Has Mars hit earth in the past?

BoJangles · Jul 6, 2008

Is there evidence against mars hitting earth at sometime in the past?Well all know the moon was formed by a mars sized object hitting the earth , maybe twice, maybe very slowly, and just recently mars has shown a large impact crater, what is the evidence against mars having hit the earth at sometime in the past.There is a lot of circumstantial evidence (In my non academic opinion) that mars has hit earth; we have an asteroid belt just outside of mars, we have plate tectonics on earth, we have the moon, we have a weird spin on earth, We have a weird tilt on earth. Why not look to our closest neighbours? An obvious answer would be in the geology and spectral analysis of the 3 objects (mars, Earth and the Moon), but would it really be that obvious? I.e. if all this has happened 4 billion years ago; with resurfacing, asteroids impacts, and general solar weathering would it be all that obvious? <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

MeteorWayne · Jul 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Is there evidence against mars hitting earth at sometime in the past?Well all know the moon was formed by a mars sized object hitting the earth , maybe twice, maybe very slowly, and just recently mars has shown a large impact crater, what is the evidence against mars having hit the earth at sometime in the past.There is a lot of circumstantial evidence (In my non academic opinion) that mars has hit earth; we have an asteroid belt just outside of mars, we have plate tectonics on earth, we have the moon, we have a weird spin on earth, We have a weird tilt on earth. Why not look to our closest neighbours? An obvious answer would be in the geology and spectral analysis of the 3 objects (mars, Earth and the Moon), but would it really be that obvious? I.e. if all this has happened 4 billion years ago; with resurfacing, asteroids impacts, and general solar weathering would it be all that obvious? Posted by Manwh0re</DIV> Probably not. If Mars had hit earth, then it likely would have been destroyed; the Mars sized object that did hit us was absorbed by the earth-moon system. In addition, if Mars was that far in toward the sun, there's no real way for it to get back to a fairly circular orbit back out at 1.5 AU or so. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

DrRocket · Jul 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Probably not. If Mars had hit earth, then it likely would have been destroyed; the Mars sized object that did hit us was absorbed by the earth-moon system. In addition, if Mars was that far in toward the sun, there's no real way for it to get back to a fairly circular orbit back out at 1.5 AU or so. Posted by MeteorWayne</DIV>Wayne.  What is the evidence for a collision with a Mars-sized object ?  Any thought on the orbit it might have been in and the orbit of the Earth prior to the collision ?  Also, I presume that this must have happened quite early in the formation of the planetary system, but any idea when or what the compositions might have been at the time ?  Was this an inelastic collision as I would guess ?  The heat generated must have been enormous. Assuming this did happen and I have no reason to doubt you, what does a meteor guy do for an encore ? <div class="Discussion_UserSignature"> </div>

MeteorWayne · Jul 6, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Wayne.  What is the evidence for a collision with a Mars-sized object ?  Any thought on the orbit it might have been in and the orbit of the Earth prior to the collision ?  Also, I presume that this must have happened quite early in the formation of the planetary system, but any idea when or what the compositions might have been at the time ?  Was this an inelastic collision as I would guess ?  The heat generated must have been enormous. Assuming this did happen and I have no reason to doubt you, what does a meteor guy do for an encore ? Posted by DrRocket</DIV> DrR, it's been a while since I've looked at the source articles in Nature or Science, so hope for the time being you'll accept my recollection. I'll try and track down the actual reports, they're in the basement, but it is in the process of reorganization....unlike Monk, I do not have unlimited recall

The evidence is primarily within the angular momentum of the earth moon system, and the differing composition of the earth and moon. The earth seems to have kept much of the iron and other siderophile elements, while the moon has a smaller iron core and more "lighter" rock..i.e. the outer layers of the earth, and a smaller, less differentiated impactor.It was inelastic for the most part, and melted what was left of the earth's surface, and vaporized most (or all) of the much smaller impactor. It's fascinating fluid dynamics stuff.Again from memory, yes it was quite early, I believe within the first few tens of thousands of years of Terran history. 50 ky seems to come to mind, but as I said it's been a while. My recall on the orbit is too weak to guess. I'll do some upgedigging and see if I can answer in more detail tomorrow.As for an encore, I'd rather not. I will get little joy out of being oblitorated by an incoming asteroid if I can't post the report on SDC and meteorobs the next day! MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Jul 6, 2008

Here's a spce.com article that at least tells me where to look. Looks like 2001 in Nature. Now if I can only find the 2001 pile in the basement..... http://www.space.com/scienceastronomy/solarsystem/moon_making_010815-1.html <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

BoJangles · Jul 6, 2008

Thanks I appreciate all your comments <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

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