A 54-pound (25-kilogram) rock. Estimated auction price: $2 million to $4 million. Why so expensive? It’s the largest piece of ...

After its voyage past Mars, Mariner 4 maintained intermittent communication with JPL and returned data about the interplanetary environment for two more years. But by the end of 1967, the spacecraft ...

Compare Mars and Earth in size, atmosphere, gravity, and potential for life. Discover their differences and shared traits. Explore the mysteries of the Red Planet!