NASA has had to put its power-starved Opportunity rover into an induced coma on Mars, but that drastic maneuver — plus some luck — should be enough to save it from one of the worst dust storms ever observed on the Red Planet.
That doesn’t mean everything’s cool at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., which has overseen the rover’s work on Mars for nearly 15 years.
“We have a very tight emotional connection with it,” John Callas, project manager for the Mars Exploration Rover mission, told GeekWire today during a teleconference.
“It’s like you have a loved one in a coma in the hospital,” he explained. “The doctors are telling you that, ‘OK, you’ve just got to give it time and she’ll wake up. All the vital signs are good, so it’s just waiting it out.’ But if it’s your 97-year-old grandmother, you’re going to be very concerned.”
Fortunately, Opportunity has advantages that your typical 97-year-old grandmother may lack. And that should help the solar-powered rover cope even though Mars’ expanding dust storm has reduced its electricity-generating capability by more than an order of magnitude.
The bad news is that the dust storm has darkened the skies over Opportunity to nearly pitch-black. Richard Zurek, chief scientist for JPL’s Mars Program Office, had to go back to 1971 to name a worse storm.
The good news is that the march of Martian seasons is heading toward summer in the Meridiani Planum region where Opportunity sits. That means temperatures are projected to stay above the range of -40 to -55 degrees Celsius (40 to 67 degrees below zero Fahrenheit), which is considered the minimum for survival of the rover’s electronics package.
Eight plutonium-powered heating units will provide an extra margin of safety, ensuring that the electronics stay warm enough to function.
Opportunity’s twin, the Spirit rover, wasn’t so lucky when it experienced a similar power drain in 2010. That rover’s electronic systems are thought to have frozen to death amid Mars’ wintry weather.
Another bit of good news has to do with Opportunity’s power system. Even after more than 14 years of operation, its batteries can hold 85 percent of the capacity they were designed for, Callas said.
“They are really the finest batteries in the solar system,” he said. “I wish my cellphone battery had half of that.”
The current dust storm came on more quickly than expected, but the rover team was prepared nonetheless. Over the past week, as mission managers saw that the storm was turning into a monster, they programmed Opportunity to deal with what Callas saw as an emergency situation.
For now, the rover has gone into an extended deep sleep and has shut down all of its systems — except for a master clock that’s timed to interrupt the snooze periodically and check the power levels. If the skies have lightened enough to keep the batteries charged, the rover will recontact Earth and get back to work.
But if the power keeps draining away, even that master clock would have to be turned off. The rover would then be forced to use a more basic survival mode. Opportunity would set an alarm clock to check its conditions every four hours. Once there’s enough sunlight to activate the solar panels, the rover would try to contact Earth even if it didn’t know what time it was.
“It means we have to be able to watch and be vigilant,” Callas said.
It’s not yet clear exactly how long the storm will last. Its extent is still growing, and within the next day or two, dust could be swirling around virtually the entire planet. But Zurek said the darkness can last only so long.
“Typically you get back to background levels in a few weeks,” he said. “For the very largest storms, that could be a few months.”
Opportunity should be able to handle even an extended outage. “As long as the rover stays warm enough, and our predictions are that it will, then it can go any number of days,” Callas said.
Because Mars’ atmosphere is so thin, there’s no danger that the rover will get blown over, despite what you may have seen on the movie screen in “The Martian.” And Mars’ winds are expected to sweep dust off the solar arrays, as they have during past episodes. But there’s a chance that Opportunity’s camera optics could be degraded by dust damage.
That’s one of the things the mission team will look for once Opportunity rouses itself from its slumber. If all checks out as hoped, the rover will resume its study of Perseverance Valley, a channel that descends from the rim of Endeavour Crater. Scientists hope to determine whether the valley was carved in ancient times by the flow of water or ice, or by wind erosion.
Meanwhile, NASA’s Curiosity rover is continuing its work in Gale Crater, on the other side of the planet. So far, Curiosity hasn’t borne the brunt of the storm, and its plutonium-fueled generator should hold it in good stead even if the skies darken.
Jim Watzin, director of the Mars Exploration Program at NASA Headquarters, said the current storm should serve as a learning experience for future Red Planet missions, including crewed exploration. Crews will have to know when such monster storms are on the way and be prepared to weather them.
“Having this dust storm occur under the visibility of the whole fleet of orbiters that we have, and eventually Curiosity participating in the research as well, is going to teach us a whole lot about how these storms behave,” he said.
Watzin marveled at the mere fact that Opportunity is still around to worry about.
“Keep in mind, we’re talking about a rover that’s been working at Mars, hanging in there for 15 years, when [it was] designed just for 90 days,” he said. “It just doesn’t get any better than that.”