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According to some of the latest New Horizons data, Pluto’s got flowing nitrogen ice and only half the atmosphere it had two years ago. Plus, the latest batch of exoplanets includes a world that’s a lot like Earth... probably.


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Hank: Welcome back to SciShow Space News!

 About Pluto

It's been a couple of weeks since New Horizon's historical flyby of Pluto, and each new batch of data we get seems to come with lots of surprises.

If you joined us on the edge of our collective seats when the pictures started coming in, you'll recall that one of the very first images we got shows that Pluto has mountains on a relatively smooth surface, signs of an active outer layer that scientists were ... really not expecting.

And according to some new data, Pluto is hiding some more strange features, like flowing nitrogen ice and an atmosphere that's disappearing a lot faster than it was just a couple of years ago.

First, check out this latest picture of Pluto's surface. You can see swirls where ice has been moving around and it seem to have filled at least one crater. Scientists say the ice is probably made of nitrogen, because at Pluto's temperatures, other types of ice on the surface wouldn't be able to flow.

Water, for instance, would be way too brittle. But in addition to this being cool to imagine, these glaciers of flowing, frozen nitrogen are more examples of a recent geologic activity on Pluto, probably within the last few tens of millions of years. 

Then there's this image, snapped by the probe as it sped away from Pluto. That hazy halo you see around the dwarf planet is part of it's atmosphere. And it's doing some very strange things.

The haze, which stretches more than a hundred and sixty kilometers from the surface, five times further than models had predicted. And it contains methane, ethene, and ethyne: compounds that are part of the process that gives Pluto it's red hue.

Radiation from the sunlight converts methane to ethene and ethyne, which fall to the surface. Eventually, those particles freeze and more radiation turns them into tarry, brown-ish compounds called tholins.

And those tholins are probably what's coating the surface. Also with the latest batch of data, mission scientists measured Pluto's atmospheric pressure using an instrument array called the Deep Space Network, here on Earth, to send radiowaves through Pluto's atmosphere so that they'd hit the New Horizon detectors on the other side.

And they found that apparently half of Pluto's atmosphere has disappeared in just the last two years. Based on how the radiowaves were bent by Pluto's atmosphere, scientists think the atmospheric pressure is only about one pascal at its surface as opposed to the two pascals measured in 2013 when Pluto passed in front of a background star. 

By comparison, the standard pressure at sea level on Earth is over a hundred and one thousand pascals. The team thinks that Pluto's atmosphere might be collapsing, because it's moving away from the sun, which is causing some of it's nitrogen to condense onto the surface. 

But Pluto passed its closest point to the sun back in 1989, so if the atmosphere was gonna collapse, the astronomers thought it would happen much sooner.

But be patient! With so much information still coming from the New Horizons, researchers just need more time to figure out what's going on in our little friend out there with a heart on its butt.

 About Earth's Cousin

And Pluto isn't the only far off place that we learned about recently. Mission scientists with the Kepler Space Telescope have released the latest set of possible exoplanets to be detected by the scope, adding 521 new worlds to its existing catalog of more than four thousand.

And twelve of them seem kind of similar to Earth, including Kepler 452B, the new record holder for most-Earth-like-planet ever discovered around the sun-like star, and the sixth most Earth-like planet orbiting any star 

NASA is calling this world: "Earth's bigger, older cousin" and it does seem a lot like the place humans call home. I mean insofar as we know anything about it.

For a planet to become considered Earth-like, it has to be within a star's habitable zone, where it's close enough that its probably not a frozen wasteland, but far enough away that life wouldn't boil to death. 

Earth-like planets also usually have a diameter that's between one and two times Earth's, making them more likely to be rocky, instead of just balls of gas.

And Kepler 452B fits all of those requirements. It orbits a sun like star at a distance of just five percent farther away than Earth orbits our sun, with a 385 day year. Temperatures would be tolerable and models predict that it could have active volcanoes, a dense atmosphere, and liquid water.

It sounds a lot like home, but there are some differences too. For one thing, the planet's diameter is 60% larger than Earth's. And while it could be rocky, it might also be gaseous. And even if the surface is solid, its mass, about five times Earth's, means that you feel double the gravitational pull.

Plus, it's star is 10% bigger, 20% brighter, and with an estimated age of six billion years, 33% older than the sun. Meaning that over the next half billion years the aging star's increased energy output might make any water on the planet evaporate, and eventually escape entirely into space. 

So even if we want to colonize a world fourteen hundred light years away, Kepler 452B might not be the best place to make a long-term real estate investment.

But there's still plenty of new Kepler data waiting to be crunched, so this is a record that might soon be broken. For now, at least, Kepler 452B is the closest thing Earth has to its twin.

 End Credits

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