A laboratory test simulating the harsh environment of Mars suggests water could exist in liquid form on the surface of the red planet without evaporating.
The results, if they can be proven to characterize the real Martian world, would be good news to any life form trying to develop or survive on the dusty planet.
A team of researchers at the University of Arkansas measured water evaporation rates in an environmental chamber in which wind, temperature, sunlight and soil conditions simulate those on Mars.
"Physicists have long argued that Mars is currently a sterile desert, completely unsuited to life," said Derek Sears, director of the Arkansas-Oklahoma Center for Space and Planetary Sciences. "This conclusion is based on their belief that water would evaporate very quickly, as soon as it appeared on the surface."
Scientists know Mars is loaded with water ice, either at or near the surface, but no firm evidence exists for any liquid water on Mars. Liquid water is crucial to life as biologists understand it.
Sears and his colleagues recorded the effects of temperature and wind on the evaporation of water. Air movement at the surface turned out to be a critical factor, the researchers explained this week.
Water evaporates more slowly when evaporated molecules build up over the water's surface. But wind sweeps away evaporated molecules: More water molecules escape the surface, and the evaporation rate increases.
"These findings suggest that even under worst-case scenarios, where wind is maximizing evaporation, evaporation rates on Mars are quite low," Sears said.
He said this implies that surface water could indeed exist, or have existed recently, on Mars.
The results were presented at a meeting of the American Astronomical Society's Division of Planetary Sciences, held in Monterey, Calif.
Mars is much colder than Earth. Days only occasionally reach shirt-sleeve temperatures, and then only near the equator at mid-day. Air pressure on Mars is, on average, less than 1 percent that of Earth at sea level.
Future studies with the new Mars-on-Earth setup may shed more light on the complex interactions between subsurface ice, liquid water and weather.
"The environmental chamber will enable us to gain new insights into the behavior of water on Mars and reduce much of the speculation on this topic," said Barney Farmer, principal investigator for the atmospheric water vapor mapping experiment during the 1970s Viking missions and a member of the University of Arkansas research group.
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