Calcium carbonate

Calcium carbonate is one of the main components of Portland cement, and therefore of concrete, the most common building material on Earth. It would be useful as a component for construction materials for Martian infrastructure.

Calcium carbonate is a chemical compound, CaCO3. It has been identified from orbit on Mars as well as through surface exploration (Spirit rover). With the realization that large areas of Mars have been under water for long periods, carbonate deposits are expected, but their extend is yet to be determined. It may be that sulfates formed on Mars rather than carbonates.

Our theories of Mars' history suggest that various carbonate minerals should be common, but they seem to be quite rare on Mars. The reason for this is unknown, but the ratio of Sulfur dioxide (SiO2) to carbon dioxide (CO2) in the early Martian atmosphere might be the part of the answer.