- NASA’s Opportunity rover hasn’t phoned home in the months after a global dust storm tore across Mars.
- Officials at NASA announced the Martian robot’s death on Wednesday.
- Now that both Opportunity and its identical-twin rover, Spirit, are silent, the longest-running Mars mission is history is over.
- Opportunity was supposed to last 90 days but survived on the red planet for nearly 15 years.
Opportunity, the longest-operating robot on the Martian surface, has died from a one-two punch of ageing hardware and a “historic” dust storm, NASA said on Wednesday.
In June, regional dust storms began to engulf Mars in a record-setting global tempest, prompting NASA to park the rover and hunker down. When the dust finally began to settle and sunlight returned, the the golf-cart-size rover did not phone home. NASA tried for months to contact Opportunity but was met with deafening silence.
On Wednesday, the US space agency held a press briefing to announce it had given up on Opportunity, and that its mission was over.
Combined with the previous loss of its identical-twin Spirit rover, this marks the operational finale of the Mars Exploration Rovers (MER) program – the longest-running Mars mission in history.
“This was a historic dust storm,” Abigail Fraeman, a MER deputy project scientist at NASA’s Jet Propulsion Laboratory, said during a live broadcast of the briefing. “We needed a historic dust storm to finish this historic mission.”
A plucky robot 14 years out-of-warranty
Opportunity and Spirit landed on Mars in January 2004.
Although each robot was designed to last a few months on the Martian surface, Spirit survived for more than six years and Opportunity for nearly 15 years. The latter rolled more than a marathon’s worth of distance across the red planet’s surface.
“When this little rover landed, the objective was to have it be able to move 1,100 yards and survive for 90 days on Mars,” Jim Bridenstine, the administrator of NASA, said during the briefing. “Instead here we are, 14 years later, after 28 miles of travel, and we get to celebrate the end of this mission.”
John Callas, the mission’s project manager, expressed disbelief at the rover mission’s overall duration and sadness at its end.
“We had no idea it would take this long,” Callas said during NASA’s briefing. “Even so, this is a hard day … We sent our final command and it said nothing. So now we say goodbye.”
“This is the worst storm Opportunity has ever seen, and we’re doing what we can, crossing our fingers, and hoping for the best,” Steve Squyres, a planetary scientist at Cornell University and leader of the rover mission, told the Planetary Society at the time.
Though Opportunity had weathered other Martian dust storms before, this particular tempest – which NASA called “one of the most intense” ever seen – blocked a record amount sunlight to the planet’s surface for an extended stretch of time.
“The sky was so dark we couldn’t see the sun,” Fraeman said.
It was too much for the ageing rover, which relies on solar energy to keep its electronics healthy.
How darkness felled Opportunity
The dust storm on Mars finally began to clear in late August.
With sunlight intensity growing, mission managers said at the time that Opportunity’s solar panels should (in theory) begin gathering enough sunlight to recharge the rover’s batteries. This prompted the team to begin attempts to contact the robot.
“If we do not hear back after 45 days, the team will be forced to conclude that the sun-blocking dust and the Martian cold have conspired to cause some type of fault from which the rover will more than likely not recover,” Callas said on August 30.
That deadline passed in October, marking the end of an “active” campaign to contact Opportunity.
But the space agency did not immediately give up. In November, NASA started a 90-day effort of “passive” listening to see if the robot somehow woke up on its own.
Opportunity still did not respond, even as light intensity increased on the sun-facing hill where engineers had parked the rover before the storm.
Too much fine Martian dust likely coated Opportunity’s panels, and no winds came soon enough to sweep it off. This probably impaired the rover’s ability to store and use electrical energy, NASA said on Wednesday.
Cold is a major threat on Mars, since temperatures can drop to -100 degrees Fahrenheit near the equator in the winter. Such cold can shrink bits of metal in electronic circuits and snap them.
While little buttons of nuclear material called plutonium-238 help keep Opportunity’s circuitry warm, they are well-decayed and not as hot as they used to be – and unable to protect the rover’s systems on their own.
Opportunity’s batteries were also very old, and the longer such batteries remain uncharged, the more electrical storage capacity they lose. This can lead to a sudden dip in voltage called a “brown out,” which puts the robot into an unrecoverable state.
Making matters worse, Opportunity developed a faulty heater in its robotic arm. The heater was “stuck on” when the rover was trying to preserve energy, Callas said, though engineers ultimately figured out a way to trick the arm into turning off.
But this trick relied on the rover’s clock, which Callas said was likely “scrambled” when Opportunity’s energy levels ran low. So if the rover did wake up from its dust-storm nap, it began using up all of its energy, leading to a battery brown out.
Spirit – Opportunity’s sister rover – is presumed to have suffered the same fate in 2010. Engineers tried for more than a year to contact Spirit, but the rover never responded. NASA gave up trying to recontact the rover in May 2011 (during winter on Mars).
The scientific fruits of the Mars rovers
Spirit and Opportunity used their suite of drills, cameras, brushes, and microscopes to definitively prove that water once flowed across the surface of Mars.
Some of the first bits of conclusive evidence the rovers found were round mineral formations known as spherules, which were most fondly called “blueberries” (for their blue hue in false-colour images).
Squyres said on Wednesday that everyone was initially very excited by the prospects of ancient Martian water and what that may mean for the prospects of alien life, though the minerals indicated there was a lot of sulphur in the water.
“It was really sulfuric acid on Mars,” he said. “It was not evidence of an evolutionary paradise.”
Still, the rovers did eventually encounter clays that suggested there were also pools of neutral or non-acidic water on the red planet.
“That’s the kind of water we could drink, and that’s the kind of water in which we think life could have gotten started,” Matt Golombek, a project scientist on the mission, said.
You can watch NASA’s broadcast of the briefing below.
This story has been updated with new information.
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