Phosphates on Mars
Phosphates are the salts and esters of phosphoric acid (H3PO4). Since phosphate is a essential nutrient for life on Earth and part of the backbone of DNA, its occurrence is important for estimating the habitability on Mars. Phosphates can be derived from minerals (e.g., apatite Ca5[(PO4)3(OH, F, Cl)]) through the weathering of igneous rocks. Calcium-phosphate minerals have a high solubility in acidic water. Measurements done by the Mars Pathfinder Rover and the Mars Exploration Rover indicate that the Martian soil is enriched in phosphorus relative to the rock.