Images sent back from the Mars Pathfinder project show sand, rocks, and other features that appear to have been created by the flow of liquid water. Water is necessary to support life. Evidence suggests that Mars was once abundant with it. Mars Valley Network Scientist study photographs of the ancient Mars surface. Features seen in some of the valleys have been considered to be evidence that Mars had liquid water running across its surface during its earliest years.
Scientists study Martian meteorites that fall to Earth to look for clues about life on that planet.
These microscopic images of meteorites suggest that primitive life may have existed on Mars more than 3.6 billion years ago. The photo above shows egg-shaped structures inside an ancient Martian rock. These objects are smaller than a human hair and may be microscopic fossils of primitive life.