  Seasonal flows on warm slopes, or recurring slope lineae ("RSL"), have been
presented as strong evidence for currently flowing water on Mars. This
assumption was supported by a correlation between activity and warm
temperatures, and by the spectral identification of hydrated salts. Here we
first demonstrate that salts spectral identification is not robust, and that
flow activity occurs on a wider range of seasons and slope orientations than
previously thought, ruling out liquid water as a probable contributor. We then
show that morphology, location and timing of flow activity is fully consistent
with the removal and deposition of bright dust above darker underlying surfaces
occurring notably in relation with seasonal dust storm activity. Mars recurring
slope lineae are thus consistent with dust movements typical of present-day dry
planet Mars.
