UPDATE: July 6, 2021, 12:02 p.m. EDT InSight was incorrectly described as being the first mission designed to last a long time. Context has been added to make it clear that it was specifically the first solar-powered Mars surface mission designed to last a long time.
Mars is dusty. Like, reallydusty. And that dust may suffocate NASA’s InSight mission.
InSightsits on the surface of Mars measuring marsquakes and observing the local weather, powering itself with a pair of solar arrays that soak up energy from the sun. Since it landed in November 2018, InSight has been operating for more than 920 sols (Mars days), equal to about 940 Earth days.
That's seven months longer than its planned two-year mission. In that time, dust has obscured around 80 percent of the arrays, InSight’s principal investigator Bruce Banerdt shared in a presentationon June 21.
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The team expects to keep InSight running through the summer, but as that dust keeps piling up, it won’t be able to press on much longer.
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Along with his work on InSight, Banerdt was project scientist on the Mars Exploration Rover Project, which launched the solar-powered Mars rovers Spirit and Opportunity in 2003. He's been dealing with Martian dust for years.
“Dust is definitely up there as one of our major design challenges,” he said in an interview. “My black piano notwithstanding, we don’t really have a lot of dust on Earth compared to Mars.”
“My black piano notwithstanding, we don’t really have a lot of dust on Earth compared to Mars.”
Where there are rocks, there is erosion, and where there is erosion, there is dust. On Earth, 71 percent of the surface is water, and when dust touches water, it sticks to it and eventually gets deposited on the ocean floor. Mars is notably devoid of water, so all the dust that’s blowing around just keeps blowing around, sometimes even resulting in planet-wide dust storms.
Shortly before InSight landed, Opportunity found itself in such a storm, which blocked out the sun for multiple sols. Having run for 14 years on the red planet, the storm was too much for Opportunity’s solar panels. Last contact with the rover was made on June 10, 2018, just a few days into the storm.
This series of images shows simulated views of a darkening Martian sky blotting out the Sun from NASA’s Opportunity rover’s point of view during the 2018 global dust storm.Credit: NASA/JPL-Caltech/TAMUSpirit and Opportunity were both encumbered by dust at various points in their journeys, but the rovers caught breaks that InSight just can’t seem to match: cleaning events. Strong Martian winds can blow dust off of technology, giving them much-needed power boosts and prolonging their operations.
"We think this is because of dust devils, or more precisely 'atmospheric vortices,' that actually passed over the spacecraft," Banerdt said, referring to the rovers' cleaning events. "We hoped that we would experience the same thing with InSight."
Alas, it seems that there just aren't as many dust devils spinning around InSight's landing site as there were around Spirit and Opportunity. If a cleaning event doeshappen for InSight though, it could remain in action for a long, long time.
Learning from the dust
As we spend more time exploring Mars, scientists can develop new strategies to tackle problems like dust in the future.
"[InSight] is the first [solar-powered Mars surface] mission that was actually designed to last a long time" Banerdt said. "We didn't really have a lot of a lot of information and data to go on."
As it happens, solar arrays tend to maintain an electric charge, as do particles banging around in the sun's radiation on Mars. That means the dust is extra attracted to solar arrays.
Future missions could use special coatings on arrays to make them less adhesive, or even a grid of electrical wires above the arrays that a spacecraft could run a charge through and zap dust off, Banerdt said. Another option involves double-sided arrays set on a revolving joint that could flip over every couple of years.
For InSight, the team has found a method that sometimes helps to push some dust off the arrays: Pouring sand on them. Using a scoop, InSight grabbed some sand and dropped it upwind of a solar array. As the grains blew over, they picked up some dust, giving InSight a measurable power boost. Unfortunately, it doesn't always seem to be very effective.
InSight's scoop can be seen lifted above the solar array on the left side of the image before it drops sand.Credit: nasa/jpl-caltech"People are always asking us why we don't just put wipers on to clean them off," Banerdt said. "The main reason we don't do that is because of weight and complexity. It's not a trivial thing to set something up there with motors, and rubber doesn't work very well in a vacuum with an oxidizing environment."
In the future, astronauts on Mars could just sweep a rover’s solar arrays every once in a while. Or future rovers could just rely on nuclear power, like NASA's Perseverance and Curiosity rovers.
But using nuclear power is expensive. Perseverance's plutonium-based power supply cost NASA $75 million. Solar arrays are much cheaper.
Nuclear power involves environmental risks, too. If something went wrong, radiation could contaminate parts of Mars and ruin the results of future research missions.
"People are always asking us why we don't just put wipers on to clean them off."
If astronauts make it to Mars, dust could also be a serious health problem.
"The dust might be kind of toxic," Banerdt said. "Mars is a very oxidizing environment, and the ultraviolet radiation hitting the ground is not filtered out by the atmosphere. So the dust could be kind of reactive, and probably not deeply poisonous, but could be very irritable to lungs and mucous membranes and things like that."
Over long periods of time, dust can mess with a rover's other parts, even corroding wheels. Spirit lost the use of two wheels, and Curiosity has some wheel damage that NASA chemist James Gaier pinned mostly on Martian dust in a Medium article.
Martian dust will continue to be a challenge, but that's just part of the fun of exploring places that aren't like Earth.
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