NASA’s Opportunity rover began its 15th year on Mars this week, although the intrepid robotic explorer may already be dead.

“I haven’t given up yet,” said Steven Squyres, principal investigator for the mission. “This could be the end. Under the assumption that this is the end, it feels good. I mean that.”

The rover, which outlasted all expectations since its landing on Mars in 2004 and helped find convincing geological signs that water once flowed there, fell silent in June when it was enveloped by a global Martian dust storm. In darkness, the solar panels could not generate enough power to keep Opportunity awake.

To be taken out by one of the most ferocious storms on Mars in decades: “That’s an honourable death,” Professor Squyres said.

NASA is still trying to contact Opportunity, as it has since the dust storm ended in August.

The hope was that once the skies cleared, Opportunity’s batteries would recharge and the spacecraft would pop back to life.

Each day, antennas on Earth call out to Opportunity and listen for a response.

On Friday, NASA announced it had begun sending a new set of commands to handle the possibility that the rover has indeed revived but has been unable to talk because of problems with its radios or its internal clock. The new effort will be tried for several weeks, NASA said.

Opportunity, and its twin rover, Spirit, both bounced to safe air bag-cocooned landings on opposite sides of Mars in January 2004.

They were designed to last just three months and travel a little more than 900 metres each. Instead, they kept going.

The designers of the spacecraft expected that dust settling out of the Martian air would pile up on the solar panels, and the rovers would soon fail from lack of power. But unexpectedly, gusts of Martian winds have repeatedly provided helpful “cleaning events” that wiped the panels clean and boosted power back up.

Footage from NASA’s Mars Exploration Rover Opportunity. Photo: NASA

In 2009, Spirit became ensnared in a sand trap and stopped communicating in March 2010, unable to survive the Martian winter.

Opportunity continued trundling across the Martian landscape for more than 45 kilometres. Instead of just 90 Martian days, Opportunity lasted 5111, if the days are counted up until it sent its last transmission. (A Martin day is about 40 minutes longer than an Earth day.)

This time, the dust may have been too thick to be blown away or something else broke on the rover. John Callas, the project manager, conceded that hopes were fading. “We’re now in January, getting close to the end of the historic dust-cleaning season,” he said.

With NASA among the agencies that was affected by the partial federal government shutdown, “We haven’t had a chance to officially brief NASA headquarters and receive their directions,” Mr Callas said.

Thomas Zurbuchen, associate administrator for NASA’s science directorate, will be the one to decide when it is time to move on. “Until he tells us to close down the project, we’ll keep going,” Mr Callas said.

Years ago, Professor Squyres said no matter when the mission ended, he was sure that there would be some tantalising mystery they would see just beyond reach.

On Thursday, he said that indeed seems to be the case. Opportunity was in the middle of exploring what looks like a gully that was formed by the flowing of water on ancient Mars. As expected, the gully looks eroded near the top, but the rover had not reached the bottom to look at where the sediments would have flowed.

The scientists had rejected some alternative hypotheses, but other ideas could also explain the landscape.

“So far, the story is uncertain,” Professor Squyres said. “The answer probably lies just down the hill.”

-New York Times