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Thread: Possible Comet Collision with Mars

  1. #61
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    Quote Originally Posted by Jens View Post
    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?

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    Quote Originally Posted by Tuckerfan View Post
    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.

  3. #63
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    Quote Originally Posted by Concerned View Post
    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.

    Quote Originally Posted by Hornblower View Post
    It also is possible that this was nothing more than the random clumping that sometimes happens with sporadic events.
    True.

  4. #64
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    Quote Originally Posted by Concerned View Post
    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.
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  5. #65
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    Quote Originally Posted by Concerned View Post
    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.
    As above, so below

  6. #66
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    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.
    I'm Not Evil.
    An evil person would do the things that pop into my head.

  7. #67
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    Does anyone know what the probability is of the comet being ripped to bits by the gravity of Mars as it flies past?

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    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.

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    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

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    Quote Originally Posted by neilzero View Post
    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?

  11. #71
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    Quote Originally Posted by Concerned View Post
    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.

  12. #72
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    Quote Originally Posted by Rhaedas View Post
    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.

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    Quote Originally Posted by Rhaedas View Post
    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.
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  14. #74
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    Quote Originally Posted by Swift View Post
    I am, of course, reminded of what Douglas Adams had to say about this:

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    Quote Originally Posted by Rhaedas View Post
    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..

    :-/

  16. #76
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    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.

  17. #77
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    Iíve 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
    For astronomical graphics and data visit
    https://www.CurtRenz.com/astronomy.html

  18. #78
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    Quote Originally Posted by Centaur View Post
    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.

  19. #79
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    Using this table 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.

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  20. #80
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    Quote Originally Posted by Centaur View Post
    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.

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    Earth and Mars crater size frequency distribution and impact rates: Theoretical and observational analysis
    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?

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

  22. #82
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    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/vi...3-a1-s-marsom/

  23. #83
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    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

  24. #84
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    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.

  25. #85
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    I think the only ones wanting a safe passage are martians, riders on the comet, and any Red Mars fanatics out there. A collision would be great science and great publicity for the cause.

  26. #86
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    Quote Originally Posted by neilzero View Post
    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.

  27. #87
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    Quote Originally Posted by Rhaedas View Post
    I think the only ones wanting a safe passage are martians, riders on the comet, and any 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.

  28. #88
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    Quote Originally Posted by Hornblower View Post
    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.
    Last edited by Centaur; 2013-Mar-06 at 05:11 AM.
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    Of course the Earth is a much better body guard for the Moon than the Moon is for the Earth.

  30. #90
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    Quote Originally Posted by Rhaedas View Post
    I think the only ones wanting a safe passage are martians, riders on the comet, and any Red Mars fanatics out there. A collision would be great science and great publicity for the cause.
    Red Mars is on my reading list

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