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In Situ Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions

Raack, Jan; Reiss, Dennis; Balme, Matthew R.; Taj-Eddine, Kamal and Ori, Gian Gabriele (2017). In Situ Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions. Astrobiology (Ahead of print).

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DOI (Digital Object Identifier) Link: https://doi.org/10.1089/ast.2016.1544
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Abstract

During a field campaign in the Sahara Desert in southern Morocco, spring 2012, we sampled the vertical grain size distribution of two active dust devils that exhibited different dimensions and intensities. With these in situ samples of grains in the vortices, it was possible to derive detailed vertical grain size distributions and measurements of the lifted relative particle load. Measurements of the two dust devils show that the majority of all lifted particles were only lifted within the first meter (~46.5% and ~61% of all particles; ~76.5 wt % and ~89 wt % of the relative particle load). Furthermore, ~69% and ~82% of all lifted sand grains occurred in the first meter of the dust devils, indicating the occurrence of ‘‘sand skirts.’’ Both sampled dust devils were relatively small (~15m and ~4–5m in diameter) compared to dust devils in surrounding regions; nevertheless, measurements show that ~58.5% to 73.5% of all lifted particles were small enough to go into suspension (<31 mm, depending on the used grain size classification). This relatively high amount represents only ~0.05 to 0.15 wt % of the lifted particle load. Larger dust devils probably entrain larger amounts of fine-grained material into the atmosphere, which can have an influence on the climate. Furthermore, our results indicate that the composition of the surface, on which the dust devils evolved, also had an influence on the particle load composition of the dust devil vortices. The internal particle load structure of both sampled dust devils was comparable related to their vertical grain size distribution and relative particle load, although both dust devils differed in their dimensions and intensities. A general trend of decreasing grain sizes with height was also detected.

Item Type: Journal Item
Copyright Holders: 2017 The Authors
ISSN: 1557-8070
Project Funding Details:
Funded Project NameProject IDFunding Body
Horizon 2020 Marie Skłodowska-Curie Individual FellowshipH2020-MSCA-IF-2014-657452H2020-MSCA-IF-2014-657452
UK Science and Technology Facilities CouncilST/L000776/1ST/L000776/1
EuroplanetTNA039TNA039
Keywords: Mars; dust devils; planetary science; desert soils; atmosphere; grain sizes
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Related URLs:
Item ID: 49240
Depositing User: Jan Raack
Date Deposited: 20 Apr 2017 14:11
Last Modified: 20 Jun 2017 08:25
URI: http://oro.open.ac.uk/id/eprint/49240
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