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[♪ INTRO]
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On Earth, Moon rocks are a very finite resource.
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We have a few hundred kilograms of them, and that's it,
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because we haven't returned samples from the Moon since the 1970s.
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On top of that, our methods for analyzing the rocks are often destructive.
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Because, like, we want to know what they're made of,
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and that usually means breaking them apart.
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So from slicing, to powdering, to feeding them to cockroaches,
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which we only did one time, but we did do,
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almost every experiment that's run on Moon rocks leaves less material to study.
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So you really have to make every bit count.
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And last week, a team published a paper
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in Meteoritics & Planetary Science describing how to do just that.
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For the first time, they used a technique called atom probe tomography, or APT,
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to study lunar soil not just grain by grain, but atom by atom.
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Which is so resource-efficient that it's almost a little funny.
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APT has been used for a while to do nanoscale materials science,
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like making nanowires for stuff like transistors and lasers.
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But it's relatively new to geology, with use starting in the past six years or so.
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APT incorporates other techniques that are more familiar to geologists,
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like time-of-flight mass spectrometry,
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where you separate a sample by the masses of its elements and compounds.
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But unlike regular mass specs, this technique can build a 3D map of a sample.
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That's a big deal, because while APT does destroy a tiny bit of your original sample,
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you end up with a digital recreation that can be used in future studies.
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Here's how it works.
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First, you use a beam of ions to carve a tip out of your sample.
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Then, you use a laser to knock individual atoms off that tip,
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which then fly into the time-of-flight mass spectrometer.
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Heavier atoms fly slower than smaller ones.
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So by calculating how long it takes for a particle to get to the mass spec,
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you can figure out the particle's mass and identify what it's made of.
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But the more important thing is, you're doing all of this
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with an unreasonably powerful microscope
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that allows you to see the locations of the individual atoms.
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So, as you work through your sample,
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you can keep track of every atom or molecule you come across.
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And with that data, you can make a 3D map
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of where every particle was before the sample was destroyed.
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With this method, the team was able to take a single grain of lunar soil,
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about the diameter of a strand of hair,
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and determine that it contained iron, water, and helium.
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Results like this are important industrially, because that's the stuff some people
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might want to pull out of the Moon when we go back there.
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So we should probably know how much of it there is.
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But they're also important scientifically.
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Iron, water, and helium are the products of space weathering,
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which is how particles from the Sun physically and chemically alter rocks.
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The better we understand how this works,
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the better we can understand the Moon's geologic history.
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And with APT, we can really dive deep into our limited stash of Moon rocks,
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or, really, rocks from anywhere in space, to explore those questions.
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In other solar system news,
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let's talk about everyone's favorite geological feature: Pluto's heart!
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Okay, it might not be everyone's favorite geologic feature,
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but it's Valentine's Day and it's pretty cute.
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And it turns out, it's not just adorable!
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The heart is a major influence on the dwarf planet's landscape and atmosphere, too.
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Pluto's atmosphere is almost entirely nitrogen.
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And Pluto's heart, especially its left lobe, called Sputnik Planitia,
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is also mostly nitrogen, just frozen solid.
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During the day, it's warm enough that some of the frozen nitrogen
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becomes gas and enters the atmosphere.
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And at night, some of the nitrogen in the atmosphere freezes back into the heart.
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So on Pluto you have this day/night cycle where the atmosphere
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gains and loses mass and pressure, which can create strong winds.
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And in a paper published last week in the Journal of Geophysical Research: Planets,
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a team of scientists demonstrated that this process
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could be causing another one of Pluto's oddities:
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the fact that part of its atmosphere rotates backward.
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“Backward” meaning that it rotates opposite the direction as the rest of Pluto.
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Which, honestly, is really weird.
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In the study, the team figured this out by running some models
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made with data from the New Horizons spacecraft.
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The models show how, in the northern part of Sputnik Planitia,
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where it's currently summer, ice turns into gas during the day
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and then raises the local air pressure.
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Then, that gas moves south to areas of lower pressure.
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And since it's currently winter in the south,
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the gas then freezes back onto the ground.
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This wind doesn't just affect Pluto's heart, though.
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As the air moves north to south,
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it actually gets deflected by the dwarf planet's rotation,
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and that ends up pushing winds westward in two regions of the atmosphere.
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It makes the upper atmosphere move east-to-west,
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instead of west-to-east like the rest of the planet.
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And it also creates a local westward current much closer to the ground.
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This current picks up all kinds of dust and haze
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and drops it right next to Sputnik Planitia,
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creating stripes that stretch out to the west side of the heart.
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These results both provide insight into broad planetary processes
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and let us talk about the local weather just inside the heart.
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That kind of view is really hard to achieve,
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and a testament both to the quality of the model,
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and the quality of the data New Horizons gathered.
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Before the mission, the best images we had of Pluto were incredibly fuzzy,
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and the only way we could study its atmosphere was by
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waiting for it to pass in front of a star and see what light filtered through.
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So New Horizons has really revolutionized our understanding of Pluto!
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And even though it passed the dwarf planet almost five years ago,
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we're still learning so much from it.
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Thanks for watching this episode of SciShow Space News.
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We put out an episode like this every week,
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so if you want to join us in keeping up with the latest space research,
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well, the more, the merrier!
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You can subscribe using the button below, or at youtube.com/scishowspace.
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