On Mars, seasonal features known as recurring slope lineae (RSL) are prevalent on Sun-facing slopes. Previous studies have suggested RSL are related to chlorine salts and noted their occurrence in regions of high sulfate outcrops. New laboratory experiments demonstrate that interactions of sulfates and chlorine salts in fine-grained soils on the Red Planet could absorb water, expand, deliquesce, cause subsidence, form crusts, disrupt surfaces, and...
