JPL: Recurring Martian Streaks: Flowing Sand, Not Water?

[bystander]

Recurring Martian Streaks: Flowing Sand, Not Water?
NASA | JPL-Caltech | MRO | 2017 Nov 20

[img3="Credit: NASA/JPL-Caltech/UA/USGS"]https://www.jpl.nasa.gov/spaceimages/im ... _hires.jpg[/img3][hr][/hr]

Dark features on Mars previously considered evidence for subsurface flowing of water are interpreted by new research as granular flows, where grains of sand and dust slip downhill to make dark streaks, rather than the ground being darkened by seeping water.

Continuing examination of these still-perplexing seasonal dark streaks with a powerful camera on NASA's Mars Reconnaissance Orbiter (MRO) shows they exist only on slopes steep enough for dry grains to descend the way they do on faces of active dunes.

The findings published today in Nature Geoscience argue against the presence of enough liquid water for microbial life to thrive at these sites. However, exactly how these numerous flows begin and gradually grow has not yet been explained. Authors of the report propose possibilities that include involvement of small amounts of water, indicated by detection of hydrated salts observed at some of the flow sites.

These features have evoked fascination and controversy since their 2011 discovery, as possible markers for unexpected liquid water or brine on an otherwise dry planet. They are dark streaks that extend gradually downhill in warm seasons, then fade away in winter and reappear the next year. On Earth, only seeping water is known to have these behaviors, but how they form in the dry Martian environment remains unclear. ...

Previous Evidence of Water on Mars Now Identified as Grainflows
U.S. Geological Survey | 2017 Nov 20

Flowing Sand, Not Water, Source of Recurring Dark Martian Surface Streaks
Planetary Science Institute | 2017 Nov 20

Granular Flows at Recurring Slope Lineae on Mars Indicate a Limited Role for Liquid Water - Colin M. Dundas et al

• Nature Geoscience (online 20 Nov 2017) DOI: 10.1038/s41561-017-0012-5

http://asterisk.apod.com/viewtopic.php?t=36284
http://asterisk.apod.com/viewtopic.php?t=35217
http://asterisk.apod.com/viewtopic.php?t=24723

[neufer]

[b][color=#0000FF][size=150]Mt fuji bonseki sandpainting[/size] [/color][/b]

---

<<Sandpainting is the art of pouring coloured sands, and powdered pigments from minerals or crystals, or pigments from other natural or synthetic sources onto a surface to make a sand painting. Unfixed sand paintings or drypaintings have a long established cultural history in numerous social groupings around the globe, and are often temporary, ritual paintings prepared for religious or healing ceremonies. Drypainting is practised by Native Americans in the Southwestern United States, by Tibetan & Buddhist monks, as well as Australian Aborigines, and also by Latin Americans on certain Christian holy days. The construction process of Tibetan Buddhist sand paintings takes several days, and the mandala is destroyed shortly after its completion. This is done as a teaching tool and metaphor for the "impermanence" of all contingent and compounded phenomena.>>