Beneath the dusty surface of Mars’ north pole, scientists have uncovered surprisingly clean layers of ice that may preserve a hidden record of the planet’s dramatic climate history.
Earth maintains a relatively steady posture in space thanks to the gravitational anchor of a massive moon. Mars lacks that stability. Tugged only by two tiny moons, the red planet “oscillates wildly,” according to University of Washington research scientist Aditya Khuller. As its axis tilts back and forth over millennia, Mars endures extreme ice ages that have left roughly one-third of the planet buried under shallow layers of frozen water.
Those frozen deposits act as a pristine archive of the ancient Martian climate, trapping falling dust and atmospheric gases much like tree rings record decades of rainfall. On Earth, climatologists physically drill deep into glaciers to extract long cylinders of ice and read this history directly. Landing hardware on Martian poles to study this ice is notoriously difficult.
This year marks 50 years since NASA’s first successful mission to Mars, a milestone that underscores how long scientists have been trying to understand the red planet from its surface. Yet reaching its frozen poles has remained especially difficult. NASA lost the Mars Polar Lander near the south pole in 1999, while the Phoenix mission succeeded in 2008, becoming the first mission to directly sample ice near the north pole.
Dust changes how Martian ice behaves
Most of the water ice around Mars’ north pole is hidden beneath a dusty surface rather than exposed in the open. That dust does more than obscure the ice. By darkening it, dust changes how much sunlight the surface reflects back into space, which affects how quickly the ice warms and vaporizes.
“We know there is water ice in the area surrounding the north pole of Mars, but there has been widespread disagreement as to how dusty that ice is,” said Khuller, a senior research scientist at the UW’s Applied Physics Laboratory. “If it is dustier, the ice will be darker. Just like a dark T-shirt in the sun makes you warmer, dusty ice gets warmer and vaporizes faster on Mars.”
A lunar method gave conflicting answers
Scientists have struggled to pin down that dust content partly because the standard calculations themselves may have been leading them astray. Several years ago, Khuller noticed a discrepancy in the leading method used to analyze the physical properties of Martian ice. The approach had originally been developed for studying soil on the Moon, and when he tested its accuracy under Earth conditions, the results appeared inconsistent.
Pari Mohan, who recently graduated from the University of Washington with a degree in geoscience, worked with Khuller to recalculate the ice properties using a different technique. Their approach was adapted from methods developed by Steve Warren, a UW professor emeritus of Earth and space science who specializes in snow and ice.
“His methods had been used successfully to study snow and ice on Earth for decades. So I thought it would be interesting to adapt these Earth-tested methods to Mars,” Khuller said.
Mars’ north polar ice is cleaner
Using observations from the Phoenix mission together with measurements from orbiting satellites, the researchers arrived at a much lower estimate for the amount of dust mixed into the north polar ice. Earlier calculations suggested that the upper layer could contain as much as 25% dust by mass. The new study, published September 8 in npj Space Exploration, places that figure closer to 3%.
Changes in brightness over the Martian seasons also revealed how the dust is arranged. Rather than forming one uniformly dirty mass, the north pole appears stacked “like an ice-cream sandwich,” with dustier layers sitting between slabs of cleaner ice.
A relatively dusty coating of frost forms over the surface each winter. When summer arrives, that seasonal layer disappears and exposes older, cleaner ice underneath.
“By looking at how the brightness changed over time, we figured out that there is a frost that forms in the winter and it’s more dusty. In the Martian summer it goes away, exposing cleaner, older ice,” Khuller said.
Layers hold climate and habitability clues
Those older layers may preserve evidence of conditions thousands of years ago, when researchers think the ice accumulated through snowfall. Each buried layer could therefore hold clues to how the Martian climate changed as the planet moved through its dramatic cycles of ice ages.
The mix of dust and ice may also affect whether small pockets of liquid water could ever form below the surface. In previous research, Khuller and colleagues proposed that darker dusty layers could absorb sunlight and trap enough heat to melt some of the surrounding ice. Dust inside those pockets could also supply nutrients, potentially creating environments that bacteria or other primitive life forms might inhabit.
Similar pockets of shallow, dusty meltwater in ice on Earth can teem with life during summer. When winter returns, the water freezes and the microbes become dormant until warmer conditions come back.
“The fact that Mars and Earth both have these similar layers of water ice and dust is interesting,” Khuller said. “Why does one planet have life and the other doesn’t?”
Khuller hopes to apply the improved analysis to other parts of Mars, using the planet’s buried ice to build a clearer record of how its climate has changed over time.
Reference: “Revised dust content and grain size of exposed water ice at the North Pole of Mars” by Pari Mohan, and Aditya R. Khuller, 8 September 2026, npj Space Exploration.
DOI: 10.1038/s44453-026-00054-9
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