This is an odd-looking image . It shows gullies during the winter while entirely in the shadow of the crater wall. Illumination comes only from the winter skylight.
We acquire such images because gullies on Mars actively form in the winter when there is carbon dioxide frost on the ground, so we image them in the winter, even though not well illuminated, to look for signs of activity. The dark streaks might be signs of current activity, removing the frost, but further analysis is needed.
NB: North is down in the cutout, and the terrain slopes towards the bottom of the image.
Written by: Alfred McEwen (audio: Tre Gibbs) (21 March 2017)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_049058_2360
Image: NASA/JPL/University of Arizona