Mars Polar Craters Grow and Lose Frost With the Seasons, Images Show

Frost and ice on the floors of craters near the north pole of Mars grow and shrink with the seasons, but not in the same way everywhere, according to a recent study. Universe Today reported that of 36 craters examined, 32 showed changes in bright deposits.

The finding points to local conditions, not a single cap-wide pattern, as the main driver of how these icy deposits behave from one Martian year to the next.

How the researchers tracked the ice

An international team studied images of craters within the northern polar ice cap region. The pictures came from the HiRISE camera on NASA's Mars Reconnaissance Orbiter and were taken between 2006 and 2025. Universe Today said that span corresponds to Mars Years 28 to 38, since one year on Mars lasts 668 Earth days.

The team wanted to learn how ice deposits on crater floors change with the seasons. In particular, it looked at whether the deposits grow in winter months and shrink in summer months. The study appeared in the Journal of Geophysical Research: Planets, according to Universe Today.

What they found

In 32 of the 36 craters, the bright deposits changed, which broadly indicates that ice is expanding and shrinking with the seasons. In the other four craters, the researchers saw no change in brightness. They noted that seasonal frost on the outside of each crater could be responsible for some of the brightness changes.

The results were also uneven from year to year. The study says not every crater shows a change in frost coverage from one Mars year to the next. In a given year, only some craters show altered frost conditions compared with earlier years, while others keep similar or nearly identical frost extents.

The researchers concluded that seasonal frost cycles and the long-term balance of ice gained and lost are localized processes. They said local terrain, the shape of each crater and small-scale climate conditions likely influence energy balance and the movement of water vapor, so each crater responds in its own way to broader climate forces.

Why Mars has an ice cap like this

Universe Today noted that Mars and Earth both have polar ice caps, but they differ. Earth's two polar caps are both made of water ice. On Mars, the north polar cap is made only of water ice, while the southern cap is carbon dioxide. The outlet said the reasons are tied to altitude, and that the northern cap is among the most studied regions of the planet because of its water ice.

Why it matters for understanding Mars

The work is aimed at a long-standing gap in knowledge about how polar ice deposits change with the seasons, specifically in craters. The researchers say that a better grasp of these seasonal shifts could help scientists understand long-term climate change on Mars.

For general readers, the main takeaway is that Martian climate is not uniform even within a small region. Universe Today pointed out that Mars goes through much larger climate swings on grand scales than Earth does, because its tilt varies far more. This study suggests that local climates can still produce their own changes that are disconnected from the bigger picture.

That matters because pinning down what triggers changes in the ice, whether seasonal or something else, is a key part of reconstructing the planet's climate history. A crater that holds more or less frost is not necessarily a sign of a planet-wide shift.

What comes next

The study offers motivation for future modeling work that could expand knowledge of localized climates on Mars. As it stands, the findings are based on image analysis, and the researchers describe the local explanation as a likely one, not a settled conclusion. Universe Today did not report a timeline for further work.

Around Prague, based on reporting by Universe Today