I've had ESA's livestream open in a background tab since Wednesday, and this morning it finally went quiet. Philae, the little washing-machine-sized lander that touched down on comet 67P/Churyumov-Gerasimenko on the 12th, ran its primary battery down to nothing around 9:30 this morning and went into hibernation. No dramatic announcement, just a status update on the mission blog and a lot of very tired-sounding scientists on Twitter.
If you missed the landing itself, the short version is this: Rosetta, the orbiter that's been chasing this comet for ten years, released Philae on Wednesday morning, and it fell for about seven hours before reaching the surface. The harpoons that were supposed to anchor it into the ground didn't fire. So it landed, bounced back off the comet (which has almost no gravity, so "bounced" here means it went up nearly a kilometer and took almost two hours to come back down), bounced again, smaller this time, and finally settled somewhere it wasn't supposed to be, wedged against what's probably a cliff or a crater wall, mostly in shadow.
That last part is the whole story of the last three days, honestly. Philae's solar panels need sunlight, and the spot it landed in only gets about ninety minutes of it per twelve-hour comet day, instead of the six or seven hours the mission planners were counting on. So the team spent Wednesday through Friday racing to squeeze in as much science as they could on the one battery charge, because nobody could promise the panels would ever get enough light to recharge it.
And they did a lot. There was a genuinely tense hour Thursday where nobody was sure if firing the drill would tip the lander over completely, given the angle it's sitting at, but they went ahead anyway. They ran the gas analyzer to sniff for organic molecules in whatever the drill brought up. They took panoramic photos of the ground around it, which is somewhere around three hundred million miles from here depending on the day. All of that got radioed up to Rosetta and relayed home before the battery gave out this morning.
I stayed up way too late Wednesday night refreshing the ESA blog on my phone, which is a genuinely dumb way to watch a space mission unfold when there's a seven-hour delay between anything happening and anyone on Earth finding out about it. My own laptop battery, for what it's worth, does not last sixty hours doing anything, let alone drilling into rock on a comet, so I'm not going to complain about Philae's stamina.
What actually gets me about this whole thing isn't the landing itself, its the shape of the plan after it went wrong. Nobody expected the harpoons to fail. Nobody expected the bounce, or the shade. And the response wasn't to abort and regroup, it was: fine, we'll just do the important measurements faster and worry about long-term survival later. Thats a pretty different posture than how most consumer tech gets built these days, where one bad review cycle sends a product back to committee for six months. This thing had one real shot at getting a drilled sample home and they took it even sitting crooked in the dark, because the alternative was nothing at all.
There's apparently still a chance Philae wakes back up. As the comet gets closer to the sun over the next several months, the angle of light on that ledge might improve enough to trickle-charge the panels and bring it back online, maybe as late as next spring. Nobody's promising it though, and there's something a little sad about a probe going quiet on a rock a comfortable walk from nowhere, having done its job with no idea if anyone will ever hear from it again.
Rosetta isn't going anywhere, at least. It'll keep orbiting 67P well into next year as the comet swings in toward the sun, taking readings the whole way, so even if Philae stays dark, we're not done watching this thing unfold.
I'm making coffee and going back to actual work now. Wanted to get this down before the news cycle moves on and Wednesday night becomes a footnote instead of the thing that kept me up past 2am refreshing a blog.