Polar water is generated during the Martian season, which occurs due to the planet’s axis being tilted at an angle of 25.2 degrees, as explained by Dr. Kevin Olsen from Oxford and his colleagues at Latmos, CNRS, CNRS, Space Research Institute, Open University, and NASA.

“The polar vortex’s atmosphere, extending from near the surface to around 30 km high, experiences extremely low temperatures, approximately 40 degrees Celsius lower than the surrounding area,” stated Dr. Olsen.

“In such frigid conditions, most of the water vapor in the atmosphere freezes and accumulates in the ice cap, resulting in ozone formation within the vortex.”

Normally, ozone is destroyed by reacting with molecules generated when ultraviolet radiation decomposes water vapor.

However, once all water vapor is depleted, there are no reactive molecules left for ozone, allowing it to accumulate in the vortex.

“Ozone plays a crucial role for Mars. It is a reactive form of oxygen that indicates the pace of chemical reactions occurring in the atmosphere,” Olsen noted.

“By investigating the levels of ozone and their variances, we gain insight into how the atmosphere evolves over time and whether Mars once had a protective ozone layer similar to Earth.”

Slated for launch in 2028, ESA’s Rosalind Franklin Rover aims to uncover evidence of life that may have existed on Mars.

The possibility that Mars had a protective ozone layer, safeguarding its surface against harmful ultraviolet radiation from space, enhances the likelihood of ancient life-sustaining conditions on the planet billions of years ago.

Polar vortices are produced during the Martian season as a consequence of the axial tilt of 25.2 degrees.

Similar to Earth, an atmospheric vortex forms above Mars’ North Pole at the end of summer and persists through spring.

On Earth, polar vortices can destabilize, losing their structure and shifting southward, often bringing cold weather to mid-latitudes.

A similar phenomenon can occur with Mars’ polar water vortex, which provides an opportunity to explore its internal dynamics.

“Studying the Northern Pole’s winter on Mars presents challenges due to the absence of sunlight, akin to conditions on Earth,” Dr. Olsen explained.

“By analyzing the vortex, one can differentiate between observations made inside and outside it, providing insight into ongoing phenomena.”

The atmospheric chemical suite aboard ESA’s trace gas orbiter examines Mars’ atmosphere by capturing sunlight filtered through the planet’s limb while the sun is positioned behind it.

The specific wavelengths of absorbed sunlight reveal which molecules are present in the atmosphere and their altitudes above the surface.

Nonetheless, this method is ineffective during the complete winter darkness on Mars when the sun does not illuminate the Arctic region.

The only chance to observe the vortex is during moments when its circular shape is lost, but additional data is required to pinpoint when and where this occurs.

To enhance their research, the scientists utilized NASA’s Mars Reconnaissance Orbiter’s Mars Climate Sounder instrument, measuring temperature variations to gauge the vortex’s extent.

“We sought sudden drops in temperature, which indicate entry into the vortex,” Dr. Olsen noted.

“By comparing ACS observations with data from Mars’ climate sounders, we observed significant atmospheric differences within the vortex compared to the surrounding air.”

“This presents a fascinating opportunity to deepen our understanding of Mars’ atmospheric chemistry and how polar night conditions shift as ozone accumulates.”

The findings were presented at the EPSC-DPS2025 Joint Meeting in Helsinki, Finland, this month.

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K. Olsen et al. 2025. What’s happening in the Arctic Vortex of Mars? EPSC Abstract 18: EPSC-DPS2025-1438; doi: 10.5194/epsc-dps2025-1438