Surface Water Possible Under Marslike Conditions
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.
EDITORS NOTE: Dr. Sears will be at the Doubletree Monterey during the meeting.
The number there is (831) 649-4511.
