re: Spirit's upcoming journey
Looks like whatever made that cave came in at a very oblique angle. Notice, the lighter material to the lowest right of the first image link you posted. It looks like ejecta from a meteor, but then there's a gouge mark that leads to the cave... maybe that's where it came to rest. Very interesting feature, but the entrance looks bumpy.
The Missoula Crater and 'Anamolous Crater' (No. 5 on the map) look interesting too. Anamolous has a "large ejecta" for a small crater.
Thanks for posting that map, Buck.