Timing of acid weathering on Mars

A kinetic-thermodynamic assessment

Mikhail Zolotov, Mikhail V. Mironenko

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

Weathering of olivine basalt by H2SO4-HCl aqueous solutions at the conditions of early Mars was investigated through numerical modeling in a system open with respect to CO2 and O2 only. The model includes dissolution rates of primary and secondary minerals and oxidation rate of aqueous Fe2+, as well as chemical equilibration among solutes, dissolved gases, and precipitates. The results reveal fast dissolution of Fe-Mg minerals at low pH, followed by preferential dissolution of plagioclase at higher pH. Correspondingly, solutions evolve from acidic, Mg-Ca-Fe2+-Fe3+-Al3+ compositions toward Na-rich alkaline fluids. The period over which neutralization and mineral precipitation may occur is shorter at higher initial pH, lower water to rock ratios, and larger mineral surface areas. Early stages of weathering are characterized by the formation of amorphous silica, goethite, and kaolinite, while zeolites and carbonates form considerably later at higher pH, where silica dissolves. Slow oxidation of Fe2+ causes precipitation of ferrous phyllosilicates. Comparison with Martian observations indicate that amorphous silica, Fe3+ oxyhydroxides, and Mg-, Ca-, and Fe2+-sulfates could have formed during multiple short-term episodes of acid weathering that were terminated by freezing and/or evaporation. Throughout history, impact generation of oxidants (e.g., O2, SO3, NO2) caused formation of strong acids and incremental Fe2+ oxidation, the processes that are not efficient during O2-deficient periods of volcanic degassing. Although impact-generated acid rainfalls could have caused intense weathering and erosion in Noachian time, dilution of acids and a prolonged existence of surface solutions favored local neutralization of solution, and formation, transport and deposition of clays.

Original languageEnglish (US)
Article numberE07006
JournalJournal of Geophysical Research E: Planets
Volume112
Issue number7
DOIs
StatePublished - Jul 20 2007

Fingerprint

weathering
Weathering
mars
Minerals
Mars
thermodynamics
time measurement
minerals
Silicon Dioxide
Thermodynamics
kinetics
dissolving
Dissolution
acids
Kinetics
Acids
silica
acid
dissolution
neutralization

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

Timing of acid weathering on Mars : A kinetic-thermodynamic assessment. / Zolotov, Mikhail; Mironenko, Mikhail V.

In: Journal of Geophysical Research E: Planets, Vol. 112, No. 7, E07006, 20.07.2007.

Research output: Contribution to journalArticle

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