Martian north polar region, Borealis Planitia.
Captured during Mars Express' 14,125th orbit of the red planet.
This stunning High-Resolution Stereo Camera (HRSC) image was captured during Mars Express' 14,125th orbit of the red planet.
It showcases the Martian north polar region, revealing the imposing north polar cap, a striking bank of stratocumulus clouds over Borealis Planitia, and the rugged highlands of Tempe Terra to the left.
Key Space Science
The image shows the Martian north polar cap, primarily composed of water ice layered with a seasonal coating of carbon dioxide (dry ice). This seasonal CO₂ frost expands and recedes with the Martian year, driven by the planet’s elliptical orbit and axial tilt. Studying this cycle helps scientists monitor atmospheric pressure variations and gain a deeper understanding of the broader Martian climate system.
The stratocumulus clouds—typically low-lying, dense, and spread out in banks—indicate active atmospheric circulation. Their presence over Borealis Planitia points to localized weather patterns driven by interactions between the cold polar air and relatively warmer equatorial regions. These clouds form when moist air cools and condenses as it rises, offering clues about temperature gradients and vertical air movement on Mars.
Moreover, the polar layered deposits beneath the ice cap act as a natural archive of Martian climate history. Like ice cores on Earth, their strata—formed by cycles of ice and dust deposition—encode information about past atmospheric conditions, obliquity shifts, and even solar variability.
Understanding the Martian water cycle, including how and where water transitions between ice, vapour, and possibly liquid under rare conditions, is vital. It not only informs models of the current climate but also improves predictions for where subsurface ice might exist, which is critical for future human missions.
Ultimately, this kind of long-term, high-resolution observation is essential for astrobiology. Tracing the past or present potential for liquid water ties directly to the search for microbial life and helps assess Mars' habitability across geological timescales.
And stratocumulus clouds are dynamic and show that Mars isn’t just a static, frozen world. Their formation hints at moisture cycles, rising air currents, and temperature layering—the kind of activity that, on Earth, contributes to weather systems. They're rare enough on Mars that seeing them is a big deal for atmospheric science—a bobby dazzler.
Higher resolutions
Borealis Planitia - Mars Express | Mars Express HRSC image o… | Flickr