Billions of years ago, Mars shifted from rivers and lakes to dry dunes; NASA says Curiosity’s hematite crystals may help date that climate shift in rock

Recent studies on hematite crystal sizes reveal insights into Mars' ancient climate shifts. The presence of these tiny crystals suggests that warmer water persisted for extended periods, with deeper rock layers indicating prolonged wet conditions, while the upper layers show evidence of dryness. This discovery implies that underground water may have remained even after surface lakes faded, enhancing our understanding of Mars' potential for past habitability.