The water content of recurring slope lineae on Mars
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Abstract
Observations of recurring slope lineae (RSL) from the High-Resolution Imaging Science Experiment have been interpreted as present-day, seasonally variable liquid water flows; however, orbital spectroscopy has not confirmed the presence of liquid H2O, only hydrated salts. Thermal Emission Imaging System (THEMIS) temperature data and a numerical heat transfer model definitively constrain the amount of water associated with RSL. Surface temperature differences between RSL-bearing and dry RSL-free terrains are consistent with no water associated with RSL and, based on measurement uncertainties, limit the water content of RSL to at most 0.5–3 wt %. In addition, distinct high thermal inertia regolith signatures expected with crust-forming evaporitic salt deposits from cyclical briny water flows are not observed, indicating low water salinity (if any) and/or low enough volumes to prevent their formation. Alternatively, observed salts may be preexisting in soils at low abundances (i.e., near or below detection limits) and largely immobile. These RSL-rich surfaces experience ~100 K diurnal temperature oscillations, possible freeze/thaw cycles and/or complete evaporation on time scales that challenge their habitability potential. The unique surface temperature measurements provided by THEMIS are consistent with a dry RSL hypothesis or at least significantly limit the water content of Martian RSL.
Publication type | Article |
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Publication Subtype | Journal Article |
Title | The water content of recurring slope lineae on Mars |
Series title | Geophysical Research Letters |
DOI | 10.1002/2016GL070179 |
Volume | 43 |
Issue | 17 |
Year Published | 2016 |
Language | English |
Publisher | AGU Publications |
Contributing office(s) | Astrogeology Science Center |
Description | 8 p. |
First page | 8912 |
Last page | 8919 |
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