The Mars InSight lander from NASA died of dust last week. The robot, which was made to study tectonic activity on Mars, has been running on less and less power for a long time. This is because its 25-square-foot (4.2-square-meter) solar power array has slowly been covered by a thick layer of dust. NASA said on Wednesday (Dec. 21) that it hadn’t heard from the lander in days, so the mission was officially over.
InSight landed in the flat, boring-looking Elysium Planitia basin south of Mars’ equator in November 2018. This was two years longer than its mission was supposed to last. Still, many people wondered if there was anything that could have been done to save the robot, which was otherwise healthy and had been giving new information about how life works on Mars.
Cost versus benefit
In a Twitter thread posted about six weeks before InSight died, NASA talked about the trade-offs engineers had to make when making a mission for Mars, which is known for being very dusty.
“People often ask: Don’t I have a way to clean myself (wiper, blower, etc.)? It’s a fair question, and here’s the quick answer: “NASA wrote something on the Twitter account of the lander. “A system like that would have cost more, taken up more space, and been harder to use. The easiest and least expensive way for me to reach my goals was to bring solar panels big enough to power my whole mission, which I did (and then some!).”
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Dust storm season
Space agencies usually try to avoid sending landers to Mars during the planet’s northern autumn and winter, when dust storms are common. Since a year on Mars is about the same length as two Earth years, most recent landers and rovers, including InSight, have survived more than one dust storm season.
The Curiosity rover has been on Mars for 11 years and is still working well. It has been through a lot of dust storm seasons. The rover even took measurements of how the amount of dust on its sensors and deck changed over time. This showed how seasonal winds and dust devils help rovers keep going for longer. As it turns out, InSight didn’t have much luck with the natural cleaner on Mars.
No dust devil car wash
Dust devils have been seen cleaning Spirit and Opportunity, two of NASA’s older Mars rovers. Opportunity, in particular, was able to keep doing its job for more than 14 years, far longer than its three-month lifespan. Regular dust devil sweeps and cleaning caused by the wind were important parts of that mission, which broke a record. In 2019, a big dust storm finally knocked out the little rover, putting an end to its record-setting journey of discovery.
Mike Williams, Chief Engineer at Airbus Defence and Space, which is currently rethinking the dust defense plan for the European ExoMars Rosalind Franklin rover, said that InSight seemed to be in a “particularly bad position for dust removal.”
Tilting solar panels
Williams agrees that NASA’s method of using big solar panels to keep dust out of Mars-exploring spacecraft is the best, safest, and least expensive way to do this. But Airbus is looking into the possibility of adding a dust defense system, and they have plenty of time to do this. The mission, which was built with help from Russia, was put on hold after Russia invaded Ukraine. The planned launch in September was canceled, and the ExoMars rover is now being kept in a clean room by Airbus while some key parts, which were built by Russia, are being replaced.
“The best and easiest solution is to make the arrays big enough to handle the less sunlight that gets to them because of the dust,” Williams told Space.com. “It’s the least complicated level. It has the lowest risk because it has the fewest subsystems and functions. From the point of view of making a mission, that is definitely the best way to do things.”
Williams said that when the ExoMars mission was first thought of, engineers looked at many ways to get rid of dust, such as brushes, wipers, gas blowers, and electrostatic wipers. At that time, they decided that the rover didn’t need to clean itself, since its mission in Oxia Planum was only supposed to last 180 sols. They are rethinking their plan again because the new launch date is not expected to happen before 2028.
“Now that ExoMars is coming back to life, we are thinking about bringing back some of those capabilities,” Williams said. “We might be able to get rid of some of that dust by tilting the solar panels. It would also help the panels face the sun more effectively, which may have other benefits.”
Williams also said that Airbus engineers, like NASA’s, have to come to terms with the fact that ExoMars, like other spacecraft on Mars, may eventually be destroyed by dust and won’t be disappointed if the rover only just outlives its planned mission life. But, like Spirit and Opportunity, they hope that the weather on Mars will help them.
“Unfortunately, that’s just the way space missions work,” Williams said.
Even though InSight wasn’t made to clean itself, NASA made some last-ditch efforts to help the lander get rid of some of the dust in its last few months as the amount of electricity it could make from its solar panels went down.
In May, people on Earth told InSight’s robotic arm to sprinkle some sand on one of the dusty panels on the lander. As the wind blew the sand across the panel, it picked up some of the dust along the way. This made the dust blanket that blocked the sun thinner.
A NASA statement says that the operation gave the lander about 30 watt-hours of power per sol at the time
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