While NASA imagery has shown evidence of ancient rivers and lakes on Mars that transitioned to dry dunes, uncertainty remains over the timing of the environmental changes that may have contributed to these shifts.
Now, data collected by NASA’s Curiosity rover has revealed that individual crystals in the iron oxide hematite can be used as a mineralogical marker of changes to Mars’ ancient climate. Because the shape and structure of these crystallites reflect the conditions – such as temperature and water presence – under which they were formed, they can serve as an indicator of when these changes occurred.
Scientists studied 20 samples collected by Curiosity across various elevations throughout Gale Crater for a paper published Thursday in Science. Gale Crater’s walls reveal Mars’ environmental history layer by layer, with deeper elevations capturing its earliest years. The team analyzed data from the rover’s Chemistry and Minerology (CheMin) instrument and discovered that hematite showed different crystallite sizes at different elevations. They also discovered that goethite, a mineral that typically forms alongside hematite, was absent in samples from lower elevations but still present in samples from higher elevations. This suggests that warm groundwater might have remained for up to 4.7 million years in the deepest layers of Gale Crater and that during much of this time, these long-lived aquifers could have been potentially habitable.
