Skip to main content

Changes in Mars’ atmosphere are driven by enormous CO2 ice cap at its pole

We’re just starting to learn about how complex the atmosphere of Mars is. We know that it is primarily composed of carbon dioxide, but there are also smaller amounts of oxygen and methane there whose levels fluctuate over time. And all the way back in 1966, scientists theorized that the planet’s stable cap of carbon dioxide at its pole could have planet-wide effects on the atmosphere.

Now, a new study has looked at the carbon dioxide ice deposit on Mars’ south pole and found that it does indeed appear to affect global atmospheric pressure. This is due to several factors: The fact that Mars’ atmosphere is very thin, with a surface pressure of 0.6% that of Earth, and the fact Mars wobbles on its axis by up to 10 degrees as it orbits the sun, so at some times its poles are exposed to more sunlight than at other times.

Together, these factors mean that the carbon dioxide ice on the south pole is occasionally exposed to direct sunlight, leading to sublimation — where the carbon dioxide turns from a solid to a gas without passing through the liquid stage. The pumping of relatively large amounts of carbon dioxide gas into the atmosphere could have profound effects on the planet over the long term.

The Martian pole
The Martian pole NASA/JPL/Malin Space Science Systems

These changes would be enough to swing the pressure of Mars’ atmosphere from down to one-quarter of where it is today to all the way up to twice where it is today, although this change would happen slowly, over tens of thousands of years.

Researchers looked at the ice cap and the layers of carbon dioxide ice and water ice which comprise it, and they formulated a model of how the layers could have developed over time. When they compared their model to the real findings, they found an excellent match.

“Usually, when you run a model, you don’t expect the results to match so closely to what you observe,” researcher Peter Buhler said in a statement. “But the thickness of the layers, as determined by the model, matches beautifully with radar measurements from orbiting satellites.”

This gives strong evidence that the sublimation of carbon dioxide ice is indeed changing the atmospheric pressure over time. And that helps us to understand how Mars’ climate has changed in the past and will continue to change in the future. “Our determination of the history of Mars’s large pressure swings is fundamental to understanding the evolution of Mars’s climate, including the history of liquid water stability and habitability near Mars’s surface,” Buhler explained.

The findings are published in the journal Nature Astronomy.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
Mars’s strange equatorial terrain could have formed under an ice sheet
mars equator terrain glaciers image 7844 1e deuteronilus mensae 1

This image shows a region of Mars named Deuteronilus Mensae. The oblique perspective view was generated using a digital terrain model and Mars Express data gathered on February 25, 2018. ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO

Mars is a mysterious place in many ways -- not least because its two hemispheres are drastically different. The northern hemisphere of the planet has low plains, with few impact craters, while the southern hemisphere is mountainous and pockmarked by craters. And scientists still aren't sure why the two halves of the planet are so different.

Read more
Mars 2020 rover stands on its own wheels for the first time
mars 2020 stand wheels pia23468 16 1

This image, taken on Oct. 8, 2019, at NASA's Jet Propulsion Laboratory in Pasadena, California, captures the first time the Mars 2020 rover carries its full weight on its legs and wheels. The rover was photographed in JPL's Simulator Building, where it underwent weeks of testing. NASA/JPL-Caltech

Progress continues for NASA's Mars 2020 rover, set to begin its journey to the red planet next year. The rover was recently lowered onto the ground, with the vehicle taking its full weight on its wheels and legs for the first time.

Read more
Mars was once an ocean-covered planet with a thick atmosphere like Earth’s
mars proton auroras water loss landscape dry wet 0 1

Today Mars is a cold, arid desert. But billions of years ago, it could have been a lush planet covered in surface water, not so different from Earth. The big difference between then and now is the Martian atmosphere, which is now thin and spare but was once thick enough to retain heat. This trapped heat allowed water to be liquid on the surface of the planet, which is key for the possibility of life existing there.

This artist’s concept depicts the early Martian environment (right) -- believed to contain liquid water and a thicker atmosphere -- versus the cold, dry environment seen on Mars today (left). NASA’s Goddard Space Flight Center

Read more