A clue to historical life? What scientists discovered inside Mars’ frozen vortex

“The atmosphere inside the polar vortex, from near the surface to about 30 kilometers high, is characterized by extreme cold temperatures, about 40 degrees Celsius colder than outside the vortex,” mentioned Dr. Kevin Olsen of the University of Oxford, who offered the outcomes on the EPSC-DPS2025 Joint Meeting in Helsinki.

At these excessive lows, the small quantity of water vapor in Mars’ environment freezes and settles onto the polar ice cap. This change has a placing impact on ozone ranges. Normally, ozone is destroyed when it reacts with molecules shaped as ultraviolet daylight breaks aside water vapor. But when the vapor freezes out fully, these reactions cease. With nothing left to interrupt it down, ozone begins to construct up contained in the vortex.

“Ozone is a very important gas on Mars — it’s a very reactive form of oxygen and tells us how fast chemistry is happening in the atmosphere,” mentioned Olsen. “By understanding how much ozone there is and how variable it is, we know more about how the atmosphere changed over time, and even whether Mars once had a protective ozone layer like on Earth.”

The European Space Agency’s ExoMars Rosalind Franklin rover, scheduled to launch in 2028, will seek for traces of historical life on the planet. If Mars as soon as had an ozone layer shielding its floor from ultraviolet radiation, that protecting barrier might have made it much more hospitable to life billions of years in the past.

How Mars’ Polar Vortex Forms

Mars’ polar vortex develops as a part of its seasonal cycle, pushed by the planet’s 25.2-degree axial tilt. Like Earth, the Red Planet experiences seasonal shifts, and as northern summer time ends, a swirling vortex kinds above the pole and lingers till spring.

On Earth, the polar vortex can typically destabilize and drift south, sending chilly air into decrease latitudes. An identical course of can happen on Mars, giving researchers beneficial possibilities to review the vortex’s inside.

“Because winters at Mars’ north pole experience total darkness, like on Earth, they are very hard to study,” says Olsen. “By being able to measure the vortex and determine whether our observations are inside or outside of the dark vortex, we can really tell what is going on.”

Probing the Vortex

Olsen works with ESA’s ExoMars Trace Gas Orbiter that’s in orbit round Mars. In explicit, the spacecraft’s Atmospheric Chemistry Suite (ACS) research Mars’ environment by gazing on the Red Planet’s limb when the Sun is on the opposite facet of the planet and is shining by means of the environment. The wavelengths at which the daylight is absorbed give away which molecules are current within the environment and the way excessive above the floor they’re.

However, this system would not work in the course of the whole darkness of martian winter when the Sun would not rise over the north pole. The solely alternatives to glimpse contained in the vortex are when it loses its round form however, to know precisely when and the place that is occurring, requires further knowledge.

For this, Olsen turned to the Mars Climate Sounder instrument on NASA’s Mars Reconnaissance Orbiter to measure the extent of the vortex by way of temperature measurements.

“We looked for a sudden drop in temperature — a sure sign of being inside the vortex,” mentioned Olsen. “Comparing the ACS observations with the results from the Mars Climate Sounder shows clear differences in the atmosphere inside the vortex compared to outside. This is a fascinating opportunity to learn more about martian atmosphere chemistry and how conditions change during the polar night to allow ozone to build up.”