Scientists have obtained the first data on wind circulations in the atmosphere of Mars. Results are based on direct measurements from the MAVEN spacecraft. The study is described in the journal Science.
The American artificial satellite for studying the atmosphere of Mars MAVEN (Mars Atmosphere and Volatile EvolutioN) has been operating near the Red Planet since September 2014. Moving in an elliptical orbit, it periodically enters the upper atmosphere, analyzing its composition and physical parameters.
In 2016, Mehdi Benna, a planetary scientist at NASA's Goddard Space Flight Center, invited colleagues from the MAVEN project to conduct a unique experiment. The idea was to remotely reprogram the spacecraft itself and the NGIMS gas and ion mass spectrometer on board so that it could collect data on atmospheric circulation.
In order to assess the complexity of the task, it suffices to say that such measurements have not yet been carried out even in the upper layers of the Earth's atmosphere. Scientists joke that they "decided to start with Mars."
In order to measure the parameters of atmospheric circulation, the usually stationary parts of the apparatus had to start swinging back and forth quickly enough when entering the atmosphere, like car windshield wipers.
Spacecraft manufacturer Lockheed Martin has confirmed that such modifications are possible without damaging the satellite. The reprogramming was successful, and for two years, from 2016 to 2018, MAVEN regularly collected data on the movement of the atmospheric masses of Mars at an altitude of 120 to 300 kilometers above its surface, two days a month.
"This is an example of 'smart' reengineering of a spacecraft in flight," Benn said in a press release.
Basically, the results obtained fit into the existing theoretical models, but there were also surprises. It turned out that against the background of a generally stable and stable circulation in the upper layers of the Mars atmosphere, it has high short-term variability.
"What we observed is broadly in line with what could be predicted from models," Benna says. "Physics works. But at every point, the direction of the wind is constantly changing."
The second surprise was that at an altitude of hundreds of kilometers above the surface, air masses still bend around the relief, repeating the contours of mountains, canyons and basins.
As Benna explains, "When air mass flows around these elements, it creates ripple effects that rise to the upper atmosphere and can be detected by instruments. On Earth, we see the same waves, but not at such high altitudes."
Scientists have two explanations for why these so-called "orthogonal waves" on Mars remain unchanged for so long. On the one hand, its atmosphere is more rarefied than on Earth, so the waves propagate in it further. On the other hand, on Mars, where the height of the mountains reaches 20 kilometers, the height difference is much greater.
The authors hope that further observations and analysis of the results will allow them to eventually create a climate model for Mars.