Evaporative meteors make clouds on Mars

Whatever planet you are on, the physics remains the same. For clouds, this means that they obey a particular law: they form only around any seed, usually a layer of dust or salt. On Earth, with its thick atmosphere and strong currents of air, it is possible to find these light particles in the atmosphere, forming clouds at all altitudes.

On Mars, this process is more difficult. Scientists have trouble understanding the high-altitude clouds they regularly see in the Mars skies, as models predict that it's hard to lift even the prolific dust of Mars high enough in the atmosphere to form the clouds.

But recent observations by NASA's MAVEN spacecraft, combined with the modeling of a group of researchers led by Victoria Hartwick, a graduate student at the University of Colorado at Boulder, may have solved the problem . They say that meteors that crash into the atmosphere of Mars and wind into dust, which they call "meteoric smoke," can provide the seeds needed to form clouds at high altitudes. The Hartwick team released its results Monday at Nature Geoscience.

Seeding in the clouds

"We are used to seeing these planets as autonomous bodies," Hartwick said. Astronomy, where the climate and weather of each world come from within. "But this is an example of the climate affected by the environment of its solar system."

Making clouds with meteor dust is not unheard of. Meteors are thought to be the seed of some of the glittering night clouds of the Earth, but even this discovery is relatively recent.

Hartwick's work is mainly based on modeling. Previously, it was difficult to recreate with computers the clouds that spacecraft observed in the middle and upper atmosphere of the Red Planet. But with the addition of meteor particles to models, the matches were much narrower.

The theory is reinforced by the results of the MAVEN mission. In 2017, the satellite observed ionized metal particles in the upper atmosphere of Mars. Researchers see it as proof that meteors entering the Martian sky are warming up and evaporating into tiny particles.

It's a common process on Earth, where up to 100 tons of meteorites rain every day. Mars receives a relative net, no more than 3 tons, and less than half a ton is converted into fine particles that can serve as cloud sprouts. "It's about the same amount as a lion or harbor seal distributed every day on the planet," says Hartwick. But even this smaller amount still contains billions of individual particles, which have a notable cumulative effect.

Although the evidence is somewhat indirect, the modeling combined with MAVEN's results is as conclusive evidence that researchers will probably have it. "On Earth, we were able to discover [cloud seeds] flying through the material and capturing the meteoric smoke. It's very difficult to do it on Mars. "

As for the impact of clouds, they are thin and often barely visible. But Hartwick says they can still affect the average atmosphere, where the temperature can fluctuate 10 degrees several times during the day, forming and dissipating clouds as part of the temperature cycle.

But Hartwick points out that the old Mars would have had much heavier meteor shower. "When you rewind the watch, it could have a bigger impact on the formation of clouds on the onset of the climate."