These spacecraft are studying Mars dust
Side-by-side movies shows how dust has enveloped the red planet, courtesy of the Mars Color Imager (MARCI) camera onboard NASA’s Mars Reconnaissance Orbiter (MRO). The view from May shows Valles Marineris chasms (left), Meridiani center, an autumn dust storm in Acidalia (top) and the early spring south polar cap (bottom). The view from July shows the same regions, but most of the surface was obscured by the planet-encircling dust cloud and haze.
Over the past month, Mars has put on a spectacular show in our night sky. The show culminates on July 27, 2018, when Earth will pass between Mars and the sun, bringing Mars to opposition on the same night that Mars will be near a totally eclipsed moon! All of that is wonderful for skywatchers, but space scientists are having a field day with Mars now, too. The same event that’s making Mars extra bright for us – that is, Mars’ September 16, 2018, perihelion or closest point to the sun – has also created conditions for a planet-wide dust storm, which has been raging now for over a month.
For scientists watching the red planet from data gathered by NASA’s orbiters, the past month has been a windfall. Global dust storms, where a runaway series of storms creates a dust cloud so large it envelops the planet, only appear every six to eight years (that’s three to four Mars years). Scientists still don’t understand why or how exactly these storms form and evolve.
For NASA’s Opportunity rover, the dust storm has not been good news. NASA said it meant:
… a sudden drop in visibility from a clear, sunny day to that of an overcast one. Because Opportunity runs on solar energy, scientists had to suspend science activities to preserve the rover’s batteries. As of July 18, no response has been received from the rover.
But other NASA spacecraft – both on the ground and in orbit – are observing the dust storm. In fact, NASA said:
The Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiters are all tailoring their observations of the red planet to study this global storm and learn more about Mars’ weather patterns. Meanwhile, the Curiosity rover is studying the dust storm from the Martian surface.
The Mars Reconnaissance Orbiter has two instruments studying the dust storm. Each day, its Mars Color Imager maps the entire planet in mid-afternoon to track the evolution of the storm. Meanwhile, its Mars Climate Sounder instrument measures how the atmosphere’s temperature changes with altitude. Rich Zurek of NASA’s Jet Propulsion Laboratory, Pasadena, California, is the project scientist for the Mars Reconnaissance Orbiter. Zurak said:
The very fact that you can start with something that’s a local storm, no bigger than a small [U.S.] state, and then trigger something that raises more dust and produces a haze that covers almost the entire planet is remarkable,
The MAVEN orbiter has been circling Mars since 2014. Since it entered Mars’ orbit, said Bruce Jakosky, the orbiter’s principle investigator,
… one of the things we’ve been waiting for is a global dust storm.
NASA said MAVEN isn’t studying the dust storm itself. Instead:
… the MAVEN team wants to study how the dust storm affects Mars’ upper atmosphere, about 62 miles (more than 100 km) above the surface — where the dust doesn’t even reach. MAVEN’s mission is to figure out what happened to Mars’ early atmosphere. We know that at some point billions of years ago, liquid water pooled and ran along Mars’ surface, which means that its atmosphere must have been thicker and more insulating, similar to Earth’s.
Since MAVEN arrived at Mars in 2014, its investigations have found that this atmosphere may have been stripped away by a torrent of solar wind over several hundred million years, between 3.5 and 4.0 billion years ago.
But there are still nuances to figure out, such as how dust storms like the current one affect how atmospheric molecules escape into space … For instance, the dust storm acts as an atmospheric insulator, trapping heat from the sun. Does this heating change the way molecules escape the atmosphere?
Most of NASA’s spacecraft are studying the dust storm from above. And the Opportunity rover is currently inoperable. But the Curiosity rover – designed to explore Gale Crater on Mars – isn’t suffering the same fate as Opportunity. That’s because Curiosity doesn’t run on solar power. It is a nuclear-powered science machine – and therefore largely immune to Mars’ dust-darkened skies – still collecting science data as the dust flies all around it.
JPL’s Ashwin Vasavada, Curiosity’s project scientist, said:
We’re working double-duty right now. Our newly recommissioned drill is acquiring a fresh rock sample. But we are also using instruments to study how the dust storm evolves.
Curiosity has a number of “eyes” that can determine the abundance and size of dust particles based on how they scatter and absorb light. That includes its Mastcam, ChemCam … its suite of weather instruments [called the Rover Environmental Monitoring Station, or REMS]. REMS can also help study atmospheric tides – shifts in pressure that move as waves across the entire planet’s thin air. These tides change drastically based on where the dust is globally, not just inside Gale crater.
The global storm may also reveal secrets about Martian dust devils and winds. Dust devils can occur when the planet’s surface is hotter than the air above it. Heating generates whirls of air, some of which pick up dust and become dust devils. During a dust storm, there’s less direct sunlight and lower daytime temperatures; this might mean fewer devils swirling across the surface.
Even new drilling can advance dust storm science: watching the small piles of loose material created by Curiosity’s drill is the best way of monitoring winds.
Scientists expect the Mars dust storm to last several more months. Expect some new science results from this grand opportunity to study nature on another world!
Bottom line: How various NASA spacecraft are studying the ongoing dust storm on Mars.