A 1 cm square cube is shown for scale. Ron Baalke Lacking more than a very few Martian meteorites as samples, we still don't have much data on the question of life itself. Unfortunately, that data is still too ambiguous to give us a really firm answer. Up to now, the general feeling has been that the Martian valley networks look more as though they were carved by groundwater sapping. But this year's LPSC papers shows both sides have much to debate yet.
Some authors take the optimistic view.