For decades, scientists have been curious about how much water Mars once had and what led to its gradual transformation into the dry planet we see today. A new study published online on September 2, 2025, in the Geology journal, sheds light on this mystery by looking deep inside Martian craters, which act like “ice archives” that store a frozen record of the planet’s past. These craters reveal that Mars went through repeated ice ages over hundreds of millions of years; however, with each cycle, the amount of remaining ice decreased steadily.