Recurring Slope Lineae (RSL)
McEwen et al. have identified a set of darkish streaks which appear every late spring on southern hemisphere slopes. They are reproducible and often leave behind a brighter deposit. There are called Recurring Slope Lineae (RSL) and may be related to liquid water.
Although we are co-authors on the paper here, our main contribution is studying the photometric effects of traces of water on Martian simulants. The darkening of sand and dust samples when wet is common knowledge but there are other subtle effects that occur when the sample is dried out again. We are investigating some of these slightly esoteric issues with our goniometer set-up.
McEwen, A.S., C.M. Dundas, S. S. Mattson, A.D. Toigo, L. Ojha, J.J. Wray, M. Chojnacki, S. Byrne, S.L. Murchie, and N. Thomas, (2013), Recurring Slope Lineae in Valles Marineris, Mars, Nature Geoscience 7, 53-58.
Pommerol, A., N. Thomas, B. Jost, P. Beck, C. Okubo, and A.S. McEwen, (2013) Photometric properties of Mars soils analogs, J. Geophys. Res. 118, 2045-2072.
McEwen, A.S., L. Ojha, C.M. Dundas, S.S. Mattson, S. Byrne, J.J. Wray, S.C. Cull, S.L. Murchie, N. Thomas, and V.C. Gulick, (2011), Seasonal Flows on Warm Martian Slopes, Science, Science, 333, 740.
Gunderson, K., B.S. Lüthi, P. Russell, and N. Thomas, (2007) Visible/NIR photometric signatures of liquid water in Martian regolith simulant, Planetary and Space Science, 55, 1272-1282.