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  • [♪ INTRO]

  • The Cassini mission to Saturn has revealed lots of new data and all kinds of mysteries.

  • And, as the spacecraft approaches its final days, the surprises just keep coming.

  • Take Saturn's rings, for example.

  • Scientists thought the rings were as old as the planet.

  • But, according to some of Cassini's recent measurements,

  • it's starting to look like we might have been wrong.

  • The Cassini spacecraft is our fourth probe to visit Saturn.

  • It was launched 20 years ago and arrived in 2004.

  • Cassini's long list of achievements include hundreds of flybys, checking general relativity,

  • discovering new moons, and detailed studies of storms on Saturn.

  • And, in the past few months, it's been helping us figure out how old Saturn's rings are,

  • by getting up close and personal.

  • One of the goals of these dangerous dives between Saturn and its rings is to figure

  • out the mass of the rings, using two pieces of data: the exact path of Cassini, and the

  • frequency of the radio signals coming from the probe.

  • Both of these things are affected by the gravitational pull of different parts of Saturn,

  • and more massive objects have stronger gravitational pulls.

  • Force depends on how much mass something has, along with its acceleration.

  • So scientists can use these data from Cassini to calculate how much of Saturn's mass

  • is in the planet, and how much is in the rings.

  • Figuring out the mass of the rings can also tell us their age,

  • when we consider what they're made of too.

  • We think Saturn's rings were originally made of pure water ice,

  • but they're constantly hit by other space debris.

  • Right now, around 5 or 10% of the rings are made of other dusty junk.

  • More massive rings would take longer to get polluted and

  • could survive a lot of bombardment over time.

  • Some scientists thought that the rings might have been formed at the same time as Saturn,

  • nearly 4.6 billion years ago.

  • This is when rocks were smashing into each other a ton,

  • gradually coalescing into the solar system we know today.

  • But, in an online news conference last week, a scientist working on the Cassini mission

  • said that these recent data are pointing more towards less massive, younger rings.

  • In fact, the rings could be just 100 million years old, maybe formed from an icy object

  • that broke apart after getting too close to Saturn and its gravity.

  • At least, that's how it looks from early calculations.

  • But there's still lots of data to analyze.

  • Cassini's final hurrah will involve snapping a few final pics of Saturn's moons, a weird

  • hexagonal jet stream at the planet's north pole, and Peggy, not the Schuyler sister,

  • but an icy mini-moon inside the rings.

  • Then, a week from today, Cassini will dive into the planet's atmosphere,

  • melt, and be torn apart.

  • During this dramatic end to its mission, the probe will be measuring the composition of

  • the atmosphere, the magnetic field strength, and the length of a day on Saturn,

  • all in greater detail than ever before.

  • So thanks, Cassini, for everything you've taught us.

  • Moving closer to home, we're still trying to figure out

  • whether there's water in our moon.

  • We've talked a little about this before on SciShow Space: the Moon might've formed

  • in a huge collision with the Earth, which could've emitted a lot of heat

  • and made all the water evaporate.

  • But underground water on the Moon is looking more likely,

  • which throws a little wrench in that idea.

  • It suggests that, somehow, water stuck around or got deposited later.

  • So scientists don't agree about what happened in our Moon's past, and two very recent

  • studies even have conflicting evidence.

  • In one paper from July, researchers at Brown University were searching for water in volcanic

  • deposits on the surface of the Moon.

  • Scientists have been interested in these deposits since 2008, when they analyzed volcanic glass

  • that was brought back from the Apollo missions and found trace amounts of water.

  • Because they think the eruptions that made these deposits come from deep underground,

  • studying them could tell us whether there's water in the Moon's mantle.

  • The researchers analyzed these deposits using spectrometers in satellites, which split the

  • light coming from an object into different frequencies.

  • Water molecules absorb and reflect specific frequencies, which we can look for.

  • And the paper published in Nature Geoscience suggests that there's water in these deposits

  • across a lot of the lunar surface, including where the Apollo samples were collected.

  • So they take this as evidence that the whole mantle could have water in it.

  • It's not just a weird find in few small areas.

  • But another study, published in August in the journal PNAS,

  • isn't so sure about water beneath the Moon's surface.

  • A group of researchers were analyzing a famous Moon rock from the Apollo era nicknamed

  • therusty rock,” because it has a patch of rust, also known as iron oxide.

  • And you can't make rust without water in the reaction, so some scientists thought this

  • was evidence of water inside the Moon.

  • But the rusty part of the rock also contained some light forms of zinc.

  • And researchers think this zinc actually evaporated and then condensed onto the rock,

  • like water droplets on a saucepan lid, in a super hot environment.

  • Like one we'd expect during the big collision that could've formed the Moon.

  • So the composition of this rock suggests that the Moon's interior was once hot enough

  • that it would've lost most of the light elements

  • because of vaporization, leaving heavier ones behind.

  • And any trace amounts of easily-evaporated stuff, like water, are just leftovers from

  • this period in the Moon's history.

  • So, despite the rust, these researchers argue that this rock is evidence

  • that the Moon's interior isn't watery.

  • The next step for scientists will be explaining these conflicting findings, maybe showing

  • how water could've survived on the Moon, or exactly how those volcanic deposits formed.

  • And we'll keep updating you here as they figure out these contradictions.

  • Thanks for watching this episode of SciShow Space News,

  • and thanks especially to our patrons on Patreon.

  • If you want to help us keep making episodes like this, just go to patreon.com/scishow.

  • And don't forget to go to youtube.com/scishowspace and subscribe!

  • [♪ OUTRO]

[♪ INTRO]

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B1 saturn cassini moon water formed rust

Cassini's Last Hurrah & Hints About Saturn's Rings

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    林宜悉 posted on 2020/04/04
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