Mars Had an Ancient Impact Like Earth

quixote9 writes "The BBC reports on a set of Nature articles showing that Mars had an impact about four billion years ago by a huge asteroid. This was about the same time that a much bigger object slammed into the Earth, throwing material into orbit around our infant planet. This material is thought to have coalesced to form the Moon. 'It happened probably right at the end of the formation of the four terrestrial planets — Mercury, Venus, Earth and Mars,' said Craig Agnor, a co-author on the Francis Nimmo study. 'In terms of the process of the planets sweeping up the last bits of debris, this could have been one of the last big bits of debris.' There's a theory that having a big moon is important to the development of life, because the much bigger tides create a bigger intertidal zone, but people used to think having a huge Moon like ours was a once-in-a-universe event."

Comments

once-in-a-universe?

[elguillelmo]

I reckon ther's not sucha a thing as a once-in-a-universe event!

Re:once-in-a-universe?

[jeiler]

I would assume that the universe itself would qualify, as any set A is a subset of itself.

Once in a universe?

[jandrese]

Having a single big moon is supposed to be ultra rare? I'm really curious why that is. Given what we know of our solar system, moons are far from rare. We may only have one example of a large unitary moon, but come on, that's out of a sample size of 9 (8 now I guess) from a universe with presumably a nearly limitless number of planetoids. The argument almost strikes me as one of those arguments for Humans being the only intelligent species in the entire universe because it must be almost impossible for life to occur. Arguments that are grounded entirely in conjecture.

Re:Hopefully.

[Digital End]

[troll]lets nit-pick things to look cool![/troll]

It means rare. I doubt it's never happened before, it's just a very rare set of events. The size of space (as noted so accuratly in hitchhikers) is big. Really big. That big makes the odds that one rock or the exact size will 'just happen to' hit a young planet of the exact size at the exact direction, while not destabalizing their orbits by increasing the mass.. blah blah... really long odds.

and to add life to that, add the odds that this planet is in the 'livable zone'... add to this the odds that it contains the right materials... add to this the odds that the right chemicals are accessable in just the right places at the right times... add to this that all of that happens at the right time in the planets life... add to that few enough asteroid strikes to prevent obliterating it every few thousand years (Jupiter saves our asses on this)... add to that a bit of luck.

Another effect of the 'really big' portion is that we have a nearly limitless number of chances for this ultra rare occurance to happen.

Of course, to us it seems like it has to happen all the time... I mean hell, we're sitting right here watching it!... but the 99.999~% of planets who were just off the mark will never talk to us about how they see the odds differently.