Nasa declared the 15-year mission of the veteran Mars rover Opportunity finally over on Wednesday, crediting the robot as having “transformed our understanding of our planet”.
The golf buggy-sized vehicle last made contact with Earth eight months ago, after being caught in a global dust storm.
Announcing the mission’s end, Thomas Zurbuchen, the associate administrator of the Science Mission Directorate at Nasa, said the rover had “remained silent” after a last-ditch effort to contact Opportunity on Tuesday.
Despite the loss, the mood at the press conference at Nasa’s Jet Propulsion Laboratory in Pasadena, California, was one of celebration on Wednesday.“I’m standing here with a sense of deep appreciation and gratitude to declare the Opportunity mission as complete,” Zurbuchen said.
“It transformed our understanding of our planet, everything we do and think about in our planetary neighborhood with Mars and elsewhere relates to the research from that and the engineering breakthroughs that came from that.”
Opportunity landed on Mars in January 2004 shortly after its twin – a rover called Spirit. Together, the pair were part of Nasa’s Mars Exploration Rover programme. However, the Spirit got stuck in soil in 2009 and was declared defunct in 2011.
By contrast, Opportunity has continued to trundle over the surface of Mars and send back data to Earth, acting as a sort of remote geologist.John Callas, Mars Exploration Rover project manager, at the Jet Propulsion Laboratory, said that epic journey had been due to a “phenomenal” effort and had “greatly expanded our understanding of the red planet”.
Over the 15 years it has spent on Mars, Opportunity has clocked up more than 45km (28 miles) – despite being designed to travel only 1,006 metres and last 90 Martian days.
“We had expected that dust falling out of the air would accumulate on the solar rays and eventually choke off power,” Callas said.
“What we didn’t expect was that wind would come along periodically and blow the dust off the arrays.
“It allowed us to survive not just the first winter, but all the winters we experienced on Mars.”
Opportunity was finally done in by a “historic” dust storm, said Abigail Fraeman, MER deputy project scientist. Fraeman said the storm had turned the sky so dark that Opportunity “couldn’t see the sun and the solar panels couldn’t recharge the battery”.
During its mission, the rover found tiny iron-rich spheres nicknamed “blueberries” at the crater that suggested a wet past, while its analyses of clay minerals near the Endeavour crater confirmed parts of Mars were once covered in neutral water, and could have been a habitable environment. It also came across the first meteorite ever to be discovered on another planet. In addition, the rover has sent back stunning images, including capturing a Martian “dust devil” twisting across the planet’s surface and panoramic shots that provided breathtaking views of Martian craters.
Another aspect of Opportunity’s legacy is the number of people who were inspired to pursue careers in science through following the rover’s trek, Fraeman said.
“There really are hundreds if not thousands of students who, just like me, witnessed these rovers and followed along their mission, from the images released to the public over the last 15 years and then because of that went on to pursue careers in science.”
“It has been a fantastically successful mission which has completely outlived its shelf life,” said Professor Andrew Coates, a planetary scientist at University College London’s Mullard Space Science Laboratory.
“One of those core things about Opportunity was it landed in this crater which was in sight of sedimentary types of rocks and that was the first time that sort of thing had been seen on Mars,” said Coates. “People compared it at the time to an interplanetary hole in one.”
Professor John Bridges from the University of Leicester, who is part of the team working on Nasa’s continuing Curiosity rover project and the European Space Agency’s ExoMars mission, said Opportunity had a fantastic roll call of achievements. He added that with its twin the rover had been key in changing the idea of Mars from being a lump of basalt in space to having a very different geological history, showing the importance of lakes and other features.
“It really sort of [turned] upside down our view of Mars and how it has evolved,” he said. “It was showing us what the Mars crust is made of.”
Coates, who is also lead scientist for the panoramic camera instrument on the ExoMars rover – recently named Rosalind Franklin – which is set to be launched in 2020, said the discoveries of Opportunity, and later the Curiosity rover, have been important for the development of new missions.
“The next step now of course is to drill and look for signs of life, and that is exactly what we are doing with the ExoMars rover, drilling up to 2 metres underneath the surface,” he said.
The final attempt at communication with Opportunity on Tuesday night was, it seems, an emotional affair. Dr Tanya Harrison, a planetary scientist who worked on the mission, tweeted: “There were tears. There were hugs. There were memories and laughs shared.”Mike Seibert, who was also part of the team, paid tribute to the rover nicknamed “Oppy”, saying “Goodbye old friend” and noting that the rover was the longest lasting surface mission yet.
Coates said Opportunity’s demise was bittersweet. “It is a matter of both celebration for what it was able to achieve and in the broad context of Mars exploration, but also tinged with sadness, losing an old friend.”