Exciting news from the Mars Spirit rover. -- it seems that Mars really was once a lot more Earth-like:
The right front wheel of Spirit stopped turning in March 2006. Since then, the rover has been driving backwards, dragging the lame wheel along. This May, scientists noticed a bright spot in the trail of overturned dirt.
They turned Spirit around for a closer look, finding high levels of silica, the main ingredient of window glass. They then aimed the rover at a nearby rock, wanting to break it apart to determine if the silica was just a surface coating, or if the rock was silica all the way through.
The target rock survived Spirit