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  • [♪ INTRO]

  • On Earth, Moon rocks are a very finite resource.

  • We have a few hundred kilograms of them, and that's it,

  • because we haven't returned samples from the Moon since the 1970s.

  • On top of that, our methods for analyzing the rocks are often destructive.

  • Because, like, we want to know what they're made of,

  • and that usually means breaking them apart.

  • So from slicing, to powdering, to feeding them to cockroaches,

  • which we only did one time, but we did do,

  • almost every experiment that's run on Moon rocks leaves less material to study.

  • So you really have to make every bit count.

  • And last week, a team published a paper

  • in Meteoritics & Planetary Science describing how to do just that.

  • For the first time, they used a technique called atom probe tomography, or APT,

  • to study lunar soil not just grain by grain, but atom by atom.

  • Which is so resource-efficient that it's almost a little funny.

  • APT has been used for a while to do nanoscale materials science,

  • like making nanowires for stuff like transistors and lasers.

  • But it's relatively new to geology, with use starting in the past six years or so.

  • APT incorporates other techniques that are more familiar to geologists,

  • like time-of-flight mass spectrometry,

  • where you separate a sample by the masses of its elements and compounds.

  • But unlike regular mass specs, this technique can build a 3D map of a sample.

  • That's a big deal, because while APT does destroy a tiny bit of your original sample,

  • you end up with a digital recreation that can be used in future studies.

  • Here's how it works.

  • First, you use a beam of ions to carve a tip out of your sample.

  • Then, you use a laser to knock individual atoms off that tip,

  • which then fly into the time-of-flight mass spectrometer.

  • Heavier atoms fly slower than smaller ones.

  • So by calculating how long it takes for a particle to get to the mass spec,

  • you can figure out the particle's mass and identify what it's made of.

  • But the more important thing is, you're doing all of this

  • with an unreasonably powerful microscope

  • that allows you to see the locations of the individual atoms.

  • So, as you work through your sample,

  • you can keep track of every atom or molecule you come across.

  • And with that data, you can make a 3D map

  • of where every particle was before the sample was destroyed.

  • With this method, the team was able to take a single grain of lunar soil,

  • about the diameter of a strand of hair,

  • and determine that it contained iron, water, and helium.

  • Results like this are important industrially, because that's the stuff some people

  • might want to pull out of the Moon when we go back there.

  • So we should probably know how much of it there is.

  • But they're also important scientifically.

  • Iron, water, and helium are the products of space weathering,

  • which is how particles from the Sun physically and chemically alter rocks.

  • The better we understand how this works,

  • the better we can understand the Moon's geologic history.

  • And with APT, we can really dive deep into our limited stash of Moon rocks,

  • or, really, rocks from anywhere in space, to explore those questions.

  • In other solar system news,

  • let's talk about everyone's favorite geological feature: Pluto's heart!

  • Okay, it might not be everyone's favorite geologic feature,

  • but it's Valentine's Day and it's pretty cute.

  • And it turns out, it's not just adorable!

  • The heart is a major influence on the dwarf planet's landscape and atmosphere, too.

  • Pluto's atmosphere is almost entirely nitrogen.

  • And Pluto's heart, especially its left lobe, called Sputnik Planitia,

  • is also mostly nitrogen, just frozen solid.

  • During the day, it's warm enough that some of the frozen nitrogen

  • becomes gas and enters the atmosphere.

  • And at night, some of the nitrogen in the atmosphere freezes back into the heart.

  • So on Pluto you have this day/night cycle where the atmosphere

  • gains and loses mass and pressure, which can create strong winds.

  • And in a paper published last week in the Journal of Geophysical Research: Planets,

  • a team of scientists demonstrated that this process

  • could be causing another one of Pluto's oddities:

  • the fact that part of its atmosphere rotates backward.

  • Backwardmeaning that it rotates opposite the direction as the rest of Pluto.

  • Which, honestly, is really weird.

  • In the study, the team figured this out by running some models

  • made with data from the New Horizons spacecraft.

  • The models show how, in the northern part of Sputnik Planitia,

  • where it's currently summer, ice turns into gas during the day

  • and then raises the local air pressure.

  • Then, that gas moves south to areas of lower pressure.

  • And since it's currently winter in the south,

  • the gas then freezes back onto the ground.

  • This wind doesn't just affect Pluto's heart, though.

  • As the air moves north to south,

  • it actually gets deflected by the dwarf planet's rotation,

  • and that ends up pushing winds westward in two regions of the atmosphere.

  • It makes the upper atmosphere move east-to-west,

  • instead of west-to-east like the rest of the planet.

  • And it also creates a local westward current much closer to the ground.

  • This current picks up all kinds of dust and haze

  • and drops it right next to Sputnik Planitia,

  • creating stripes that stretch out to the west side of the heart.

  • These results both provide insight into broad planetary processes

  • and let us talk about the local weather just inside the heart.

  • That kind of view is really hard to achieve,

  • and a testament both to the quality of the model,

  • and the quality of the data New Horizons gathered.

  • Before the mission, the best images we had of Pluto were incredibly fuzzy,

  • and the only way we could study its atmosphere was by

  • waiting for it to pass in front of a star and see what light filtered through.

  • So New Horizons has really revolutionized our understanding of Pluto!

  • And even though it passed the dwarf planet almost five years ago,

  • we're still learning so much from it.

  • Thanks for watching this episode of SciShow Space News.

  • We put out an episode like this every week,

  • so if you want to join us in keeping up with the latest space research,

  • well, the more, the merrier!

  • You can subscribe using the button below, or at youtube.com/scishowspace.

  • [♪ OUTRO]

[♪ INTRO]

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冥王星の心臓が大気を逆回転させる仕組み|サイゾーウーマンニュース (How Pluto's Heart Makes Its Atmosphere Spin Backward | SciShow News)

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    林宜悉 に公開 2021 年 01 月 14 日
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