(click for larger image)
Ten years ago, the mini rovers Spirit and Opportunity landed on Mars. Spirit crapped out, with two broken wheels, and the loss of communications ability. The pint-sized Opportunity is still going strong, exploring away, and sending pictures back of what it finds. There is a huge mystery of what it found.
The photo on the left was taken twelve days before the photo on the right. In the intervening time, a strange white rock with a red depression in it, appeared in the scene. This is a huge mystery.
The depression in the mystery rock is strange as well. Instruments show scientists that the red depression part is very high in sulfur and magnesium, and it has twice as much manganese as has ever been seen in anything on Mars.
There are a couple of theories of how the rock appeared. One is that it is ejecta from a small volcanic explosion and was blown there. Another is that the wheels of Opportunity flipped it in place. None of these explanations are totally satisfying.
The obvious explanation is that someone or something put the rock there. Is there life on Mars?