Recurrent Slope Linae on the Palikir Crater walls on Mars.
Credit: NASA/JPL/University of Arizona

New research suggests deep groundwater on Mars could still be active and creating surface streams in some near-equatorial areas on the planet.

Once again, scientists point to the planet’s recurring slope linea – RSL for short – that are akin to dried, short streams of water that appear on some crater walls.

NASA Mars Reconnaissance Orbiter’s HiRISE image of recurring slope lineae in Melas Chasma, Valles Marineris. Arrows point out tops and bottoms of a few lineae.
Credit: NASA/JPL-Caltech/University of Arizona

The new work suggests that the source of RSL could be natural discharge along geological structures from briny aquifers within the Red Planet’s cryosphere.

University of Southern California (USC) research scientist, Essam Heggy and co-author Abotalib Z. Abotalib, a postdoctoral research associate at USC, studied the characteristics of the planet’s RSL. Their research findings are presented in the journal Nature Geoscience.

“We suggest that deep groundwater occasionally surfaces on Mars in present-day conditions,” the scientists note in their paper.

Alternative hypothesis

Previously, scientists put forward the idea that these features were affiliated with surface water flow or close subsurface water flow, said Heggy, who added that the new research suggests that may not be true.

“We propose an alternative hypothesis that they originate from a deep pressurized groundwater source which comes to the surface moving upward along ground cracks,” Heggy explains in a USC press statement.

Features called recurrent slope lineae (RSL) have been spotted on some Martian slopes in warmer months. Some scientists think RSL could be seasonal flows of salty water. Red arrows point out one 0.75-mile-long (2 kilometers) RSL in this image taken by NASA’s Mars Reconnaissance Orbiter.
Credit: NASA/JPL-Caltech/Univ. of Arizona

Desert hydrology

Abotalib, the paper’s first author, noted that their research in desert hydrology helped lead to this conclusion.

“We have seen the same mechanisms in the North African Sahara and in the Arabian Peninsula, and it helped us explore the same mechanism on Mars,” Abotalib explains.

The two scientists concluded that fractures within some of Mars’ craters enabled water springs to rise up to the surface as a result of pressure deep below. These springs leaked onto the surface, generating the sharp and distinct linear features found on the walls of those craters.

Wanted: deep-probing

The new study suggests that the groundwater that is the source of these water flows could be at depths starting at 2, 460 feet (750 meters) deep.

Heggy adds that such depth requires consideration of more deep-probing techniques to look for the source of this groundwater versus looking for shallow sources of water.

The paper — A deep groundwater origin for recurring slope linea on Mars — is the first Mars paper by the newly created water research center at USC. The work is funded under the NASA Planetary Geology and Geophysics Program and is available here:

https://www.nature.com/articles/s41561-019-0327-5

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