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Squink
2007-Dec-21, 04:02 AM
Asteroid may hit Mars in next month (http://news.yahoo.com/s/ap/20071221/ap_on_sc/mars_asteroid_2)
A newly discovered hunk of space rock has a 1 in 75 chance of slamming into the Red Planet on Jan. 30, scientists said Thursday.
...
If the asteroid does smash into Mars, it will probably hit near the equator close to where the rover Opportunity has been exploring the Martian plains since 2004.

The article also claims that "The robot is not in danger because it lies outside the impact zone", but just for the sake of going against the mainstream, I'm going to ignore that bit and spend the next month worrying.

novaderrik
2007-Dec-21, 04:09 AM
it would be cool if Oppy got some shots of the after effects of the impact..
which would, no doubt, inspire many threads about the nuclear bombs we sent there to kill the hostile martians..

01101001
2007-Dec-21, 06:15 AM
BA Blog: Mars to get an asteroid impact? (http://www.badastronomy.com/bablog/2007/12/20/mars-to-get-an-asteroid-impact/)

Mainly an alert. Little detail, but the BA does intend to investigate.

Jens
2007-Dec-21, 06:27 AM
It's kind of funny, because there has been a lot of discussion on how to deflect an asteroid from impact. In this case, I think it would kind of cool to deflect the asteroid into impact! Think of the science that we could get from this.

djellison
2007-Dec-21, 10:20 AM
I'm going to ignore that bit and spend the next month worrying.

If a 1:75 chance of an asteroid impact is the worst thing that Opportunity has to deal with - she's doing well :)

Doug

Argos
2007-Dec-21, 11:54 AM
Link (http://www.latimes.com/news/science/la-sci-mars21dec21,0,6729483.story?coll=la-home-center)


An asteroid similar to the one that flattened forests in Siberia in 1908 could plow into Mars next month, scientists said Thursday.

John Kierein
2007-Dec-21, 01:16 PM
What are the chances that this could be a spacecraft that disappeared near Mars, got gravitationally deflected and is finally returning on a later orbit? hmmm

John Kierein
2007-Dec-21, 01:32 PM
When and if it misses Mars, it sounds like 2007 WD5 could be a good candidate to hitchhike onto to get to Mars easier? hmmm

Ivan Viehoff
2007-Dec-21, 01:35 PM
What are the chances that this could be a spacecraft that disappeared near Mars, got gravitationally deflected and is finally returning on a later orbit? hmmm
It's about 160 feet (about 50m) across. Chance that's a spacecraft is rather low, unless you think advanced alien civilisations are trying to visit us.

Romanus
2007-Dec-21, 02:02 PM
That's almost the coolest astronomy story I've read. :) If it happens, it'll be better than SL-9, because it'll show us the firsthand effects of a significant impact on a solid body. Even if it doesn't hit, perhaps it can be targeted for observations by currently orbiting craft; the deflection of the asteroid's orbit would also be worth studying.

NEOWatcher
2007-Dec-21, 02:05 PM
Same story (http://www.cnn.com/2007/TECH/space/12/21/mars.asteroid.ap/index.html) but different wording on CNN with a couple of sentences related to the rover.


If the asteroid does smash into Mars, it will probably hit near the equator close to where the rover Opportunity has been exploring the Martian plains since 2004. The robot is not in danger because it lies outside the impact zone. Speeding at 8 miles a second, a collision would carve a hole the size of the famed Meteor Crater in Arizona.

Ivan Viehoff
2007-Dec-21, 02:22 PM
When and if it misses Mars, it sounds like 2007 WD5 could be a good candidate to hitchhike onto to get to Mars easier? hmmm
And, in the real universe ignoring what happens in "Hitchhiker's Guide to the Galaxy", how exactly does hitchhiking on asteroids work? Isn't it actually harder to stop at an asteroid than a planet, given the lack of a strong gravitational field to catch you? What orbit would you want this asteroid to have that it would provide a useful hitch? If this asteroid regularly comes anywhere usefully close to both Earth and Mars, wouldn't that mean that the actual approaches were rather uncommon, so finding a useful transit would be very uncommon, given the lack of any resonance between Earth and Mars orbits?

George
2007-Dec-21, 04:01 PM
I heard about this possible event on the radio this morning. The news person stated that there is a "1 and 75 percent chance" it will hit Mars. :wall:

soylentgreen
2007-Dec-21, 06:09 PM
I agree with Romanus that this is a very exciting development. My enthusiasm is tempered a bit, though, by the fact that if it does in fact hit, this will be the second major planetary impact in, not my lifetime, but in the last decade and a half! It's not so much the odds of an Earth impact that trouble me, but how this underscores just how underprepared we seem to be for it.

Will this be enough for some serious consideration to be given to programs working to soften the blow, if not actually avoid it happening here?

Or (attendant gene pool benefits aside) does something actually have to smash into Washington DC to get any action?

Argos
2007-Dec-21, 06:20 PM
I agree with Romanus that this is a very exciting development. My enthusiasm is tempered a bit, though, by the fact that if it does in fact hit, this will be the second major planetary impact in, not my lifetime, but in the last decade and a half! It's not so much the odds of an Earth impact that trouble me, but how this underscores just how underprepared we seem to be for it.

Will this be enough for some serious consideration to be given to programs working to soften the blow, if not actually avoid it happening here?

Or (attendant gene pool benefits aside) does something actually have to smash into Washington DC to get any action?

Add to it the possibility that Smaller asteroids may pose greater danger than previously believed (http://www.sandia.gov/news/resources/releases/2007/asteroid.html)

In discussion [well, sorta] here (http://www.bautforum.com/astronomy/68250-another-explanation-tunguska-event.html)

tony873004
2007-Dec-21, 06:21 PM
If the current estimate holds, 2007 WD5 should miss Mars by less than 50,000 km on January 30, 2008 at 9:11 in the morning UT. But Mars and its two moons, Phobos and Deimos are well within the error bars of this estimate and may be struck. It will be interesting to follow the updated predictions and see if the odds of impact improve.

It would be very good for science if this thing did strike Mars. With several orbiting spacecraft, we'd get some good data from below Mars' surface if it makes a crater. With Mars' thinner atmosphere, if this is a Tunguska-sized impactor, it may make it intact to the surface.

Here's a simulation from Gravity Simulator with JPL's current data. Mars, and the orbits of Phobos and Deimos are visible. The green line is the trajectory of 2007 WD5. The first image is looking top-down on the ecliptic plane. The second is from the ecliptic plane.

http://orbitsimulator.com/gravity/images/MarsHt2.GIF

http://orbitsimulator.com/gravity/images/MarsHt1.GIF

If you have Gravity Simulator and want to run the simulation yourself, here's the simulation file:
http://orbitsimulator.com/gravity/simulations/2007WD5.gsim

Veeger
2007-Dec-21, 07:43 PM
If it should strike, it will provide a lot very interesting science but I am afraid the doomsdayers will flood cyberspace with their dire warnings.

I find myself wishing it hits. :)

-Veeger

Celestial Mechanic
2007-Dec-21, 08:06 PM
If it should strike, it will provide a lot very interesting science but I am afraid the doomsdayers will flood cyberspace with their dire warnings. I find myself wishing it hits. :)

-Veeger
I haven't gone looking at GLP, (why waste my time there?), but I'm sure they've all gone through several changes of Depends since the news broke. :eek: I hope it hits too. Better there than here.

DISCLAIMER: Celestial Mechanic does not own stock in any of the manufacturers of incontinence garments.

NGCHunter
2007-Dec-21, 08:38 PM
If it should strike, is there any chance that amateur scopes could witness the impact occuring? I know that the crater will be way too small to resolve, but could any kind of flash be visible? An 8 km per second impact has got to release a ton of heat and energy, right? I'm probably being overly optimistic, but I want a chance to see this kind of event since I wasn't really into astronomy during SL9 :(.

George
2007-Dec-21, 08:48 PM
If it should strike, is there any chance that amateur scopes could witness the impact occuring? I know that the crater will be way too small to resolve, but could any kind of flash be visible? An 8 km per second impact has got to release a ton of heat and energy, right? I'm probably being overly optimistic, but I want a chance to see this kind of event since I wasn't really into astronomy during SL9 :(.
Good question.

This impact calculator (http://www.lpl.arizona.edu/impacteffects/) says iit would generate 1x1017 Joules (prior to entry into the atmosphere). You would think that would light things up nicely, but they claim it would not make much of a fireball, and not much vaporization would take place. I wonder if I entered the data correctly, as I would have guessed a little more of a show would be seen.

tony873004
2007-Dec-22, 02:34 AM
If it should strike, is there any chance that amateur scopes could witness the impact occuring?

A year or so ago, there was enough speculation that when NASA slammed a copper disc into a comet that it would be visible to amateur scopes, and perhaps even to the naked eye. This speculation caused me to bring my telescope to a dark sky, where others with telescopes were doing the same thing.

The comet was a dud, no flash or post-impact cloud. But I imagine an asteroid impact would be much brighter than a 200kg copper disc.

John Kierein
2007-Dec-22, 04:00 PM
If it were a spacecraft, the solar panels would be pointed nearly directly at us since we are so close to opposition. They tend to be unusually bright which could cause us to estimate it to be 50 meters wide when it actually could be only a ~5 meters long solar array. Mars Climate Orbiter failed to go into orbit because of a mixup between metric and english units as I recall and supposedly burned up in the atmosphere; but who knows where it actually went? I think some other s/c failed to go into orbit and could have been deflected instead of entering mars orbit, including some Russian probes.

I think others have suggested hitchhiking on an asteroid to Mars. Not my idea.
http://space.newscientist.com/article/dn10358-hitch-hike-to-mars-inside-an-asteroid.html

tony873004
2007-Dec-22, 05:23 PM
2007 WD5 has an aphelion at about 4 AU, almost all the way to Jupiter. If it were a failed Martian spacecraft, you would expect its aphelion not to exceed 2 AU.

soylentgreen
2007-Dec-22, 05:56 PM
If it should strike, it will provide a lot very interesting science but I am afraid the doomsdayers will flood cyberspace with their dire warnings.


My bigger concern is an inevitable media build up in the last weeks of January, along with the rushed-back-into the schedule comet/asteroid impact docs with the imperious tones of Edward Herrmann or the reasonable and confident ruminations of Duncan Steel.

Then...nothing happens. And the general populace goes back into sedentary mode, with another example of science panicking the masses for no reason under it's belt.

Remember when that bridge collapsed a few months ago and the media went into the "mass bridge collapse" frenzy. People in their cars yelped about having to avoid bridges on their way to work because "THEY'RE ALL ABOUT TO DROP!"....all the politicians raced for face-time and pr claiming they were going to spearhead a look into "the river spanning death-traps that litter our Great Land!"....America declares a "War on Unsafe Bridges"!...then...well **cough** Oh hey, is Deal or No Deal on tonight? :rolleyes:

People, and by "People" I mean Americans, have short easily hyper-stimulated attention spans. The bogus doomsdayism the mainstream(nevermind the fringe flagellants!) could create, especially if the object doesn't hit, could do more damage to serious efforts to help with an Earth-involved scenario than Paris Hilton driving blindfolded and drunk through the Special Olympics parking lot.

Dave Mitsky
2007-Dec-22, 06:15 PM
Here's another link on 2007 WD5 - http://www.skyandtelescope.com/news/home/12713937.html

Dave Mitsky

Nick Theodorakis
2007-Dec-22, 09:19 PM
It's just Brennan the Protector lobbing an ice asteroid at Mars to kill all the Martians hiding in the dust.

Nick

Veeger
2007-Dec-22, 11:03 PM
People, and by "People" I mean Americans, have short easily hyper-stimulated attention spans. The bogus doomsdayism the mainstream(nevermind the fringe flagellants!) could create, especially if the object doesn't hit, could do more damage to serious efforts to help with an Earth-involved scenario than Paris Hilton driving blindfolded and drunk through the Special Olympics parking lot.

:lol::lol::lol:

Sorry. My hyper-stimulated attention span just collapsed with me onto the floor.

tony873004
2007-Dec-24, 05:36 AM
It's predicted path is getting closer to Mars. The media won't run another story until NASA makes another press release, but the updated numbers from some additional observations are now available. December 23rd's data shows it is now predicted to pass 17631 km above the Martian surface, more than twice as close as the prediction made with December 21st's data.

This doesn't necessarily mean that the odds of 1 in 75 have improved. I don't know what the error bar is on the new data. Perhaps as well as the asteroid's trajectory moving closer to Mars, the error bar has shrunk enough to confidently exclude a Martian collision. Or perhaps not.

http://orbitsimulator.com/gravity/images/MarsDec21.GIF

Uranut
2007-Dec-24, 08:49 AM
As long as we're speculating, does anyone here have the math skill or software to determine if an impact with Deimos could create a ring around Mars:think::question:

Romanus
2007-Dec-24, 04:10 PM
My *very* preliminary guess is that it will get closer to Deimos than it will to Mars, but an impact with it is even less likely. Deimos has gotten hit by many objects this size many times in its history; still, the ejecta effects would be well worth studying.

Correction:
On second thought, it looks like Deimos will be on the other side of the planet when 2007 WD5 approaches; it may actually get closer to Phobos.

Kullat Nunu
2007-Dec-24, 10:25 PM
One has to remember that this object hardly deserves to be called an asteroid, so small it is. Still, if it actually hits Mars we should consider ourselves really lucky. Asteroid strikes aren't that common.

ryanmercer
2007-Dec-26, 12:00 AM
Since I heard about this a few days ago I've been hoping it hits... just imagine all we could learn from the impact with everything we've got on and around Mars.

spaceboy0
2007-Dec-26, 12:43 AM
I'm interested to know how the asteroid's ephemerides and orbital data such as inclination, longitude of ascending node, etc. are so accurately arrived at?

How do they determine the distance to the asteroid? With radar bounces?

spaceboy0
2007-Dec-26, 12:51 AM
How can they be so sure that it will hit Mars' equatorial region if they're not even sure if it will even hit at all? Mabey it will hit the Polar regions; is that possible?

What is the difference between the orbital inclination of Mars and this asteroid? Do they have exactly the same orbital inclination to the ecliptic?

tony873004
2007-Dec-26, 02:29 AM
I don't think they did radar on this one. Simply by observing it over a period of time you can fit an orbit that agrees with its motion. Even if they had the same inclination, (which they don't), it could still hit Mars' polar region.

There's a diagram on this page: http://www.jpl.nasa.gov/news/news.cfm?release=2007-152 that shows the target regions.

Kyle Edwards
2007-Dec-26, 03:34 AM
If it happens to hit on the side of Mars facing Earth that might be a great astrophotography opportunity.

01101001
2007-Dec-26, 07:43 AM
How can they be so sure that it will hit Mars' equatorial region if they're not even sure if it will even hit at all?

Didn't see this reference previously:

NASA Near Earth Object Program: Recently Discovered Asteroid Could Hit Mars in January (http://neo.jpl.nasa.gov/news/news151.html)

Has images and animations of the area of uncertainty.


The uncertainty region during the Mars encounter currently extends over a million kilometers (700,000 miles) along a very slender ellipsoid only 1200 km (700 miles) wide, but the ellipsoid does intersect Mars.

The uncertainty region is long and narrow. They know when and where the uncertainty region passes through Mars, so they can know the narrow swath of Mars' surface, said equatorial region, that is eligible to be hit.

Kullat Nunu
2007-Dec-26, 02:08 PM
I'm interested to know how the asteroid's ephemerides and orbital data such as inclination, longitude of ascending node, etc. are so accurately arrived at?

Don't take the accuracy too seriously. The parameters will change as the observational timespan lengthens.


How do they determine the distance to the asteroid? With radar bounces?

There is no way to use radar, the object is tiny and very distant. If they could, the orbital parameters would be much better known.

Squink
2007-Dec-26, 10:28 PM
How can they be so sure that it will hit Mars' equatorial region if they're not even sure if it will even hit at all?-And miss Opportunity to boot.
This my initial thought, when I decided to spend the next few weeks worrying.

spaceboy0
2007-Dec-26, 11:31 PM
If they only discovered the asteroid last month, how do they arrive at the orbital elements as of last April 10? Interpolation?

01101001
2007-Dec-27, 01:30 AM
If they only discovered the asteroid last month, how do they arrive at the orbital elements as of last April 10? Interpolation?

Take what they know and run it backward to estimate where 2007 WD5 may have been at the start of a convenient epoch.

2007 WD5 Orbital Elements (http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007%20WD5;orb=0;cov=0;log=0#elem)


Orbital Elements at Epoch 2454200.5 (2007-Apr-10.0) TDB
Reference: JPL 6 (heliocentric ecliptic J2000)

Orbital determination parameters, there, lists:


# obs. used (total) 28
data-arc span 41 days
first obs. used 2007-11-08
last obs. used 2007-12-19

spaceboy0
2007-Dec-27, 02:07 AM
to calculate the trajectory of the asteroid, once location data is compiled, is that data entered in a computer and a computer gives the trajectory information or are trajectory calculations possible to be done on a calculator?

Kaptain K
2007-Dec-27, 07:01 AM
to calculate the trajectory of the asteroid, once location data is compiled, is that data entered in a computer and a computer gives the trajectory information or are trajectory calculations possible to be done on a calculator?
Well, they were done before there were computers. :whistle:

I did it on a desk top calculator in the early 70s.

George
2007-Dec-27, 04:41 PM
Well, they were done before there were computers. :whistle:

I did it on a desk top calculator in the early 70s. I am curious how much time was needed to do those calculations back then. Did your caclulator do hyperbolic trig functions? I recall a book intro stating how long it would have taken to recalculate Apollo 13's orbital corrections using slide rulers; it would have been far too long to help the crew.

Kaptain K
2007-Dec-27, 05:21 PM
Did your caclulator do hyperbolic trig functions?
Nope. Just spherical trig + conversion from Sun centered to Earth centered coordinates.
It took me several days to determine when (date) and where (R.A and Dec) a certain comet would be within 5 AU of the Sun (we figured that was the maximum distance at which comets were discovered/recovered).

ngc3314
2007-Dec-27, 05:30 PM
I am curious how much time was needed to do those calculations back then. Did your caclulator do hyperbolic trig functions? I recall a book intro stating how long it would have taken to recalculate Apollo 13's orbital corrections using slide rulers; it would have been far too long to help the crew.

There were assorted tricks in common use, some amounting to approximations which would save lots of time and lose little accuracy if used intelligently. One tool I remember seeing was a book tabulating definite integrals commonly encountered in calculations of position along eccentric orbits (from the Government Printing Office, I'm sure at the behest of NASA - son of a gun, Google knows all, 100 pages, 1961). From my feeble attempts to do something similar, I suspect the values might be from elliptic integrals of the worst (err, first) kind, which show up in the position-prediction direction of the problem. From even trying to do this "by hand", I agreed completely that the first few people to calculate comet orbits accurately deserved to have their names memorialized.

I remember at least one science-fiction story dealing with a communications failure in deep space and how the entire crew was harnessed with abaci to compute a return trajectory. In early space exploration, the goal was sometimes to perform a correction maneuver to put them close to a pre-calculated trajectory rather than necessarily go for optimal fuel consumption, since initially the new trajectory could not be calculated close to real time. Even for the early rockets from White Sands, with plenty of tracking data, it could take weeks for the computing center near Washington to kick back an after-the-fact trajectory table.

Hmm - upon reflection, this is a day I really like computers.

danscope
2007-Dec-27, 07:19 PM
Hi, Try to read "Starman Jones " by Robert Heinlein. As I recall,
Jones could do this stuff in his head. Phenomenal.
Dab

Argos
2007-Dec-27, 07:59 PM
I remember at least one science-fiction story dealing with a communications failure in deep space and how the entire crew was harnessed with abaci to compute a return trajectory.

Reminds me of Clarke´s Into the Comet (http://en.wikipedia.org/wiki/Into_the_Comet) [computer malfunction].

tbm
2007-Dec-27, 10:30 PM
So if by the remotest of chances the rover gets destroyed by the asteriod, how long do you thinkd RCH or some other genius claims that NASA did it on purpose?

tbm

Anthrage
2007-Dec-28, 04:12 AM
Have not posted here in some time, good to be back.

I've been considering this occurrence - or more accurately one like it, though much more controlled and calculated - as an excavation tool towards future construction on Mars. A crater could serve well as the base for a domed enclosure, one that could be capped and pressurized.

While there are no doubt may natural or pre-existing craters, one created artificially, or with precision, could perhaps be more desirable in terms of size, depth, location and structure. While it would no doubt be a significant engineering project, it occured to me that performing the excavation in this fashion may be more cost effective than by conventional methods, and is, perhaps surprisingly but also very certainly within our technological means.

It may be a ways further down the road, but the time is not so terribly far into the future when we will have to address these construction questions - and it would be wonderfully ironic if selling such a concept as a time/money saving contruction tool would result in a more appropriate level of practical study and indeed experimentation where impactors are concerned.

It is a very suitable area of scientific study to be sure - through a better understanding of the process (and we have a decent grasp of it now), it is not unreasonable to imagine that by precisely controlling the variables involved - shape, composition and density of impactor, impact angle and velocity, target area composition etc. - one could get a reasonably good result. :)

So with that in mind, I too am favoring an impact. It would be interesting - and possibly useful - to see how ejecta behaves in the low gravity, thin atmosphere enviroment of Mars.

Rue
2007-Dec-28, 04:28 AM
Have not posted here in some time, good to be back.

Welcome....back!



I've been considering this occurrence - or more accurately one like it, though much more controlled and calculated - as an excavation tool towards future construction on Mars. A crater could serve well as the base for a domed enclosure, one that could be capped and pressurized.

You may, or may not, recall seeing a similar design from another young BABB member long ago.

Lunar Crater Base: http://www.geocities.com/wandererofthewastes/LCB.html

Anyways, I am wondering what the probabilities are for the formation of a crater as opposed to a Tunguska-style airburst. Is an airburst less likely to occur in a thin atmosphere? Either sceneario would make good viewing for Oppy.

01101001
2007-Dec-28, 04:39 AM
New odds. 1 in 25. Or 1 in 300. Take your pick.

Planetary Society Weblog: Potential Mars impactor update (http://planetary.org/blog/article/00001273/)


Vitagliano said that the precovery observations reduced the impact probability to around 0.3%, or less than 1 in 300. But then another member, Christian Kjaernet, replied today to say that the Jet Propulsion Laboratory's HORIZONS system, [...] gives a Mars impact probability of 3.949%, or 1 in 25.

Anthrage
2007-Dec-28, 04:49 AM
Thank-you. :)

I had not seen that actually, though it certainly demonstrates the 'after' result well enough. It is the 'before' - and specifically, tailoring the resulting crater by controlling the impactor variables - that I find interesting to ruminate on, and could perhaps be a lovely excuse for more funding in the context of practical testing at a large scale. ;)

As regards the crater, I am of the opinion that we are dealing with vastly different objects in terms of density, and of course a thinner atmosphere. The Tunguska airburst WAS an airburst because of the object's nature as regards composition, given they have stated the result if there was an impact in this case would be a Meteor Crater-type crater, my assumption was they had taken it's composition into account - and it being 'crater-making' shall we say.

I believe the Tunguska comparison was one more of the energy involved, as relates to the object's speed/size, where the Meteor Crater reference was a question of the resulting crater size - taking into account the density of both the object and the atmosphere of Mars. I could be wrong however, I've not delved into this as of yet to a level of detail that would allow me to be precise or even correct on that point. :)

Now that it seems the odds of an impact may increase - and following my possibly fanciful entertaining of the idea of impactors as construction tools - I will take a closer look at the details.

Anthrage
2007-Dec-28, 04:51 AM
New odds. 1 in 25. Or 1 in 300. Take your pick.

Planetary Society Weblog: Potential Mars impactor update (http://planetary.org/blog/article/00001273/)


I know 2007 WD5 is an Amor-class object, but does anyone know what the period is on it's close - and not sometimes so close - passes by Mars is?

Anthrage
2007-Dec-28, 04:55 AM
Some detailed info 2007 WD5 can be found here (http://cfa-www.harvard.edu/iau/lists/Amorsq.html).

MaDeR
2007-Dec-28, 11:10 AM
New odds. 1 in 25. Or 1 in 300. Take your pick.
URL does not work, at least now. But... plot thickens! Hit or miss? Stay tuned! :D

01101001
2007-Dec-28, 03:48 PM
URL does not work, at least now.

Yeah the whole Planetary Society Weblog (http://planetary.org/blog) seems hosed today. No articles there. Even /home shows:


Warning: mysql_fetch_object(): supplied argument is not a valid MySQL result resource in /home/zoom/_php/template_machine_home.php(69) : eval()'d code on line 243

Dave Mitsky
2007-Dec-28, 06:45 PM
The site is working for me at the moment.

Dave Mitsky

tony873004
2007-Dec-28, 07:02 PM
The Planetary Society link did not work last night, but now it works. From that link:

...But then another member, Christian Kjaernet, replied today to say that the Jet Propulsion Laboratory's HORIZONS system, which provides highly detailed information on the orbits of (as of 8:15 Pacific time on December 27, 2007) "395,667 asteroids, 2,453 comets, 168 planetary satellites, 9 planets [guess HORIZONS hasn't demoted Pluto yet], the Sun, L1, L2, select spacecraft, and system barycenters," gives a Mars impact probability of 3.949%, or 1 in 25.

I've never seen the Horizons system give impact odds. How would you get odds out of Horizons?

01101001
2007-Dec-28, 10:32 PM
Near Earth Object Program News: Mars Impact Probability Increases to 4 Percent (http://neo.jpl.nasa.gov/news/news153.html) (December 28)


The impact probability for a collision of asteroid 2007 WD5 with Mars on January 30 has increased from 1.3% to 3.9%.
[...]
The uncertainty region during the Mars encounter now extends over 400,000 km along a very narrow ellipsoid that is only 600 km wide. Since the uncertainty region intersects Mars itself, a Mars impact is still possible. However, the most likely scenario is that additional observations of the asteroid will allow the uncertainty region to shrink so that a Mars impact is ruled out.

spaceboy0
2007-Dec-28, 11:29 PM
what is the probability it could go into Mars orbit? or is it travelling too fast to get captured by Mars' gravity?

Kaptain K
2007-Dec-29, 01:34 AM
A two-body capture is not possible!

ToSeek
2007-Dec-29, 03:25 AM
A two-body capture is not possible!

There would have to be some aerobraking to make it happen. Not very likely.

spaceboy0
2007-Dec-29, 03:48 AM
There must be some mathematical possibility. If it is going at a high speed and managed to snug into a low orbit (lower orbits require higher orbital velocity), could it not maintain an orbit for a little while even if highly elliptical?

Romanus
2007-Dec-29, 04:12 AM
^
The thing is, the asteroid would be entering Mars's sphere of influence well above escape velocity, making its trajectory hyperbolic; it would have to lose a great deal of energy to "close" that into an orbit.

Kaptain K
2007-Dec-29, 05:13 AM
As ToSeek said, Not without aerobraking.

Any object coming in from outside the gravity well will reach (at least) escape velocity at closest approach. See what Romanus said above.

tony873004
2007-Dec-29, 05:32 AM
There are some non-aerobraking possibilities for capture. For example, Jupiter captured Shoemaker-Levy 9 about a century before its collision with Jupiter. After crossing into the sphere of influence, an object with only a small amount of excess hyperbolic velocity can be robbed of the excess velocity by the Sun's gravity gradient. So for slow encounters it becomes a 3-body problem with the Sun as the 3rd body. The problem with such captures is that they do not lead to stable orbits. SL-9 was an example. After a few 10s of orbits it collided with Jupiter. An ejection from the Jupiter system was another high-probability outcome.

But in the case of 2007 WD5, its velocity is way too fast for such a capture. It's aphelion is nearly out to Jupiter, meaning that it will speed through Mars' SOI. I don't even think an aerobrake could capture this asteroid. The amount of velocity it needs to lose over such a short period of time would create a g-force strong enough to destroy such a small asteroid. Just my guess.

spaceboy0
2007-Dec-29, 06:05 AM
The asteroid's orbital period is a little over 4 years. My research indicates they come very close again around February, 2166.

spaceboy0
2007-Dec-29, 06:31 AM
future close kisses between asteroid and Mars:

March 15, 2056

Sept 30, 2060

Nov 18, 2108

June 5, 2113

I'm just going by the orbit diagrams so how close they would actually be around these times would have to be studied further... they can look close on the orbit diagram but still be 50,000 km apart

01101001
2007-Dec-29, 06:39 AM
There must be some mathematical possibility. If it is going at a high speed and managed to snug into a low orbit (lower orbits require higher orbital velocity), could it not maintain an orbit for a little while even if highly elliptical?

When you figure it out, please tell NASA so they can send Mars orbiters with more instruments because they need no fuel to accomplish orbit insertion.

For instance, Wikipedia: Mars Reconnaisance Orbiter (http://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter#Launch_and_orbital_ins ertion):


MRO began orbital insertion by approaching Mars on March 10, 2006, and passing above its southern hemisphere at an altitude of 370–400 km (190 mi). All six of MRO's main engines burned for 27 minutes to slow the probe from ~2,900 m/s to ~1,900 m/s (6,500 mph to 4,250 mph).

(And it then did economize as best it could by doing aerobraking for the next 5 months.)

spaceboy0
2007-Dec-29, 10:10 PM
How big does an asteroid have to be to survive Earth reentry?

Is there an approximate radius an asteroid has to be to be large enough for part of it to survive reentry and hit the Earth? Is the composition of the asteroid, how much iron its composed of, also a factor?

In the case of Tunguska, the theory is it was a comet resulting in an airburst and no crater. Being made up mostly of ice none of it survived.

Would WD 5 survive our atmosphere? I hear its about half a football field across

Noclevername
2007-Dec-29, 11:13 PM
How big does an asteroid have to be to survive Earth reentry?

Is there an approximate radius an asteroid has to be to be large enough for part of it to survive reentry and hit the Earth? Is the composition of the asteroid, how much iron its composed of, also a factor?


It's definitely all about composition and internal structure. Most asteroids appear to be composed of loose rock and dust held together gravitationally; not enough pressure to compress it into solid rock.

spaceboy0
2007-Dec-30, 12:53 AM
yes, and SkyLab almost entirely burned up cause it's all metal. Given a rock the same diameter you could have a very different outcome!

Kaptain K
2007-Dec-30, 01:07 AM
yes, and SkyLab almost entirely burned up cause it's all metal. Given a rock the same diameter you could have a very different outcome!
It's not that it was all metal, it's that it was all thin metal sheets!

Jetlack
2007-Dec-30, 12:05 PM
Lets hope it hits. If it does I'll take it as an omen we should not ignore. This would be the second large impact on a solar system planet in the last 10 years which we've witnessed.

Jupiter and Mars, relatively close by.

If that doesnt send alarm signals to planet earth - not much will wake us from our slumber.

01101001
2007-Dec-30, 03:03 PM
If it does I'll take it as an omen we should not ignore.

I suppose if it misses you'll take it as an omen that we should ignore?

How do events become omens for you? And how does your classification of omens become what we should do?

dhd40
2007-Dec-30, 08:25 PM
A two-body capture is not possible!

Phobos and Deimos are said to be captured asteroids. See this link (sorry, it´s in Garman):

http://www.esa.int/esaKIDSde/SEMVOCWJD1E_OurUniverse_0.html

How could Mars manage to capture these? I also remember to have read that a two-body capture may be possible via a Lagrange-point-passage, provided speed (velocity), etc. were nicely fitting. Vague recollection?

Anthrage
2007-Dec-30, 08:40 PM
Lets hope it hits. If it does I'll take it as an omen we should not ignore. This would be the second large impact on a solar system planet in the last 10 years which we've witnessed.

Jupiter and Mars, relatively close by.

If that doesnt send alarm signals to planet earth - not much will wake us from our slumber.

I agree - some may object to the word 'omen', assigning some mystical or supernatural meaning to it, but strictly speaking it is "...anything perceived or happening that is believed to portend a good or evil event or circumstance in the future..."; I would say that definition certainly applies here.

Simply put, it would underline that impacts of a substantial nature do occur, and that we should not assume otherwise. A higher level of preparedness would be wise in such a cirumstance. Honestly, SL9, as well as the close passes of numerous other objects - some detected only AFTER their passing - should be sufficient, but we are a rather slow-witted species sometimes. :)

01101001
2007-Dec-30, 08:48 PM
I would say that definition certainly applies here.

Ugh. Portend?

But, I'll ask you, too: What does a miss signify?

Noclevername
2007-Dec-30, 09:18 PM
Most people have the "it can't happen here" syndrome. To them nothing that happens in space has anything to do with "real life" on Earth. If SL9, with its Earth-sized explosions, didn't make a dent in that attitude, no mere Martian Tunguska will. Only something that actually hits a populated area of Earth will do that, and even then some will say "Oh, it already happened, so we don't have to worry for another few thousand years."

Anthrage
2007-Dec-30, 09:30 PM
Ugh. Portend?

Semantic arguments are typically beneath most intelligent people. The negative association with the word 'portend' comes from you, not the word iteself. :)



But, I'll ask you, too: What does a miss signify?

Exactly the same thing actually, if it is a near miss. The crucial point, in this context, is not whether it did or did not result in an impact, but that the risk of an impact is/was very real, and the consequences extreme.

People who downplay the impact risk - normally by painting those who consider the risk worth serious-minded attention and action as alarmists, doomsayers or worse - are ironically, more likely to have a greater effect on a strong prevention and defense position than those who base their opinions on the science involved, and not the rhetoric. Such is the world we live in unfortunately.

You may choose to focus your attention on the use of partcular words, like 'omen' and 'portend', but I prefer to assign importance to certain letters and numbers, such as 1989 FC, 2003 SQ22, 2004 YD5, 2004 FH and on and on and on.

Call me crazy. :)

spaceboy0
2007-Dec-30, 11:04 PM
How did our Moon come about? Another object's collision with Earth and the debris formed the present Moon, or captured object? What's the leading theory?

01101001
2007-Dec-31, 12:23 AM
Semantic arguments are typically beneath most intelligent people. The negative association with the word 'portend' comes from you, not the word iteself. :)

Smile when you say that. Otherwise, I'd think you were trying to call me unintelligent. Thanks so much.

OK. An anecdote of one impact or, more likely, the lack thereof, is not an omen and portends nothing. We read neither tea leaves nor tarot cards nor entrails here. The divinitory arts are covered elsewhere. Cool.

I'm glad I suggested it. This feels like a science-oriented forum again.

Perhaps lurking in the background you have a theory based on observation and physics that says Earth will soon be enduring a significant impact. Wow, I sure want to know about that. Proceed. How soon? When? Why?

The NEO program risk table (http://neo.jpl.nasa.gov/risk/) still looks like a big yawn to me. You have better data?

Noclevername
2007-Dec-31, 01:13 AM
Semantic arguments are typically beneath most intelligent people.

No, actually clarifying meaning is the act of an intelligent person. It makes for clearer communication.

Jetlack
2007-Dec-31, 10:33 AM
I suppose if it misses you'll take it as an omen that we should ignore?

How do events become omens for you? And how does your classification of omens become what we should do?

It was a figure of speech. Lets just call it a warning so we dont get into some mystical conversation.

The point is the human race sometimes needs somehting to scare the crap out of them before they decide on action.

If this asteroid hits Mars and gives us all a good display of planetary demolition then we may start treating the existential threat to humans with a bit more seriousness.

Jetlack
2007-Dec-31, 10:38 AM
No, actually clarifying meaning is the act of an intelligent person. It makes for clearer communication.

No I think actually he wanted to ridicule the concept of "omens" from the traditional perspective that "omens" were usually meant to be signs from the Gods.

Its a sign, its a sign! :-)

Neverfly
2007-Dec-31, 10:39 AM
It was a figure of speech. Lets just call it a warning so we dont get into some mystical conversation.

The point is the human race sometimes needs somehting to scare the crap out of them before they decide on action.

If this asteroid hits Mars and gives us all a good display of planetary demolition then we may start treating the existential threat to humans with a bit more seriousness.

We didn't seem to after Jupiter got a Cosmic Black Eye (http://seds.lpl.arizona.edu/sl9/sl9.html)

Jetlack
2007-Dec-31, 11:07 AM
We didn't seem to after Jupiter got a Cosmic Black Eye (http://seds.lpl.arizona.edu/sl9/sl9.html)

Yes thats true though I think the effects of the Jupiter impacts were relatively minor because with no surface to speak of; we could not see the destruction from a rocky planet point of view.

Though you could be right and even a huge impact on Mars might not have the desired affect of waking up the earthlings.

Kullat Nunu
2007-Dec-31, 02:05 PM
How did our Moon come about? Another object's collision with Earth and the debris formed the present Moon, or captured object? What's the leading theory?

The leading theory is that the proto-Earth collided with a Mars-sized object. The impact was glancing (otherwise Earth would have been destroyed) and send massive amounts of mantle material orbiting Earth. From this material the Moon coalesced. This theory neatly explains several properties of the Earth-Moon system.

Kullat Nunu
2007-Dec-31, 02:06 PM
Yes thats true though I think the effects of the Jupiter impacts were relatively minor because with no surface to speak of; we could not see the destruction from a rocky planet point of view.

Well, the "bruises" were as large as the Earth...


Though you could be right and even a huge impact on Mars might not have the desired affect of waking up the earthlings.

A casualty-free, predicted Tunguska-like explosion on Earth could be a better wake-up call.

Neverfly
2008-Jan-01, 12:46 AM
Um... I'm just curious... Are we in need of a major wake up call?:neutral:

Jetlack
2008-Jan-01, 01:29 AM
Well, the "bruises" were as large as the Earth...



A casualty-free, predicted Tunguska-like explosion on Earth could be a better wake-up call.

That would certainly do the trick :-)

Veeger
2008-Jan-01, 04:44 AM
Wake-up call? The fact that we found this object is proof enough we're looking for NEO's which could prove dangerous. This particular detection was quite remarkable in my opinion; a relatively small object 10's of millions miles away.

I believe the search for NEOs can be fairly automated with software designed to "flash" images and look for changes (i.e. movement). I am not sure of the funding level for projects like LONEOS and others nor do I know the amount of sky-coverage we have, but I am quite impressed with this detection.

-Veeger

Jetlack
2008-Jan-01, 10:51 AM
Wake-up call? The fact that we found this object is proof enough we're looking for NEO's which could prove dangerous. This particular detection was quite remarkable in my opinion; a relatively small object 10's of millions miles away.

I believe the search for NEOs can be fairly automated with software designed to "flash" images and look for changes (i.e. movement). I am not sure of the funding level for projects like LONEOS and others nor do I know the amount of sky-coverage we have, but I am quite impressed with this detection.

-Veeger


Im not sure how impressed we should be about discovering this asteroid only a couple of months or so before potential impact with Mars.

If this asteroid was threatening Earth instead of Mars we would have noticed too late to do anything about it.

We need detection many years in advance.

Kaptain K
2008-Jan-01, 02:35 PM
Im not sure how impressed we should be about discovering this asteroid only a couple of months or so before potential impact with Mars.

If this asteroid was threatening Earth instead of Mars we would have noticed too late to do anything about it.

We need detection many years in advance.
Exactly! It could have been an asteroid that was headed toward Earth that was discovered a couple of months in advance! Some potential Earth impactors were not discovered until they had already passed (IIRC, one had come within a few tens of thousands of Km). We need much better detection!

Veeger
2008-Jan-01, 03:04 PM
Fellow posters, in my opinion you're missing the point. This object is small and millions of miles away; we saw it, and calculated its trajectory. If it was headed for earth we would have a decent early warning. It so happens it was headed to Mars. I grant you, discovery is often a lucky accident of position relative to the available sunlight and a wide-angle camera trained to the right location, but someone is obviously looking. The real problem is not one of detection, rather one of protection. How to stop or divert it when we find one with our name written on it?

Best,
-Veeger

Kullat Nunu
2008-Jan-01, 03:09 PM
Wake-up call? The fact that we found this object is proof enough we're looking for NEO's which could prove dangerous. This particular detection was quite remarkable in my opinion; a relatively small object 10's of millions miles away.

*We* know that NEOs are potentially dangerous. The problem is that the odds of any impact are very low in short term which makes the threat too academical to the general public. SL9 impact did help, but not enough.


I believe the search for NEOs can be fairly automated with software designed to "flash" images and look for changes (i.e. movement). I am not sure of the funding level for projects like LONEOS and others nor do I know the amount of sky-coverage we have, but I am quite impressed with this detection.

Impressive it is, yet our coverage is not enough. Even a much larger object could hit us without warning if it came from the direction of the Sun.

LONEOS has not been nearly as effective as originally promised. Recently, no one has been able to beat the Catalina Sky Survey at finding new NEOs (which by the way found this asteroid).

Jetlack
2008-Jan-01, 04:10 PM
Fellow posters, in my opinion you're missing the point. This object is small and millions of miles away; we saw it, and calculated its trajectory. If it was headed for earth we would have a decent early warning. It so happens it was headed to Mars. I grant you, discovery is often a lucky accident of position relative to the available sunlight and a wide-angle camera trained to the right location, but someone is obviously looking. The real problem is not one of detection, rather one of protection. How to stop or divert it when we find one with our name written on it?

Best,
-Veeger

We came, we saw, it conquered :-)

Calculating trajectories is no longer leading edge science. We do it all the time and multitask thousands of combined trajectories throughout our solar system.

The key factor is discovery of these objects within a reasonable advance timeframe in order to be able to take emergency measures if need be.

I'm not sure of what kind of damage a 50 metre asteroid would do if it fell near a city like NY, but I dont think it would be considered "small" for the local population. But if we get hung up on the relatively smallish size of this asteroid we are missing the wider point. We cannot count on them always being no bigger than this one. Wish we could.

In fact apparently WD5 (sounds like a lubricant) already marginally missed earth and we did'nt even notice. So theoretically we were already too late because of our ignorance of this object in the first place.

I dont share your sentiment of self-satisfaction in regards to our detection capabilties. Wish i could.

spaceboy0
2008-Jan-01, 07:04 PM
any update on WD 5 trajectory?

01101001
2008-Jan-01, 07:46 PM
any update on WD 5 trajectory?

It's holiday time. The astronomers get nights off.

NASA News Release (http://www.jpl.nasa.gov/news/news.cfm?release=2007-152) (December 21, updated December 28)


NASA and its partners will continue to track asteroid 2007 WD5 and will provide an update in January when further information is available. For more information on the Near Earth Object program, visit: http://neo.jpl.nasa.gov/.

danscope
2008-Jan-02, 01:10 AM
"Exactly! It could have been an asteroid that was headed toward Earth that was discovered a couple of months in advance! Some potential Earth impactors were not discovered until they had already passed (IIRC, one had come within a few tens of thousands of Km). We need much better detection!"
*******************

Hi, Maybe now, you percieve the tenants of the plan I suggested and why.
A system already in orbit awaiting the command to accelerate toward the
object in question would do the job. No question.

spaceboy0
2008-Jan-02, 06:12 AM
when they give WD 5's speed as 28,000 mph, is that the relative speed of the asteroid with Mars or the asteroid's orbital speed around the Sun?

Maksutov
2008-Jan-02, 09:54 AM
[edit]I remember at least one science-fiction story dealing with a communications failure in deep space and how the entire crew was harnessed with abaci to compute a return trajectory. In early space exploration, the goal was sometimes to perform a correction maneuver to put them close to a pre-calculated trajectory rather than necessarily go for optimal fuel consumption, since initially the new trajectory could not be calculated close to real time. Even for the early rockets from White Sands, with plenty of tracking data, it could take weeks for the computing center near Washington to kick back an after-the-fact trajectory table.

Hmm - upon reflection, this is a day I really like computers.I got all that beat. Since I had three rooms in the basement I wasn't using, I installed a differential analyzer (http://en.wikipedia.org/wiki/Differential_analyser).

NEOWatcher
2008-Jan-02, 02:26 PM
Fellow posters, in my opinion you're missing the point. ...The real problem is not one of detection, rather one of protection. How to stop or divert it when we find one with our name written on it?
I believe they go hand in hand. We have the potential technology to deflect one, but only if it were detected with more than an orbits notice.
The later we discover one, the harder it will be to do something, and the less likely we will have the technology to do it.

A few weeks or months notice allows us to do evacuations, but, no matter how prepared that is, it will still be devestating (which is what I think you are getting at)

So; yes, we need the technology to stop it, but early detection is a great asset in that battle.

Jetlack
2008-Jan-02, 04:52 PM
I believe they go hand in hand. We have the potential technology to deflect one, but only if it were detected with more than an orbits notice.
The later we discover one, the harder it will be to do something, and the less likely we will have the technology to do it.

A few weeks or months notice allows us to do evacuations, but, no matter how prepared that is, it will still be devestating (which is what I think you are getting at)

So; yes, we need the technology to stop it, but early detection is a great asset in that battle.

By the way I'm in no way knocking the efforts of NEO watchers :-)

Just think the effort should be given a lot more funding and resources.

NEOWatcher
2008-Jan-02, 06:56 PM
Just think the effort should be given a lot more funding and resources.
I don't know exactly where the effort is, and how much will be gained with incremental advances in Space travel.

But; what I do know is that the models funding the watch VS funding for deflection technology is completely different. Not in how it's done, but more in how it can be applied.

With watching and warning, you can throw more and more money at it and get more people watching, and funding shortfalls just means less operation.
With deflection, you need an entire plan in place, a goal in mind, and complete funding to maintain that plan. If funding falls short, the entire goal falls apart.

Now; if you were a politician, would you do token funding to say you did something, or stick your neck out by commiting a risky and expensive plan? (Rhetorical, of course)

Not that I agree with it, but that is the reality of it.

Jetlack
2008-Jan-02, 08:03 PM
Now; if you were a politician, would you do token funding to say you did something, or stick your neck out by commiting a risky and expensive plan? (Rhetorical, of course)

Not that I agree with it, but that is the reality of it.

Personally I'd go with both. Increased funds for more observers with more telescopes, and a project to test how to deflect a large asteroid.

Of course I'm not a politician.

frankuitaalst
2008-Jan-02, 10:48 PM
A few more observations were made from Apache Point on 31/12/2007.
( source : Neodys and JPL Nea site ) .
The nominal path is now estimated to be more than 30.000 km from the center of Mars . Sounds as if it will miss ...

Veeger
2008-Jan-03, 12:19 AM
There are enormous political problems to overcome when considering an impact scenario. For example, let's say we detect an object two weeks in advance and are reasonably sure it may strike near the asian subcontinent, or it may strike in the region of the gulf of Mexico. Which scenario will get the greatest response? Which governments will be responsible for evacuations, relocations, infra-structures, preparation of medical and food supplies, and so on and so on? What kind of treaties are needed that do not now exist? Or do we let it happen and then react as any other natural disaster such as an earthquake or tsunami?

A large impact has global implications but we are a world of nations which rarely care to act or react beyond our individual borders except through private sector organizations. I am willing to bet most nations are electing to choose the reactionary course and deal only with those things which affect them after the smoke clears, if such reaction is even possible.

-Veeger

01101001
2008-Jan-03, 01:26 AM
NASA News Release (http://www.jpl.nasa.gov/news/news.cfm?release=2007-152) (December 21, updated December 28, updated January 2)


Updated Jan 2, 2008 – With new observations taken Dec. 29, Dec. 31 and Jan. 2 by the Magdalena Ridge Observatory in New Mexico, scientists at NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., have updated their trajectory estimates for the asteroid. Based on this latest analysis, the odds for the asteroid impacting Mars on Jan. 30 are now about 1-in-28, or 3.6 percent.

Edit: Also, JPL NEO News: New Observations Slightly Decrease Mars Impact Probability (http://neo.jpl.nasa.gov/news/news154.html) (January 2)


Additional position observations for asteroid 2007 WD5 taken on December 29 through January 2 have been used to improve the accuracy of the asteroid's orbit. As a result, the range of possible paths past Mars has narrowed by a factor of 3 and the most likely path has moved a little farther away from the planet, causing the Mars impact probability to decrease slightly to 3.6% (about one chance in 28). The new positional observations were made using the 2.4 meter telescope at New Mexico Tech's Magdalena Ridge Observatory and reported by astronomer Bill Ryan. It seems likely that as additional observations further shrink the uncertainty region of this asteroid, the region will no longer intersect Mars and the impact probability will quickly drop to zero.

Jetlack
2008-Jan-03, 11:21 AM
Oh well, good news for Mars, bad news for Earth.

loglo
2008-Jan-04, 06:29 PM
Shame... I'm getting tired of waiting for a sample return mission... a few more Martian meteorites would have been welcome.

Maksutov
2008-Jan-05, 08:13 AM
For you brave souls who still visit GLP, have the woos there started in with the asteroid being deflected by Mars into a collision path with Earth?

You have to love woo orbital mechanics, BTW. Thank you, Immanuel. :sick:

Kaptain K
2008-Jan-05, 05:05 PM
Well, I put in my nose plugs and took a look. Nothing in the first four pages, at least going by the thread titles. I didn't read any of the threads. I value my brain cells too much!

01101001
2008-Jan-06, 10:21 PM
Here ya go, seekers of demolition demonstrations:

Potentially Hazardous Asteroids, PHA Close Approaches To The Earth (http://cfa-www.harvard.edu/iau/lists/PHACloseApp.html)

2007 TU24: Less than 0.004 AU from Earth 2008 January 29.

(See Bad Astronomy Blog: Asteroid to miss Earth January 29 (http://www.badastronomy.com/bablog/2008/01/06/asteroid-to-miss-earth-january-29/). Boy, that BA sure knows how to quench a near-thrill with a boring title.)

spaceboy0
2008-Jan-07, 04:22 AM
20,000 miles is a very close shave. That's less than one tenth the lunar distance. Let's put on some shaving creme.

How large is Apophis?

Halcyon Dayz
2008-Jan-07, 07:01 AM
How large is Apophis?
99942 Apophis (2004 MN4) (http://neo.jpl.nasa.gov/risk/a99942.html)

Guesstimated at 250 metres, with an estimated impact energy (IF it hits) of ca 400 MT.

Not a dinosaur-killer, but you wouldn't want to be in the neighbourhood.

01101001
2008-Jan-08, 10:26 PM
NASA NEO Program news: Mars Impact Seems Less Likely (http://neo.jpl.nasa.gov/news/news155.html) (January 8, 2008)


We have updated the orbit of 2007 WD5 using new observations from the 3.5-meter telescope at the Calar Alto Observatory in Spain. This update also incorporates refinements to the Sloan precovery observations mentioned previously. While the best estimate of close approach distance remains steady at about 30,000 km, the uncertainty in position at the close approach has decreased by a factor of three. As a result, the impact probability estimate has fallen to 2.5%, or 1-in-40 odds. If the estimated miss distance remains stable in future updates, the impact probability will continue to fall as continuing observations further constrain the uncertainties.

Noclevername
2008-Jan-08, 10:52 PM
If the estimated miss distance remains stable in future updates, the impact probability will continue to fall as continuing observations further constrain the uncertainties.

The whole point of observing is precicely because we don't know what the observations will reveal.

Ken G
2008-Jan-08, 11:09 PM
Yeah, that's a pretty silly statement to make-- there's no reason to expect the miss distance to "remain stable", as if they expected that, the probability would not "continue to drop", it would have already dropped. The very fact that the probability is 1/40 means they have no idea if the miss distance will drop or increase, and if it means anything, it should be roughly equally likely to do either.

spaceboy0
2008-Jan-08, 11:29 PM
this is all very upsetting

ToSeek
2008-Jan-10, 05:16 AM
Yeah, that's a pretty silly statement to make-- there's no reason to expect the miss distance to "remain stable", as if they expected that, the probability would not "continue to drop", it would have already dropped. The very fact that the probability is 1/40 means they have no idea if the miss distance will drop or increase, and if it means anything, it should be roughly equally likely to do either.

Well, I'd interpret a probability of 1/40 to mean that there's one chance in forty that the probability is going to increase and 39/40 that it's going to decrease.

In any case, it's a moot point:

2007 WD5 Mars Collision Effectively Ruled Out As Impact Odds Widen To 1 In 10000 (http://www.marsdaily.com/reports/2007_WD5_Mars_Collision_Effectively_Ruled_Out_As_I mpact_Odds_Widen_To_1_In_10000_999.html)


Since our last update, we have received numerous tracking measurements of asteroid 2007 WD5 from four different observatories. These new data have led to a significant reduction in the position uncertainties during the asteroid's close approach to Mars on Jan. 30, 2008. As a result, the impact probability has dropped dramatically, to approximately 0.01% or 1 in 10,000 odds, effectively ruling out the possible collision with Mars.

Our best estimate now is that 2007 WD5 will pass about 26,000 km from the planet's center (about 7 Mars radii from the surface) at around 12:00 UTC (4:00 am PST) on Jan. 30th. With 99.7% confidence, the pass should be no closer than 4000 km from the surface.

Bummer.

01101001
2008-Jan-10, 06:08 AM
2007 WD5 Mars Collision Effectively Ruled Out As Impact Odds Widen To 1 In 10000 (http://www.marsdaily.com/reports/2007_WD5_Mars_Collision_Effectively_Ruled_Out_As_I mpact_Odds_Widen_To_1_In_10000_999.html)

Same material I think, just provided for consistency and archival purposes:
NASA NEO Program news: 2007 WD5 Mars Collision Effectively Ruled Out - Impact Odds now 1 in 10,000 (http://neo.jpl.nasa.gov/news/news156.html) (January 9, 2008)

Shh... It's an omen...

From the animation of regions of uncertainty (http://neo.jpl.nasa.gov/2007wd5/2007wd5d.gif) the centers have pretty much, to my taste, "remained stable" since Dec. 31 (while, as expected, the size of the regions consistenly shrank).

01101001
2008-Jan-29, 12:00 AM
Nothing new. Just marking the upcoming close-approach event, lest poor 2007 WD5 thinks nobody cares anymore...

NASA NEO Program news: 2007 WD5 Mars Collision Effectively Ruled Out - Impact Odds now 1 in 10,000 (http://neo.jpl.nasa.gov/news/news156.html) (January 9, 2008)


Our best estimate [January 9] is that 2007 WD5 will pass about 26,000 km from the planet's center (about 7 Mars radii from the surface) at around 12:00 UTC (4:00 am PST) on Jan. 30th. With 99.7% confidence, the pass should be no closer than 4000 km from the surface.

About 36 hours to Mars close appoach, January 30:
Approximately 1200 UTC
Approximately 0700 EST
Approximately 0400 PST

Anthrage
2008-Jan-29, 04:18 AM
I wonder, while it seems clear an impact is out of the question, it is still rather close - would there be any possibility of imaging via the assets currently in orbit?

Romanus
2008-Jan-29, 03:07 PM
^
Probably not; besides the attitude maneuvering and programming necessary to image it, it will zip past them very quickly.

01101001
2008-Jan-29, 11:01 PM
Planetary Society Weblog: Hubble is pointing at 2007 WD5 (and Mars) tomorrow (http://planetary.org/blog/article/00001310/)


Now that asteroid 2007 TU24 has passed harmlessly by us, we should turn to consider again 2007 WD5, the near-Earth and then near-Mars asteroid. When we last caught up with WD5 on January 10, the chances of a Mars impact had dropped to 1 in 10,000. This is not zero but is low enough that the Mars missions that had been considering performing observations related to WD5 dropped those plans and returned to business as usual. Since then, it seems that loss of interest, coupled with WD5's rapidly decreasing brightness, has resulted in there being no new observations of it to track its path.

However, that's about to change: tomorrow night, they're going to try to catch WD5 with the Hubble Space Telescope.
[...]
So we should wind up with a nice red, green, blue color image of Mars, with, hopefully, a tiny little dot off to one side of the disk that represents WD5's position. The scientific value of the observation is that it'll help constrain WD5's future course. But I'd say the observation is justifiable just on its coolness value.

About 13 hours to Mars close approach, January 30:
Approximately 1200 UTC
Approximately 0700 EST
Approximately 0400 PST

01101001
2008-Jan-30, 04:21 PM
Space.com: Space Rock Misses Mars, Barely (http://www.space.com/scienceastronomy/080130-mars-miss.html)


"Mars sees these kinds of near-miss encounters every ten or twenty years, but the impact rate for asteroids this size is about once in a thousand years," said Steve Chesley, an astronomer at the Jet Propulsion Lab in Pasadena, California.
[...]
The asteroid missed Mars by a distance of approximately 6.5 Mars radii.
[...]
Chesley and other astronomers considered having one of the Martian rovers eyeball the passing 2007 WD5, but judged the task too difficult for the robotic explorers. None of the orbiting spacecraft turned their cameras or other equipment on the passing rock, either.

"After we knew it was going to miss, it's really a pretty ordinary asteroid cruising around the solar system," Chesley said.

01101001
2008-Feb-04, 10:39 PM
Planetary Society Weblog: WD5 most likely missed Mars, but we may never know (http://www.planetary.org/blog/article/00001316/)


Now, a 6.5-Mars-radius flyby is quite close enough to alter the course of WD5 significantly. Where's it going to go next? The answer is, no one knows. The uncertainty surrounding WD5's exact position with respect to Mars during the encounter hugely balloons when you try to figure out its future path. It essentially got a gravity assist from Mars, but without knowing exactly at what distance and, equally importantly, at what latitude it flew past the planet, we have no idea where Mars flung it.

[...]WD5 is now considered lost. That may sound sad or possibly even dangerous, but [JPL's Steven Chesley] emphasized to me that becoming lost is quite the norm for objects as small as WD5, which is estimated to be roughly 50 meters in diameter.