The gamma-ray spectrometer (GRS) aboard NASA's Mars Odyssey probe has detected surface soils rich in hydrogen, an indication of water under the surface.
The amount of hydrogen detected by the GRS corresponds to 20-50% ice by mass in the lower layer. As rock has a greater density than ice, this totals more than 50% ice by volume, says NASA.
The GRS detects underground water by measuring the energy from gamma-rays and neutrons that come out of the soil when cosmic rays from space hit Mars's surface.
The amount of water contained in the deposits - enough to fill Lake Michigan twice - could support future human exploration with life support and potential rocket propellant for the return journey. NASA has no firm plans for a human expedition to Mars, however.
The findings confirm earlier measurements that water ice is stable close to the surface, but for the first time indicate the amount of near-surface water on Mars. The findings reveal that Martian soil is richer in hydrogen than the moon's soil - discovered by a spectrometer aboard the Lunar Prospector orbiter - by 1,000 times.
Images of the Martian surface taken by spacecraft for the last 30 years have indicated that water once flowed across the surface and the question had been where that water went.
Source: Flight International
