The Top 4 Sites To Land On Mars And Their Biggest Mysteries

Holden Crater

From Popular Mechanics:

The Spirit Rover is nearly history, stuck deep in sand, and while Opportunity travels on, it's not likely that it will travel much farther. Now, scientists are building the next rover to be sent to Mars. But before they fuel the rockets, researchers have to pick a spot to explore. Here are NASA's frontrunners.

Call it the Jet Propulsion Laboratory's version of the Final Four. Scientists at the Pasadena, Calif.–based NASA research center will decide within the next two years where to send the Mars Science Laboratory (MSL) rover after it launches in the fall of 2011. MSL's mission is to scour the Red Planet for environments that may once have harbored, or may still harbor, microbial organisms. Such an environment would have to contain the basic ingredients of life—including water, organic carbon and a source of energy to sustain the microbes' metabolism.

Read more ....