Name: 冥王星的心臟如何使其大氣層向後旋轉｜科學秀新聞 (How Pluto's Heart Makes Its Atmosphere Spin Backward | SciShow News)
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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.

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,

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.

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

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

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,

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 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.

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

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.

“Backward” meaning that it rotates opposite the direction as the rest of Pluto.

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

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.

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,