Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water. Issue 12 (December 2017)

• Record Type: Journal Article
• Authors: Dundas, Colin; McEwen, Alfred; Chojnacki, Matthew; Milazzo, Moses; Byrne, Shane; McElwaine, Jim; Urso, Anna
• Is Part Of: Nature geoscience. Volume 10:Issue 12(2017)
• Page Start: 903
• Page End: 907
• Publication Date: 2017-12
• Subjects: Earth sciences -- Periodicals; 551
• DOI: 10.1038/s41561-017-0012-5
• Languages: English
• ISSNs: 1752-0894

Abstract

Abstract Recent liquid water flow on Mars has been proposed based on geomorphological features, such as gullies. Recurring slope lineae — seasonal flows that are darker than their surroundings — are candidate locations for seeping liquid water on Mars today, but their formation mechanism remains unclear. Topographical analysis shows that the terminal slopes of recurring slope lineae match the stopping angle for granular flows of cohesionless sand in active Martian aeolian dunes. In Eos Chasma, linea lengths vary widely and are longer where there are more extensive angle-of-repose slopes, inconsistent with models for water sources. These observations suggest that recurring slope lineae are granular flows. The preference for warm seasons and the detection of hydrated salts are consistent with some role for water in their initiation. However, liquid water volumes may be small or zero, alleviating planetary protection concerns about habitable environments. Recurring slope lineae are likely to be dry granular flows with little-to-no requirement for large volumes of liquid water on Mars, according to an emerging view that is supported by topographic analyses.