Mars mission’s last gasp?

Shortly after making its most dramatic observation to date, NASA’s InSight Mars lander appears to be on its last legs.

The new observation was a magnitude 5.0 marsquake that occurred on May 4, nearly an entire order of magnitude more powerful than the largest one previously observed, which was magnitude 4.2.

That’s important, because InSight’s primary task is to use seismic waves from such quakes to probe the Martian interior, all the way to the core, and the bigger the quake, the better.

“So, even as we are getting close to the end of our mission, Mars is giving us great things to see and add to the data record,” the mission’s principal investigator, Bruce Banerdt, said at a recent press conference.

The reason the mission appears to be coming to the end, added InSight’s deputy project manager, Kathya Zamora Garcia, is the steady accumulation of dust on the lander’s solar panels.

When InSight landed in November 2018, she says, these panels were able to generate about 5,000 watt-hours of power (5 kilowatt hours) per Martian day. Now that’s down to one-tenth that figure, and dropping. “Our solar panels are covered with Martian dust,” she says.

Last year, the InSight team fended off a similar problem by using the lander’s robotic arm to sprinkle sand on the lander’s body, upwind from the solar panels. When wind gusts picked up these sand grains, they tumbled across the panels, sweeping away some of the dust in the process.

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Since then, Garcia says, the team has done this five more times, but they are fighting a losing battle, especially because the lander’s part of Mars is moving into a dustier time of year, when haze will further reduce the amount of sunlight reaching its panels.

In the next two to three weeks, she estimates, power will fall too low for continuous operation of the seismometer. In a couple of months, possibly in mid-to-late July, it will no longer be possible even to run the seismometer episodically. By late December, power will be so low that the lander probably won’t even be able to take the occasional picture or communicate back to Earth.

That said, the scientists are thrilled the dust held off long enough to allow the seismometer to record the recent marsquake. “This quake was far and away bigger and more clear [in its seismic details] than anything else we’ve seen,” Banerdt says.

Once these details are fully untangled, they will add to scientists’ understanding of how seismic waves propagate through the Martian interior, moving at different speeds in different layers and bouncing off boundaries between layers – thereby revealing important details about the deep Martian interior. “This quake is really going to be a treasure trove of information once we can get our teeth into it,” Banerdt says.

And, he says, even though InSight is probably coming to the end of its life, the data it collected will persist, keeping scientists busy for decades to come as they come up with ever-better ways of teasing information out of it.

“The sunset of the spacecraft is not the sunset of the science that is to come,” says Lori Glaze, director of NASA’s Planetary Science Division.

Not that the lander’s fate is sealed. It is possible that a dust devil (whirlwind) will pass over it, blowing dust off the solar panels and restoring power, as happened repeatedly to keep NASA’s Spirit and Opportunity rovers operating from 2004 to 2019.

It’s not like there aren’t dust devils around to do the trick. Banerdt says that the lander’s super-sensitive air-pressure gauge has detected fluctuations from several thousand of them passing within a few hundred metres of the site. Some seem to have come within tens of metres. But Banerdt says these dust devils appear to be quite small, and nothing less than a direct hit on one of the panels would do the trick. “It could still happen,” he says. “But it hasn’t happened yet in three and a half years, so we’re not too hopeful.”