Water Activity and the Challenge for Life on Early Mars

  title={Water Activity and the Challenge for Life on Early Mars},
  author={Nicholas J. Tosca and Andrew H. Knoll and Scott M. McLennan},
  pages={1204 - 1207}
In situ and orbital exploration of the martian surface has shown that acidic, saline liquid water was intermittently available on ancient Mars. The habitability of these waters depends critically on water activity (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(a_{\mathrm{H}_{2}\mathrm{O}}\) \end{document}), a thermodynamic measure of salinity, which, for terrestrial organisms, has… 

Geologic Constraints on Early Mars Climate

  • E. Kite
  • Geology, Environmental Science
    Space Science Reviews
  • 2019
Early Mars climate research has well-defined goals (MEPAG 2018). Achieving these goals requires geologists and climate modelers to coordinate. Coordination is easier if results are expressed in terms

Juvenile Chemical Sediments and the Long Term Persistence of Water at the Surface of Mars

New Constraints on Early Mars Weathering Conditions From an Experimental Approach on Crust Simulants

A denser CO2 atmosphere and higher temperatures than present‐day conditions are frequently invoked as prevailing conditions for the formation of some ancient hydrous mineralogical associations

Soluble sulfate in the martian soil at the Phoenix landing site

Sulfur has been detected by X‐ray spectroscopy in martian soils at the Viking, Pathfinder, Opportunity and Spirit landing sites. Sulfates have been identified by OMEGA and CRISM in Valles Marineris

A Field Guide to Finding Fossils on Mars

It is concluded that Noachian‐Hesperian Fe‐bearing clay‐rich fluvio‐lacustrine siliciclastic deposits, especially where enriched in silica, currently represent the most promising and best understood astropaleontological targets.

Ionic Strength Is a Barrier to the Habitability of Mars.

It is demonstrated experimentally that high ionic strength, driven to extremes on Mars by the ubiquitous occurrence of multivalent ions, renders these environments uninhabitable despite the presence of biologically available water.

A cold and wet Mars

Physicochemical properties of concentrated Martian surface waters

Understanding the processes controlling chemical sedimentation is an important step in deciphering paleoclimatic conditions from the rock records preserved on both Earth and Mars. Clear evidence for

A synthesis of Martian aqueous mineralogy after 1 Mars year of observations from the Mars Reconnaissance Orbiter

Martian aqueous mineral deposits have been examined and characterized using data acquired during Mars Reconnaissance Orbiter's (MRO) primary science phase, including Compact Reconnaissance Imaging



Jarosite as an indicator of water-limited chemical weathering on Mars

It is concluded that the presence of jarosite combined with residual basalt at Meridiani Planum indicates that the alteration process did not proceed to completion, and that following jarosite formation, arid conditions must have prevailed.

Crystal molds on Mars: Melting of a possible new mineral species to create Martian chaotic terrain

Images sent back by the Mars Exploration Rover Opportunity from the Meridiani Planum show sulfate-rich rocks containing plate-shaped voids with tapered edges that are interpreted as crystal molds

Meridiani Planum and the global hydrology of Mars

It is demonstrated that Meridiani is one of the few regions of currently exposed ancient crust predicted to have experienced significant groundwater upwelling and evaporation, and the evaporite formation coincided with a transition to more arid conditions that increased the relative impact of a deep-seated, global-scale hydrology on the surface evolution.

Acid-sulfate weathering of synthetic Martian basalt: The acid fog model revisited

The acid fog model has received considerable attention as a model of soil formation on Mars. Previous evaluations of this model have focused on experimental weathering of terrestrial basalt samples.

Geochemical and mineralogical indicators for aqueous processes in the Columbia Hills of Gusev crater, Mars

[1] Water played a major role in the formation and alteration of rocks and soils in the Columbia Hills. The extent of alteration ranges from moderate to extensive. Five distinct rock compositional

In Situ Evidence for an Ancient Aqueous Environment at Meridiani Planum, Mars

The geologic record at Meridiani Planum suggests that conditions were suitable for biological activity for a period of time in martian history.