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.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

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.

Data availability

The authors declare that the data supporting the findings of this study are available within the article and its Supplementary Information.


  1. 1.

    McEwen, A. S. et al. Seasonal flows on warm Martian slopes. Science 333, 740–743 (2011).

    Article  Google Scholar 

  2. 2.

    McEwen, A. S. et al. Recurring slope lineae in equatorial regions of Mars. Nat. Geosci. 7, 53–58 (2014).

    Article  Google Scholar 

  3. 3.

    Ojha, L. et al. Spectral evidence for hydrated salts in recurring slope lineae on Mars. Nat. Geosci. 8, 829–832 (2015).

    Article  Google Scholar 

  4. 4.

    Martinez, G. M. & Renno, N. O. Water and brines on Mars: current evidence and implications for MSL. Space Sci. Rev. 175, 29–51 (2013).

    Article  Google Scholar 

  5. 5.

    Chevrier, V. F. & Rivera-Valentin, E. G. Formation of recurring slope lineae by liquid brines on present-day Mars. Geophys. Res. Lett. 39, L21202 (2012).

    Article  Google Scholar 

  6. 6.

    Stillman, D. E., Michaels, T. I., Grimm, R. E. & Hanley, J. Observations and modeling of northern mid-latitude recurring slope lineae (RSL) suggest recharge by a present-day Martian briny aquifer. Icarus 265, 125–138 (2016).

    Article  Google Scholar 

  7. 7.

    Heinz, J., Schulze‐Makuch, D. & Kounaves, S. P. Deliquescence‐induced wetting and RSL‐like darkening of a Mars analogue soil containing various perchlorate and chloride salts. Geophys. Res. Lett. 43, 4880–4884 (2016).

    Article  Google Scholar 

  8. 8.

    Massé, M. et al. Transport processes induced by metastable boiling water under Martian surface conditions. Nat. Geosci. 9, 425–428 (2016).

    Article  Google Scholar 

  9. 9.

    Schmidt, F., Andrieu, F., Costard, F., Kocifaj, M. & Meresescu, A. G. Formation of recurring slope lineae on Mars by rarefied gas-triggered granular flows. Nat. Geosci. 10, 270–273 (2017).

    Article  Google Scholar 

  10. 10.

    Heldmann, J. L. & Mellon, M. T. Observations of Martian gullies and constraints on potential formation mechanisms. Icarus 168, 285–304 (2004).

    Article  Google Scholar 

  11. 11.

    Heldmann, J. L. et al. Formation of Martian gullies by the action of liquid water flowing under current Martian environmental conditions. J. Geophys. Res. 110, E05004 (2005).

    Article  Google Scholar 

  12. 12.

    Stillman, D. E., Michaels, T. I. & Grimm, R. E. Characteristics of the numerous and widespread recurring slope lineae (RSL) in Valles Marineris, Mars. Icarus 285, 195–210 (2017).

    Article  Google Scholar 

  13. 13.

    Farrell, W. M. et al. Is the Martian water table hidden from radar view? Geophys. Res. Lett. 36, L15206 (2009).

    Article  Google Scholar 

  14. 14.

    Nunes, D. C. et al. Examination of gully sites on Mars with the shallow radar. J. Geophys. Res. 115, E10004 (2010).

    Article  Google Scholar 

  15. 15.

    Heggy, E. et al. On water detection in the martian subsurface using sounding radar. Icarus 154, 244–257 (2001).

    Article  Google Scholar 

  16. 16.

    Heggy, E. et al. Ground penetrating radar sounding in mafic lava flows: Assessing attenuation and scattering losses in Mars analog volcanic terrains. J. Geophys. Res. 111, E06S04 (2006).

    Google Scholar 

  17. 17.

    Orosei, R. et al. Radar evidence of subglacial liquid water on Mars. Science 361, 490–493 (2018).

    Google Scholar 

  18. 18.

    Kumar, P. S. & Kring, D. A. Impact fracturing and structural modification of sedimentary rocks at Meteor Crater, Arizona. J. Geophys. Res. 113, E09009 (2008).

    Google Scholar 

  19. 19.

    Kumar, P. S., Head, J. W. & Kring, D. A. Erosional modification and gully formation at Meteor Crater, Arizona: insights into crater degradation processes on Mars. Icarus 208, 608–620 (2010).

    Article  Google Scholar 

  20. 20.

    Singhal, B. B. S. & Gupta, R. P. in Applied Hydrogeology of Fractured Rocks (Springer Science & Business Media, 2010).

  21. 21.

    Andrews‐Hanna, J. C., Zuber, M. T. & Hauck, S. A. Strike‐slip faults on Mars: observations and implications for global tectonics and geodynamics. J. Geophys. Res. 113, E08002 (2008).

    Article  Google Scholar 

  22. 22.

    Montgomery, D. R. et al. Continental-scale salt tectonics on Mars and the origin of Valles Marineris and associated outflow channels. Geol. Soc. Am. Bull. 121, 117–133 (2009).

    Google Scholar 

  23. 23.

    Treiman, A. H. Ancient groundwater flow in the Valles Marineris on Mars inferred from fault trace ridges. Nat. Geosci. 1, 181–183 (2008).

    Article  Google Scholar 

  24. 24.

    Montgomery, D. R. & Gillespie, A. Formation of Martian outflow channels by catastrophic dewatering of evaporite deposits. Geology 33, 625–628 (2005).

    Article  Google Scholar 

  25. 25.

    Marra, W. A., Braat, L., Baar, A. W. & Kleinhans, M. G. Valley formation by groundwater seepage, pressurized groundwater outbursts and crater-lake overflow in flume experiments with implications for Mars. Icarus 232, 97–117 (2014).

    Article  Google Scholar 

  26. 26.

    Osinski, G. R. & Lee, P. Intra‐crater sedimentary deposits at the Haughton impact structure, Devon Island, Canadian High Arctic. Meteorit. Planet. Sci. 40, 1887–1899 (2005).

    Article  Google Scholar 

  27. 27.

    Osinski, G. R. & Spray, J. G. Tectonics of complex crater formation as revealed by the Haughton impact structure, Devon Island, Canadian High Arctic. Meteorit. Planet. Sci. 40, 1813–1834 (2005).

    Article  Google Scholar 

  28. 28.

    Carr, M. H. Formation of Martian flood features by release of water from confined aquifers. J. Geophys. Res. 84, 2995–3007 (1979).

    Article  Google Scholar 

  29. 29.

    Gaidos, E. J. Cryovolcanism and the recent flow of liquid water on Mars. Icarus 153, 218–223 (2001).

    Article  Google Scholar 

  30. 30.

    Mellon, M. T. & Phillips, R. J. Recent gullies on Mars and the source of liquid water. J. Geophys. Res. 106, 23165–23179 (2001).

    Article  Google Scholar 

  31. 31.

    Hauber, E. et al. Asynchronous formation of Hesperian and Amazonian aged deltas on Mars and implications for climate. J. Geophys. Res. 118, 1529–1544 (2013).

    Article  Google Scholar 

  32. 32.

    Scheidegger, J. M., Bense, V. F. & Grasby, S. E. Transient nature of Arctic spring systems driven by subglacial meltwater. Geophys. Res. Lett. 39, L12405 (2012).

    Article  Google Scholar 

  33. 33.

    Pope, K. O., Rejmankova, E. & Paris, J. F. Spaceborne imaging radar-C (SIR-C) observations of groundwater discharge and wetlands associated with the Chicxulub impact crater, northwestern Yucatan Peninsula, Mexico. Geol. Soc. Am. Bull. 113, 403–416 (2001).

    Article  Google Scholar 

  34. 34.

    Komatsu, G. et al. Drainage systems of Lonar Crater, India: contributions to Lonar Lake hydrology and crater degradation. Planet. Space Sci. 95, 45–55 (2014).

    Article  Google Scholar 

  35. 35.

    Abotalib, A. Z., Sultan, M. & Elkadiri, R. Groundwater processes in Saharan Africa: implications for landscape evolution in arid environments. Earth Sci. Rev. 156, 108–136 (2016).

    Article  Google Scholar 

  36. 36.

    Andersen, D. T., Pollard, W. H., McKay, C. P. & Heldmann, J. Cold springs in permafrost on Earth and Mars. J. Geophys. Res. 107, 5015 (2002).

    Article  Google Scholar 

  37. 37.

    Forte, E., Dalle Fratte, M., Azzaro, M. & Guglielmin, M. Pressurized brines in continental Antarctica as a possible analogue of Mars. Sci. Rep. 6, 33158 (2016).

    Article  Google Scholar 

  38. 38.

    Goldspiel, J. M. & Squyres, S. W. Groundwater discharge and gully formation on martian slopes. Icarus 211, 238–258 (2011).

    Article  Google Scholar 

  39. 39.

    Stillman, D. E., Michaels, T. I., Grimm, R. E. & Harrison, K. P. New observations of Martian southern mid-latitude recurring slope lineae (RSL) imply formation by freshwater subsurface flows. Icarus 233, 328–341 (2014).

    Article  Google Scholar 

  40. 40.

    Chojnacki, M. et al. Geologic context of recurring slope lineae in Melas and Coprates Chasmata, Mars. J. Geophys. Res. 121, 1204–1231 (2016).

    Article  Google Scholar 

  41. 41.

    Kirk, R. L. et al. Ultrahigh resolution topographic mapping of Mars with MRO HiRISE stereo images: Meter scale slopes of candidate Phoenix landing sites. J. Geophys. Res. 113, E00A24 (2008).

    Article  Google Scholar 

  42. 42.

    Clifford, S. M. A model for the hydrologic and climatic behavior of water on Mars. J. Geophys. Res. 98, 10973–11016 (1993).

    Article  Google Scholar 

  43. 43.

    Clifford, S. M. et al. Depth of the Martian cryosphere: revised estimates and implications for the existence and detection of subpermafrost groundwater. J. Geophys. Res. 115, E07001 (2010).

    Article  Google Scholar 

  44. 44.

    Levy, J. Hydrological characteristics of recurrent slope lineae on Mars: evidence for liquid flow through regolith and comparisons with Antarctic terrestrial analogs. Icarus 219, 1–4 (2012).

    Article  Google Scholar 

  45. 45.

    Archer, D. G. & Carter, R. W. Thermodynamic properties of the NaCl H2O system. 4. Heat capacities of H2O and NaCl (aq) in cold-stable and supercooled states. J. Phys. Chem. B 104, 8563–8584 (2000).

    Article  Google Scholar 

Download references


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.

Corresponding author

Correspondence to Essam Heggy.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary information

Supplementary Figs 1 and 2

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Abotalib, A.Z., Heggy, E. A deep groundwater origin for recurring slope lineae on Mars. Nat. Geosci. 12, 235–241 (2019). https://doi.org/10.1038/s41561-019-0327-5

Download citation

Further reading


Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing