First Truly Pristine Comet Discovered

It's more space news this week, as there's been a new study published about Comet 2I/Borisov, an interstellar object that passed through the solar system back in 2019. As if that wasn't unique enough, apparently this comet was completely pristine, in that it had never previously been affected by a star's heat. The scientists who conducted the research were able to determine this by studying the polarization of light emitted by the comet's coma, which was brighter than any other comet save for Comet Hale-Bopp . Hale-Bopp was quite the sight back in 1997, as I can personally attest, and it was also almost completely pristine, with scientists believing that it had only visited the Sun once.

While Hale-Bopp and 2I/Borisov were similarly bright, the polarization of 2I/Borisov was uniform while Hale-Bopp was not, indicating 2I/Borisov hadn't even had that one visit that its predecessor had. It's actually quite the stroke of luck, finding all this out; I can't imagine truly pristine objects come flying through the solar system on a regular basis. In fact, I'm willing to bet we don't see a truly fresh comet in our lifetime. Slightly depressing, but hey, cosmic time scales just work differently.

New Type of Comet Discovered

Credit: ESO/M. Kornmesser

We all know what comets are. There may be some variation between each one, some are bigger and more pristine than others, and some put on a spectacular show as they sail past the Earth. But they're all basically "dirty snowballs". Comets are mostly ice, with some rock mixed in. As the comet falls closer to the sun, the ice begins to vaporize, forming a tail that can stretch for millions of miles behind it. They're all the same because they come from the same basic place. Sure, there may be half a light year between the Kuiper Belt and the outer Oort Cloud, but there's not a whole lot of difference in the materials in an Oort Cloud comet and a Kuiper Belt comet. They're all big interplanetary icebergs left over from the formation of the solar system. At least, they were. Not anymore.

To be honest, it's almost cheating to call Comet C/2014 S3 an actual comet. It has a 860 year long orbit, which is very comet-like, it enters the inner solar system like a comet, but it has very little ice and has a very minimal tail. An analysis of the limited dust from the comet's tail revealed that the comet is mostly made of rock. That makes it more of an asteroid than a comet. Indeed, the astronomers who discovered S3 theorize that the comet is actually from the inner Solar System, but was flung outwards early on in the formation of the solar system by some larger body. Comet S3 might be one of the most well-preserved relics of the formation of the rocky inner planets in the entire solar system. It's spent most of its time floating in the cold of the Oort Cloud, away from the harshest portion of the solar wind. Finding more objects like this comet would give clues as to how exactly the solar system was created, specifically how much material was in the early inner solar system.

Philae and the Comet Landing

From ESA

Philae landed on Comet 67P/Churyumov-Gerasimenko today. Probably. Maybe even twice. Considering two of the three device designed to keep the probe down, a small rocket and the harpoons, didn't even work right, I'd say it was a pretty good day's work for the little lander. We'll have to wait until tomorrow to get more information, as Rosetta, the main craft, is out of communications range. I guess this must happen often, if not, this doesn't seem like the greatest time to drop the lander, a couple hours before all communication is lost. Ah well, I'm not on the project, what do I know?

I have to admit, I was a bit worried about it today. This hasn't been a great time for space flight, with 2 rockets experiencing what can modestly be called catastrophic failure. It looks like Philae has survived the slowest fall in the solar system (okay, not literally, but come on, the comet's pretty small.) and will transmit some useful information.

On a side note, it seems like people were really impressed with what Philae did today, and yes, it is a remarkable achievement. But it wasn't that hard. Basically, all they did was point the thing in the right direction and give it a little nudge. The rocket on Philae is not designed to slow the descent, but to keep the probe anchored to the moon. Same with the harpoons. Unless it's landed on a cliff or on top of a boulder, Philae should be just fine. The real achievement was getting Rosetta in orbit around the comet in the first place. Come on, after ten years, perfectly intercepting a tiny rock hundreds of millions of miles away? That's some serious math skill right there.

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Close Comet Encounter with Mars

Getting up close to a comet is hard. Getting up close to a pristine comet fresh from the Oort Cloud is even harder. Getting close to a pristine comet while orbiting another planet and in fact, on an entirely separate mission is...well, those are some long odds. And as you might have guessed, that is exactly what happened this past weekend when Comet Siding Spring came within 100,000 miles of Mars. That is very, very close.  Normally, we wouldn't have an opportunity to get a real good look at a comet from the Oort Cloud, because there just isn't enough warning. But wouldn't you know it, we've got spacecraft orbiting Mars. So, they diverted their attention for a while and hopefully we'll get some great images, and useful information. This is hopefully just the prequel post to a more substantial post with actual images of the comet. It takes time for things to process.

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