One of the Red Planet’s mysteries is what exactly causes the landslides that can be seen in orbital images that create dark streaks on the planet’s surface. A team of researchers led by SETI Institute Senior Research Scientist Janice Bishop has a new theory about what causes landslides on the surface of Mars. A past theory suggested that liquid debris flows or dry granular flows caused that movement.
However, neither of those models can completely account for seasonal marginal flow features known as Recurring Slope Lineae (RSL). The research group has an alternative hypothesis that suggests small-scale ice melting in the near-surface regolith is causing changes at the surface, making it vulnerable to dust storms and wind. As a result, RSL features appear to form or expand on the surface of Mars today.
The team also believes that thin layers of melting ice result from interactions between underground water ice, chlorine salts, and sulfates to create an unstable liquid-like flowing slush. According to the theory, that flowing slush causes sinkholes, ground collapse, surface flows, and upheave.
Bishop is excited about the prospect of microscale liquid water in the near-surface environment of Mars. Bishop believes this could revolutionize the perspective on active chemistry below the surface of Mars. Past studies suggested RSL are related to chlorine salts and noted their occurrence in regions of high sulfate outcrops. The current study extends those observations with near-surface cryosalt activity based on field observations and laboratory experiments.
The researchers are clear that the precise mechanism of RSL formation on Mars is still a mystery. The team tested their theory using lab experiments to observe what would occur if they froze and thawed Mars analog samples comprised of chlorine salts and sulfates at low temperatures similar to those found on Mars. The result was a slushy ice formation near -50 degrees Celsius followed by the gradual melting of ice from -40 to -20 degrees Celsius.