Recurring slope lineae (RSL) are dark linear flows that tend to form on warm and steep slopes on Mars. The RSL in this image are located in the central peak region of Hale Crater. (The central peak is the uplifted region of bedrock resulting from crater formation processes.)

Because Hale Crater contains some of the most active and longest RSL on the planet, the HiRISE team monitors this site to try to better understand the formation of these features. RSL are a yearly occurrence when the weather warms from spring to summer forming dozens to hundreds of dark linear flow-like features (see this image for context).

Recurring slope lineae begin to fade when the weather cools only to start up again the following year. Whether RSL are completely dry flows that are driven by gravitational forces or if they require small quantities of brine activity to disrupt the surface materials and initiate flow is still not understood.

Written by: Ginny Gulick  (21 April 2021)