Last night, NASA reached out one final time to the Opportunity rover on Mars, hoping the golf-cart-sized machine would phone home with good news. Since June, the robot has been unresponsive, likely because a planet-wide sandstorm coated its solar panels in dust. NASA has pinged it over 1,000 times in those gloomy eight months, to no avail. Last night’s attempt was no exception: NASA has announced that Opportunity is officially dead.

“I was there yesterday and I was there with the team as these commands went out into the deep sky,” said NASA associate administrator Thomas Zurbuchen in a briefing this morning, titled A Lifetime of Opportunity. “And I learned this morning that we had not heard back and our beloved Opportunity remained silent.”

“I am standing here with a sense of deep appreciation and gratitude that I declare the Opportunity mission as complete,” Zurbuchen added. “I stand here surrounded by the team and I have to tell you, it's an emotional time.”

So yes, Opportunity is technically dead. But perhaps it’s more accurate to say it’s bravely completed its mission—and then some. It was only expected to scoot about the martian surface for three months, yet here we are 15 years later. It was designed to travel just 1,100 yards, yet ended up roving a stunning 28 miles. With its companion rover Spirit, the two robots studied the hell out of the Red Planet, exploring geology and dust devils and even finding meteorites.

But how on Earth (or Mars) did Opportunity last this long? Two reasons. First, NASA had anticipated that dust would be a problem and expected the stuff to gather on Opportunity’s solar arrays and choke off power in around three months. “What we didn’t expect was that wind would come along periodically and blow the dust off the arrays,” said John Callas, project manager of Opportunity, at the press event. “This, on a seasonal cycle, actually becomes pretty reliable and allowed us to survive not just the first winter but all the winters we experienced on Mars.”

Second, NASA knows a thing or two about engineering robots. “These rovers actually have the finest batteries in the solar system,” Callas said. Opportunity’s lasted 5,000 charge-discharge cycles and remained at 85 percent capacity up until the robot’s demise. “We’d all love it if our cell phone batteries lasted this long.”

Callas also offered insights into why Opportunity couldn’t recover from June’s historic global dust storm. The lack of light meant its battery couldn’t charge. But in an ironic turn of events, it may have been a clever emergency workaround in the rover’s early days that ended up sealing its fate 15 years later.