Seasonal flows on warm Martian slopes

Area of Science:

• Planetary Science
• Geology
• Astrobiology

Background:

• Ancient Mars is thought to have had surface water, but current liquid water presence is debated.
• Recurring slope lineae (RSL) are dark, narrow markings observed on Martian slopes.
• RSL exhibit seasonal changes, appearing and growing in warmer periods and fading in colder ones.

Purpose of the Study:

• To investigate the nature and potential causes of recurring slope lineae (RSL) on Mars.
• To determine if RSL activity is linked to the presence of transient liquid water or brines.
• To understand the seasonal behavior and formation mechanisms of RSL.

Main Methods:

• Analysis of repeat images from the Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE).
• Observation of RSL appearance, growth, and fading patterns over Martian seasons.
• Correlation of RSL activity with specific Martian latitudes, slope angles, and surface temperatures.

Main Results:

• RSL appear and lengthen during the late southern spring and summer in specific latitudes (48°S to 32°S).
• RSL activity favors equator-facing slopes experiencing peak surface temperatures between approximately 250 to 300 Kelvin.
• RSL are associated with bedrock outcrops and small channels, with hundreds forming in some locations.

Conclusions:

• The seasonal behavior of RSL is consistent with the presence of transient liquid brines near the Martian surface.
• The precise mechanism and origin of water involved in RSL formation remain undetermined.
• RSL represent a key phenomenon for understanding current water activity on Mars.