& # 39; Storm Chasers & # 39; on Mars looking for dusty secrets

Storm Hunting takes the chance and the patience on Earth – and even more so on Mars.

For scientists observing the red planet from data collected by NASA's orbiters, last month 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 became global

. For the Opportunity rover, this 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 the beginning of September may be enough before the haze has cleared enough to allow Opportunity to get going.

Credit: NASA

Solar panels can be covered with a thin 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 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) adapt their observations of the Red Planet to study this storm and learn 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 [19659003] 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. "Having another example of a dust storm really helps us understand what's going on."

Since the beginning of the dust storm, the THEMIS team has increased the frequency of global atmospheric observations from two to ten times 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 appearance 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 gives a powerful feedback: The solar warming of the projected dust in the atmosphere changes the temperatures, which changes the winds, which can amplify the storm by lifting more dust from the surface.

Scientists want to know the details of the storm. the air rising or falling? 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 become global.

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

Scientists want to know why these storms occur every few years, which is difficult to Without a long record of such events, it would be as if the extraterrestrials were observing the Earth and seeing the climatic effects of El Niño over many years of observations – they wondered why some regions were more rainy and some regions became drier in an apparently regular pattern.

MAVEN

Since the MAVEN orbiter is entered the orbit of Mars, "one of the things we expected was a global dust storm," said Bruce Jakosky, principal investigator of the MAVEN orbiter

. But MAVEN does not study the dust storm itself. On the contrary, 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 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 rises enough to be broken by sunlight, the solar wind sweeping the hydrogen atoms into space, said 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 are studying 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 sample of fresh rock. But we also use instruments to study the evolution of the dust storm. "

Curiosity has a number of" "eyes" that can determine the abundance and size of dust particles according to their dispersion.This includes its Mastcam, ChemCam, and an ultraviolet sensor on REMS, its suite of meteorological instruments. help to study atmospheric tides – pressure changes that move in the form of waves in the thin air of the entire planet These tides change dramatically depending on where the dust is located in the world, not only inside the crater of Gale.

The global storm can also reveal secrets about the devils and winds of the Martian dust.Dust devils can occur when the surface of the The planet is hotter than the air above.Heating generates air swirls, some of which pick up dust and become dust devils.When a dust storm, there is 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. Every time 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.