Carbonates on Mars

[1] Moreover, due to their utility in registering changes in environmental conditions such as pH, temperature, fluid composition,[2] carbonates have been considered as a primary target for planetary scientists' research.

Previously, most remote sensing instruments such as OMEGA and THEMIS—sensitive to infrared emissivity spectral features of carbonates—had not suggested the presence of carbonate outcrops,[5] at least at the 100 m or coarser spatial scales available from the returned data.

[6] Though ubiquitous, a 2003 study of carbonates on Mars showed that they are dominated by magnesite (MgCO3) in Martian dust, had mass fractions less than 5%, and could have formed under current atmospheric conditions.

[clarification needed] Nevertheless, the morphology was distinct from typical terrestrial sedimentary carbonate layers suggesting formation from local aqueous alteration of olivine and other igneous minerals.

[14] In 2010 analyses by the Mars Exploration Rover Spirit, identified outcrops rich in magnesium-iron carbonate (16–34 wt%) in the Columbia Hills of Gusev crater, most likely precipitated from carbonate-bearing solutions under hydrothermal conditions at near-neutral pH in association with volcanic activity during the Noachian era.

[15] After Spirit Rover stopped working scientists studied old data from the Miniature Thermal Emission Spectrometer, or Mini-TES and confirmed the presence of large amounts of carbonate-rich rocks, which means that regions of the planet may have once harbored water.

Even if this explanation provides an insight in the reasons why carbonates are not present, it is in disagreement with the geomorphological and mineralogical evidence supporting the existence of liquid water on Mars' surface.

[20] According to this notion, the carbonates indeed formed and are still exist on Mars, but they remain undetected due to the limited sensitivity of the current tools used for mineralogical detection on the planet.

[20] This concept involves the potential for secondary chemical alteration of ancient carbonates on Mars, due to the formation of acid rain[21] resulting from the combination of water vapor and sulfates.