Document Type

Article

Publication Date

2022

DOI

10.3389/fspas.2021.797591

Publication Title

Frontiers in Astronomy and Space Sciences

Volume

8

Pages

797591 (1-19)

Abstract

Salar de Pajonales, a Ca-sulfate salt flat in the Chilean High Andes, showcases the type of polyextreme environment recognized as one of the best terrestrial analogs for early Mars because of its aridity, high solar irradiance, salinity, and oxidation. The surface of the salar represents a natural climate-transition experiment where contemporary lagoons transition into infrequently inundated areas, salt crusts, and lastly dry exposed paleoterraces. These surface features represent different evolutionary stages in the transition from previously wetter climatic conditions to much drier conditions today. These same stages closely mirror the climate transition on Mars from a wetter early Noachian to the Noachian/Hesperian. Salar de Pajonales thus provides a unique window into what the last near-surface oases for microbial life on Mars could have been like in hypersaline environments as the climate changed and water disappeared from the surface. Here we open that climatological window by evaluating the narrative recorded in the salar surface morphology and microenvironments and extrapolating to similar paleosettings on Mars. Our observations suggest a strong inter-dependence between small and large scale features that we interpret to be controlled by extrabasinal changes in environmental conditions, such as precipitation-evaporation-balance changes and thermal cycles, and most importantly, by internal processes, such as hydration/dehydration, efflorescence/deliquescence, and recrystallization brought about by physical and chemical processes related to changes in groundwater recharge and volcanic processes. Surface structures and textures record a history of hydrological changes that impact the mineralogy and volume of Ca-sulfate layers comprising most of the salar surface. Similar surface features on Mars, interpreted as products of freeze-thaw cycles, could, instead, be products of water-driven, volume changes in salt deposits. On Mars, surface manifestations of such salt-related processes would point to potential water sources. Because hygroscopic salts have been invoked as sources of localized, transient water sufficient to support terrestrial life, such structures might be good targets for biosignature exploration on Mars.

Rights

© 2022 Hinman, Hofmann, Warren-Rhodes, Phillips, Noffke, Cabrol, Chong Diaz, Demergasso, Tebes-Cayo, Cabestrero, Bishop, Gulick, Summers, Sobron, McInenly, Moersch, Rodriguez, Sarazzin, Rhodes, Riffo Contreras, Wettergreen and Parro.

This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Data Availability

Article states: "The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author."

"The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fspas.2021.797591/full#supplementary-material"

Corresponding author: Nancy W. Hinman

Original Publication Citation

Hinman, N. W., Hofmann, M. H., Warren-Rhodes, K., ... Riffo Contreras, C. J., Wettergreen, D., & Parro, V. (2022). Surface morphologies in a Mars-analog Ca-sulfate Salar, High Andes, northern Chile. Frontiers in Astronomy and Space Sciences, 8, 1-19, Article 797591. https://doi.org/10.3389/fspas.2021.797591

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