Wednesday, November 4, 2015

How Much Liquid Water Flows on Mars?

These dark, narrow, 100 meter-long streaks called recurring slope lineae flowing downhill on Mars are inferred to have been formed by contemporary flowing water. Image credit: NASA/JPL/University of Arizona

It’s been more than a month since NASA confirmed the presence of liquid water on Mars. Using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard NASA’s Mars Reconnaissance Orbiter (MRO), the researchers detected signatures of hydrated minerals on downhill flows, known as recurring slope lineae (RSL). Now, when we are richer in conclusions from this breakthrough finding, the next perplexing question that shows up is how much water really flows on the Red Planet?

“It has been estimated that each cluster of recurring slope lineae, has the equivalent of several Olympic swimming pools full of water. The two unknowns are, how accurate is that estimate and - more importantly - how many RSL are active across the planet at any one time?” Scott Murchie of the Johns Hopkins University Applied Physics Laboratory (APL), principal investigator for CRISM, told

RSL often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads on Earth causes ice and snow to melt more rapidly.

“Sure the answer will be infinitesimal compared to the volume of flowing water on Earth, but infinitely larger than the amount of flowing water that was suspected before the Mars Reconnaissance Orbiter - zero!” Murchie said.

Murchie is one of the co-authors of the Nature Geoscience paper that describes the discovery of liquid water on Mars. He revealed that scientists tried to maintain a very open mind on the question of flowing water, and not to expect a particular hypothesis to be the correct one. Finally, he and his colleagues had to admit that the dependence of RSL on warmer temperatures, their shape and downslope orientation, as well as their previously known spectral properties can only be explained by flowing water.

“Their gradual growth does not resemble at all what one would expect to result from dry processes,” Murchie concluded.

It took multiple spacecraft over several years to solve the mystery of RSL and liquid water on Mars. NASA’s Phoenix lander and Curiosity rover both found salts in the planet’s soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this latest study of RSL detected hydrated minerals, in different areas than those explored by the landers. This also is the first time when hydrated minerals have been identified from orbit.

Murchie believes that future orbital missions that could observe the surface at even higher spatial resolutions should tell us much more about RSL and about the presence of liquid water on the Red Planet.

1 comment:

  1. Scott Murchie of the Johns Hopkins University Applied Physics Laboratory (APL), principal investigator for CRISM, told