Finger Rocks on Mars
Above: Image PIA25362 from NASA's Curiosity rover!
Check out this incredible rock formation on the surface of Mars! What you're seeing here is a strange but not unknown phenomenon that was photographed by NASA's Curiosity rover. It appears as though these rocks are sticking straight out of the ground, growing upward not unlike a tree. In actuality though, this is a representation of the deep time of geologic progress and a key indicator as to what the red planet once looked like.
These formations are thought to have been formed by the movement of groundwater through rock. As the water flowed, it carried small pieces of minerals that were left behind over the course of millennia. The leftover sediment made new rocks inside the former waterways that were tougher than the surrounding stone.
These rocks eventually became exposed to the surface as harsh winds eroded the softer material around them. Today, they are left standing as a reminder of the water which once flowed there!