Opportunity Mars Rover Stuck in Sand
http://www.space.com/missionlaunches/050428_rover_update.html
Looks like that soil has a crust. Icy layer on top?
Here's a question. Go to the link cabojoe gave, click on the image that shows the small crater. What is it about the human brain that makes that crater look like a bump, but if you turn the picture upside down, it looks like a crater? Where did we get the inability to see craters correctly if they are lit "wrong"? And why?