Earthlike Mars? Options

[glennwsmith]

All, I know this isn't the right place for this post, but I've looked around and can't find an appropriate, current UMSF forum (Doug, perhaps you could give me some guidance on establishing such) -- so here goes: I think a [the] new paradigm for Martian geology is rapidly coalescing, namely, that Mars is very much like the Earth in terms of the preponderance of water -- except that it is all frozen, and covered under a thin layer of dust/regolith! See, for example, this article:

http://www.skyandtelescope.com/news/41995902.html

Hence the "seepages" found in crater walls; hence the evidence of catastophic flooding -- the result of volcanism melting huge pockets of ice. And I am going to add my own wrinkle (probably not original): that the differentiation of Mars into a rougher southern hemisphere and smoother northern hemsphere represents something like Earth's Pangea stage, ie, the northern hemisphere is a vast frozen sea covered with a thin layer of ice.

[dvandorn]

My only problem with the concept going around that the *entire* Martian northern hemisphere was excavated down a few km below mean by an enormous impact, whose basin is the entire northern half of the planet, is that I'd have to think such an impact would disrupt the entire planet, causing it to re-accrete rather as Earth and Moon re-accreted after the impact of a Mars-sized body on the proto-Earth.

How could Mars retain its structural integrity during an impact whose crater is roughly half the size of the planet? I'm not a mathematician, but it seems to me that the energies released by such an impact would have to be enough to disrupt the entire planet... in other words, I can't imagine a solid body that wouldn't come apart under such an impact, no matter the angle of impact.

-the other Doug