I wonder how old Fram is?

Perhaps the most striking thing about Meridiani is the almost complete absence of rocks. Until Fram, just about the only rock to be seen was Bounce, an impact erratic if I can coin a phrase.

But, lots of little boulders around Fram. Clearly newer than the average crater in the vicinity.

So how long does it take for a rock from Opportunity Formation the on the surface here to weather away? Or, are the rocks getting buried rather than eroded (eroded seems more likely).

I realize the answer will be "really slowly!" relative to terrestrial processes, but it must be pretty fast relative to nice solid chunks of basalt, which seem able to last for a very long time on the surface.

If you knew the age of the surface then you could make an estimate (i.e., very simplistically, if 10% of the craters have uneroded rocks around them, then the time to weather is the time it took to accumulate the last 10% of the total number of impacts).

More usefully, if you can make a decent guess at the weathering rate, then you could do the reverse calculation and get the length of time the surface has been exposed. Insert much hand waving here about assuming no burial and exhumation, and a zillion other things.

The point being, that finding a crater with much less eroded debris is useful -- getting statistics on what fraction of craters show what degree of erosion is quite useful, and the fact that the craters are so easy to map here helps with part of the problem, even if it might not be easy to get enough craters to reduce the error bars to something useful.