Hey! Remember 67P, that big ole comet we landed a spacecraft on last fall? Kind of a big deal? We've been spending a lot of time talking about Pluto recently and I do not blame us but you should know that comet 67P is making its closest approach to the Sun next week. And just in time, the journal Science published a whole new set of results from the data that the lander called Philae sent back in November during its first 63 hours on the comet, and we've learned a lot.

First of all, as you probably remember there was a mishap when Philae landed, instead of harpooning itself into the surface of the comet, it bounced and landed somewhere in the shade where it didn't get enough sunlight to stay powered up. So in January the mission team used radio signals sent back and forth between the Rosetta orbiter and Philae to try and pinpoint the lander's location. Now, they managed to use that data to narrow down Philae's landing spot to a 21 by 34 meter area, and now that we know roughly where Philae is, other experiments like the one mapping the inside of the comet using radio waves will be much more accurate. 

Another group of researchers used images taken by the lander along with data collected by its other sensors to reconstruct Philae's trajectory, and they were able to use that information to figure out what the comet's surface is like. Based on the way Philae bounced, it seems like the place where it first hit is coated in a 20 centimeter layer of soft material with a hard layer underneath. The spot where it landed up though doesn't seem to have that soft layer, it's just a whole bunch of hard rock. It does however have lots of organic molecules. 

Originally Philae was going to drill down into the comet and analyze whatever particles it came across to figure out what they were made of, but after that messy landing it went into the safer so-called sniffer mode instead, studying the particles that had splattered off the surface with all of its bouncing around using an instrument called COSAC. It found plenty of molecules that you'd expect like water, carbon monoxide, and methane but some were much more unusual like 4 complex carbon-containing compounds that have never before been found in a comet.

Finding more complex organic compounds is always exciting because among other things, it's further confirmation that the building blocks of life might not be that hard to manufacture outside of Earth, and Philae's adventures aren't over yet. The lander woke up in mid-June and though it's had some trouble communicating with Earth, partly because of a broken transmitter, it's still collecting data and sending it back whenever it has a decent connection. Hopefully we'll be able to learn a lot more but so far it seems like comet 67P is a pretty neat place.

And speaking of comets, in the fall of 1992, comet Swift-Tuttle swept past the Sun leaving behind a trail of dust as part of its 133-year orbit right in Earth's path. It leaves those particles behind each time it swings by and when Earth passes through them every August we get the Perseids meteor shower as they burn up in our atmosphere. This year the shower will peak in the morning of August 13th at around 8 am UTC with 90 to 100 meteors an hour. But assuming there are clear skies and you're away from city lights, you should be able to see plenty of meteors all night long and on the few nights before and after too. 

The shower gets its name because its radiant point or the spot in the sky where the meteors all seem to be streaking from is the constellation Perseus in the northern sky. Meaning that the Perseids are more visible from the Northern hemisphere but some of them streak out far enough to be visible from the Southern hemisphere too.

But with its 10-kilometer diameter, Swift-Tuttle is famous for more than just making the Perseids happen. Scientists weren't exactly sure of its orbit until the 1990's which led to a bit of a scare. An astronomer named Brian Marsden calculated that is the comet's next predicted brush by Earth in 2126 was off by just 15 days, we'd have a collision on par with the one that killed the dinosaurs. By looking through records of comets spotted as far back as 69 BCE, Marsden figured out that in 2126, Swift-Tuttle should miss Earth by about 24 million kilometers, more than a tenth the average distance to Mars so there's plenty of wiggle room. But it'll probably pass within just two million kilometers in 3044, so future astronomers will probably be on the lookout but for now, we get to enjoy the Perseids worry-free.

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