NASA's has landed five robots on Mars over the past three decades. Its latest spacecraft, Phoenix Mars, will touch down in the Martian arctic region Sunday.
Unlike the rovers that landed four years ago, the $420-million Phoenix lander will stay in place after touchdown and dig into the soil.
Phoenix will study whether there was once water at the site and sample the soil for traces of organic compounds, two essential ingredients for life. If Phoenix finds out there are ingredients for life, the Martian arctic region would suddenly be an attractive site for future exploration. NASA currently does not have plans to go back to Phoenix's landing site.
Phoenix will use a parachute to slow down, then fire its thrusters to land. If successful, it will be the first time since the twin Viking missions of 1976 that a spacecraft has done a powered landing on Mars.