NASA has found a rock on Mars that it has dubbed Skull Hill. The rock is known as a "float rock," and NASA has no idea where it came from.

A rock containing many smaller round stones could indicate that there was once a large amount of liquid water on the Red Planet.

NASA's Perseverance rover on Mars has discovered unusual "float" rocks on the rim of Jezero Crater while searching for signs of ancient microbial life. Scientists are investigating their origin.