Space rock on my mantlepiece

[M Holmes]

Eric Siegerman writes:

> On Wed, Feb 09, 2005 at 01:58:03PM +0000, M Holmes wrote:
> > I'm puzzled by that. Surely anything knocked off the Moon by meteoric
> > impact would already be in an Earth-crossing orbit. Seems therefore much
> > more likely that these would hit Earth than the same situation on Mars.

> Completely uneducated guess, but ... maybe Mars takes a lot more
> hits than the Moon, by virtue of being farther out -- oh, and
> next door to the asteroid belt, too.

Could be, and there's obviously the *BIG* hit on Mars which produced
the Tharsis bulge, the Hellas crater and the canyon system that makes
the Grand Canyon look like a scratch. That must have thrown a few bits
into solar orbit.

Presumably the Moon, which was produced by a giant impact on Earth, is
also younger than Mars?

FoFP