Mars is a planet in the SoL solar system which is the nearest planet to Earth. Mars plays a role in alien research because it is rumored that there may or has been Alien life of some kind on the planet. As since evidence of icy water has been found on the planet. In popular culture, Little green men were once said to have lived on Mars.
Bacteria was found on a Martian meteorite in Atarctica, but the evidence is still being argued with by scientists, as the meteorite could have been contaminated. Also, a Martian being was photographed by the Spirit rover in November 2007, but the photo is still in controversy because it could easily be some kind of rock.
In 2008 the NASA Phoeneix program confirmed there is water on Mars, leading to strong possibilities that life has exsisted in the planet's past. If the supposed being photographed in 11/07 happened to be amphibious, there is even a possibility that not only life, but intelligent life is present there (speculation).