Mars’ Water Now Ice, Geologist Says

Mars once may have had enough water to cover the entire planet to 150 feet deep and most of that water is probably still there in the form of polar and underground ice, a geologist has concluded, based on findings that indicate that the Red Planet once had a milder climate than its current subfreezing weather.

If so, this would suggest that there may be great frozen reservoirs that future Mars explorers might be able to tap for oxygen, water and fuel, said Ronald Greeley of Arizona State University.

He based his estimate of the amount of water on Mars on the extent of volcanic rock now visible in satellite pictures of the planet.

Much more water may have been produced early in Mars’ history but, Greeley said, the planet’s early crust has largely been erased by geological activity, so that it is impossible to say how much additional water Mars had.

Since 1972, when the Mariner 9 satellite photographed great networks of channels on Mars’ surface that strongly resembled dry riverbeds on Earth, scientists have believed that Mars once had water on its surface.

Because there is little water vapor in Mars’ thin atmosphere and the gravity is too great to lose the water to space, Greeley said, most of the water must be locked up in polar ice caps and in subsurface ice. If so, astronauts flying to Mars in the next century might have a readily available source of water. “The trick is to find out where these reservoirs are,” Greeley wrote in the current issue of Science magazine.