While it is true that actual seashells would have crumbled away fairly quickly, what we might be viewing are fossilized seashells hundreds of milions years old. Of course it's unlikely that these images are authentic images taken by a Mars Rover.

Still, it's fun to ponder on. I'm reminded of when I was leading a group of geology students up a dry river valley cutting into the escarpment towering over Dira Dawa in Ethiopia in 1964. We came across gigantic fossilized sea mollusks in the riverbed, some of their spiral shells over two feet in diameter. It was kind of neat to think we were walking along some ancient sea bed. A more recent sea bed was in evidence in the outcrops on the plains at the foot of the escarpment. There you could see wave cut cliffs, the remains of coral reefs, from when the Red Sea extended into the Danakil Depression only a few thousand years ago. My photographs of that landscape would have been much more convincing than the ones posted above. Maybe I'll dig them up!

Cheerily,
Charley Noble