On December 3, 1999, NASA's Mars Polar Lander descended towards the surface of Mars. It was not heard from again. Now, Malin Space Science Systems (MSSS) is using the Mars Orbiter Camera on the Mars Global Surveyor to photograph the wreckage in hopes of determining what went wrong. The leading theory is that spurious signals were created when the craft's legs were deployed during descent, although others believe the Polar Lander's engines may have shutdown prematurely during entry.
For more on the "Mystery of the Mars Polar Lander", check our previous report.
Mars CSI: What happened to the Polar Lander?
Contaimination
