Changes in the geography of Mar always attract significant scientific and even public attention. The hope for signs of liquid water (and therefore life) is probably one of the main driving forces behind this interest. A particularly noticeable change feature are the Recurring Slope Lineae (RSL), which were originally found by the Mars Reconnaissance Orbiter (MRO). Now scientists at the SETI Institute have a modified theory of where these RSLs could develop – a combination of water ice and salt just below the Martian surface.
According to the SETI team, led by Janice Bishop, Senior Research Scientist, these RSLs are created in two steps. First, underground water ice must mix with a combination of chlorine salts and sulfates to create a kind of slurry that destabilizes the regolith in the area. Then the dry wind and dust storms of Mars take over and blow the destabilized material in new patterns over the Martian surface.
This landslide was discovered and colored by Stu Atkinson, a steep cliff on the North Pole boundary.
Photo credit: NASA / JPL / University of Arizona
This isn’t the first time researchers have suggested that chlorine salts may be involved in the formation of RSL. As with much good science, this theory has now been further substantiated by data collected from both field and laboratory experiments.
Unfortunately, the field tests could not be carried out on Mars itself (at least not yet). However, there are several places on our home planet that are considered “Mars analogues,” including the Dead Sea in Israel, Salar de Pajonales in the Atacama Desert and the arid valleys in Antarctica.
Image of the McMurdo Dry Valleys in Antarctica, where some of the field work for this experiment was carried out. Acquired through the Enhanced Thematic Mapper plus (ETM +) instrument from Landsat 7.
Photo credit: NASA / EO
The SETI team collected data at some of these points and found that surface destabilization was already observed when salt interacted with gypsum, a type of sulfate. For this project, the team collected data in the dry valleys, where the soil geology and temperature are remarkably similar to what the Phoenix lander and MRO found on Mars.
Landslides in a crater near Nili Fossae on Mars Credit: NASA / UofA HiRiseteam / MRO
Fieldwork was followed by laboratory work when the team subjected the Mars analog regolith tests using colored indicators that showed how the regolith simulant would react if subjected to the same chemical reactions that occurred in Antarctica.
UT video about some things we can expect on Mars.
All of this data collection resulted in a geological model with sulfates, chlorides, and water that can explain the occurrence of RSLs on the Martian surface. The model also has implications for the habitability of Mars subsurface and how the presence of that slurry could affect the red planet’s biosphere. Until there is more on-site testing, this model will be difficult to prove, but many are planned for Mars in the near future.
Learn more:
SETI Institute: Mars landslides through underground salts and melting ice?
CNN: Landslides on Mars can be caused by melting ice and salt beneath the surface
UT: Mars is still an active world. Here is a landslide in Nili Fossae
Mission statement:
Image from MRO’s HiRISE camera with RSLs forming on the side of Krupac crater.
Photo credit: NASA / JPL / University of Arizona
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