Scientists' latest observations have discovered that there is an unusual and mysterious surge of ozone in the polar vortex of Mars' north pole. In winter, the temperature in this area is much lower than outside the vortex, and the polar night produces abnormally high ozone concentrations. The scientific research team recently conducted winter observations of the polar vortex in the North Pole of Mars. The results show that the temperature inside the polar vortex, from the surface to an altitude of about 30 kilometers, is about 40 degrees Celsius lower than outside the vortex. Because the Arctic cannot see sunlight for a long time, it is extremely cold, causing a small amount of water vapor in the atmosphere to condense and deposit on the ice sheet.

This map of the Martian North Pole was synthesized from images taken by the European Space Agency's "Mars Express" probe and combined with topographic data from the Mars orbiting laser altimeter carried by NASA's retired "Mars Global Surveyor" mission. Image source: ESA/DLR/FU Berlin/NASA MGS MOLA science team

This change had a major impact on the chemical processes of the Martian atmosphere. Normally, ozone is broken down when water vapor interacts with molecules produced by ultraviolet light. But when the water vapor disappears, this decomposition process stops, and ozone quickly accumulates in the polar vortex.

Dr. Kevin Olsen of the University of Oxford said at the 2025 EPSC-DPS joint conference in Helsinki: "The temperature in the polar vortex from the surface to an altitude of 30 kilometers is about 40 degrees lower than outside. At this extreme low temperature, water vapor in the atmosphere will condense and settle, and the lack of water vapor allows ozone to accumulate in large quantities."

Ozone is a highly reactive form of oxygen and an important indicator of the rate of chemical reactions in the Martian atmosphere. Olsen added: "By understanding the content of ozone and its changes, we can further understand the evolution of the Martian atmosphere and whether Mars once had a protective ozone layer like the Earth." The European Space Agency plans to launch the ExoMars Rosalind Franklin rover in 2028, focusing on searching for signs of ancient life on Mars. If Mars had had an ozone layer that shielded it from ultraviolet rays, the chances of life on Mars billions of years ago would have been higher.

The Martian polar vortex is the product of seasonal changes on Mars, and its rotation axis is tilted at an angle of 25.2 degrees. At the end of summer in the northern hemisphere, a polar vortex forms over the North Pole, which lasts until spring.

The temperature measurement diagram shows that the temperature inside the Arctic vortex (the area marked by the yellow line) is 40 degrees Celsius lower than the temperature outside the vortex. Image credit: Kevin Olson (University of Oxford) et al.

On Earth, the polar vortex sometimes moves south due to instability, bringing cold weather to mid-latitudes. Mars' polar vortex occasionally changes shape and shifts in position, allowing scientists to peer into its internal structure.

Olsen said: "The Martian North Pole presents a polar night state in winter, which is similar to the Earth's polar winter and is very difficult to observe. By measuring the temperature and composition differences inside and outside the vortex, we can uncover the secret behind the surge of ozone in the polar night."

Olsen's team used ESA's ExoMars Trace Gas Orbiter and the Atmospheric Chemistry Suite (ACS) to analyze the wavelength of sunlight as it passes through the atmosphere from the other side of the planet to infer the properties and height of atmospheric molecules. However, during the Arctic polar night, the sun does not rise at all, so conventional methods cannot work and can only seize short-term opportunities when the polar vortex deforms.

To this end, Olsen also referred to the Mars Climate Sounder on NASA's Mars Reconnaissance Orbiter to determine whether it has entered the polar vortex through a sudden drop in temperature. Comparing the data from ACS and climate measuring instruments, the atmosphere inside the polar vortex appears significantly different from the outside, which provides valuable clues for studying atmospheric chemical changes and ozone accumulation mechanisms during the Martian polar night.

Compiled from /ScitechDaily