well, but it is closer to the main asteroid belt and lacks the protection that our massive moon gives Earth. Possibly Jupiter protects Earth by diverting orbits closer to Mars orbit. My guess is the smaller cross sectional area is by far the most important factor. If so, Earth gets hit about twice as often as Mars. Neil

How would the Moon give us any significant protection? Once in a while it might block an interloper that otherwise would hit the Earth, but many other incoming trajectories would be unobstructed. As for gravitational deflection, the Moon could divert what would have been a hit into a miss, but it could just as easily divert what would have been a miss into a hit.

Tuckerfan
2013-Mar-06, 03:48 AM
I think the only ones wanting a safe passage are martians, riders on the comet, and any Red Mars (http://en.wikipedia.org/wiki/Red_Mars) fanatics out there. A collision would be great science and great publicity for the cause.
Well, they do send an ice ball to whack Mars in the book, but I, for one, wouldn't be too mad at anything which made the Red Mars fans upset. An awful, awful book, IMHO.

Centaur
2013-Mar-06, 04:59 AM
How would the Moon give us any significant protection? Once in a while it might block an interloper that otherwise would hit the Earth, but many other incoming trajectories would be unobstructed. As for gravitational deflection, the Moon could divert what would have been a hit into a miss, but it could just as easily divert what would have been a miss into a hit.

That's essentially true regarding a comet coming toward Earth and Moon from a random direction on a nearly parabolic orbit relative to the Sun. In the case of an asteroid in a heliocentric elliptical orbit not greatly inclined to the ecliptic, it's orbit is quite slowly perturbed. If it's orbit is destined to eventually intersect with the Earth's orbit, it will do so gradually over many centuries. Before it does, it will make many passes in the torus defined by the Moon's wobbly orbit around Earth. The Moon is something like a puny bodyguard who is nevertheless willing to take the first shots. If there is a hit on the Moon, the asteroid will have lost all chance of ever hitting Earth despite Earth being a larger target. Regarding the Moon's gravity, it's rather weak and any diversions of asteroids toward Earth or turning a probable hit of Earth into a miss would be extremely rare.

eburacum45
2013-Mar-06, 08:37 AM
Of course the Earth is a much better body guard for the Moon than the Moon is for the Earth.

Concerned
2013-Mar-06, 09:14 AM
I think the only ones wanting a safe passage are martians, riders on the comet, and any Red Mars (http://en.wikipedia.org/wiki/Red_Mars) fanatics out there. A collision would be great science and great publicity for the cause.

Red Mars is on my reading list :)

Concerned
2013-Mar-08, 11:56 PM
Any updates on this, I have not seen anything in a few days? Must be over 150 days of observation now.

Concerned
2013-Mar-09, 09:41 AM
Interesting article posted by space access on the feasibility of our ability to defend ourselves against a sliding spring style comet can be found at:-http://www.space-access.org/updates/sau130.html. Basically, we might be able to prevent a total catastrophe, but, best not to be tested at this present time. We're not ready, but, we need to be and more funding should be made available.

An overview article can be found on msnbc news http://cosmiclog.nbcnews.com/_news/2013/03/08/17241258-marsageddon-comet-scenario-adds-to-concerns-about-threats-from-space?lite.

moozoo
2013-Mar-09, 12:18 PM
Due to the latest (March 1) observational data for comet C/2013 A1 (Siding Spring), today Aldo Vitagliano provided me with initial conditions for 2000 clones to be entered into his Solex numerical integrator. The clones represent deviations from the nominal solution within the range of reasonable error. He has upgraded the probability of collision with Mars to 1 / 333 from his previous figure of 1 / 8333.


I'd very much like to know exactly how to do this calculation.
Leonids Elenin has done something similar.
http://spaceobs.org/en/2013/03/04/histogram-of-close-approach-distances/

My attempt..
Take the raw observations from the Minor Planet Center and feed them into Find_orb.
Then after filtering them do a Monte Carlo fit to generate a largish number of virtual comets.
Take the state.txt file and turn it into a small.in file for the mercury6 intergrator.
Update the big.in (Planets + large asteroids) with current epoch values using jpl horizon.
i.e. match the epoch to that in small.in. I chose march 4th 2013 as the start epoch.
Run mercury6 from now until late 2014 and sure enough the virtual comets all have a close approach to mars.
But the closest I get is 0.0089 AU.

note to find mercury6 google it with John Chambers

Centaur
2013-Mar-09, 03:08 PM
I'd very much like to know exactly how to do this calculation.

Download Aldo Vitagliano’s free Solex astronomical numerical integration program: http://main.chemistry.unina.it/~alvitagl/solex/

For a free Solex library upgrade and occasional e-mail receipt of parameters for newly discovered objects you must register. That involves mailing a picture postcard to Aldo as described in the REGISTER file within the DOCS folder within the Solex110 folder.

In addition to precise output of a body’s accurate coordinates at specific times, Solex can produce osculating orbital elements for any desired epoch.

If you have further questions, Aldo’s e-mail address is on his website where he writes that inquiries are appreciated.

Numerical integration avoids the inaccuracies inherent in Keplerian two-body osculating orbital elements. It involves an iteration procedure utilizing Newton’s two more basic force formulae. This could not be accomplished until the development of modern high-speed computers. When seeking Solex data involving a minor body's close approach to a major planet, choose the adaptive stepsize option "V".

neilzero
2013-Mar-09, 04:30 PM
A two body analysis of Sun and Comet (Siding Springs) is quite accurate up to Oct 19, 2014: Quite inaccurate after that date if the Comet misses Mars by a few thousand kilometers, or skims the upper atmosphere then continues in a new orbit. If the comet hits on October 19, 2014, there is no Comet after that date. The comet will gain or lose speed due to the close approach and will change direction at least slighly.
The error bar for a hit or miss of Dimos or Phobus will be huge until seconds before impact or closest approach due to the gravity of Mars. Neil

Rhaedas
2013-Mar-09, 05:01 PM
Well, they do send an ice ball to whack Mars in the book, but I, for one, wouldn't be too mad at anything which made the Red Mars fans upset. An awful, awful book, IMHO.

I wasn't clear enough, I was actually referring to the Red/Green debate within the books, with the Greens obviously more pro terraforming activity than the preservational Reds.

Concerned
2013-Mar-09, 05:24 PM
Update from NASA as of 5 march 2013 showing orbital path of the comet, and possible magnitude from mars:- http://neo.jpl.nasa.gov/news/news179.html.

Concerned
2013-Mar-09, 05:32 PM
Has anybody plotted where the comet will be in relation to earth, assuming the comet does not smash into mars, beyond October 19. Where will earth be in relation to the comet, when the comet passes the orbital path of earth? Any ideas?

Concerned
2013-Mar-09, 05:45 PM
Has anybody plotted where the comet will be in relation to earth, assuming the comet does not smash into mars, beyond October 19. Where will earth be in relation to the comet, when the comet passes the orbital path of earth? Any ideas?

Whoops, please disregard my last post. I just re-viewed the orbital diagram from CENTAUR, available via:- http://www.CurtRenz.com/comets.html. Answered my query. Thank you.

publiusr
2013-Mar-09, 06:39 PM
Now if it makes like Teton and grazes but doesn't hit (breaking apart in the process) each fragment would need to be recalculated I would think.

Concerned
2013-Mar-09, 08:08 PM
Now if it makes like Teton and grazes but doesn't hit (breaking apart in the process) each fragment would need to be recalculated I would think.

I thought that usually if a comet breaks up, the pieces tend to keep on going in the same direction.

Concerned
2013-Mar-09, 08:20 PM
Interesting blog from Emily Lakdawalla http://www.planetary.org/blogs/emily-lakdawalla/2013/03051422-siding-spring-meteor-shower-mars.html. Looks like, as long as the comet passes far enough away from mars, then no satellite should be at risk.

Ara Pacis
2013-Mar-09, 08:55 PM
I still hope it manages to hit Mars. The data would be invaluable and it might spur investment in space infrastructure and maybe it would even help make Mars more habitable to life.

tony873004
2013-Mar-10, 12:19 AM
Odds of hitting Mars just went way down, as JPL released new numbers today, based on 183 observations. The nominal path now gives it a close-approach distance of 110,000 km, on October 19, 2014 @ 18:50:33. That's twice the earlier estimate. The error bars probably shrank considerably as well.

Concerned
2013-Mar-10, 12:46 AM
Odds of hitting Mars just went way down, as JPL released new numbers today, based on 183 observations. The nominal path now gives it a close-approach distance of 110,000 km, on October 19, 2014 @ 18:50:33. That's twice the earlier estimate. The error bars probably shrank considerably as well.

Hi, the link to jpl data here:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad

I just found the update.

Concerned
2013-Mar-10, 12:59 AM
Nominal distance is being shown as 110061.70710406246 Km with 57 minutes of uncertainty Approximately, I'm not entirely sure what that means? I'm sure more observation is still required.

tony873004
2013-Mar-10, 01:12 AM
I think it means that there is uncertainty is in the "along-track" position. This comet has a very large radial velocity with respect to Earth at the moment. So determining the exact time of the close passage is difficult. Mars travels a few 10s of thousands of km per hour. The current nominal trajectory has it arriving at Mars 40 minutes earlier than the previous estimate. So perhaps a later arrival increase the odds of a collision. The link you give still shows a minimum distance of 0, so a collision isn't ruled out yet.

Centaur
2013-Mar-10, 01:43 AM
I thought that usually if a comet breaks up, the pieces tend to keep on going in the same direction.

That's generally true when the cause of disintegration is melting by the Sun. In that case the orbits would diverge only very slightly. However, if disintegration is due a tidal effect from close approach to a planet or especially contact with the atmosphere, then the divergence would be greater.

Concerned
2013-Mar-10, 02:51 AM
I think it means that there is uncertainty is in the "along-track" position. This comet has a very large radial velocity with respect to Earth at the moment. So determining the exact time of the close passage is difficult. Mars travels a few 10s of thousands of km per hour. The current nominal trajectory has it arriving at Mars 40 minutes earlier than the previous estimate. So perhaps a later arrival increase the odds of a collision. The link you give still shows a minimum distance of 0, so a collision isn't ruled out yet.

Understood, thank you. Yes, I noted the minimal distance still indicated that a collision is not entirely ruled out. I guess more observations, really into next year would be required?

Concerned
2013-Mar-10, 02:56 AM
That's generally true when the cause of disintegration is melting by the Sun. In that case the orbits would diverge only very slightly. However, if disintegration is due a tidal effect from close approach to a planet or especially contact with the atmosphere, then the divergence would be greater.

Thank you. Also understood. :)

Hornblower
2013-Mar-10, 03:21 AM
Understood, thank you. Yes, I noted the minimal distance still indicated that a collision is not entirely ruled out. I guess more observations, really into next year would be required?

Yes indeed, more observations will be needed over the next year and a half, and I would say there is a 100% certainty that they will be done.

Ara Pacis
2013-Mar-10, 06:55 AM
Now, if only we can convince NASA or Tito or Musk to divert or blow up the comet so that Mars gets hit. Then the Mars Terraformers may see our plans commence ahead of schedule.

BTW, can solar radiation and the Yarkovsky Effect have an effect on a comet and can it cause much change in the orbit? Could a CME cause a change in trajectory or could a sudden outburst of material, such as with Comet Holmes, cause a change in trajectory enough to hit Mars?

Tuckerfan
2013-Mar-10, 07:00 AM
I wasn't clear enough, I was actually referring to the Red/Green debate within the books, with the Greens obviously more pro terraforming activity than the preservational Reds.Can't get more "natural" than a comet strike! The "unnatural" thing to do would be to stop it. :D

Centaur
2013-Mar-10, 07:28 AM
BTW, can solar radiation and the Yarkovsky Effect have an effect on a comet and can it cause much change in the orbit? Could a CME cause a change in trajectory or could a sudden outburst of material, such as with Comet Holmes, cause a change in trajectory enough to hit Mars?

Yes.

Rhaedas
2013-Mar-10, 08:09 PM
It's got a good year and a half still, so even if observations continue to point to a miss, one good outgassing in the right direction, especially early on, would change things again.

On the other hand, if we wanted to change its path, either to hit or miss Mars, it's already too late. Whatever our method, we would either have to already be rendezvousing, or have something on the way and closing in, to have enough time to make an effect. And that would have involved getting out there quickly and then matching the velocity, so we would've had to seen this comet a long time ago to do all that. Or have a system in place designed to detect and react right away, like Clarke's Spaceguard.

Ara Pacis
2013-Mar-10, 08:13 PM
It's got a good year and a half still, so even if observations continue to point to a miss, one good outgassing in the right direction, especially early on, would change things again.

On the other hand, if we wanted to change its path, either to hit or miss Mars, it's already too late. Whatever our method, we would either have to already be rendezvousing, or have something on the way and closing in, to have enough time to make an effect. And that would have involved getting out there quickly and then matching the velocity, so we would've had to seen this comet a long time ago to do all that. Or have a system in place designed to detect and react right away, like Clarke's Spaceguard.

Do you mean using current off the shelf tech or that it's not possible even with new, plausible tech such as big rockets stages with ion engine later stages and multiple thermonukes.

Rhaedas
2013-Mar-10, 08:54 PM
Do you mean using current off the shelf tech or that it's not possible even with new, plausible tech such as big rockets stages with ion engine later stages and multiple thermonukes.

The main point was that to do anything we have to get to the comet first, and that takes time. Then it takes more time, because we'd likely want to match its velocity to do whatever we're going to do instead of hitting it head on at a huge difference of speed.

Could we do it with future tech? I don't know...I suppose eventually we could have something that can get out there quickly and/or be able to make a large change of the comet's direction in a short time. Certainly we don't have it now.

Concerned
2013-Mar-10, 09:01 PM
The main point was that to do anything we have to get to the comet first, and that takes time. Then it takes more time, because we'd likely want to match its velocity to do whatever we're going to do instead of hitting it head on at a huge difference of speed.

Could we do it with future tech? I don't know...I suppose eventually we could have something that can get out there quickly and/or be able to make a large change of the comet's direction in a short time. Certainly we don't have it now.

Realisation, that with our current incapability to deal with such an event, we should probably be terrified.

Rhaedas
2013-Mar-10, 09:19 PM
Realisation, that with our current incapability to deal with such an event, we should probably be terrified.

Terrified, no. We do have the odds in our favor. First, space is large, so even the Earth is a small target. Second, the number of objects out there is inversely proportional to the size, so bigger ones are much rarer than the small ones. Third, we do have a thick atmosphere that helps break up things.

But we do need to be doing more, particularly with detection of things while they are far away. We can't do anything about something we don't know about.

neilzero
2013-Mar-10, 11:38 PM
For lots of money, we could deliver a tiny payload about 2020 = obviously too late. Most of that time would be spent finding some things that exist, assembly and testing. Failure would be likely due to haste which often makes waste. We could assemble and launch for pre need about 2030, several slightly effective comet and asteroid movers, but odds are none of them will be in the right place at the right time, when and if the need arises about 2030. Worse we would likely decide not to move the likely impactor because of the risk of changing a likely hit of Earth to a hit on a very large Earth city. After the city was destroyed we could quite acurately calulate that the results would have been better, had we nuged the impactor in any slightly different direction. This not to say we should not do pre need, but it will be very costly and it may take a century to get it right, longer if we wait 50 more years before we start building comet and asteroid movers. We have to learn to walk, before we can run. Neil

moozoo
2013-Mar-11, 03:47 AM
What I would do, given the limited time and resources, would be to find a NEO that passes near the comet and modify its orbit so it collides with it. Hopefully early enough that the debris misses the earth or comes down in smaller bits over many years.
Perhaps nuke the larger pieces of debris.
The effort involved might be less than trying to get to the comet in time and modify its orbit.

Perhaps we should park an asteroid at one of the Earth Moon Lagrange points and build a propulsion system on it in advance. Rig it with nukes.
How hard would it be to move a 300m (say) rocky asteroid into the correct collision orbit say one lunar distance from earth.
I assume a 300m rocky asteroid would probably be vaporized by the collision. If not we could explode it just before impact and shotgun the comet.

Rhaedas
2013-Mar-11, 04:02 AM
What I would do, given the limited time and resources, would be to find a NEO that passes near the comet and modify its orbit so it collides with it. Hopefully early enough that the debris misses the earth or comes down in smaller bits over many years.
Perhaps nuke the larger pieces of debris.
The effort involved might be less than trying to get to the comet in time and modify its orbit.

Perhaps we should park an asteroid at one of the Earth Moon Lagrange points and build a propulsion system on it in advance. Rig it with nukes.
How hard would it be to move a 300m (say) rocky asteroid into the correct collision orbit say one lunar distance from earth.
I assume a 300m rocky asteroid would probably be vaporized by the collision. If not we could explode it just before impact and shotgun the comet.

Not to shoot down your idea, but...

The logistics of being able to move a mass big enough to do something in the way at the right moment would present their own issues. At the minimum you'd need very accurate locations of both bodies as well as the problem if the comet has any changes from eruptions or other forces.

As for nukes, there's two problems. One, in space they don't do that much unless they in contact with the object. No atmosphere to carry a blast wave. Two, if the comet is a very loose snowball, a lot of the blast from the outer part might get absorbed, or it could just break apart with the course not all that changed. It's even a problem with the technique of just pushing it, we're not sure yet how well that would work.

moozoo
2013-Mar-11, 08:39 AM
Not to shoot down your idea, but...

That is cool. :)
If we had an extinction level event coming right at us, we would throw thousands of trillions of dollars (every thing we had) at the problem and try every possible idea we had.
Hitting it with a NEO isn't a great option, but then none of the other options are that great either.

The main problems are the short time frame (<2yrs notice) and the high velocity of the comet.
I suspect if we where really faced with this today, we would end up nuking it with everything we could. It might make a nice fireworks show before the end...

Ara Pacis
2013-Mar-11, 09:39 AM
I know it's hard but I'm not sure it's impossible to achieve an intercept if we treat this as a trial run for an Earth-bound comet and throw lots of resources into it. I know it's coming in from a high angle to the ecliptic and retrograde at that, but even a huge amount of delta-v might be possible with assembly in space of current and near-term tech (NTR) if money is no object and we put the world economy on a war footing. This could be the thing we need to get out of the recession and get into space. Better to blow up a comet than blow up ourselves.

I just hope it *is* a comet and not an friendly alien race invading Mars and not Earth because, ya know, they're friendly.

Embrace the Race to stop Comet Siding Spring from causing a Martian "Silent Spring".

(On the other hand, I kinda want to see what would happen if it hit. I suppose a trial run that proves the ability to deflect can serve as a proof of concept either way.)

Concerned
2013-Mar-11, 09:48 PM
I truly wonder whether we would spend trillions of dollars saving the world. It's more than likely a cost/benefit ratio would indicate the best option to be to place several hundred thousand people into protective bunkers (like in the movie deep impact) and let the rest of humanity perish. It's a scary idea, but, if you consider the world in which we live, I know this is pessimistic, but, would we actually pay for our survival (I know I would), but, if the cost in resources and money is to great, would the powers that be actually try and save the world, or simply as many as they could. You only require 50 breeding pairs minimum. Very scary notion, but, which is more likely?

Sorry, off topic babble, I'm sure We'd give any comet/asteroid hell :)

Concerned
2013-Mar-19, 01:26 AM
Nominal distance update available from the jpl. Please see http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1;orb=0;cov=0;log=0#elem.

Rhaedas
2013-Mar-19, 01:46 AM
Again, minimum is still at zero, but max has tripled since last posted link. At what point would the minimum begin to move from zero?

Centaur
2013-Mar-19, 03:09 AM
Again, minimum is still at zero, but max has tripled since last posted link. At what point would the minimum begin to move from zero?

Any miss could still be on either side of Mars. So the possible distance vectors could be positive or negative depending on the chosen standard. That means zero is not one of the extremes, but is somewhere in between.

Rhaedas
2013-Mar-19, 03:20 AM
Any miss could still be on either side of Mars. So the possible distance vectors could be positive or negative depending on the chosen standard. That means zero is not one of the extremes, but is somewhere in between.

That was my first impression, but then wouldn't that mean that the new estimate has a bigger range of error? I realize that over time there are likely going to be variations, particularly with a comet as it warms and out-gases. Is this why the numbers have gone up?

Centaur
2013-Mar-19, 03:42 AM
That was my first impression, but then wouldn't that mean that the new estimate has a bigger range of error? I realize that over time there are likely going to be variations, particularly with a comet as it warms and out-gases. Is this why the numbers have gone up?

I don't really know, since I don't have updated parameters for numerical integration. It's possible that the range is not much greater, since the absolute distance value on one side of Mars or the other may have shrunk. Indeed, non-gravitational factors such as out-gassing are wild cards, especially considering the considerable time still remaining until the comet approaches Mars.

moozoo
2013-Mar-19, 02:29 PM
This is what Exorb and Solex give for the best fit solution. Closest approach 135132 km = 0.000903302 AU
#1 #2 Date TT JD2000 Dm (Gm) V(km/s) pImp pDefl pDa pDn Err(Gm) long (ř) lat lat2 r1 (AU) r2
-4 14C 2014/10/19 18:37:21 5405.27594 0.135132 55.9632 1.60 -1.62 - 0.44 1.33 0.000000 302.5779 -1.7642 -1.7328 1.401340 1.401170 Mars C2013A1

Histogram of 1256 virtual clones (monty Carlo) is below
18327

Really based on the orbit data alone the collision is unlikely.
To further the discussion we really need input from someone with knowledge of non-gravitational forces that affect comets.
i.e. what is the order of the effects and are there any general statements that apply.

rafaelg
2013-Mar-21, 01:55 AM
If the dispersion of possible paths of comet is symmetrical around the nominal, Mars remain outside (minimum greater than 0 ) when the maximum distance of approach results less than twice the distance of nominal approach

Concerned
2013-Mar-25, 09:25 PM
Jpl data updated:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad

Concerned
2013-Mar-28, 01:32 AM
NASA have posted a news story about siding spring a1, available at:- http://sluggerotoole.com/2013/03/27/comet-2013-a1-rendezvous-with-mars/

Concerned
2013-Mar-28, 09:09 PM
Are there any other legitimate sources indicating the possible size of the comet, other than NASA - http://science.nasa.gov/. I'm just curious, NASA are suggesting a comet 1-3 km in diameter. I've seen other crazy estimates of 50km. Surely a more exact idea of the comets size should be available now. I'm guessing NASA is the most accurate source?

Romanus
2013-Mar-29, 02:32 AM
IIRC, they've considerably reduced the estimated size to a few kilometers.

Concerned
2013-Mar-29, 02:36 AM
IIRC, they've considerably reduced the estimated size to a few kilometers.

Cool, thanks for responding.

Concerned
2013-Mar-29, 10:58 PM
Article from space.com, suggests that there is still some uncertainty as to the comets size :- http://www.space.com/20443-mars-comet-2014-flyby-science.html. I'm guessing they mean whether the comet is 1km or 3km in diameter.

Concerned
2013-Apr-08, 09:18 PM
Any updates on this? Jpl not updated since 24 march.

antoniseb
2013-Apr-08, 09:41 PM
Any updates on this? Jpl not updated since 24 march.
I imagine that once they determined that it would miss Mars by a wide margin there wasn't any pressing need for anything more accurate.

NEOWatcher
2013-Apr-09, 12:54 PM
I imagine that once they determined that it would miss Mars by a wide margin there wasn't any pressing need for anything more accurate.
They who?
Yes; I would imagine the media is now yawning over the situation because there's really nothing to say.
But; from the scientist point of view, it's just your normal "it takes time" to study.

From the article:

"We are not worrying about that right now, since the probability is very low and likely to be ruled out in the next few months by continued monitoring of the comet's progress," Zurek said.

It seems as though the focus is on studying the orbit which will take months of refinements.

Concerned
2013-Apr-09, 06:26 PM
They who?
Yes; I would imagine the media is now yawning over the situation because there's really nothing to say.
But; from the scientist point of view, it's just your normal "it takes time" to study.

From the article:

It seems as though the focus is on studying the orbit which will take months of refinements.


I thought that was more likely to be the case. I thought that the jpl data would continue to be updated periodically regardless. The current periodicity has been about every 7 or 8 days, so I had been expecting an update this past week.

Concerned
2013-Apr-09, 06:35 PM
Speak of the ....., the JPL has been updated today http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad; This time they have included a minimum distance 5.93029353760146e-05 au (887159285.7977762 km).
Nominal distance is 0.000755438465290256 au (113011.98584549922 km) and maximum distance is 0.00198685746849923 au (297229.64665399544 km).

Not sure what the e-05 is on the minimum distance?

Concerned
2013-Apr-09, 07:26 PM
I'm guessing the minimum distance is still to be refined

Bynaus
2013-Apr-09, 08:54 PM
e-05

That is 0.00001.Therefore, the minimal distance is 0.00001 x 5.93 AU = 0.0000593 AU = ~9'000 km (nominal distance = 100'000 km). So this means that an impact on Mars is now effectively excluded.

Concerned
2013-Apr-09, 11:34 PM
That is 0.00001.Therefore, the minimal distance is 0.00001 x 5.93 AU = 0.0000593 AU = ~9'000 km (nominal distance = 100'000 km). So this means that an impact on Mars is now effectively excluded.

Thanks for the update.

Squink
2013-Apr-10, 05:06 PM
So, closest approach is expected to be somewhere between the orbits of Deimos and Phobos.
I don't suppose anyone's calculated the probability of a 4 body gravitational capture event? :whistle:

antoniseb
2013-Apr-10, 05:21 PM
So, closest approach is expected to be somewhere between the orbits of Deimos and Phobos.
I don't suppose anyone's calculated the probability of a 4 body gravitational capture event? :whistle:

I don't think we need to calculate that. The relative velocity of the comet is huge compared to any delta-V that the gravity of Deimos and Phobos could give even IF they were perfectly positioned for maximum effect.

schlaugh
2013-Apr-10, 06:03 PM
From NASA (http://www.nasa.gov/mission_pages/asteroids/news/comet20130305.html):


March 21, 2013 Update:

New observations of comet C/2013 A1 (Siding Spring) have allowed NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif. to refine the comet's orbit.


Using observations through March 15, 2013, the latest orbital plot places the comet's closest approach to Mars a little farther out than previously estimated, at about 73,000 miles (118,000 kilometers) from the surface of the Red Planet. The impact probability has decreased accordingly; it is now about 1 in 8,000.

The latest estimated time for close approach to Mars is about 11:45 a.m. PDT (18:45 UTC) on Oct. 19, 2014. At the time of closest approach, the comet will be on the sunward side of the planet. The comet and its tail should be a spectacular sight in the pre-dawn Martian sky just before closest approach, as well as in the post-dusk sky just after closest approach.



So...pretty sight, no boom.

Squink
2013-Apr-10, 09:26 PM
even IF they were perfectly positioned for maximum effect. Deimos could be placed to acquire its own version of Phobos' Stickney crater. That'd allow considerable transfer of momentum. However, that scenario is likely probing the once every billion or two years levels of probability (http://cosmoquest.org/forum/showthread.php?142631-Possible-Comet-Collision-with-Mars&p=2113641#post2113641).

Concerned
2013-Apr-10, 09:39 PM
So what's the chances of either Deimos or Phobos getting slammed?

Ara Pacis
2013-Apr-12, 03:28 PM
From NASA (http://www.nasa.gov/mission_pages/asteroids/news/comet20130305.html):



So...pretty sight, no boom.

No boom today. Boom tomorrow. There's always a boom tomorrow.

We'll have to wait and see if out-gassing causes a change in the comet's orbit.

Concerned
2013-Apr-13, 02:20 AM
No matter what, I am sure this comet will be watched very closely. I wonder how bright it will appear from earth.

Concerned
2013-Apr-13, 10:39 AM
Interesting universetoday article http://www.universetoday.com/101437/new-calculations-effectively-rule-out-comet-impacting-mars-in-2014/. I noted from the comments that it has been suggested that if the comet comes close enough to the planet, then it may break up, at which point, the orbits of the fragments would diverge to who knows where. Starting to think that a direct hit on mars might not be a bad thing.

Ara Pacis
2013-Apr-14, 02:01 AM
Interesting universetoday article http://www.universetoday.com/101437/new-calculations-effectively-rule-out-comet-impacting-mars-in-2014/. I noted from the comments that it has been suggested that if the comet comes close enough to the planet, then it may break up, at which point, the orbits of the fragments would diverge to who knows where. Starting to think that a direct hit on mars might not be a bad thing.

Well, the comet isn't expected to come back around for a long time and there's nothing to hit on it's way in or out except Mars and its moons... unless there's an errant asteroid somewhere near mars and way off the ecliptic.

I'm more interested in the statement that the comet will be sun-ward of Mars. I know comets and their jets can be hard to predict, but it would seem to be that jets created by sunlight are more likely to thrust on the side exposed to the sun, which might mean a higher probability that any such activity will push it towards the orbit of mars (and an impact) instead of away. Or am I wrong and jets probabilistically prefer a different direction?

Romanus
2013-Apr-14, 05:05 PM
1.) Even though it won't hit, a sunward CA will be the best scenario for science, as we'll see a comet's coma interact directly with a planet's atmosphere.
2.) I wonder if it will create a new meteor stream that Mars will intersect once per orbit.
3.) Comets with orbits like this are extremely sensitive to perturbations; I will be *very* interested to see the post-encounter changes to Siding-Spring's orbit.

Concerned
2013-Apr-14, 08:11 PM
1.) Even though it won't hit, a sunward CA will be the best scenario for science, as we'll see a comet's coma interact directly with a planet's atmosphere.
2.) I wonder if it will create a new meteor stream that Mars will intersect once per orbit.
3.) Comets with orbits like this are extremely sensitive to perturbations; I will be *very* interested to see the post-encounter changes to Siding-Spring's orbit.


Hi, sorry, what might be so interesting? Looking at the orbital path diagram provided by centaur earlier on in the thread, I don't imagine the comets path would be changed so much. Orbital diagram available at:- http://www.CurtRenz.com/comets25.html.

Concerned
2013-Apr-14, 08:54 PM
1.) Even though it won't hit, a sunward CA will be the best scenario for science, as we'll see a comet's coma interact directly with a planet's atmosphere.
2.) I wonder if it will create a new meteor stream that Mars will intersect once per orbit.
3.) Comets with orbits like this are extremely sensitive to perturbations; I will be *very* interested to see the post-encounter changes to Siding-Spring's orbit.


Possible threat to earth?

schlaugh
2013-Apr-15, 01:23 AM
No threat....Siding Spring has a hyperbolic orbit with an eccentricity of 1.00038. IOW this will be its only pass through the inner solar system. Once it's gone, it's gone for good.

Romanus
2013-Apr-15, 03:42 AM
Hi, sorry, what might be so interesting? Looking at the orbital path diagram provided by centaur earlier on in the thread, I don't imagine the comets path would be changed so much. Orbital diagram available at:- http://www.CurtRenz.com/comets25.html.

When you're dealing with orbits like this--orbits that are barely bound to the Sun to begin with--a small change in conditions near perihelion can have huge effects on the comet's final orbit. I'm guessing that this pass will greatly shorten the comet's orbital period, though it it will still remain many thousands of years.

Concerned
2013-Apr-15, 07:34 AM
No threat....Siding Spring has a hyperbolic orbit with an eccentricity of 1.00038. IOW this will be its only pass through the inner solar system. Once it's gone, it's gone for good.

Hi, cool, thanks for the reply.

Concerned
2013-Apr-15, 07:34 AM
When you're dealing with orbits like this--orbits that are barely bound to the Sun to begin with--a small change in conditions near perihelion can have huge effects on the comet's final orbit. I'm guessing that this pass will greatly shorten the comet's orbital period, though it it will still remain many thousands of years.

Thanks, understood.

moozoo
2013-Apr-15, 08:35 AM
It might have an hyperbolic orbit in heliocentric orbital elements but may not be in barycentric orbital elements.
I found this link that talks about non-gravitational effects http://www.lpi.usra.edu/books/CometsII/7009.pdf

On spaceorbs.org I saw a comments post (in russian, via google translate) that was saying (if I understood correctly) that non-gravitational effects tended to make perihelion occur earlier.
Also (and from what I can tell) the comet passes Mars on the opposite side to the sun and after perihelion. The effect of perihelion being earlier meant that the comet would be closer to the sun when it passed Mars. i.e. the non-gravitational effects increased the chances of impact.
That said, it was in Russian, being translated by Google and I know nothing of comet non-gravitational effects....
So if anyone actually knows what the general effects of non-gravitational comet out gassing is on the comets orbit I would love to know.

Romanus
2013-Apr-16, 12:45 AM
^
IIRC, those non-gravitational effects depend a great deal on the nucleus's rotation; in one direction the jets on the nucleus will "brake" the comet somewhat, in another they will accelerate it slightly. The effect is slight, though.

There is a freely-available paper linked here, though I'll be the first to admit that most of it's over my head: "Cometary Orbit Determination and Nongravitational Forces", http://www.lpi.usra.edu/books/CometsII/7009.pdf

Ara Pacis
2013-Apr-18, 08:46 AM
No boom today. Boom tomorrow. There's always a boom tomorrow.

We'll have to wait and see if out-gassing causes a change in the comet's orbit.

One of these days I'll learn to stop making prediction in jest. :(

Concerned
2013-May-11, 05:30 PM
It might have an hyperbolic orbit in heliocentric orbital elements but may not be in barycentric orbital elements.
I found this link that talks about non-gravitational effects http://www.lpi.usra.edu/books/CometsII/7009.pdf

On spaceorbs.org I saw a comments post (in russian, via google translate) that was saying (if I understood correctly) that non-gravitational effects tended to make perihelion occur earlier.
Also (and from what I can tell) the comet passes Mars on the opposite side to the sun and after perihelion. The effect of perihelion being earlier meant that the comet would be closer to the sun when it passed Mars. i.e. the non-gravitational effects increased the chances of impact.
That said, it was in Russian, being translated by Google and I know nothing of comet non-gravitational effects....
So if anyone actually knows what the general effects of non-gravitational comet out gassing is on the comets orbit I would love to know.

Nice study. Thanks for the link.

Concerned
2013-May-12, 03:16 AM
does anybody know if there have been any updates as to the size of the comets nucleus?

Concerned
2013-May-13, 11:18 PM
does anybody know if there have been any updates as to the size of the comets nucleus?

I read that the comet has a magnitude m2 value of 10.5, available at:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad. NASA has stated that the comet is probably about 5km in diameter, whereas I have heard estimates of 10-50km. What does the magnitude mean and indicate?

Concerned
2013-May-14, 02:07 AM
I read that the comet has a magnitude m2 value of 10.5, available at:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad. NASA has stated that the comet is probably about 5km in diameter, whereas I have heard estimates of 10-50km. What does the magnitude mean and indicate?
Sorry, looked this up. Magnitude as in visibility. 10.5 would not be considered visible to the naked eye. Apologies.

Amber Robot
2013-May-14, 04:28 PM
Sorry, looked this up. Magnitude as in visibility. 10.5 would not be considered visible to the naked eye. Apologies.

It looks like that 10.5 is only for the nucleus, though the page does not define specifically what they are calling the "nucleus". The total brightness of the comet, including the coma, is listed as 5.2 magnitude, which may be visible to the eye.

Concerned
2013-May-14, 08:27 PM
It looks like that 10.5 is only for the nucleus, though the page does not define specifically what they are calling the "nucleus". The total brightness of the comet, including the coma, is listed as 5.2 magnitude, which may be visible to the eye.

Hi, thanks for your response.

Concerned
2013-May-20, 09:05 PM
Any updates as to the comets expected trajectory?

I have checked the jpl site, http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad, no updates since 7 may 2013.

Concerned
2013-May-23, 08:55 PM
Any updates as to the comets expected trajectory?

I have checked the jpl site, http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad, no updates since 7 may 2013.

I know this is probably paranoid, but, should we not have heard more about this comet by now. The jpl was last updated on 07/05/2013. Would the data have been refined since then?

Ara Pacis
2013-May-23, 09:10 PM
I know this is probably paranoid, but, should we not have heard more about this comet by now. The jpl was last updated on 07/05/2013. Would the data have been refined since then?

IIRC, the rapid updates were due to the discovery of previous detections of the comet on older photos. If they've completed data mining of old photos, then they'd be limited to real-time detections of movement, which may not be very large considering how slowly it may be moving against the background stars at this point in its orbit.

antoniseb
2013-May-23, 09:12 PM
I know this is probably paranoid, but, should we not have heard more about this comet by now. The jpl was last updated on 07/05/2013. Would the data have been refined since then?
How often should they update it? It takes some man-hours to make the updates happen, and they are a scarce enough resource that someone has to pay for them. For a comet that won't get very bright, and won't get to perihelion until Oct 2014, I'd think every month or two should be enough.

Concerned
2013-May-23, 10:40 PM
IIRC, the rapid updates were due to the discovery of previous detections of the comet on older photos. If they've completed data mining of old photos, then they'd be limited to real-time detections of movement, which may not be very large considering how slowly it may be moving against the background stars at this point in its orbit.

Thank you.

Concerned
2013-May-23, 10:41 PM
How often should they update it? It takes some man-hours to make the updates happen, and they are a scarce enough resource that someone has to pay for them. For a comet that won't get very bright, and won't get to perihelion until Oct 2014, I'd think every month or two should be enough.

Thanks for the response, though I would have thought that the possibility of collision would have made the object higher priority and of greater interest.

Hornblower
2013-May-24, 02:46 AM
Of greater interest, yes indeed, but if continued studies of its motion have not significantly changed the preliminary orbital elements or reduced the uncertainty over the last few weeks, I do not see much point in going through the motions of giving updates.

Concerned
2013-May-24, 11:39 AM
Of greater interest, yes indeed, but if continued studies of its motion have not significantly changed the preliminary orbital elements or reduced the uncertainty over the last few weeks, I do not see much point in going through the motions of giving updates.

Hi , thank you, ok. However, I would not have thought that it was necessary for a significant change to have occurred, for an update to be made. I thought that standard practice would simply call for an update. Whether the change (large or small, if any), should not mean that no update is made, surely?

Concerned
2013-May-25, 01:06 PM
Hi,

The JPL has updated the data for comet c\2013 1a. Available at:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad. Updated: 24/05/2013.

Minimum Distance:- 0.000176708986721842 au / 26435.28814555176 km
Nominal Distance:- 0.000806622781124662 au / 120669.050507102 km
Maximum Distance:- 0.00173822370413009 au / 260034.56492248428 km
Time uncertainty:- 35.663471212153 minutes

Concerned
2013-Jun-01, 12:21 PM
No. Mars is very far away, and space is very big. Plus a lot of other factors, but those are the main ones that make this a non-event for Earth itself.

Hi,

I read in a forum, http://answers.yahoo.com/question/index?qid=20130304153719AAJbxjW, someone suggested that the comet could knock mars out of its present orbit. Is this possible?

Bynaus
2013-Jun-01, 01:42 PM
No. Even if it had the huge diameter first suggested (50 km), it would still have a mass of only about one in ten trillions of that of Mars. In other words, you are asking if you can use a dust grain with a mass of a few micrograms to knock a 50 ton truck off the highway. No, you can't.

Ara Pacis
2013-Jun-01, 07:38 PM
Well, since momentum is conserved, the orbit of mars would have to change. IIRC, the trajectory of the comet, upon a hypothetical impact, would cause a change to the planet's orbital plane and also slightly slow the planet's forward motion, which would result in the planet moving closer to the sun (and Earth's orbit). However, the alteration to the orbit of Mars would be miniscule. I haven't worked out the numbers, because I don't know how, but I'd guess it would be measured in millimeters to centimeters.

Most of the other statements on that Yahoo answers page are wrong as well.

publiusr
2013-Jun-03, 07:41 PM
That ranks right up there with a co-worker who thought rocket launches would shove Earth out of orbit.

Too much Frisky Dingo.

TooMany
2013-Jun-03, 07:46 PM
That ranks right up there with a co-worker who thought rocket launches would shove Earth out of orbit.

Too much Frisky Dingo.

Well they do don't they? Just not very much. :)

Concerned
2013-Jun-09, 05:33 PM
Updated trajectory data available from the JPL:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad

Nominal Distance:- 0.000821096877243536 au / 122834.3444666624 km
Maximum Distance:- 0.0015767796335406 au / 235882.87572660905 km
Minimum Distance:- 9.77353283338091e-05 au / 14620.997010023604 km

I think that I have the minimum distance correct from the data. Please update if not the case.

Concerned
2013-Jun-09, 05:34 PM
The previous Minimum distance was 0.000176708986721842 au \ 26435.28814555176 km. That change seems significant. Is it?

Concerned
2013-Jun-09, 06:02 PM
An impact appearing more likely?

I guess the comet still might miss by several hundred kilometres. An impact has still not been ruled out from the results.

Concerned
2013-Jun-09, 06:19 PM
A impact is appearing more likely?

How close does the comet have to be, to be within the Roche limit of Mars?

Tuckerfan
2013-Jun-09, 07:20 PM
5000 KM (http://burro.astr.cwru.edu/stu/advanced/mars_moons.html)

Concerned
2013-Jun-09, 07:24 PM
Thanks

Concerned
2013-Jun-09, 07:24 PM
5000 KM (http://burro.astr.cwru.edu/stu/advanced/mars_moons.html)

Thanks

Concerned
2013-Jun-09, 09:14 PM
Updated trajectory data available from the JPL:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad

Nominal Distance:- 0.000821096877243536 au / 122834.3444666624 km
Maximum Distance:- 0.0015767796335406 au / 235882.87572660905 km
Minimum Distance:- 9.77353283338091e-05 au / 14620.997010023604 km

I think that I have the minimum distance correct from the data. Please update if not the case.

So, any thoughts on the updated trajectory?

Hornblower
2013-Jun-10, 01:27 AM
So, any thoughts on the updated trajectory?

I would say the changes from the ones you posted two weeks ago are insignificant. The nominal separation has changed by about 2% of the magnitude of the error bars, which now are somewhat larger than before. For a comet that is well over a year out, two weeks hardly seems like enough to reasonably expect a significant reduction in the uncertainty.

Swift
2013-Jun-10, 01:58 AM
Updated trajectory data available from the JPL:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad

Nominal Distance:- 0.000821096877243536 au / 122834.3444666624 km
Maximum Distance:- 0.0015767796335406 au / 235882.87572660905 km
Minimum Distance:- 9.77353283338091e-05 au / 14620.997010023604 km

I think that I have the minimum distance correct from the data. Please update if not the case.
By the by, there is no way that that many those values are significant to that many digits. It looks to me that the webpage is just filled automatically, and the results of the calculations are just reported to as many digits as the calculation is made. They don't report the 1-sigma distance uncertainty for the close approach data, but the time uncertainty is 29 minutes, and I suspect the min and max are plus/minus one sigma (or maybe more).

I suspect a "more better" way to report that would be minimum of 14600 km, nominal of 123000, and max of 236000 (or something like that).

Concerned
2013-Jun-10, 11:51 AM
By the by, there is no way that that many those values are significant to that many digits. It looks to me that the webpage is just filled automatically, and the results of the calculations are just reported to as many digits as the calculation is made. They don't report the 1-sigma distance uncertainty for the close approach data, but the time uncertainty is 29 minutes, and I suspect the min and max are plus/minus one sigma (or maybe more).

I suspect a "more better" way to report that would be minimum of 14600 km, nominal of 123000, and max of 236000 (or something like that).

Hi, thank you. I will remember that for my next update. : )

antoniseb
2013-Jun-10, 12:56 PM
By the by, there is no way that that many those values are significant to that many digits. ...
Going one step further with Swift's point, the values you gave are to the nearest 10th of a micron. Given that the nucleus of the comet is a few billion times that size in diameter, and that the nucleus itself is shrouded in gas and dust, we definitely don't know the position that closely. Swifts suggestion to round to the nearest 100 km if you don't see any other indicator for accuracy in the tables is a good choice.

Concerned
2013-Jun-10, 01:56 PM
Going one step further with Swift's point, the values you gave are to the nearest 10th of a micron. Given that the nucleus of the comet is a few billion times that size in diameter, and that the nucleus itself is shrouded in gas and dust, we definitely don't know the position that closely. Swifts suggestion to round to the nearest 100 km if you don't see any other indicator for accuracy in the tables is a good choice.

understood

Swift
2013-Jun-10, 01:59 PM
By the by, there is no way that that many those values are significant to that many digits.
Nice grammar Swift. :doh:

I should also say that I wasn't posting that to correct you or give you a hard time Concerned. One, I have a pet peeve about significant digits, back to my Teaching Assistant days grading lab reports. Second, they are important, because reporting the values to 16 digits gives a completely false sense as to how well the orbit of this comet is understood. Third, I don't know about you, but I can't look at that many digits and get a real good sense of the values, particularly the relative values of min, max and nominal.

Concerned
2013-Jun-10, 06:31 PM
Nice grammar Swift. :doh:

I should also say that I wasn't posting that to correct you or give you a hard time Concerned. One, I have a pet peeve about significant digits, back to my Teaching Assistant days grading lab reports. Second, they are important, because reporting the values to 16 digits gives a completely false sense as to how well the orbit of this comet is understood. Third, I don't know about you, but I can't look at that many digits and get a real good sense of the values, particularly the relative values of min, max and nominal.

That's okay Swift. No hard time experienced. There is nothing wrong with constructive criticism : ). All is learning and refinement. Thanks.

Concerned
2013-Jun-17, 09:51 PM
Just found a PDF. Very interesting. Suggesting requirement to mitigate meteoroid impacts on our satellites around mars. http://solarsystem.nasa.gov/docs/Comet_Siding_Spring_and_Mars_Spacecraft.pdf. From:- http://tech.groups.yahoo.com/group/meteorobs/message/42615. Article is by Dr Althea Moorhead and Dr Bill Cooke of the Marshall Space Flight Center.

Concerned
2013-Jun-17, 09:52 PM
Just found a PDF. Very interesting. Suggesting requirement to mitigate meteoroid impacts on our satellites around mars. http://solarsystem.nasa.gov/docs/Comet_Siding_Spring_and_Mars_Spacecraft.pdf. From:- http://tech.groups.yahoo.com/group/meteorobs/message/42615. Article is by Dr Althea Moorhead and Dr Bill Cooke of the Marshall Space Flight Center.

What will happen to Mars when showered with meteors?

Swift
2013-Jun-18, 01:29 AM
Very interesting presentation, particularly that NASA is thinking of measures to protect the orbiting satellites.

schlaugh
2013-Jun-18, 01:57 AM
I found this very interesting:


Meteor shower will accompany Siding Spring

Zenithal hourly rate (ZHr) ~40,000 at Mars

Lasts a few hours, may be observable from Opportunity

Subradiant location:
- Near Opportunity
- Timing close to local dawn

Meteoroids (100 \mum or larger): 20% chance of impact per square meter due to coma and tail


As the presentation says, 40,000 an hour is unprecedented, even if they are all 100 micron and sub-micron sized particles. How many will make it through the atmosphere of Mars? These will be very tiny, so maybe enough to raise a great deal of impact dust?

Concerned
2013-Jun-18, 08:36 PM
I found this very interesting:


As the presentation says, 40,000 an hour is unprecedented, even if they are all 100 micron and sub-micron sized particles. How many will make it through the atmosphere of Mars? These will be very tiny, so maybe enough to raise a great deal of impact dust?

very cool

Jens
2013-Jun-18, 11:17 PM
What will happen to Mars when showered with meteors?

It will get more craters, I suppose. Since its atmosphere is much thinner than ours, more of the meteors will hit the surface.

Concerned
2013-Jun-24, 10:07 PM
Could a direct hit from comet c\2013 1a, cause the rotation of mars to alter? I was just reading about Venus, and the suggestion that billions of years ago, a large impact event is believed to have altered the planets spin. Could this happen on mars?

antoniseb
2013-Jun-24, 10:53 PM
Could a direct hit from comet c\2013 1a, cause the rotation of mars to alter?...
We might have clock on Mars precise enough to detect the difference in rotation from a comet hit, but I don't know of such a clock.

Concerned
2013-Jun-24, 11:08 PM
We might have clock on Mars precise enough to detect the difference in rotation from a comet hit, but I don't know of such a clock.

Understood

Hornblower
2013-Jun-25, 01:18 AM
Could a direct hit from comet c\2013 1a, cause the rotation of mars to alter? I was just reading about Venus, and the suggestion that billions of years ago, a large impact event is believed to have altered the planets spin. Could this happen on mars?

If Venus originally had a prograde spin similar to that of most other planets, something vastly larger than any known comet would have been needed to change it to the present slow retrograde rotation.

schlaugh
2013-Jun-25, 02:14 AM
During the formation of the solar system planets were built up through accretion (http://en.wikipedia.org/wiki/Accretion_%28astrophysics%29)with planetesimals (http://en.wikipedia.org/wiki/Planetesimals) which could have enough mass to affect spin and orbit. That may be the basis for what you read about an impact to Venus.

From the Wikipedia article on Venus:


Alex Alemi's and David Stevenson (http://en.wikipedia.org/wiki/David_J._Stevenson)'s 2006 study of models of the early Solar System at the California Institute of Technology (http://en.wikipedia.org/wiki/California_Institute_of_Technology) shows Venus likely had at least one moon created by a huge impact event (http://en.wikipedia.org/wiki/Impact_event) billions of years ago.[83] (http://en.wikipedia.org/wiki/Venus#cite_note-83) About 10 million years later, according to the study, another impact reversed the planet's spin direction and caused the Venusian moon gradually to spiral inward (http://en.wikipedia.org/wiki/Tidal_deceleration) until it collided and merged with Venus.[84] (http://en.wikipedia.org/wiki/Venus#cite_note-84)

Ara Pacis
2013-Jun-25, 06:53 AM
Could a direct hit from comet c\2013 1a, cause the rotation of mars to alter? I was just reading about Venus, and the suggestion that billions of years ago, a large impact event is believed to have altered the planets spin. Could this happen on mars?

Not only Venus, but Earth is also thought to have suffered an impact that significantly altered its spin.

Kullat Nunu
2013-Jun-25, 09:17 PM
Venus was probably slowed down, at least partly, by its massive atmosphere.

Concerned
2013-Jun-27, 06:19 PM
Updated JPL data available at:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad. [Updated 26/06/2013] [Accessed 27/06/2013]

Nominal Distance:- 0.000821096887836991 au / 122834 km
Minimum Distance:- 9.77353231892713e-05 au / 14621 km
Maximum Distance:- 0.00157677964498512 au / 235883 km

Time uncertainty still stands at 29 minutes.

Concerned
2013-Jun-30, 10:10 PM
Just found a blog http://transientsky.wordpress.com/2013/01/28/vatt-comets/, which features an image of comet c\2013 1a. The blog is from 26 January of this year. Thought it interesting :).

Concerned
2013-Aug-02, 08:41 AM
Hi,

Any updates on this. Last time I checked, the jpl had not been added to since the 26 June. I found a link stating the ephemeris as of 1 August http://in-the-sky.org/cometephem.php?obj=ck13a010.

Concerned
2013-Aug-04, 12:56 PM
I'm wondering if a comet collision with mars could send fragments from the impact our way. A recent scientific American article suggests that this has possibly happened before http://www.scientificamerican.com/article.cfm?id=solved-the-mystery-of-the-meteorites.

antoniseb
2013-Aug-04, 04:34 PM
I'm wondering if a comet collision with mars could send fragments from the impact our way. ...
Fragments? Probably nothing big enough to worry about. I suspect anything that has landed on Earth after being ejected from Mars was the result of a much bigger collision than a mere average-sized comet. Also worth noting, such a journey takes millions of years. Nothing would get the energy required for a direct trip.

Concerned
2013-Aug-04, 08:42 PM
Fragments? Probably nothing big enough to worry about. I suspect anything that has landed on Earth after being ejected from Mars was the result of a much bigger collision than a mere average-sized comet. Also worth noting, such a journey takes millions of years. Nothing would get the energy required for a direct trip.

Cool, thank you for your response.

Concerned
2013-Aug-12, 09:36 PM
The jpl have updated maximum, minimum distances etc for this comet, available at:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad. I haven't checked the numbers yet.

Concerned
2013-Aug-12, 10:22 PM
Nominal Distance 0.000822691843217601 au / 123073 km
Minimum Distance 0.000252791569606213 au / 37817 km
Maximum Distance 0.00139402219257945 au / 208543 km

Sourced Monday 12 August 2013. Available at:- http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad

JohnD
2013-Aug-14, 06:32 PM
http://science.nasa.gov/science-news/sc ... marscomet/

At 1-3kms in diameter, that's between 7^11 and 7^12 litres of water, or less depending on how much rock is in the comet.
How much of that water will stay on Mars and what changes might that little drop effect?

John

Concerned
2013-Aug-14, 06:44 PM
The link you posted is no longer active. What was the story?

Concerned
2013-Aug-14, 06:49 PM
Did you mean to post this link:-http://science1.nasa.gov/science-news/science-at-nasa/2013/26mar_marscomet/ or
http://science.nasa.gov/science-news/science-at-nasa/2013/26mar_marscomet/, which is the same thing.

ravens_cry
2013-Aug-14, 09:08 PM
Poor Opportunity. Unlike his little big brother, Curiosity, he needs sunlight to live.
That being said, the idea we could actually witness a comet collision on a rocky planet is undeniably cool.

neilzero
2013-Aug-14, 11:14 PM
If the comet almost misses Mars, It might disintegrate in the atmosphere, with some fragments traveling as much as 10,000 kilometers though the atmosphere before hitting the surface at a few hundred kilometers per hour. Most of the rest (perhaps a billion tons) will become water vapor in the atmosphere of Mars within minutes. Some snow may fall just before sunrise, for a night or two, but most will remain in the atmosphere for up to a million years, as about 1% humidity. The regloth is very dry so it will soak up any liquid water, in some cases combining chemically with the minerals. Nearly all of the kinetic energy will be radiated into space within a week so any temperature rise will be brief. Most comets have other volatiles and solids besides water. Neil

schlaugh
2013-Aug-14, 11:36 PM
Already a thread cooking.
http://cosmoquest.org/forum/showthread.php?t=142631

JohnD
2013-Aug-16, 07:39 PM
Thanks to all, esp. neil - I feared that it would be a drop in the deser and to schlaugh for the existing thread on this.

John
PS Mods. Merge threads?

Concerned
2013-Aug-30, 11:08 PM
JPL modified 26/08/2013 http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad.

Nominal Distance: 0.000822691843212269 au / 123072 km
Minimum Distance: 0.000252791569609116 au / 37817 km
Maximum Distance: 0.00139402219254594 au / 208542 km

[Retrieved 30/08/2013]

antoniseb
2013-Aug-31, 02:02 AM
Not much change in the last two weeks.

Concerned
2013-Aug-31, 10:21 AM
Not much change in the last two weeks.

No I noticed.

Concerned
2013-Sep-06, 12:42 PM
If the comet were to strike, what effect would this have on the geological activity of Mars? Could Olympus Mons go boom boom?

antoniseb
2013-Sep-06, 03:01 PM
If the comet were to strike, what effect would this have on the geological activity of Mars? Could Olympus Mons go boom boom?
First, it isn't going to hit Mars. Second, we don't really know how big the comet is, or where it would hit.
The answer to your question is probably not, but if it hit close enough to Olympus Mons, it might shake it and collapse the rim of the caldera a bit.

Concerned
2013-Sep-06, 03:40 PM
First, it isn't going to hit Mars. Second, we don't really know how big the comet is, or where it would hit.
The answer to your question is probably not, but if it hit close enough to Olympus Mons, it might shake it and collapse the rim of the caldera a bit.

Cool, thanks for the response.

chornedsnorkack
2013-Sep-06, 04:59 PM
First, it isn't going to hit Mars. Second, we don't really know how big the comet is, or where it would hit.
The answer to your question is probably not, but if it hit close enough to Olympus Mons, it might shake it and collapse the rim of the caldera a bit.

If the impact is into a relatively flat and hard rock target, how big would the resulting crater rim be?

Concerned
2013-Sep-06, 06:53 PM
If the impact is into a relatively flat and hard rock target, how big would the resulting crater rim be?

Hi, you can check this on the wiki for the comet http://en.wikipedia.org/wiki/C/2013_A1. At the bottom of the page, there is a small table, giving a rough estimate of the comet - crater ratio. Although it is looking highly probable that the comet will miss mars, similarly intimated by Antoniseb. The reason I asked the question is, usually impacts will cause stress on the mantle, and of course, this I understand would cause earth tremors and volcanic eruptions, you probably dont just get a clean crater out of such things. However, I may be wrong, this is something that I heard of awhile ago, I could not point you to a valid source of hand, if asked.

chornedsnorkack
2013-Sep-06, 07:28 PM
Hi, you can check this on the wiki for the comet http://en.wikipedia.org/wiki/C/2013_A1. At the bottom of the page, there is a small table, giving a rough estimate of the comet - crater ratio.
Applicable to Earth 1 g, not to Martian 0,37 g.

Concerned
2013-Sep-06, 08:30 PM
Applicable to Earth 1 g, not to Martian 0,37 g.

So, it would be lighter and not penetrate as deep?

antoniseb
2013-Sep-06, 09:10 PM
Applicable to Earth 1 g, not to Martian 0,37 g.
I don't think gravity makes much difference.

chornedsnorkack
2013-Sep-06, 09:56 PM
So, it would be lighter and not penetrate as deep?

No. The energy of the comet is over 99% its kinetic energy far from the planet.

So the total energy released in hypocentre would be the same as on earth. The difference is that higher gravity on earth would be more efficient in keeping earth in place - more energy is needed to pile up crater walls on earth, and same energy under Mars might displace more earth out of the crater and into crater walls.

Tuckerfan
2013-Sep-07, 06:47 AM
No. The energy of the comet is over 99% its kinetic energy far from the planet.

So the total energy released in hypocentre would be the same as on earth. The difference is that higher gravity on earth would be more efficient in keeping earth in place - more energy is needed to pile up crater walls on earth, and same energy under Mars might displace more earth out of the crater and into crater walls.It could also potentially eject material into space, as has happened in the past.

Concerned
2013-Oct-01, 08:28 AM
Jpl updated http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad.

Nominal distance 0.000894431318064509 au / 133805 km
Minimal distance 0.000546945932448485 au / 81822 km
Maximum distance 0.00124196795282943 au / 185796 km

Time uncertainty: 00:12 minutes.


[retrieved 1 October 2013].

Concerned
2013-Dec-27, 11:25 PM
jpl updated on 25th December 2013:-

Nominal distance: 0.000958249905773255 au / 143352 km
Minimal distance: 0.000892107901854257 au / 133457 km
Maximum distance: 0.00102449218247498 au / 153261 km

With 2 minutes time uncertainty.
[retrieved 27 December 2013]
ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1#cad