Comet 67P/Churyumov–Gerasimenko is currently about 300 million miles away from the Earth, whizzing around the sun at a speed of 84,000 miles an hour. The Rosetta spacecraft was launched in 2004, and has spent the past decade traveling over 4 billion miles in order to match the comet’s orbit.
To get in sync with the ancient, misshapen hunk of ice and rock, Rosetta swung around the Earth three times to pick up speed, and spent nearly three years in hibernation due to its distance from the sun. Finally, in August, it fell into stride with the comet, which is less than 3 miles across.
The world wasn’t immediately interested in Rosetta’s success: After all, while the orbiter was collecting data on the comet from the moment it approached it (and will continue doing so for a year), there was no real climax of the story – no “giant leap,” as Neil Armstrong said back in the day, for the world to hang on.
That is, until the little probe named Philae came along.
It had all the makings of a great story: Rosetta, after years and years of work, would drop its payload. Philae was instantly cast as an underdog. It lacked any propulsion system – so once ejected, it had a seven hour free-fall. The Rosetta mission team, which included scientists from both the ESA and NASA, were very clearly prepared for the worst. In preparing for the landing, every interview seemed to emphasize how successful Rosetta had been and would continue to be — even if Philae never sent back data from the comet.
Philae could fail to land or land upside down (a tragedy, as the probe has no way to flip over). And no matter what happened, viewers of the ESA’s livestream would only be able to watch the mission control room in Darmstadt, Germany. They’d see the faces of scientists apprehensively reading data from the probe’s sensors, and they’d be treated to periodic updates. But the only thing the landing could promise with any certainty was an extremely tense morning.
And yet we tuned into that livestream in droves, and tweeted the related hashtags with vigor and glee. Trying to follow all of the tweets tagged with #cometlanding was a fool’s errand as the predicted landing time of 11am ET approached – there were too many messages being tweeted too fast, and they passed by in an incomprehensible blur.
When Philae touched down safely, mission control’s jubilation was contagious, and rang out across social media. And shockingly, the world stayed interested. Philae’s future was uncertain, and intriguing: As the hours went by, it became apparent that Philae’s harpoons, meant to anchor it into the comet, hadn’t deployed. Would it bounce right off the comet and back into space?
It’s a credit to those managing Rosetta and Philae’s social media presence that people became more excited, and not less, when it became clear that the lander’s days were numbered. While Philae had a surprisingly precise landing at its chosen spot, it had then bounced off into a shady area. Its solar panels didn’t get access to nearly enough light to keep it operating, and the probe’s 60-hour battery life was running out.
No doubt inspired by the brilliant social media campaign of NASA’s Mars rovers, those tweeting for Rosetta and its lander did an incredible job of making the hunks of metal seem like living extensions of the intrepid explorers who sent them to space. Rosetta and Philae were presented as friends, tweeting adorably at each other, and their faux personalities roped us into following Philae’s nail-biter of a journey.
By Friday night, we knew it was coming to an end: That morning, Rosetta scientists had told the public that Philae’s batteries were almost certainly going to die during their next communication link with the probe. And sure enough, Philae’s Twitter account followed through until the end, tweeting out a series of messages about going to sleep that made many (myself included) express grief for – and immense pride in – the little lander that could.
Several missions in the near future will take us to asteroids, the slower-moving (and easier to chase down) cousins of comets. In 2016, NASA’s OSIRIS-REx will use a spacecraft with a robotic arm to pluck some asteroid off and take it home. And while we wait for another Philae-like comet trip – which probably won’t come in the next 10 years – we still have Rosetta. The spacecraft will follow its comet for a year, studying it as it passes the sun. And during that time, if enough light hits its solar panels, Philae could even make a comeback – reuniting the world’s new favorite pair of space buddies.