The longest-lived robot ever sent from Earth to the surface of another planet, Opportunity snapped pictures of a strange landscape and revealed surprising glimpses into the distant past of Mars for over 14 years. But today, NASA announced that the rover is dead.

“It is therefore that I am standing here with a deep sense of appreciation and gratitude that I declare the Opportunity mission is complete,” said Thomas Zurbuchen, NASA’s associate administrator for science.

For the scientists, that ends a mission of unexpected endurance.

The rover was designed to last only three months.

Opportunity provided scientists a close-up view of Mars that they had never seen: finely layered rocks that preserved ripples of flowing water several billion years ago, a prerequisite for life.

The steady stream of photographs and data from Opportunity — as well as its twin, Spirit, which survived until 2010 — also brought Mars closer to people on Earth.

Because the rovers continued so much longer than expected, NASA has now had a continuous robotic presence on Mars for more than 15 years.

That streak seems likely to continue for many more years.

A larger, more capable rover, Curiosity, arrived in 2012, and NASA is planning to launch another in 2020.

“Rovers and their observations resonate with people,” said Raymond E. Arvidson, a professor of planetary geology at the University of Washington in St. Louis and the deputy principal investigator for the mission. “It’s as if you were walking on the surface. It has that kind of perspective, and it’s not a particularly alien landscape.”

On Tuesday night, NASA made one last call to Opportunity, which was silenced last summer by a giant dust storm. There was no answer.

“It was an incredibly somber moment,” said Tanya Harrison, a member of the mission’s science team who was present in Pasadena, Calif., at the Jet Propulsion Laboratory during the final attempt to reach the rover. “Just waiting for the inevitable, basically.”

The cause was system failure precipitated by power loss during a catastrophic, planetwide dust storm that engulfed the Mars rover last summer.

“It’s going to be very sad to say goodbye,” said John Callas, the mission’s project manager. “But at the same time, we’ve got to remember this has been 15 years of incredible adventure.”

Opportunity’s mission was planned to last just 90 days, but it worked for 5,000 Martian “sols” (which are about 39 minutes longer than an Earth day) and traversed more than 28 treacherous miles — two records for NASA.

“It will be a very long time,” Callas predicted, “before any other mission exceeds that duration or distance on the surface of another world.”