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  • [♩INTRO]

  • Sometimes, astronomers can seem obsessed with finding water

  • on other planets and moons, so you'd think it was super rare in the solar system.

  • But it's really not, and now we know of yet another place that might have water.

  • It's just not one you might expect.

  • In this month's edition of the Astronomical Journal,

  • scientists reported hints of a water cloud deep within Jupiter's Great Red Spot.

  • It's not a sign astrobiologists should start looking for life there or anything,

  • but it could help solve the mystery of how the largest planet in our solar system actually

  • formed.

  • Like the other gas giants, Jupiter is mostly made of hydrogen and helium.

  • But astronomers have spent over a century trying to pin down

  • what other compounds it's made of, and how abundant they are.

  • Among other things, that could help us understand how and where the planet formed.

  • For example, knowing how much water, or how much oxygen, Jupiter has

  • could help answer the question of how far away from the Sun it had to have started.

  • So far, computer models have been able to help a bit with these questions.

  • They suggest Jupiter has three different cloud layers:

  • The uppermost has a lot of ammonia, and below that it's ammonia and sulfur.

  • The bottom layer, though, is suspected to have water, both in solid and liquid form.

  • But physical evidence of that water has been a bit elusive over the decades.

  • And that's where this new study helped.

  • This team analyzed data of the Great Red Spot, a centuries-old storm larger than Earth.

  • Specifically, they used infrared data from a few telescopes and the Cassini spacecraft,

  • which allowed them to penetrate Jupiter's opaque upper layers

  • and get a look beneath the planet's surface.

  • They weren't directly looking for water, though.

  • Instead, they were mostly measuring the amount of a type of methane gas.

  • The abundance of this gas is roughly uniform in Jupiter's atmosphere,

  • so if the group saw that abundance changing at all,

  • it was likely that something, like a cloud layer, was blocking their signal.

  • And that's exactly what they found!

  • By studying the light traveling through Jupiter's clouds,

  • the team could determine exactly how far down those different layers were.

  • Then, based on the pressures and temperatures at those depths,

  • they could figure out what kinds of compounds could exist there.

  • In the end, they did find three cloud layers, just as earlier models predicted.

  • The deepest was 160 kilometers down,

  • where the atmospheric pressure is around five times that of Earth's at sea level,

  • and the temperature is just above the corresponding freezing point of water.

  • That pressure and temperature suggests the presence of water down in those clouds,

  • but right now, it definitely doesn't prove it.

  • We'll need more research to actually be sure.

  • Luckily for us, we currently have someone, or someTHING, on the case.

  • Right now, the Juno spacecraft is investigating water on, or in, Jupiter.

  • And it can look deeper than any of our other tech,

  • up to where the pressures are 100 times that of Earth's atmosphere.

  • So the team is waiting for our local planetary probe to back up their work.

  • If it does, then we'll be able to further investigate water on Jupiter

  • and maybe learn more about its origins, too.

  • Finding water on Jupiter would stick it in the same category

  • as a bunch of other objects in the solar system,

  • but don't worry: Jupiter is still super special.

  • In fact, according to research published in Nature this Wednesday,

  • it might have a magnetic field completely unlike any other planet.

  • For the last couple of years, our little friend Juno has been doing more

  • than just looking for water: It's been mapping Jupiter's magnetic field.

  • Astronomers had already crafted a new, more accurate model

  • for the field outside Jupiter, based on eight of the spacecraft's passes

  • around the planet, things like how strong it is and where.

  • But instead of looking at its surface, this team looked beneath

  • the planet's cloud tops, up to a depth of 15% of Jupiter's radius.

  • There, it's suspected that the hydrogen inside Jupiter becomes a metallic fluid,

  • which allows it to conduct electricity and generate a magnetic field.

  • But that analysis showed something super weird.

  • The team found that Jupiter's magnetic field

  • looks different across the northern and southern hemispheres.

  • In the north, it's not a dipole, like you see in diagrams of the Earth's magnetic field.

  • But in the south, it isand it's much weaker.

  • The group measured something called the magnetic flux,

  • or how strong a magnetic field is as it passes through a certain area.

  • And they found that most of the flux comes out of the planet in a small band in the north.

  • Then, some of it loops back around

  • and reenters the planet in a region near Jupiter's equator, called the Great Blue Spot.

  • Based on this, the team proposes that

  • the mechanism that powers Jupiter's magnetic field has to operate differently

  • than what we're used to seeing elsewhere in the solar system.

  • It's not like on Earth,

  • where a thick shell of some electrically conductive fluid rotates as a single body.

  • Instead, there could be different layers,

  • like different densities of metallic hydrogen at different depths.

  • Or the layers could be better or worse at conducting electrical charge.

  • Maybe some helium rain is up to something,

  • or maybe it has to do with dissolved parts

  • of the planet's rocky, icy core, which is predicted by some studies.

  • This new paper brought up a bunch of cool new questions,

  • and we just don't know what's going on yet.

  • Like with the water mystery, we need Juno to collect more data.

  • For the moment, though, it definitely looks like Jupiter's magnetic field

  • isn't like anything we've seen before.

  • So even if the planet turns out to be full of water, Jupiter is still in a class all its own.

  • Thanks for watching this episode of SciShow Space News!

  • If you'd like to learn even more about the weirdness of Jupiter's Great Red Spot,

  • like where it came from and how long it'll exist, you can watch our episode all about it.

  • [♩OUTRO]

[♩INTRO]

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木星に水があるという新たな証拠が発見された!| 木星に水があることが判明!|SciShow News (New Evidence of Water on Jupiter! | SciShow News)

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    林宜悉 に公開 2021 年 01 月 14 日
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