A feature called recurring slope lineae (RSL), dark narrow streaks that form on slopes primarily in the warm season, has been widely considered evidence for liquid water on Mars. These occur in rugged terrain and there are stark temperature contrasts between pole‐facing and equator‐facing slopes, PSI Senior Scientist Norbert Schorghofer and his colleagues developed a numerical model that can calculate surface temperatures at very high spatial resolution. This makes it possible, for the first time, to model temperatures of topographic domains consisting of millions of pixels and at far higher spatial resolution than available from any Mars-orbiting spacecraft.
This model follows shadows, temperatures, and frost accumulation as the sun moves through the Martian sky day after day and year after year. This capability opens up many types of studies, including the one published by Schorghofer about the amount of frost that forms in alcoves and craters where RSL are found.
It turns out RSL are unrelated CO2 frost, subsurface water ice, or seasonal water frost. The first two of these results were clear from earlier work, but the relation to seasonal water frost, or lack thereof, demonstrates that melting of seasonal frost is not a plausible source for RSL, and hence these are likely dry features.
The article is in press in the Journal of Geophysical Research, https://doi.org/10.1029/2019JE006083
