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An Aeolian Grainflow Model for Martian Recurring Slope Lineae.

ABSTRACT: Recurring Slope Lineae (RSL) on Mars have been enigmatic since their discovery; their behavior resembles a seeping liquid but sources of water remain puzzling. This work demonstrates that the properties of RSL are consistent with observed behaviors of Martian and terrestrial aeolian processes. Specifically, RSL are well-explained as flows of sand that remove a thin coating of dust. Observed RSL properties are supportive of or consistent with this model, which requires no liquid water or other exotic processes, but rather indicates seasonal aeolian behavior. These settings and behaviors resemble features observed by rovers and also explain the occurrence of many slope lineae on Mars that do not meet the strict definition of RSL. This indicates that RSL can be explained simply as aeolian features. Other processes may add complexities just as they could modify the behavior of any sand dune.

SUBMITTER: Dundas CM

PROVIDER: S-EPMC8243843 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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An Aeolian Grainflow Model for Martian Recurring Slope Lineae.

Dundas Colin M CM

Icarus 20200203

Recurring Slope Lineae (RSL) on Mars have been enigmatic since their discovery; their behavior resembles a seeping liquid but sources of water remain puzzling. This work demonstrates that the properties of RSL are consistent with observed behaviors of Martian and terrestrial aeolian processes. Specifically, RSL are well-explained as flows of sand that remove a thin coating of dust. Observed RSL properties are supportive of or consistent with this model, which requires no liquid water or other ex ...[more]

PMID: 34211190

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Project description:Several interpretations of recurring slope lineae (RSL) have related RSL to the potential presence of transient liquid water on Mars. Such probable signs of liquid water have implications for Mars exploration in terms of rover safety, planetary protection during rover operations, and the current habitability of the planet. Mawrth Vallis has always been a prime target to be considered for Mars rover missions due to its rich mineralogy. Most recently, Mawrth Vallis was one of the two final candidates selected by the European Space Agency as a landing site for the ExoMars 2020 mission. Therefore, all surface features and landforms in Mawrth Vallis that may be of special interest in terms of scientific goals, rover safety, and operations must be scrutinised to better assess it for future Mars missions. Here, we report on the initial detection of RSL candidates in two craters of Mawrth Vallis. The new sightings were made outside of established RSL regions and further prompt the inclusion of a new geographical region within the RSL candidate group. Our inferences on the RSL candidates are based on several morphological and geophysical evidences and analogies: (i) the dimensions of the RSL candidates are consistent with confirmed mid-latitude RSL; (ii) albedo and thermal inertia values are comparable to those of other mid-latitude RSL sites; and (iii) features are found in a summer season image and on the steep and warmest slopes. These results denote the plausible presence of transient liquid brines close to the previously proposed landing ellipse of the ExoMars rover, rendering this site particularly relevant to the search of life. Further investigations of Mawrth Vallis carried out at higher spatial and temporal resolutions are needed to identify more of such features at local scales to maximize the scientific return from the future Mars rovers, to prevent probable biological contamination during rover operations, to evade damage to rover components as brines can be highly corrosive, and to quantify the ability of the regolith at mid-latitudes to capture atmospheric water which is relevant for in-situ-resource utilization.

Project description:Asian dust comprises a large portion of the northern hemisphere atmospheric dust load, thereby exerting substantial influence on the Earth's climate, global biogeochemistry and hydrological cycle through accelerated snow and ice melt. Dust deposited on alpine glaciers encodes information on broad scale atmospheric-environmental processes. The (234U/238U) values of dust fine particulates can reflect the comminuting time and intermediate processes; thus, it provides a new method for the provenance of aeolian dust in the glacial snowpack/cryoconite. Here we present results from a comprehensive survey of uranium isotopic concentrations in dust collected from cryoconites on the glaciers of the northern Tibetan Plateau (TP). These results indicate significant spatial heterogeneity in the (234U/238U) values associated with snowpack/cryoconite dust over a broad range of glaciers in the northern TP. The values of the (234U/238U) ratio in the glaciers of western Qilian Mountains (Qiyi Glacier, Shiyi Glacier, Laohugou Glacier No.12) were the highest, followed by the Tanggula (Dunkemadi Glacier) and Kunlun Mountains (Yuzhufeng Glacier), whereas these values were the lowest in the eastern Qilian Mountains (Jingyangling Snowpack, Dabanshan Snowpack, Lenglongling Glacier). By including the analysis of Sr-Nd isotopic compositions, we find the spatial isotopic distribution reflects a combination of local dust, which is associated with short comminuting times, and dust transported over long ranges. Meteorological data indicate that the dust production in the west and north TP, Alxa arid lands and Gobi Deserts, may have a significant impact on the TP glaciers. Moreover, U-Sr-Nd isotopic composition and end-member mixing models (EMMA) were used in our study to find out the relative contribution of distinct Asian dust sources to the dust budget in the TP glaciers. The results reveal that snowpack/cryoconite dust is derived from both local sources (low comminution signatures) as well as other dust sources in the Asian region. Our study demonstrates the potential of U isotope composition as a dust tracing method. In particular, by investigating this composition on dust collected from glacier snowpack and cryoconite holes, we arrive at a map of the distribution characteristics of (234U/238U) values in different regions of the TP. Our study is the first to deploy uranium comminution age for Tibetan dust source tracing, and the results are important to elucidate the multiple origins and dynamics of dust in the Tibetan Plateau.

Dataset Information

An Aeolian Grainflow Model for Martian Recurring Slope Lineae.

Publications

An Aeolian Grainflow Model for Martian Recurring Slope Lineae.

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