Recurring Slope Lineae (RSL) are dark flows on steep slopes that extend downhill gradually or incrementally and recur each Mars year. RSL activity often occurs at temperatures exceeding 255 K, meeting one requirement for potential habitability. The temperature-dependent activity is consistent with the stability of brines likely on Mars, and hydrated salts are transiently detected from orbit. These may be the most promising locations for habitable conditions on Mars today, especially in equatorial regions. However, topographic evidence strongly points to formation of RSL as granular flows, not seepage of water, so the water activity value is probably quite low (<0.5) and habitability remains very challenging. Future spacecraft experiments and laboratory experiments are needed to understand how RSL form and whether they need to be treated like Specials Regions, requiring extra procedures for Planetary Protection (quarantine).
 
About the Speaker:

Professor Alfred McEwen of the Lunar and Planetary Lab, University of Arizona, studies volcanology, cratering, slope processes, and remote sensing of planetary surfaces. His spacecraft mission experience includes Voyager, Galileo, Clementine, Cassini, Mars Observer/MGS, Mars Odyssey, Lunar Reconnaissance Orbiter, ExoMars Trace Gas Orbiter; he is PI of the High Resolution Imaging Science Experiment (HiRISE) on Mars Reconnaissance Orbiter and Deputy-PI of the Europa Imaging System (EIS) for Europa Clipper. He was awarded NASA's distinguished public service medal in 2011 and the AGU Whipple award in 2015.
                   
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