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Opportunity is already buried – all that’s left is to say goodbye. The ageing Mars rover became mired in a colossal dust storm in June 2018, and operators haven’t been able to reach it since then. NASA has now announced that Opportunity’s mission is officially over.

In January 2004, two rovers – Spirit and Opportunity – touched down on the surface of the Red Planet. NASA hoped that one of the two rovers would last for 90 days, but this turned out to be a huge underestimate. Spirit roved the surface for over five years before getting stuck in a patch of soft dirt, while Opportunity has lasted well into its 15th year before joining its sibling.

During their time on the surface, the rovers gathered data that allowed us to construct our current vision of Mars’s past. “We cared for them and watched over them and shepherded them through so much, and in return they gave us an entire planet,” says former rover driver Scott Maxwell. “Opportunity gave us an entirely new view of what that world must have been like.”

Water water everywhere

Before Spirit and Opportunity landed, the accepted picture was that Mars was pretty much dry except for its polar ice caps, and may have always been that way. That was overturned when the rovers found evidence for ancient water on Mars – repeatedly.

There were minerals that are only created in salty water. There were clays formed in potentially drinkable water that may have once presented a habitable environment for microbes. There were veins that formed when water flowed through the cracked ground.

“The water story just kept getting more and more interesting,” says former Opportunity flight director Mike Seibert. “Everything we take for granted about that planet basically changed in 2004.”

Over the course of its mission, Opportunity drove about 45 kilometres, exploring more than 100 craters along its way and weathering bitter cold and numerous dust storms.

“Mars has gone from this very distant, very poorly-understood place to a real world that humans can look into,” says Steve Squyres, the lead scientist for Spirit and Opportunity. “We’ve climbed mountains, and we’ve descended into craters and looked across panoramic vistas, and I think that’s transformed how people look at Mars.”

Then, in June 2018, the big one came: a cloud of dust that quickly grew dense enough to blot out the sun from Mars’s surface and coat the rover – including the all-important solar panels that power it.

On 10 June, Opportunity sent its last signal to Earth. Since then, operators have frantically sent more than 1000 wake-up calls to the rover instructing it to turn on and phone home, testing every kind of spacecraft error that they know how to correct.

Nothing worked. There was no call home. 5499 days into its 90-day mission, Opportunity is finished. “It’s the end of the first great Martian road trip,” says Seibert.

Ultimately, the rovers will be remembered for their incredible longevity. “I thought we might get six to eight months on these things, maybe as much as a year” says Squyres. “If a spacecraft functions for 15 years and dies in one of the biggest dust storms Mars has seen in decades, that’s an honourable death.”