NASA announced on Sunday that the rover had briefly checked in with engineers at the Jet Propulsion Laboratory in California, which is a good sign for Opportunity. It means the rover still has enough power to communicate with Earth. Engineers suspended Opportunity’s science operations on Friday, June 8, a week after the Mars Reconnaissance Orbiter detected the first signs of a brewing storm. Within a few days, the storm exploded into a 7 million-square-mile monster, larger than North America, which threatens to swallow Opportunity whole.
Of course, this isn’t Opportunity’s first encounter with Mars’ particular brand of inclement weather. In July 2007, after weathering a monthlong series of summer storms, the rover found itself engulfed by a storm of apocalyptic proportions, which wrapped itself around the whole planet and left only the peak of Olympus Mons above the dust clouds.
Despite the dramatic opening sequence of The Martian, the real threat to NASA’s intrepid Mars robot is the dust, not the wind. The most violent storm winds ever recorded on Mars peaked at around 60 mph, but Mars’ atmosphere is only about 1% as dense as Earth’s, so a 60 mph wind on Mars doesn’t pack much of a punch.
But it’s still enough to lift a lot of light Martian dust into the air, where it blocks sunlight and makes it awfully hard for a solar-powered rover to eke out a living. The 2007 storm blocked about 99% of the direct sunlight to Opportunity’s solar panels, leaving the rover to scrape by with the faint, scattered light that filtered through the swirling dust clouds.
Opportunity, like its late twin Spirit, relies on solar panels to power its instruments, its motors, and the electric heaters that keep the Rover warm. If there’s not enough power to run the heaters, the deep Martian cold—it’s about -29 degrees Fahrenheit in Perseverance Valley at the moment—could easily kill the Rover’s electronics.
On a normal day, Opportunity’s solar panels produce about 700 watt-hours of electricity, which is enough to light a 100 watt lightbulb for seven hours. That’s enough to run the rover so it can do a full day’s quota of science and exploration and have a little left over to charge the battery. Back in 2007, NASA cut back Opportunity’s workload once the skies had dimmed enough to cut power generation to 400 watt-hours a day. In the robot equivalent of telling an employee not show up for work if the roads are too icy, NASA stopped movement and science operations, leaving the rover to focus on keeping itself warm and phoning home once in a while.
By the peak of the 2007 storm, it was so dark that Opportunity’s solar panels were able to produce only 128 watt-hours of power, barely enough to keep it hanging on. The rover even had to cut communications with Earth. Opportunity caught the brunt of that 2007 storm, because its twin Spirit was working in an area where the storm was less intense, letting more light filter through the dust, but even Spirit had to cut back on work to ensure enough power to keep itself warm.
Both rovers survived the global dust storm of 2007, but a dust storm in the equatorial plains killed Spirit in November of the following year, when the darkness cut the rover’s power down to 89 watt-hours per day, about half what it needed to keep itself alive even in hibernation mode. So the risk Opportunity now faces is very real.
NASA says this storm is more intense than the 2007 storm. In late July 2007, NASA estimated that the storm dimmed the Martian skies to 5.5 tau, which is a scale planetary scientists use to measure how much a planet’s atmosphere is blocking incoming sunlight. This year’s storm is already at 10.8 tau, and it’s not clear when the skies will clear. Meanwhile, the Curiosity Rover is enjoying clear skies and relatively smooth roving 5,000 miles away in Gale Crater.
Engineers at NASA are doing everything they can to keep Opportunity from meeting the same fate as its twin.
“The rover needs to balance low levels of charge in its battery with sub-freezing temperatures. Its heaters are vitally important to keeping it alive, but also draw more power from the battery. Likewise, performing certain actions draws on battery power, but can actually expel energy and raise the rover’s temperature,” the agency explained in a press release.
If the worst should happen, it’s important to remember that Opportunity has had a phenomenal run, extending what was supposed to be a 90-day mission into nearly 15 years of exploration. Here’s hoping it gets many more.
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