Scientists studying the harsh winter at Mars’s north pole have uncovered surprising conditions inside the planet’s polar vortex—an enormous, swirling current of air that forms each year.
They found that the vortex traps extremely cold air, plunging temperatures to about 40°C colder than those outside it.
These conditions allow a rare buildup of ozone in the Martian atmosphere, offering new clues about how the planet’s climate and chemistry have evolved over time.
The discovery was presented at the EPSC-DPS 2025 Joint Meeting in Helsinki by Dr. Kevin Olsen of the University of Oxford.
He explained that inside the vortex, the atmosphere from near the surface up to 30 kilometers high is locked in frigid darkness during the northern winter.
The cold is so intense that the tiny amount of water vapor in Mars’s atmosphere freezes out and settles onto the polar ice cap.
On Earth, ozone is constantly being broken down by byproducts of water vapor exposed to ultraviolet sunlight.
But on Mars, with water vapor removed by freezing and no sunlight during the polar night, this destructive process halts. As a result, ozone is able to accumulate inside the vortex.
“Ozone is a very reactive form of oxygen that tells us how fast chemistry is happening in the atmosphere,” Olsen explained.
“By studying how much ozone there is and how it changes, we can better understand how Mars’s atmosphere has evolved. It might even reveal whether the planet once had a protective ozone layer, like Earth’s, that shielded the surface from harmful ultraviolet radiation.”
If Mars did once have such a shield, it would have increased the chances that life could have survived on the surface billions of years ago.
The European Space Agency’s Rosalind Franklin rover, set to launch in 2028, will search for evidence of past life, and understanding ozone’s role could be a crucial piece of that puzzle.
The polar vortex itself forms because of Mars’s tilted axis, which creates seasons much like Earth’s. Each northern winter, a vortex develops over the north pole and lasts until spring. Sometimes the vortex wobbles or stretches, just as Earth’s does, and when this happens, scientists get rare opportunities to peer inside.
Olsen and his colleagues used the Atmospheric Chemistry Suite aboard ESA’s ExoMars Trace Gas Orbiter to detect gases in the atmosphere by observing sunlight passing through it.
But since there’s no sunlight during the Martian polar night, they also relied on NASA’s Mars Climate Sounder to measure temperatures and pinpoint when the spacecraft’s instruments were inside the vortex.
By comparing the two data sets, Olsen’s team confirmed that the atmosphere inside the vortex was dramatically different from outside, with ozone concentrations higher than expected.
“This is a fascinating chance to explore Martian atmospheric chemistry,” Olsen said. “It shows how the long, dark winters at the north pole create conditions where ozone can thrive, giving us new insights into the Red Planet’s past and present climate.”
Source: KSR.
