Mars, one of our closest planetary neighbors, has fascinated people for hundreds of years, partly because it is so similar to Earth. It is about the same size, contains similar rocks and minerals, and is not too much farther out from the Sun.
Because Mars and Earth share so many features, scientists have long wondered whether Mars could have once harbored life. Today, Mars is very cold and dry, with little atmosphere and no liquid water on the surface − traits that make it a hostile environment for life. But some observations suggest that ancient Mars may have been warmer, wetter and more favorable for life.
