Article

Abstract

• Although previous studies have shown that the near-surface environmental conditions on Mars may permit salt deliquescence and therefore brine production, there is significant uncertainty in the kinetics of the process. Indeed, experimental studies have shown that deliquescence is either very rapid or too slow to be relevant to Mars. To resolve this uncertainty, we performed laboratory experiments to investigate the growth rate of Mars-relevant calcium perchlorate brines over a range of temperatures (184–273 K) and water vapor pressures (0.2–220 Pa). We show that the brine growth is faster at higher water vapor pressures and lower temperatures and for smaller particles. From our data, we determined a temperature-dependent net uptake coefficient for gas phase water molecules colliding with a perchlorate brine surface in the range of 3.8 × 10⁻⁴ at 185 K to 4.2 × 10⁻⁶ at 273 K. These values suggest that deliquescence on Mars is likely to be slow even when conditions thermodynamically permit a brine to form. We find that along the Curiosity rover traverse at Gale Crater, the near-surface conditions would only allow particles <1 μm to fully deliquesce over a typical sol. At the higher-latitude Phoenix landing site, deliquescence may be 30% faster due to the higher water vapor pressures, but still, only micron-scale salt grains or coatings would be expected to deliquesce during a typical sol. These results suggest that brines formed via deliquescence on the surface of Mars are likely only present on small scales that may not be readily detected using conductivity or imaging techniques.

   

Creator

• Tolbert, Margaret A
• Rivera-Valentín, Edgard G
• Primm, Katherine M
• Nuding, Danielle L
• Gough, Raina V
• Martínez, Germán M

Date Issued

• 2023

Additional Information

• Publication was funded by the University of Colorado Boulder Libraries Open Access Fund.

Academic Affiliation

• Cooperative Institute for Research in Environmental Sciences

Journal Title

• The Planetary Science Journal

Journal Issue/Number

• 3

Journal Volume

• 4

Last Modified

• 2023-04-10

Resource Type

• Article

Rights Statement

• In Copyright

DOI

•  https://doi.org/10.3847/PSJ/acbd98

ISSN

• 2632-3338

Language

• English [eng]

License

• Creative Commons BY Attribution 4.0 International

Relationships

In Collection:

• University Libraries Open Access Fund Supported Publications

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