NASA | JPL-Caltech | Mars Odyssey | 2016 Aug 23
Seasonal dark streaks on Mars that have become one of the hottest topics in interplanetary research don't hold much water, according to new findings from a NASA Mars orbiter.
[img3="Blue dots on this map indicate sites of recurring slope lineae (RSL) in part of the Valles Marineris canyon network on Mars. RSL are seasonal dark streaks that may be indicators of liquid water. The area mapped here has the highest density of known RSL on Mars. Image Credit: NASA/JPL-Caltech/Univ. of Arizona"]http://www.jpl.nasa.gov/images/mro/2016 ... 756-16.jpg[/img3][hr][/hr]The new results from NASA's Mars Odyssey mission rely on ground temperature, measured by infrared imaging using the spacecraft's Thermal Emission Imaging System (THEMIS). They do not contradict last year's identification of hydrated salt at these flows, which since their 2011 discovery have been regarded as possible markers for the presence of liquid water on modern Mars. However, the temperature measurements now identify an upper limit on how much water is present at these darkened streaks: about as much as in the driest desert sands on Earth.
When water is present in the spaces between particles of soil or grains of sand, it affects how quickly a patch of ground heats up during the day and cools off at night. ...
The features, called recurring slope lineae or RSL, have been identified at dozens of sites on Mars. A darkening of the ground extends downhill in fingerlike flows during spring or summer, fades away in fall and winter, then repeats the pattern in another year at the same location. The process that causes the streaks to appear is still a puzzle. ...
The Water Content of Recurring Slope Lineae on Mars - Christopher Edwards, Sylvain Piqueux
- Geophysical Research Letters (online 17 Aug 2016) DOI: 10.1002/2016GL070179