Analysis of polygonal cracking patterns in chloride-bearing terrains on Mars: Indicators of ancient playa settings

Elmaarry, Mohamed Ramy; Pommerol, Antoine; Thomas, Nicolas (2013). Analysis of polygonal cracking patterns in chloride-bearing terrains on Mars: Indicators of ancient playa settings. Journal of Geophysical Research: Planets, 118(11), pp. 2263-2278. Wiley 10.1002/2013JE004463

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The ancient southern highlands on Mars (~3.5 Gyr old) contain > 600 regions that display spectral evidence in the infrared for the presence of chloride-bearing materials. Many of these locations were previously reported to display polygonal cracking patterns. We studied more than 80 of the chloride-bearing terrains using high-resolution (0.25-0.5 m/pixel) images, as well as near-infrared spectral data, to characterize the surface textures and the associated cracking patterns and mineralogies. Our study indicates that ~75% of the studied locations display polygonal cracks that resemble desiccation cracks, while some resemble salt expansion/thrust polygons. Furthermore, we detect, spectrally, the presence of smectites in association with ~30% of the studied fractured terrains. We note that smectites are a special class of swelling clay minerals that can induce formation of large desiccation cracks. As such, we suggest that the cracking patterns are indicative of the presence of smectite phyllosilicates even in the absence of spectral confirmation. Our results suggest that many chloride-bearing terrains have a lacustrine origin and a geologic setting similar to playas on Earth. Such locations would have contained ephemeral lakes that may have undergone repeated cycles of desiccation and recharging by a near-surface fluctuating water table in order to account for the salt-phyllosilicates associations. These results have notable implications for the ancient hydrology of Mars. We propose that the morphologies and sizes of the polygonal cracks can be used as paleoenvironmental, as well as lithological, indicators that could be helpful in planning future missions.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Elmaarry, Mohamed Ramy; Pommerol, Antoine and Thomas, Nicolas

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics

ISSN:

2169-9097

Publisher:

Wiley

Language:

English

Submitter:

Cléa Serpollier

Date Deposited:

13 Aug 2014 11:44

Last Modified:

13 Dec 2014 12:29

Publisher DOI:

10.1002/2013JE004463

BORIS DOI:

10.7892/boris.45629

URI:

https://boris.unibe.ch/id/eprint/45629

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