CU Boulder Researchers Find Possible Source Of Clouds On Mars

BOULDER, CO — A new study by University of Colorado Boulder researchers may have unlocked the secret behind clouds on Mars. Astronomers have long observed clouds in Mars’ middle atmosphere, which begins about 18 miles above the surface, but have struggled to explain how the clouds form.

The study found that the clouds may owe their existence to meteoric smoke — the icy dust created by space debris breaking apart in the planet’s atmosphere.

Victoria Hartwick, a graduate student in CU Boulder's Department of Atmospheric and Ocean Sciences and lead author of the new study, said the findings are a good reminder that planets and their weather patterns aren’t isolated from the solar systems around them.

“We’re used to thinking of Earth, Mars and other bodies as these really self-contained planets that determine their own climates,” Hartwick said in a CU Boulder media release. “But climate isn’t independent of the surrounding solar system.”

In order to form clouds, water molecules must first coalesce around some kind of particles in the air, such as tiny grains of sea salt or dust, Hartwick said. But, as far as scientists can tell, those sorts of cloud seeds don’t exist in Mars’ middle atmosphere. That’s what led her and her colleagues, who included Brian Toon, a professor at CU Boulder, and Nicholas Heavens, an assistant professor at Hampton University, to meteors.

About two to three tons of space debris crash into Mars every day on average. And as those meteors rip apart in the planet’s atmosphere, they inject a huge volume of dust into the air.

To find out if such smoke would be enough to give rise to Mars’ mysterious clouds, Hartwick’s team turned to massive computer simulations that attempt to mimic the flows and turbulence of the planet’s atmosphere.

And sure enough, when they included meteors in their calculations, clouds appeared.

“Our model couldn’t form clouds at these altitudes before,” Hartwick said. “But now, they’re all there, and they seem to be in all the right places.”

The idea might not be as outlandish as it sounds, she said. Research has shown that similar interplanetary dust may help to seed clouds near Earth’s poles.

But you shouldn’t expect to see gigantic thunderheads forming above the surface of Mars anytime soon, Hartwick said. The clouds her team studied were much more like bits of cotton candy than the clouds Earthlings are used to. Those clouds, however, are still important for the climate of Mars. The group’s simulations showed that such accumulations could cause temperatures at those high altitudes to swing up or down by as much as 18 degrees.

The team’s findings on modern-day Martian clouds may also help to reveal the planet’s past evolution and how it once managed to support liquid water at its surface, Toon said.

“More and more climate models are finding that the ancient climate of Mars, when rivers were flowing across its surface and life might have originated, was warmed by high altitude clouds,” he said. “It is likely that this discovery will become a major part of that idea for warming Mars.”