University Researchers Show Liquid Water Can Exist on Mars
Last updated Monday, November 7, 2005 10:21 PM CST in News
By Denise Malan
The Morning News
University of Arkansas researchers punched some holes in prevailing theories that liquid water can't exist on Mars.
Scientists have long speculated that liquid water couldn't last long on the Red Planet's surface, under extremely low temperatures and atmospheric pressure less than 1 percent of Earth's.
Graduate student Julie Chittenden and Professor Derek Sears, however, recreated Mars conditions and used salt water to show that water could exist in the liquid state for hours.
"I believe that it's definitely possible that we have liquid water on Mars and it created some of these features that we're seeing on the surface," Chittenden said.
The planet has gullies and channels that appear to be formed by liquid. However, scientists theorized that ice would evaporate directly to gas, bypassing the liquid state, in Mars' conditions.
These experiments were the first conducted with salt water and at low pressures. Researchers used a chamber at the W.M. Keck Laboratory for Space Simulation to recreate the environment.
The chamber is a large cylinder, about 7 feet by 2 feet, and scientists lower a platform with instruments to measure temperature, humidity, pressure and other conditions. Researchers pumped air out to create a near vacuum, then added a carbon-dioxide atmosphere and cooled the chamber to zero degrees Celsius to 25 degrees below zero.
"We're the first to do (the experiment) in such a controlled environment that's the closest to Mars that you can get," said Chittenden, a Jonesboro native who is pursuing a doctorate in chemistry with an emphasis on space and planetary science.
The research will be published in an upcoming edition of the Geophysical Research Letters.
"We had a gut feeling that it would happen this way, but it was very satisfying to actually say, 'Yes, we can keep water liquid for extended periods of time,'" Chittenden said.
Temperatures on Mars range from 125 degrees below zero Celsius and 28 degrees above zero at different latitudes and different times of the day. The researchers found that the salt-water mixtures could remain liquid at subzero temperatures, even under the low pressure.
"Depending on the (salt) concentration and the temperature, it could be liquid from a few hours or the majority of the day," Chittenden said. "Mars has the same kind of temperature cycles that Earth has. (The water) could remain liquid for the majority of the day."
Salt lowers the freezing point of water, which is zero degrees Celsius for pure water. The researchers used high concentrations of sodium chloride -- normal table salt -- and calcium chloride because water can rarely be found in its pure form.
"We've done experiments with pure water," Chittenden said. "This was building on that, adding salt to it, because any time you get water interacting with rock or soil it leaches ions into the water."
The freezing points for the mixtures drop to minus 21 degrees Celsius for water containing sodium chloride and 50 degrees below zero for calcium chloride, according to a university news release.
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