'Storm chasers & # 39; on Mars looking for dusty secrets

For scientists looking at the red planet from data collected by NASA's orbiters, last month was a boon. "Global" dust storms, where a series of fleeing storms create a dust cloud so large that it envelops the planet, appear only every six to eight years (ie three to eight years). four years of March). Scientists still do not understand why and how these storms form and evolve.

In June, one of these dust events quickly engulfed the planet. Scientists first observed a smaller-scale dust storm on May 30th. On June 20, it had become worldwide

For the Opportunity rover, it meant a sudden drop in visibility from a clear, sunny day to a cloudy sky. Because Opportunity works with solar energy, scientists had to suspend their scientific activities to preserve the robot's batteries. As of July 18, no response has been received from the rover

Fortunately, all this dust acts as an atmospheric insulator, preventing nighttime temperatures from falling below what the Opportunity can withstand . But the rover of nearly 15 years has not yet come out of the woods: it could take weeks, even months, for the dust to begin to settle. Based on the longevity of a global storm in 2001, NASA scientists estimate that it will be early September before the haze has cleared enough to allow Opportunity to climb and return home. .

a beautiful film of dust. This could delay the recovery of the rover while it recovers energy to recharge its batteries. A gust of wind would help, but is not a condition for a complete recovery.

While the Opportunity team is seriously waiting to hear from the rover, the scientists on the d & # 39; Other Mars missions have had a rare chance to study this head

Orbiter Mars Reconnaissance Orbiter, Mars Odyssey and Mars Atmosphere and Volatile EvolutioN (MAVEN) are adapting their observations of the red planet to study this global storm and in learn more about the weather conditions of Mars. Meanwhile, the Curiosity rover studies the dust storm of the Martian surface

Here is how each mission is currently studying the dust storm, and what we could learn:

Mars Odyssey [19659005] With THEMIS (Thermal Emission Imaging System) instrument, scientists can track the surface temperature of Mars, the atmospheric temperature and the amount of dust in the atmosphere. This allows them to watch the dust storm grow, evolve and dissipate over time.

"It's one of the biggest meteorological events we've seen on Mars," since space ship observations began in the 1960's a scientist at NASA's Goddard Spaceflight Center at Greenbelt, Maryland, who works on the THEMIS instrument. "The arrival of another example of a dust storm really helps us understand what is happening."

Since the beginning of the dust storm, the THEMIS team has increased the frequency of global atmospheric observations every ten days to twice a week. A mystery that they are still trying to solve: how do these dust storms become globalized? "Every March, during the dusty season, there are a lot of storms at the local or regional scale that cover an area of ​​the planet," Smith said. But scientists do not yet know how these smaller storms can sometimes end up encircling the entire planet.

Mars Reconnaissance Orbiter (MRO)

Mars Reconnaissance Orbiter has two instruments that study the dust storm. Every day, the Mars Color Imager (MARCI) maps the entire planet in the middle of the afternoon to follow the evolution of the storm. Meanwhile, the MRO Mars Climate Sounder (MCS) instrument measures how the temperature of the atmosphere changes with altitude. Since the end of May, the instruments have observed the onset and rapid expansion of a dust storm on Mars

With these data, scientists are studying how the dust storm changes the atmospheric temperatures of the planet. Just like in the Earth 's atmosphere, temperature changes on Mars can affect wind patterns and even the circulation of the entire atmosphere. This provides powerful feedback: The solar heating of the projected dust in the atmosphere changes the temperatures, which changes the winds, which can amplify the storm by raising more dust from the surface.

Scientists want to know the details of the storm, where does the air melt or fall? How do atmospheric temperatures now compare to a year without a storm? And as with Mars Odyssey, the MRO team wants to know how these dust storms are globalizing.

"The very fact that you can start with something that is a local storm, no bigger than a small state, and then trigger something that raises more dust and produces a haze that covers almost the entire planet is remarkable, "said Rich Zurek of NASA's Jet Propulsion Laboratory in Pasadena, California, the MRO project scientist

every few years, which is hard to do without a long record of such events. as if the extraterrestrials were observing the Earth and observing the climatic effects of El Niño over many years of observations – they would wonder why some regions were more rainy and some areas were getting drier in an apparently regular pattern.

MAVEN

Since the MAVEN orbiter has entered the orbit of Mars, "one of the things we are waiting for dions is a global dust storm, "said Bruce Jakosky, principal investigator of the MAVEN orbiter

. But MAVEN does not study the dust storm itself. The MAVEN team wants to study how the dust storm affects the upper atmosphere of Mars, about 62 miles (over 100 kilometers) above the surface, where the dust does not even reach . MAVEN's mission is to understand what happened to the atmosphere of Mars. We know that at one point, billions of years ago, liquid water came together and sank along the surface of Mars, which means that its atmosphere was to be thicker and more insulating, similar to that of the Earth. Since MAVEN arrived in March in 2014, his research has shown that this atmosphere has been stripped by a torrent of solar wind over several hundred million years, between 3.5 and 4.0 billion dollars. ; years.

But there are nuances to understand outside, like how dust storms like the current affect how atmospheric molecules escape into space, said Jakosky. For example, the dust storm acts as an atmospheric insulator, trapping the heat of the sun. Does this heating change the way molecules escape from the atmosphere? It is also likely that as the atmosphere heats up, more water vapor builds up enough to be broken by sunlight, the solar wind sweeping the atoms away. 39, hydrogen in the space, says Jakosky.

The team will not have answers though, but each of MAVEN's five orbits a day will continue to provide invaluable data.

Curiosity

Most of NASA's spacecraft study the dust storm from above. The Mars Science Laboratory's Curiosity robot has a unique perspective: the nuclear-powered scientific machine is largely immune to the blackened sky, allowing it to collect scientific data inside the beige veil that envelops the planet. .

"said Ashwin Vasavada of JPL, the Curiosity project scientist. "Our newly commissioned drill builder acquires a fresh rock sample, but we also use instruments to study the evolution of the dust storm."

Curiosity has several "eyes" capable of determining the amount of dust. abundance and size of dust particles. how they disperse and absorb light. This includes its Mastcam, ChemCam, and an ultraviolet sensor on REMS, its suite of meteorological instruments. The REMS can also help study atmospheric tidal changes in pressure that move in the form of waves in the thin air of the entire planet. These tides change drastically depending on where the dust is in the world, not just inside the crater of Gale.

The global storm can also reveal secrets about devils and Martian dust winds. Dust devils can occur when the surface of the planet is warmer than the air above. The heater generates air swirls, some of which pick up dust and become dust devils. During a dust storm, there is less direct sunlight and less heat during the day; it could mean fewer devils swirling on the surface.

Even new drilling can advance the science of dust storms: watching the small piles of loose materials created by Curiosity's exercise is the best way to monitor the winds. last at least two months. Whenever you see Mars in the sky in the coming weeks, remember the amount of data collected by scientists to better understand the mysterious weather of the red planet.

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Image: Mars dust storm