A massive Martian dust storm knocked out communication with NASA’s Opportunity rover in early June, and now, as the dust settles and the rover remains unresponsive, NASA is forced to reconsider the future of one of its most famous missions.
“Our rover, which was designed to last for 90 days and has been on Mars for 14 and a half years, has just been through the most traumatic event of its long and eventful life,” Prof. Steven Squyres ’78 Ph.D. ’81, the James A. Weeks Professor of Physical Sciences, principal investigator of the Mars rover missions, told The Sun.
Though large dust storms can be common on Mars’ dry surface, this is the planet’s most severe global dust storm in decades, Squyres said. However, the storm is now dissipating and Opportunity continues to to remain unresponsive.
“The skies are clearing; the dust is settling,” he said. “So either the rover is still alive and we’ll hear from it, or it’s not alive and we won’t.”
The rover runs on solar power from several solar arrays, which make dust storms a particular problem. Dust blocks direct light from reaching the arrays, “dramatically” affecting the amount of power that can be produced, Squyres said.
For now, investigators are waiting to see if Opportunity will eventually regain enough power to respond to messages from mission control.
“If there’s enough power, it will wake up and talk to us,” Squyres said. “The thing doesn’t have an off switch. There’s no way to actually turn it off. The problem with having an off switch is that you might accidentally use it.”
NASA will continue “actively listening” for approximately the next month and a half, sending commands to the rover instructing it what to do rather than simply waiting for communication.
NASA currently transmits these commands multiple times per day according to a status update, which Squyres described as “time-consuming, costly, a lot of effort and, frankly, probably unnecessary.”
“If we get enough power on the solar arrays, it will wake up and try to talk to us,” he said.
Eventually, if the rover does not respond, the frequency of commands sent will decrease or stop, though locations around the world will continue to “passively” listen in case Opportunity regains power and transmits a message.
“Projecting a date when we might hear from it is impossible,” Squyres told The Sun. “There’s also the question of whether it’s alive or not, and we have no way of knowing that either. It will be either a miraculous recovery or an honorable death.”
As the rover has not communicated and is coming out of a dust storm, NASA has no idea whether it is permanently nonfunctional.
“It’s not low power that would kill a vehicle,” Squyres said. “It’s low temperature.”
The rover contains many sensitive electronic components within a warm enclosure, but that enclosure only remains warm while electric power is supplied.
Before flying 15 years ago, every component of the rover was tested to survive temperatures down to minus 55 degrees celsius. Nights on Mars, however, can commonly reach down to minus 80 degrees celsius, which Squyres described as “seriously, badass cold.”
In terms of rover-killing temperatures, however, the dust storm is actually functioning in Opportunity’s favor. Squyres explained that the sun heats the dust particles, causing them to radiate heat into the surrounding gas and keep the temperature within a much smaller range — a possibly survivable one.
“Now how cold is too cold?” Squyres asked. “We don’t know.”
The rover also has to deal with stress caused by the expansion and contraction of components as it goes through cycles of day and night, Squyres said. Opportunity has currently survived around 5,000 Martian days — over 14 Earth years — longer than it was ever expected to last.
“I am now teaching adults, college students, who cannot remember a time when there wasn’t a rover on Mars,” Squyres told The Sun. “And to me that’s just extraordinary.”
Chris O’Connor grad told The Sun that he remembers following Opportunity and its twin, Spirit, when he was in fourth grade. Though he was already “waist-deep” in astronomy, he described the rover missions as “something great to see as a little kid who wanted to be a scientist.”
Spirit ceased communication in 2011 after scientists just “wore it out” with stress, Squyres said. If this is the end of the Opportunity rover as well, Squyres mused that he would be okay with the outcome.
“I always felt that the only two acceptable ways for a mission like this to end would be either we wear a rover out [like Spirit]…. [or] Mars just reaches out and kills it,” he said.
Unless the rover regains power and communication, it will remain where it stands on Mars.
“People have asked me ‘would you like to see the thing brought back to Earth?’” Squyres told The Sun. “I mean, I’d love to see him again, but that’s okay.”
“We built it for Mars,” he continued. “I think Mars is where it should stay.”