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Caitlin: In the last couple of weeks, we've learned a lot about our solar system, with new discoveries teaching us all about Mars, comet 67P and Pluto. First, there's the announcement that Mars definitely has liquid water, which you can learn more about from Hank here, but there's also been news about comet 67P, home to the Rosetta Probe and Ophelia Lander.

It turned out that the comet we've been studying for almost a year probably formed from two different rocks. If you've ever seen a picture of 67P, you might have noticed that it looks kind of adorable. Plenty of the more famous comet that we've seen close up are bumpy looking ovoids, the 3D version of an oval, basically, they look like potatoes. But 67P looks more like a rubber duck, with two lobes connected by a thinner neck. Which got the astronomers wondering: did the comet get that shape gradually, as one big rock eroded unevenly, or were the two lobes ones unattached?

To figure it out, an international group of researchers used a computer program plus a lot of high resolution images of 67P to map the comet's strata, or layers. Comets are a lot like candy jawbreakers because they're made up of layers around a central core, but with all that time they spend flying around the solar system, parts of those layers get eroded and they end up a little uneven. That's how 67P ended up with terraces, little areas that jet out from the surfaces, and cuestas which are a specific kind of pock mark.

Basically, if the comet began as one big rock, then the chips would radiate outward from one central core. But if it started out as two different pieces that fused together, each lobe's features would look like they were spreading out from a different source, and you;d know that they were originally two cores. And when the researchers mapped the strata on 67P, they found that it fit the two rock model.

The patterns of layers on both lobes look very similar, so they probably both came from areas of the Kuiper belt that weren't too far apart, where they formed in similar environments. At some point, the kilometer-sized halves crashed into each other, but they wouldn't have been going very fast or else they would have broken up into pieces. Instead, it was more of a gentle bump with gravity keeping the lobes together so they eventually became one comet.

So what a body in space looks like can teach us a lot about it, or in the case of the new status from Pluto, it can show us just how much we still have to learn. The latest batch of new photos from the New horizons probe has just created more mysteries, with features like pockmarked ice plains and weird rock formations, scientists aren't sure how a lot of Pluto's surface formed.

Take this picture of Sputnik Planum, a big sheet of ice on the left side of the heart shape on Pluto's surface. It's definitely not as smooth as earlier images made it seem. This might mean that the ice is piled up in little dunes, or that the ice is different somehow in a way that makes it vaporize more easily. Then there are these mountains, just along the line that separated day and night on Pluto when the photo was taken.

They're calling it Tartarus Dorsa, after the area of the underworld where, according to Greek mythology the gods imprisoned their enemies. The mission team points out that the formation looks like tree bark or dragon scales, not like any mountains you'd see on Earth. Which is a problem for geologists because one of the best ways to figure out what's happening on another world is to compare it to something that's easier to study up close, like Earth. But we'll probably know more once researchers have a chance to study the rest of New Horizons' data, which it'll keep beaming back for another year.

Meanwhile, NASA also released a new photo of the whole visible side of Pluto which adds more color detail, especially blue. Though it's not exactly what you'd see if you flew by, all those colors would be there but they'd be much more subtle. There are probably mysteries in that picture that we don't even know exist yet, but there are more closeups on the way.

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