A previous image, ESP_025954_1835 showed some striking dark downslope flows. Since this is a dark, low-dust setting, these are probably not slope streaks (which form in bright dusty areas).
This image can provide us with another look, particularly in order to detect any changes. Recurring slope lineae (RSL) are another type of dark streak seen on Martian slopes and are thought to form from flow of liquid water. Do these streaks behave like RSL? Additional images such as this one allow us to test whether these streaks grow seasonally and recur annually.
Written by: HiRISE Science Team (audio: Tre Gibbs) (22 April 2015)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_039655_1835
Image: NASA/JPL/University of Arizona