Martian polar crater ice shifts with seasonal frost

Mars shares many landforms and weather patterns with Earth, including changing seasons, volcanoes, canyons, dust storms, dust devils and water ice. Another feature that Earth and Mars share is polar ice caps. These are among each planet’s striking features, but the major difference is that Earth’s polar ice caps are both composed of water, while Mars’ north polar ice cap is composed only of water and its southern polar ice cap is carbon dioxide.

The reasons for this are determined by altitude. Mars’ northern polar ice cap is one of the most studied regions, primarily because of its water ice composition. But how does the water ice in the north polar ice cap change with the seasons compared with Earth’s, and what can this teach scientists about Mars’ climate history?

Now, an international team of researchers might have shed new light on this conundrum. As discussed in a recent study published in the Journal of Geophysical Research: Planets, the researchers challenged our understanding of ice deposits in Mars’ northern polar ice cap region. The primary motivation behind this study was to fill a longstanding knowledge gap regarding the seasonal changes in Martian polar ice deposits, specifically focusing on craters. The researchers note that better understanding seasonal changes in polar ice cap deposits could provide insights into long-term climate changes on the red planet.

Tracking ice across 36 craters

For the study, the researchers analyzed images of 36 craters within the northern polar ice cap region of Mars. The images were obtained from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter between 2006 and 2025. This period is also referred to as Mars Years (MY) 28–38 since one year on Mars is about 668 Martian days. The goal of the study was to identify how polar ice deposits on crater floors changed with the seasons, specifically whether the deposits increased in size during winter or decreased during summer.

The researchers found that 32 of the 36 craters exhibited changes in bright deposits, broadly indicating that ice deposits are expanding and shrinking with the seasons. In the remaining four craters, the researchers didn’t observe changes in brightness. The researchers note that seasonal frost deposits on the outside of each crater could be responsible for the changes in brightness.

“Not all craters exhibit changes in frost coverage from one Mars year to the next,” the study notes. “For a given Mars year, only a subset of craters show altered frost conditions relative to previous years, while others maintain similar or nearly identical frost extents. This spatial heterogeneity suggests that seasonal frost cycles and interannual mass balance are localized processes rather than cap-wide phenomena. Local topography, crater geometry and microclimatic conditions likely modulate energy balance and vapor transport, leading to crater-specific responses to broader climatic forcing.”

Local climates shape crater ice

Essentially, the researchers found that changes in crater ice deposits are triggered by local climate changes rather than larger-scale climate changes. Understanding Mars’ climate changes is important to help pin down specific triggers, whether seasonal or related to other factors. For example, Mars experiences much larger climate changes on broader scales than Earth because the red planet’s axial tilt has much larger swings than Earth’s.

However, as this study demonstrates, local climates are still capable of delivering their own changes disconnected from the larger climate picture. This study identifies seasonal changes in polar ice deposits while providing motivation for future modeling work that could help expand our understanding of localized climates on Mars.

What new insights into Mars’ polar crater ice will researchers gain in the coming years and decades?

Who’s behind this story?

Swati Mestri

Swati Mestri holds a bachelor’s degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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