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The rotating globes of May 28 and July 1 show a global dust storm that completely masks the surface of Mars. Credits: NASA / JPL-Caltech / MSSS
Eyeballs, human and robotic, are not lacking. Scientists are constantly exploring the red planet from telescopes on Earth, as well as the six spacecraft circling the planet from its orbit and two others on the surface. Thus, when the dust filled the atmosphere during the recent dust storm on the planet, the observations were numerous.
The Mars Reconnaissance Orbiter (MRO) of NASA provided early information on May 30, when it observed a build-up of dust in the atmosphere near Perseverance Valley, where NASA's Opportunity robot is in train to explore. The increasingly foggy storm, the largest since 2007, forced Opportunity to close its science business on June 8, knowing that sunlight could not penetrate the dust to power the solar panels of the rover. Scientists are eagerly waiting for the itinerant explorer to regain power and phone home.
Meanwhile, on June 5th, on the other side of the world, the evidence materialized that the storm was rising and was beginning to hit Gale Crater, NASA's Curiosity rover search site. (The storm was officially ranked World Jun 20.)
It comes from an unexpected source: an actuator, or motor, that feeds a lid into a funnel that receives samples of Martian rock powder introduced by the Curiosity drill. The samples are then subjected to chemical analysis by the SAM (Sample for At Analysis) portable chemistry laboratory, designed by scientists at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and integrated into Curiosity's belly. .
Benito Prats, an electromechanical engineer from Goddard, noticed that the dust storm was slowly reaching Curiosity thanks to the continuous temperature readings that he had collected using actuator sensors.
"All my graphics showed the dust storm effect on the actuator as it was exposed; he's sitting over there on the rover's bridge, "Prats said. "Suddenly, I saw the daytime temperature drop very quickly."
At night too, Prats said, he has seen temperatures rise above normal levels. This happens during a dust storm because less sun enters the dusty atmosphere during the day, which cools the surface of the planet, while at night, a warmer, dusty atmosphere heats the soil. Other weather tools from the explorer, such as the Rover Environmental Monitoring Station, which measures air temperature, atmospheric pressure and other environmental conditions, were also beginning to indicate the accumulation of dust.
The photo on the left shows the Curiosity rover's bridge, the ground (Martian day) 36, or September 10, 2012, which had come in about a month after his Mars mission. The deck is clean except for some particles and the shadow of the MastCam, which broke the picture. The photo on the right, taken from # 2,068 or May 31, 2018, shows dirt particles, powder and dust on the rover deck, surrounding an actuator. However, all the dust does not come from the recent storm. Mars is generally dusty, so most of the illustrated dust has accumulated over six years. Sometimes, particles are thrown into the air when the rover rolls, other times, dust devils or a gust of wind lift the dust and lay it on the deck of the rover. Credits: NASA / JPL-Caltech
Unlike Opportunity, the Curiosity is powered by a plutonium generator, so its activities are not affected by dust protection. The temperature changes also did not affect the SAM actuators – there are two sampling funnels, in case they get clogged – because they prefer warmer and less extreme temperatures.
SAM analyzes Martian rocks and soils in search of organic materials. For SAM to work properly, its actuators must be at minus 40 degrees Celsius (minus 40 Fahrenheit). That's why Prats closely monitors their temperature. When Martian temperatures in the spring fall to minus 60 degrees Celsius at night, SAM heaters must warm the motors to lift the funnel cover to allow samples to fall.
After discovering the effects of the dust storm in its temperature data, Prats combined it with averages of the actuator temperatures to estimate when the dust storm would subside.
"On the ground 2,125 (July 28), I noticed a linear trend," he said. "So I said OK, I can predict that soil 2180 (September 23rd) will be the day we go out of the dust storm and the temperature will return to normal, although I put today updated 21 September (18 September). 18, indicating that the dust above the crater Gale was installed at that time. Much of the dust is also installed at Perseverance Valley.
Data from all sources, even the most unexpected ones, are useful to planetary scientists, because we still do not know why some Martian dust storms last for months and become huge, while others remain small and last only one week. week.
Scientists hope to be able to predict these global events, as they can predict hurricanes on Earth, to better understand the current and past climate of the planet and to properly design robotic and human missions on the planet, scientists say. The NASA.
"Some things about Mars make it more predictable and others less than Earth," said Scott D. Guzewich, an atmospheric scientist from Goddard who conducted the investigation into the Curiosity dust storm.
"I can estimate, two years in advance, the temperature, the atmospheric pressure and whether there will be dust or clouds in the air during the dust-free season in the world," he said. he declares. "But during the rainy season, in places exposed to dust storms, I can not predict at all that there will be a dust storm one day and not another."
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