mars
Simulated Martian soil supports plant life, but questions about extraterrestrial plant growth remain.
Evidence of life could be preserved in blades of salt crystals on the Red Planet.
After initial water escaped into space, the rest froze.
Curiosity may already have done some work in paving the way for human exploration of Mars
NASA's new Curiosity rover mission will assess odds for life in one of four promising locations on Mars.
Astrobiologists look for places here at home to practice for missions on other planets
Astronauts discuss the retirement of the space shuttle program and NASA's plans for a new spacecraft.