Mars Odyssey is a robotic spacecraft orbiting the planet Mars. Its mission is to use spectrometers and a thermal imager to detect evidence of past or present water and ice, as well as study the planet's geology and radiation environment.[2] It is hoped that the data Odyssey obtains will help answer the question of whether life existed on Mars and create a risk-assessment of the radiation that future astronauts on Mars might experience. It also acts as a relay for communications between the Mars Science Laboratory, and previously the Mars Exploration Rovers and Phoenix lander, to Earth. .