https://www.uahirise.org/sim/science-2011-aug-4.php
https://www.uahirise.org/sim/RSL-GIFs-text.pdf
Alfred S. McEwen, Lujendra Ojha, Colin M. Dundas, Sarah S. Mattson, Shane Byrne, James J. Wray, Selby C. Cull, Scott L. Murchie, Nicolas Thomas, Virginia C. Gulick
ABSTRACT
Water likely flowed across ancient Mars, but whether it ever exists as a liquid on the surface today remains debatable. Recurring slope lineae (RSL) are narrow (0.5-5 m), relatively dark markings on steep (25°-40°) slopes; repeat MRO/HiRISE images show them to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock outcrops, often associated with small channels, and hundreds of them form in rare locations. RSL appear and lengthen in the late southern spring/summer from 48°S to 32°S latitudes favoring equator-facing slopes--times and places with peak surface temperatures from ~250-300 K. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.
