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Opportunity rover's shadow
Ths colorized image of the Opportunity rover’s shadow was taken on July 26, 2004, by the rover’s front hazard-avoidance camera as it moved farther into Endurance Crater in the Meridiani Planum region of Mars. (NASA / JPL-Caltech Photo)

After months of silence from Mars, NASA finally read the rites over its Opportunity rover, hailing the six-wheeled machine as an overachiever that found some of the first and best evidence of the Red Planet’s warmer, wetter past.

The solar-powered rover’s demise was no surprise: It fell out of contact with controllers at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., last June — due to a globe-girdling Martian dust storm that kept Opportunity from charging its batteries.

Mission managers tried all sorts of tricks to wake up the comatose rover and re-establish communications, but it was to no avail. The last attempt was made on Tuesday night.

Today’s final Opportunity news briefing took on the trappings of a memorial service, featuring far more ceremony than NASA employed when the Spirit rover — Opportunity’s twin in the Mars Exploration Rover mission — went dead in 2011.

“I was there with the team as these commands went out into the deep sky, and I learned this morning that we had not heard back, and our beloved Opportunity remained silent,” said Thomas Zurbuchen, NASA’s associate administrator for science. “It is therefore that I’m standing here, with a sense of deep appreciation and gratitude, that I declare the Opportunity mission as complete, and with it, the Mars Exploration Rover mission as complete.”

Both rovers bounced to the Martian surface, wrapped in protective airbags, in January 2004. On opposite sides of the planet, each rover came upon evidence that water once flowed on the Red Planet. Near its landing site in the Meridiani Planum region, Opportunity found “Martian blueberries” containing hematite, a mineral that forms in the presence of water.

Cornell astronomer Steve Squyres, who was the principal investigator of the Mars Exploration Rover mission, recalled that the initial evidence suggested Mars’ ancient water was highly acidic. “We were running around saying, ‘Water on Mars! Water on Mars!’ It was really sulfuric acid on Mars, right?” he said, half-jokingly.

Later evidence gathered at Endeavour Crater indicated that the water at that location in ancient times might have been drinkable.

Opportunity and Spirit were designed to last at least 90 days on Mars, but scientists marveled that both rovers lasted years longer than expected. Project manager John Callas said there were two main reasons why the rovers were such overachievers.

He explained that scientists expected the rovers to grind to a halt when enough of Mars’ red dust settled on their solar panels to choke off their power generation systems. They were surprised to find out that Martian winds periodically swept the panels clean.

“This, on a seasonal cycle, actually became pretty reliable,” Callas said.

The second factor had to do with the rovers’ batteries. Opportunity’s batteries went through more than 5,000 charging cycles, and were still capable of holding an 85 percent charge after more than 14 years of use. “We would all love it if our cellphone batteries lasted this long,” Callas said.

Opportunity’s odometer logged 28.06 miles of travel, which set the record for the longest trek on a world beyond Earth.

Over the years, Opportunity’s support team of scientists and engineers had to figure out work-arounds to get the rover out of numerous jams — ranging from Martian sand traps, to a bad case of robotic amnesia, to a heater with a stuck “on” switch.

Callas speculated that the balky heater may have played a role in Opportunity’s demise. When the rover’s electrical power dwindled, it probably put itself into a low-power mode that scrambled its sense of timing. “It wouldn’t know when to deep-sleep,” Callas said, and that may have led the rover to keep the heater on and exhaust the last of its energy.

For months, Callas and his colleagues hoped that Opportunity kept enough power in reserve to wake itself up and get back in contact with Earth. But with winter setting in at Opportunity’s location, the team determined that the Martian nights were getting too cold for the electronics to survive.

“Even though it’s a machine, we’re saying goodbye, and it’s hard,” Callas said.

Today’s briefing provided ample opportunity for team members to celebrate Opportunity’s legacy. JPL’s director, Michael Watkins, said Opportunity and Spirit created a “new paradigm for solar system exploration.”

“A robotic geologist on Mars, and an integrated science and engineering operations team here on Earth, all set out together on a mission of discovery,” Watkins said.”They didn’t know what they would find, they didn’t know which direction they would go, sometimes from one day to the next, and they made it work.”

The legacy is being carried on by NASA’s nuclear-powered Curiosity rover, which arrived on Mars in 2012 and found even stronger evidence that the Red Planet could have been habitable billions of years ago. NASA’s Mars InSight lander, which touched down on Mars last November, has just finished deploying its scientific instruments and will be monitoring Mars’ interior.

Yet another Mars rover, built on a Curiosity-style chassis with a different set of scientific instruments, will head for a promising target known as Jezero Crater next year. “If life ever did come to be on Mars, there ought to be evidence of it there,” said Lori Glaze, acting director of NASA’s Planetary Science Division.

NASA Administrator Jim Bridenstine said such robotic missions will set the stage for human missions to the Red Planet.

“Friends, there is a day coming when we’re going to need the entire NASA family to come together and say, ‘We’re going to put humans on Mars, and humans are going to be working side by side with landers, and rovers, and robots.’ ”

In that future age, will someone visit Opportunity’s resting place? Jennifer Trosper, who served as project systems engineer for the Mars Exploration Rover mission and is playing a similar role in the 2020 Mars rover mission, suggested that future explorers might bring Opportunity and Rover back to Earth.

Bridenstine liked that idea: “Bring ’em all back,” he joked.

But Squyres had a better idea. He recalled visiting Antarctica and seeing the huts of early explorers’ preserved exactly as they were when the expeditions ended. In Squyres’ view, that would be the most fitting tribute to Spirit and Opportunity.

“We built them for Mars. That’s the place that they were designed to go. That’s their home. That’s where I would like them to stay,” Squyres said. “Also, if you had the opportunity to bring 180 kilograms of stuff back from the surface of Mars, the last thing I’d want to bring is something where I know exactly what it’s made of.”

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