ASU Professors of geological sciences L. Paul Knauth and Donald Burt think meteorites, rather than lakes, created the rock formations discovered by NASA's Opportunity rover.

http://www.spacedaily.com/reports/Impacts_...ogists_Say.html

This is an approach to the theory of impact of an extint planet: Astra which were orbiting between Mars and Jupiter. The debris of this planet have impacted in a radius of the Mars South Hemisphere (Argyre, Hellas, Syrtis) as the core and lots of small craters around these three biggest craters. The moons Phobos and Deimos were formed when Astra was desintegrating before impacting to the Mars.

Scars of Mars

Rodolfo

Here's another discussion about this new theory:

http://www.unmannedspaceflight.com/index.p...topic=1884&st=0 - The Great Meridiani Debate

I take it that this "Astra" theory is the latest entry in the quest to explain the lunar cataclysm (what geologists call the Late Heavy Bombardment)?

Well, if the Moon got it as badly as it did, 'stands to reason Mars got it a lot worse.