Martian craters record repeated ice ages as planetary ice stores dwindle

Martian craters record repeated ice ages as planetary ice stores dwindle
by Riko Seibo
Tokyo, Japan (SPX) Oct 10, 2025

Scientists have long debated how much water Mars once held and how it faded to today's arid world. A new study in Geology mines "ice archives" preserved inside impact craters to reconstruct a climate history marked by multiple ice ages, each leaving progressively less ice behind.

Led by Associate Professor Trishit Ruj of Okayama University, with colleagues Hanaya Okuda, Hitoshi Hasegawa, and Tomohiro Usui, the team mapped glacial landforms in craters between 20oN and 45oN. The record points to repeated glaciations over hundreds of millions of years, with diminishing icy remnants after each cycle.

"Mars went through repeated ice ages, but the amount of ice deposited in craters steadily shrank over time. These icy 'time capsules' not only reveal how Mars lost its water but also mark places where future explorers might tap into hidden ice resources."

Using high-resolution imagery from NASA's Mars Reconnaissance Orbiter, the researchers cataloged ridges, moraines, and brain terrain indicative of ice-rich deposits. Comparing these features with climate models, they found ice favored colder, shadowed southwestern crater walls across glacial episodes from roughly 640 million to 98 million years ago.

The driver is Mars' wildly varying axial tilt, or obliquity, which redistributes sunlight over million-year timescales. Low obliquity concentrates volatiles at the poles, while high obliquity spreads ice toward mid-latitudes. Over time, however, each swing trapped less water as the planet gradually dried.

"By tracing how Mars stored and lost its ice, this study guides future explorers to water supplies and offers insights that can be applied to Earth's changing environment."

Buried ice is more than a scientific prize. It represents an in-situ resource for future missions: drinking water, oxygen production, and, through electrolysis, hydrogen and oxygen for rocket propellants. Such local sourcing could transform mission logistics and costs.

"Knowledge of long-lived ice deposits helps identify safe and resource-rich regions for future robotic and crewed landings," notes Prof. Usui.

The work also echoes lessons for Earth. Similar imaging and modeling approaches refine understanding of glaciers, permafrost, and hidden aquifers in a warming climate. As Dr. Hasegawa emphasizes, "Mars serves as a natural laboratory for understanding how ice behaves over vast timescales. The insights we gain here can sharpen our understanding of climate processes on Earth as well."

Together, these crater "ledgers" depict a Mars that cycled through icy episodes while steadily losing its frozen capital. That long view informs both planetary science and the practical task of picking resource-rich landing zones for the next wave of exploration.

Research Report:Long-term and multi-stage ice accumulation in the martian mid-latitudes during the Amazonian