FAYETTEVILLE, Ark. - A team of researchers from the University of Arkansas has measured water evaporation rates under Mars-like conditions, and their findings favor the presence of surface water on the planet. Water on the planet’s surface makes the existence of past or present life on Mars a little more likely, according to the group.

Derek Sears, director of the Arkansas-Oklahoma Center for Space and Planetary Sciences, and his colleagues graduate student Shauntae Moore and technician Mikhail Kareev reported their initial findings at the fall 2003 meeting of the Division of Planetary Sciences of the AAS.

The researchers have brought on-line a large planetary environmental chamber in which temperature, pressure, atmosphere, sunlight and soil conditions can be reproduced. Sears and his colleagues use the chamber to investigate the persistence of water under a range of physical environments and to study its evaporation.

For their first experiments, reported at the DPS meeting, the group chose to measure one of the most important properties of water on a planetary surface, the rate at which it evaporates.

"Physicists have long argued that Mars is currently a sterile desert, completely unsuited to life," Sears said. "This conclusion is based on their belief that water would evaporate very quickly, as soon as it appeared on the surface."

The University of Arkansas group examined the effect of Mars’ atmospheric conditions - temperature and wind - on the evaporation rate. The movement of the atmosphere close to the surface is a crucial factor in the survival of water on Mars. Water evaporates more slowly when evaporated molecules build up over the water’s surface, but wind sweeps away evaporated molecules, allowing more water molecules to escape the surface and increasing evaporation rates.

"These findings suggest that even under worst case scenarios, where wind is maximizing evaporation, evaporation rates on Mars are quite low," Sears said. This implies that surface water could indeed exist, or have existed recently, under the given conditions on Mars.

In addition to the evaporation experiments, the group examines the ways in which water-ice behaves when frozen at depth and how it reacts when covered with layers of frost or dust. They also explore how ice behaves when exposed on the surface, and whether it can exist in a transient liquid phase that could harbor life.

The subtle balance between the input of heat from the Sun and subsurface sources and the strength of the surface atmospheric motions determines the fate of the water; whether it remains as ice, becomes liquid, and if so how long it remains as a liquid, or how quickly it evaporates.

"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 Viking missions and a member of the Arkansas research group.