After two years orbiting Comet 67P/Churyumov–Gerasimenko, the European Space Agency's Rosetta orbiter met its end Friday morning. But the spacecraft did useful science to the last, delivering data packets as it slowly crashed into a particularly active area of the comet. Now its signal has been lost, indicating that the spacecraft has finally rejoined its ill-fated lander Philae, which was recently located after dying and evading detection for nearly two years after its historic landing on the comet's surface.
— ESA Operations (@esaoperations) September 30, 2016
It might sound like a waste of a perfectly good $1.6 billion spacecraft, but letting Rosetta slowly crash into a cometary grave was like turning space lemons into lemonade. Comet 67P is now on the outward leg of its orbit around the sun, and soon Rosetta wouldn't have gotten enough sunlight to power her systems. As she tumbled farther and farther from Earth, the mission team had to decide whether to let her hibernate – something the robot did for several years during her journey to get to the comet – or give up on her now.
It's unlikely that Rosetta would wake up again after the four to five years it would take for Comet 67P to swing back into the sunlight, since the robot wasn't designed to survive this second hibernation. In the meantime, the ESA would have to pay for the crew it took to keep the mission running on Earth. But the team didn't want to let Rosetta go gently into that goodnight, slowly powering down after weeks or months of sun deprivation. So instead, Rosetta went out with a bang – albeit a very soft one, since the orbiter approached the comet's surface at a speed of just a few miles per hour.
Emotions ran high in the mission control room — and around the world via Twitter — when the landing was confirmed at 7:19 a.m. Eastern time. The mission's official Twitter account marked the moment by tweeting out "Mission Complete" in different European languages, accompanied by the sugary sweet cartoons that have peppered mission updates over the past two years:
— ESA Rosetta Mission (@ESA_Rosetta) September 30, 2016
The Rosetta spacecraft, the first ever to orbit a comet, was beloved by scientists and laypeople around the world. The saga of its lost lander captured the public imagination, arguably helping to make the orbiter and its scientific results more intriguing to those who might otherwise ignore research about an ancient comet.
Never watched a spacecraft slowly die before now. Very emotional. Yes, it was just a machine, but dozens of people put their hearts into it.
— Katie Mack (@AstroKatie) September 30, 2016
In the world of space robot nerds, it felt like the beginning of a bigger end: NASA's Cassini mission, which has been studying Saturn and its moons for around a decade, will perform its own deadly dive in September 2017. The long-anticipated Juno spacecraft arrived at Jupiter to much fanfare in July, but because of planet's high levels of radiation it has less than two years left to live. New Horizons, which visited Pluto in 2015, is hurtling into the outer region of the solar system known as the Kuiper Belt. It's set to take observations on a mysterious, distant object in the first days of 2019, but the data downlink from its primary mission is starting to wind down, and the extended mission will be over in the cosmic blink of an eye.
But while we're sad to see Rosetta go, there's no denying that the mission has been a huge success. Researchers have used the orbiter's data to help disprove a long-held hypothesis that Earth's water might have been carried to the newborn planet by comets. But the discovery of certain life-giving organic molecules suggests that comets such as 67P may have seeded our planet in other ways. Even though Rosetta is gone, researchers will continue poring over the orbiter's data for months and years. Project scientist Matt Taylor tells the LA Times that the high school students of today could still help make new discoveries using Rosetta's data when they get to graduate school.
“Just as the Rosetta Stone after which this mission was named was pivotal in understanding ancient language and history, the vast treasure trove of Rosetta spacecraft data is changing our view on how comets and the Solar System formed,” Taylor said in a statement.
“Inevitably, we now have new mysteries to solve. The comet hasn’t given up all of its secrets yet, and there are sure to be many surprises hidden in this incredible archive. So don’t go anywhere yet — we’re only just beginning.”
This post has been updated.