Mars Odyssey spacecraft detecting ice. Computer illustration of ice-rich layers in the soils of Mars being detected by instruments onboard NASA's 2001 Mars Odyssey spacecraft. 2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. Measurements by its gamma ray spectrometer suite of instruments indicate that the upper metre of soil on Mars contains an ice-rich zone with an ice abundance of 20 to 50 percent by mass. The ice-rich areas surround the polar regions of Mars. The instruments only detect the signature of hydrogen, indicating water ice, to a depth of about one metre so it is not known whether or how deep the ice-rich zone continues below that depth.