“It’s made its way around to more than a few people at this point, which makes me surprised that no official statement has actually been made to the team yet as to what’s going on,” she said when we spoke early Thursday. “The people that have heard about it on the Opportunity team are like, what’s going on? And not getting an answer from anybody. It’s making everybody a little bit worried.”
This Opportunity staffer said the rumors prompted several of her colleagues to begin tweeting in support of Opportunity earlier this week, in an attempt to show JPL leadership that the rover is popular and beloved by the public. Starting Tuesday night, tweets featuring #WakeUpOppy and #SaveOppy started cropping up. A JPL spokesperson told me they did not know what prompted the sudden grassroots campaign.
“The campaign got a lot of attention from the higher-ups,” this Opportunity staffer said, “which is good. That was the intent.”
When the new recovery plan was made public, there was “a lot of anger, some sadness, some shock” among members of the team, she said.
NASA officials came to this conclusion based on their understanding of how opaque the Martian atmosphere is, a measure known as tau. The greater that value, the less sunlight permeates the atmosphere to reach the surface. Before it went silent, Opportunity’s instruments recorded a tau of a 10.8—far greater than the usual tau in the southern hemisphere, which oscillates between 1 and 2. (During the last big dust storm on Mars, in 2007, the tau barely topped 6.)
Without Opportunity, NASA has relied on an instrument on the Mars Reconnaissance Orbiter to provide measurements of the tau. They’re less precise, but they provide good estimates. According to the orbiter’s latest measurements, tau is now at 1.7. JPL officials believe that when that level dips to 1.5, there should be enough sunlight peeking through the atmosphere to let Opportunity charge. That’s when they’ll start the clock.
Former and current Opportunity team members and others say the 45-day period is not long enough to account for the potential of atmospheric phenomena known as dust-cleaning events. In the past, dust devils have swept away grains on Opportunity’s solar arrays. Sometimes, the wind was so effective that the panels were restored to their original sheen.
“I think our best hope has nothing to do with how much dust you estimate is in the sky. I think our best hope for the rover is when it gets windy, the dust blows off,” says Mark Lemmon, an associate professor at Texas A&M University who works on daily operations of the Opportunity rover. “That has happened reliably and repeatedly with Opportunity, and the season for that is approaching.” Such dust-cleaning events are common between November and late January.
Engineers have carried out simulations predicting Opportunity’s current conditions. But they can’t account for how much dust remains—if any—on Opportunity’s solar panels. “The initial results [of the simulations] suggest that if tau was below about 1.5, there is a chance, depending on the dust loading on the panels, that we would be able to hear from Opportunity,” says Matt Golombek, the project scientist for the Mars Exploration Rover mission, which covers Opportunity and the now-defunct Spirit. “Although we have an estimate of the dust in the atmosphere, we have no idea how much dust is on the panels.”