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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We think Saturn’s rings were originally made of pure water ice,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
the“rusty 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!
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