[meteorite-list] NASA Scientists Find Evidence for Liquid Water on a Frozen Early Mars

[Ron Baalke]

http://www.nasa.gov/topics/moonmars/features/mars_freeze_052709.html

NASA Scientists Find Evidence for Liquid Water on a Frozen Early Mars
05.27.09
 
NASA scientists modeled freezing conditions on Mars to test whether
liquid water could have been present to form the surface features of the
Martian landscape.

Evidence suggests flowing water formed the rivers and gullies on the
Mars surface, even though surface temperatures were below freezing.
Dissolved minerals in liquid water may be the reason. Photo Credit: NASA
Researchers report that fluids loaded with dissolved minerals containing
elements such as silicon, iron, magnesium, potassium and aluminum, can
remain in a liquid state at temperatures well below freezing. The
results of this research appear in the May 21 issue of Nature magazine
entitled "Stability Against Freezing of Aqueous Solutions on Early Mars."

"We found that the salts in water solutions can reduce the melting point
of water, which may help explain how liquid water existed in a frozen
Martian environment," said Alberto Fairén, a space scientist at NASA
Ames Research Center, Moffett Field, Calif. and the lead author of the
study.

To understand what formed the surface features on Mars, scientists have
focused on the early Martian conditions. Was early Mars warm and wet, or
cold and dry? Surface features throughout most of the Martian landscape
suggest the presence of water ponds ranging from seas to lakes, and
rivers and gullies formed by flowing water, which imply that early Mars
was wet.

But there also is some evidence that suggests that Mars may have been
permanently cold, with global temperatures well below the freezing point
of pure water. To study the 'liquidity' of water on Mars, climate
modelers first simulated various concentrations of greenhouse gases in
its atmosphere. They found that these gases cannot efficiently raise the
surface temperature above freezing.

A greenhouse atmosphere produced by carbon dioxide and water would have
been saturated well below freezing. In addition, the amount of methane
needed to raise the surface temperature above freezing, implies the
planet had a terrestrial-like biological source for its methane supply,
according to previous investigations.

Scientists then took another approach and looked at water solutions
containing weathering basalts, similar to those seen at the Mars landing
sites. They calculated these fluids' freezing points and evaporative
processes. Results showed that a significant amount of weathering fluids
containing silicon, iron, magnesium, calcium, chloride, sodium,
potassium and aluminum remain in the liquid at temperatures well below
freezing.

In addition, they studied the minerals that precipitated in the liquid
solutions over time. These minerals are similar to those actually found
on the Martian surface. Scientists concluded that salty liquid water on
Mars may explain the stability of fluids against freezing on the Martian
surface at temperatures below 0°C.

"Our goal was to learn how a combination of different processes of
evaporation and freezing affect the freezing point of a hypothetical
Martian solution. We also wanted to see how the liquid phases formed and
destabilized over the evolution of different solutions," added Alfonso
Davila, a co-author of the paper at NASA Ames Research Center, Moffett
Field, Calif.

 
Ruth Dasso Marlaire
Ames Research Center, Moffett Field, Calif.