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A deep groundwater origin for recurring slope lineae on Mars


The recurring slope lineae on Mars have been hypothesized to originate from snow melting, deliquescence, dry flow or shallow groundwater. Except for the dry flow origin, these hypotheses imply the presence of surficial or near-surface volatiles, placing the exploration and characterization of potential habitable environments within the reach of existing technology. Here we present observations from the High Resolution Imaging Science Experiment, heat-flow modelling and terrestrial analogues, which indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers within the cryosphere, at depths of approximately 750 m. Spatial correlation between recurring slope lineae source regions and multi-scale fractures (such as joints and faults) in the southern mid-latitudes and in Valles Marineris suggests that recurring slope lineae preferably emanate from tectonic and impact-related fractures. We suggest that deep groundwater occasionally surfaces on Mars in present-day conditions.

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The authors are grateful to M. Sultan from Western Michigan University, R. Elkadiri from Middle Tennessee State University, H. El Safty from USC and Y. Gim from JPL for the discussions that helped to generate this manuscript. The first author is a postdoctoral research associate currently funded by the University of Southern California under the NASA Planetary Geology and Geophysics award NNX15AV76G awarded to the principal investigator E.H.

Author information

A.Z.A. and E.H. designed the project, A.Z.A. performed the measurements, and A.Z.A. and E.H. wrote the manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to Essam Heggy.

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Fig. 1: RSL locations along fractured crater walls in the southern mid-latitudes of Mars.
Fig. 2: RSL occurrences in VM.
Fig. 3: Fault control on RSL emergence in Palikir Crater.
Fig. 4: Correlation between faults and RSL.
Fig. 5: The control of seasonal melting and freezing of the shallow subsurface on RSL activity.
Fig. 6: Modelled outflow temperatures of groundwater discharge along the surface of Palikir Crater fractured walls.