Philae: The Sleeper Has Awakened!
Space professionals and aficionados the world-over are rejoicing over the news that Philae, the first vehicle to ever make a “soft” landing on a comet, has awakened from its hugely disappointing shadow-induced slumber.
It wasn’t that long ago, November of 2014, that the monumental achievement was announced. After 30 years of effort and a decade of circuitous space travel, the European Space Agency’s Rosetta probe had disgorged its lander module, Philae, which landed on comet 67P. This had never been done before and this milestone was made even sweeter coming after a host of problems and technical issues that continually plagued the mission.
The final problem preceding this historic landing was perhaps the most dramatic of all. The sensors on the lander clearly indicated that it had in fact landed but some of the scientists were not celebrating like the others. The craft seemed to be rotating which can only mean that it was still in free space. It turned out that the two harpoons that were designed to make Philae stay put had not fired. This caused it to bounce off the comet, reaching a height of more than a kilometer before coming down, bouncing yet again, and then finally settling down. If you were on the comet to witness that extraordinary event, it wouldn’t look at all like your average earth-bound bounce. Remember, Philae might be big but it has a trivial gravity. No retro rockets were needed to slow the descent and I hope it’s obvious that parachutes could not have been used either. Instead, the low gravity of the comet allowed the lander to be put in a state of free-fall that caused it to close-in on the comet at a meager one mile per hour. Still, with no harpoon glue to hold it down, the tiny impact from a 1 mph hit was still enough to send it careening back into space. That’s kinda sorta like dropping a refrigerator on the earth from a height of just 0.4* inches and watching it leap (slowly) off the earth many hundreds of feet into the air.
When it finally settled onto the comet (after sliding around a bit) there was much drinking (I assume) and revelry…at least until the first pictures started down-loading. It was immediately obvious that Philae had the incredibly bad luck to land in a dark ditch near a very high wall that obscured the sun from its solar panels. This meant that there would be no way to charge its battery once it was drained. That also meant that everyone working for the European Space Agency (ESA) then did one thing; they set their smartphone’s countdown-timer to 60 hours because that’s how much time there was before power levels would hit zero. This would likely end all the data gathering that the lander was likely to ever do. They immediately scrambled to prioritize the tasks that needed to be done and could be done before that last second ticked away. They were ultimately able to accomplish a surprising number of them but when that last second did finally arrive and Philae was put into hibernation, there was still large amounts of data on its hard-drive that it never sent.
So what now? The only hope was that calculations had shown that as the comet got closer and closer to the sun, the meager yet increasingly potent sunlight hitting the panels might be able to recharge its battery. The only thing to do about the lander now was to hope, listen, and wait.
While we’re waiting I think the comet itself deserves a bit more attention.
Its full name is 67P/Churyumov–Gerasimenk…67P for short. It is of course named after its discoverers in 1969, astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko (my guess is they’re Russian :-p ).
67P is known as a Jupiter-class comet. Comets with this designation typically have three or four characteristics:
- They are nudged into an orbit closer to the sun due to interactions with the planet Jupiter
- They have an orbital periods less than 20 years (in this case it’s 6.5 years)
- They orbit at a tiny angle above the plane of our solar system (the ecliptic)
- They usually hail from the Kuiper belt beyond Neptune
This contrasts to what are called Halley-type comets which orbit every 20-200 years with a high inclination to the ecliptic and come from the Oort cloud of comets. One final type, called long-period comets, come from the Oort cloud as well but they orbit at intervals greater than 200 years. 67P is roughly the size of Mount Fuji with a mass of 10 billion tonnes giving it a density comparable to some types of wood. It rotates every 12.5 hours or so and may in fact consist of 2 separate comets that fused together when the solar system was very young. This odd looking conglomeration has often been compared to a fuck…..sorry, autocorrect. I meant a duck.
I remember in the middle of this past March that ESA had begun listening for signals from Rosetta that had been relayed from the possibly newly awakened Lander. When those signals were not detected even after many days I remember thinking…Oh well, that’s it then. I was very proud that we were able to accomplish as much as we did but I couldn’t help feeling like I did when Ned Stark was killed at the end of the first book/season of The Game of Thrones (spoiler alert). There was so much more that he needed to do, so much more that I wanted to see him do. For example, Philae was supposed to drill into 67P to give us our first analysis of comet material from the birth of the solar system. This was considered the “jewel in the crown” of the Rosetta mission and as cool as a crown can be, it just seems greatly diminished to me if there isn’t a damn jewel in it.
Then last Saturday happened.
On the 13th of June, Rosetta sent an 85 second message from none other than Philae!! It said….”Send more Chuck Berry”
Actually, the content of the message was about 663 kilobits of housekeeping telemetry that was incredibly encouraging even if it was probably recorded weeks ago. Apparently, the lander’s subsystems are in fine working order with no degradation even after 211 days on a bitterly cold dirty snowball in the middle of space. The following day another 3 second burst of data gave an even more current status including the good news that the lander was warming up and was already at a balmy -5 Celsius.
This of course was all amazing news. So much so that BBC science editor David Shukman said:
“This is one of the most astonishing moments in space exploration and the grins on the faces of the scientists and engineers are totally justified”
Now it really looks like we’re going to finally put that jewel in the crown. Not only will we be able to drill and examine primordial solar-system stuff, we’ll also be able to carry out a host of other experiments that simply could not have been carried out in a mere 60 hours. We may even be able learn if life on earth was seeded from space. Comets, after all, not only have the H20 that earth’s ugly-bags-of-mostly-water need to be alive, they also likely harbor carbon-bearing molecules which are just as critical to life as we know it (we aren’t called carbon-based life for nothing).
I was surprised to learn that the water on Philae was determined to have a chemical signature distinct from earth water. That means that comets (at least comets like Philae) probably did not seed the earth with this precious liquid.
Another surprise derives from Philea’s hibernation itself. The fact that it was shaded and not used for all this time means that it will last long enough to be able to record the formation of a comet’s tail from the surface of the comet itself.
Seems worth the wait doesn’t it?
*Thank you Kate Xian for that 0.4 inch calculation you were able to do in your head
Featured Image: http://blogs.esa.int/rosetta/2015/03/10/waiting-for-a-signal-from-philae/