In November 1996, NASA and the Jet Propulsion Laboratory began America's return to Mars after a 20-year absence by launching the Mars Global Surveyor (MGS) spacecraft. This mission will usher in a new and exciting era of scientific missions to study the red planet.

Over the course of a full Martian year, Surveyor will return an unprecedented amount of data regarding Mars' surface features, atmosphere, and magnetic properties. Scientists will use the data gathered from this mission both to learn about the Earth by comparing it to Mars, and to build a comprehensive data set to aid in planning future missions.

Mars and Earth shared similar conditions billions of years ago, but appear much different today. A comparison of Mars and Earth will allow scientists to understand Earth's history and possibly its future.