Nitrates on Mars
Nitrates are salts of the nitric acid (HNO3). It has been estimated that one quarter of the initial Martian atmospheric molecular nitrogen today is fixed in the form of nitrates in the soil. A possible formation process of these nitrates is the dissociation of the atmospheric molecular nitrogen through shock heating caused by impacts or through photochemical reactions (Smith et al. 2014). Nitrates are highly soluble in water, hence nitrates entrained in the Martian cryosphere may contribute to the generation of brines near the surface. Because nitrates are a fundamental source of nitrogen for life on Earth, the detection of nitrates on Mars is an important parameter for the assessment of potential habitable environments. Recent analyses of “Rocknest” sand samples at Gale crater by the NASA rover “Curiosity” tentatively indicate the presence of nitrates.