A New Case for Liquid Water on Mars

Published: 1998 July 23 3:25 pm ET (1925 UT)
http://www.spaceviews.com/1998/07/23b.html

A father-son team of scientists, including one who worked on the Viking missions in the mid-1970s, believe that liquid water -- in limited amounts and for limited times -- can exist on present-day Mars.

Dr. Gilbert Levin of Biospherics, Inc. and his son, Dr. Ron Levin of MIT's Lincoln Laboratory, presented their analysis, based on Viking and Mars Pathfinder data, July 20 at the annual meeting of the Society of Photo-Optical Instrumentation Engineers (SPIE) in San Diego.

According to their research, a thin frost forms in some regions of the planet overnight, as the atmosphere cools and the trace amounts of water vapor freeze out. This frost was seen on a number of Viking images. As the Sun rises, the ground warms enough to melt the ice.

The ice would not sublime directly to vapor and return to the atmosphere, the Levins conclude, because the atmosphere just a meter above the surface remains too cold to hold much water vapor. Data collected by Mars Pathfinder showed that temperatures a meter above the surface were often dozens of degrees colder that those at the surface.

Since the atmosphere is too cold to hold the water as vapor and the ground is warm enough to melt the ice, the Levins conclude, the water must melt into a liquid. The liquid water would remain on the surface until the temperature of the atmosphere rises enough to allow the water to evaporate.

The Levins believe that this liquid water would be enough to support the existence of microorganisms in the Martian soil. "Terrestrial experiments in natural environments, including the Death Valley sand dunes of California, demonstrated that the amount of soil water moisture predicted by the model is sufficient to sustain survival and growth of common soil microorganisms," the elder Levin said.

Gilbert Levin has been a long-time proponent of life on Mars. A scientist involved with the Viking missions in the mid-1970s, he believes data from the Labeled Release (LR) experiment on the Viking landers showed that primitive life does exist on present-day Mars. Most scientists believe the data from the experiment are inconclusive, and that the existence of strong ultraviolet radiation at the surface and highly oxidizing chemistry rules out life on the surface.

"This model [for the formation of liquid water] removes the final constraint preventing acceptance of the biological interpretation of the Viking LR Mars data as having detected living microorganisms in the soil of Mars," Levin said. "It comes at a time when a growing body of evidence from the Earth and space are supporting the presence of life not only on Mars, but on many celestial bodies."