Rover-Induced Mineral Transformations: Extent of the Effect for the Mars Science Laboratory and Opportunities for Future Landed Mission

X-ray amorphous sulfate hydrates are a substantial component (up to 23 wt%) of the sedimentary rocks and sands analyzed to date by the Mars Science Laboratory Curiosity rover at Gale crater.

Recently, the CheMin X-ray diffractometer observed the amorphization of the crystalline sulfate starkeyite (MgSO₄ · 4H₂O) upon exposure to the dry and relatively warm atmosphere inside the rover body.

To assess the extent to which interactions between minerals and the rover environment contribute to the amorphous component, we investigated the stability of several hydrated minerals under Curiosity-like conditions. Our results show that highly hydrated minerals are more prone to transformation inside the rover than lower hydrates.

Minerals that readily become amorphous under rover conditions are also likely to be unstable when exposed to the dry Martian atmosphere during the warm periods at noon. We therefore suggest that much of the observed amorphization occurred at the Martian surface prior to sampling.

Future missions such as the Rosalind Franklin rover and Mars Life Explorer propose to drill into the substantially colder subsurface at Martian mid-latitudes and are likely to encounter temperature and humidity-sensitive cryohydrates. To evaluate the original mineral assemblage of rocks on such missions, it will be critical to maintain controlled temperature and relative humidity (RH) conditions inside the rover body.

We find that increasing ambient humidity may induce the recrystallization of amorphous salt hydrates, thus controlling RH and temperature inside the rover would significantly enhance the analytical capabilities of a next generation X-ray diffractometer on Mars.

Rover-Induced Mineral Transformations: Extent of the Effect for the Mars Science Laboratory and Opportunities for Future Landed Mission, JGR Planets (open access)

Astrobiology,