Martian clouds look and behave similarly to those on Earth. • The registry

While Mars once looked a bit like Earth, today they couldn’t be much more different. One is a red bowl of dust, the other a beautiful blue marble containing all life we ​​know. But ESA and NASA scientists have found a surprising common ground – clouds.

OK, Mars is made of dust and Earth is made of water, but cameras on ESA’s Mars Express and NASA’s Mars Reconnaissance Orbiter have found that they behave similarly despite the extreme differences in the atmosphere.

During the Martian spring of 2019, orbital probe cameras were focused on the planet’s north pole as many storms swirl around the receding ice cap.

What they saw was that “the storms appear to wax and wane in repeated cycles over a period of days, sharing common features and shapes,” ESA said.

“Spiral shapes are particularly visible… The spirals are between 1,000 and 2,000 km long and share the same origin as the extratropical cyclones observed in the middle and polar latitudes of the Earth.”

Cloud patterns on Mars and Earth. (Mars: ESA/GCP/UPV/EHU Bilbao; Earth: EUMETSET)

Essentially, the clouds on Mars and Earth look similar. This is due to convection, where hot air rises because it is less dense than the cool air around it.

“On Earth, the rising air contains water that condenses into clouds. The dust clouds imaged by Mars Express show the same process, but on Mars the rising air columns contain dust rather than water,” ESA said. “The sun heats dust-laden air, causing it to rise and form dust cells. The cells are surrounded by areas of sinking air that contain less dust. This creates the grainy pattern seen in the image of clouds on Earth.”

Note that Mars has no “air” per se; its atmosphere consists almost entirely of carbon dioxide.

NASA and ESA were indeed able to measure wind speeds by tracking the movement of cloud cells in images taken by the probes, and found gusts of up to 140 km/h. They were also able to measure the height of the clouds by combining the length of their shadows with knowledge of the sun’s position: “The results showed that dust can be about 6 to 11 km above the ground and the cells have a typical horizontal size of 20 to 40 km. “

Colin Wilson, Mars Express project scientist, commented: “When you think of a Martian-like atmosphere on Earth, you might easily think of an arid desert or polar region. It is quite unexpected, therefore, that by tracing the chaotic motion of dust storms, parallels can be drawn with the processes occurring in the humid, hot, and decidedly very unmarsian tropical regions of Earth.

Agustín Sánchez-Levaga of the Visual Monitoring Camera science team added: “Despite the unpredictable behavior of dust storms on Mars and the strong wind gusts that accompany them, we have seen that within their complexity, organized structures such as fronts and cellular convection patterns can emerge.

“Our work on Mars dry convection is another example of the value of comparative studies of similar phenomena occurring in planetary atmospheres to better understand the mechanisms underlying them in different conditions and environments.”

While it makes sense to study planetary atmospheres for scientific reasons, it’s also useful for future missions to Mars. Remember the sad story of the rover Opportunity, whose mission was ended in 2018 by a planet-wide dust storm that clogged its solar panels. In 2022, the Mars InSight lander faces a similar predicament and may only have a matter of days.

“Monitoring the development of dust storms is crucial to protect future solar-powered missions – and eventually human missions to the planet – from such powerful phenomena,” ESA said.

The scientists have published their full results in Icarus Diary. ®