"ahh" writes:

There searching for past water evidence be examing rocks (pretty simple).

I keep wondering why they're looking for evidence of water, while they
admit that that there's ubiquitous visual evidence of it. What else
could explain the huge gully cutting through the wall of Guseve crater?

All rocks come from bedrock. It is better to get bedrock that is broken up
than bedrock that is one big sheet. The lander can only "shave" It can not
dig.

I'm not sure what difference you have in mind, but the rover can lock
5 wheels and spin the 6th down at least 30 cm.

They did imply they didn't want to go in the crater on Spirit.

When? I think you implied on landing earlier, which wasn't the
concern I heard raised. They were mostly worried about landing with
a high horizontal speed, which was apt to tear the bounce bags. That
it might also have also taken them into that crater would have been
bad luck probably if it was deep and didn't have a good way out,
unlike the lucky Opportunity.

One
reason is perfectly clear by looking at Opportunity pictures is all the fine
material collects in the hole. Dirt blows in but doesn't blow out.

Good point. I've been wondering why nobody has brought that up with
them. I'm thinking that all smallish craters on Mars should have in
them pretty-much the same wind-blown mixture of stuff from everywhere
else, based on my memories of the Viking-era dust storms. But it's an
unfamiliar environment; maybe there's just a small amount of very fine
stuff that blows around, giving a dense fog that slowly settles out to
a thin coat and sand-type drifts only shift back and forth fairly near
the area from which they originated (as on Earth, though the Sahara
blows at least as far as England).

They might also be happy that luck put them in a crater where they
would not dare to drive, as long as they think they can get out.