People celebrated in the Rosetta spacecraft mission control room at the European Space Operations Centre in Darmstadt, Germany, after it touched down on Comet 67P, sending its final signal to Earth Sept. 30, 2016.

DARMSTADT, Germany — When Paolo Ferri went into the control room this morning, the atmosphere was a little gloomy.

"I've experienced this with other missions," Ferri, who is head of mission operations here at the European Space Operations Centre (ESOC), told Space.com. "It's always difficult to accept the end. Me personally, I'm very sad."

Today (Sept. 30) marks the end of operations for the European Space Agency's (ESA) historic Rosetta mission. The orbiter had been in space for 12.5 years and had been flying around Comet 67P/Churyumov-Gerasimenko for a little over two years. At 1:19 p.m. local time (7:19 a.m. EDT), project managers received the last signal from Rosetta as the spacecraft made a controlled impact with the comet. [Photos: Europe's Rosetta Comet Mission in Pictures]

The scene inside the control room did not at all resemble the jubilation in 2014 when Rosetta woke up from its risky 2.5-year hibernation. Though there was some applause and hugging today, many of the mission managers looked choked up and the mood felt almost funereal as the postlanding celebration began.

"A party is probably the best way to fight off depression," said Rolf Densing, director of operations at ESOC.

Carrying a suite of 11 scientific experiments and a small lander named Philae, Rosetta was launched in March 2004. But for some at ESA, the mission's history stretches back much longer; the idea for Rosetta was conceived in the 1980s.

"That's when the scientists said, 'OK, we have to go to a comet,'" said Ferri. "In the beginning, they thought maybe we could bring a piece of the comet to Earth, but then they abandoned this idea. It made much more sense to bring the instruments there."

European Space Agency's (ESA) Rosetta spacecraft touched down on Comet 67P on Sept. 30, 2016. This is one of its final shots, when the spacecraft was 14.2 miles (22.9 km) from the comet's surface. (Image credit: ESA )

The mission wasn't formally approved by ESA until 1993, and after 1996, there was a long preparation and spacecraft-building phase. Rosetta was supposed to launch in 2003 and rendezvous with Comet 46P/Wirtanen. But the rocket that was meant to lift Rosetta into space exploded on its launch pad, and the mission had to be revised because of the delay. The spacecraft finally launched in 2004 on a new rocket, and with a new target: Comet 67P.

During Rosetta's 12.5-year journey through space, the spacecraft hit many milestones: It sailed past Mars and two asteroids, but most importantly, in 2014, it became the first spacecraft to orbit a comet, escort the object around the sun and then deploy a lander to the surface. (Philae's bouncy landing, however, didn't go exactly as planned.)

As Rosetta and the comet hurtled farther away from the sun, the solar-powered craft was starting to run low on power. To get every last bit of science out of the expedition, ESA managers decided to end the mission by landing Rosetta on the face of the comet, snapping high-resolution images and analyzing gas and dust on the way down.

Holger Sierks, the principal investigator for Rosetta's OSIRIS camera, presented the spacecraft's last images, showing Rosetta's final resting place.

"I have spent the last 20 years with this mission," Sierks told reporters. "I never imagined such an end of the story. We never really discussed the end of Rosetta. … It's overwhelming."

Comets are pristine leftovers from the early days of the solar system's formation 4.6 billion years ago. Rosetta's observations have given scientists an unprecedented, up-close look at one of these icy, primitive cosmic objects. Even though Rosetta's operations have ended, the scientific legacy of the mission is only just beginning to be understood, Ferri said.

"Before Rosetta, comets had only been observed in proximity for up to a few hours," Ferri said. "[The mission] will bring a revolution in cometary science. There's been already some spectacular results published, but I think these results have for the moment mostly put into question our existing theories. The most important part will be when the data are processed and new theories are developed. This will take years."

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