[INTRO ♪]
When New Horizons set off toward Pluto in 2006,
we had almost no idea what we would find there.
We knew a little about its size and composition, but that was mostly it.
We didn’t even really know what it looked like.
Then, on July 14, 2015, New Horizons showed up at Pluto, and totally blew our minds.
We found out the Pluto system is one of the coolest places we’ve ever explored.
So to celebrate the fly-by’s two-year anniversary,
here are some of the most exciting things that we’ve learned.
First, there’s that giant, super cute heart,
which scientists informally called Sputnik Planum.
That area is made up mostly of slowly flowing, frozen nitrogen.
The mass of moving ice is one of the largest glaciers in the solar system!
But what’s especially neat is that the nitrogen ice is undergoing convection,
the circular current that forms as material heats up and cools down.
Pluto is pretty cold, at around -230 degrees Celsius on average.
But the elements slowly decaying in Pluto’s core create just enough heat
to make underground nitrogen ice all soft and mushy.
Then, that soft ice rises to the surface, cools down, and sinks underground again,
kinda like a gigantic, groovy lava lamp.
A lot of scientists didn’t expect to see active geology on Pluto,
which made this discovery an awesome surprise.
New Horizons found that Pluto has plenty of mountains, too,
including some covered in methane ice.
And some of those mountains, like one called Wright Mons,
even look like they could be cryovolcanoes, or ice volcanoes.
We didn’t see anything actively erupting when New Horizons flew by,
so we don’t know for sure, but these volcanoes might erupt
with a mixture of water ice, ammonia, methane, or frozen nitrogen.
Which is pretty neat for a little world so far away.
And the discoveries about Pluto weren’t limited to the ground,
or what could potentially erupt out of it.
New Horizons also found out that Pluto’s sky is blue.
It’s just like home!
That is, besides the freezing temperatures, lack of sunlight, and toxic air.
Here on Earth, the sky is blue because molecules like nitrogen in the atmosphere scatter sunlight,
but on Pluto, molecules called tholins do the scattering.
Tholins are complex, organic molecules that form when UV light from the Sun reacts with
the nitrogen and methane in Pluto’s atmosphere.
The tholins themselves are probably grey or red,
and they help give Pluto’s surface some of its color.
But their small size makes them perfect for scattering blue light.
Aww! There’s nothing like finding little reminders of home billions of kilometers away.
While it was flying past Pluto, New Horizons also got our closest look at Pluto’s moons:
Charon, Hydra, Nix, Styx, and Kerberos.
And the largest moon, Charon, had some fun surprises.
For one thing, its north pole, which the New Horizons team dubbed Mordor, is dark red,
and Pluto might have had something to do with that.
In a paper published in the journal Nature last year, scientists suggested Charon’s
pole is red because Pluto’s atmosphere is staining it.
After methane escapes from Pluto’s atmosphere, it’s caught by Charon’s gravity and then
collects and freezes on the moon’s north pole, one of the only places on Charon
cold enough to have frozen methane all year.
Then, ultraviolet rays from the Sun cause a chemical reaction in the methane,
which turns it into tholins, those same reddish, organic molecules
that make Pluto’s sky blue.
We’ve never seen coloring like Charon’s before,
and it looks like we can thank Pluto for that, too.
But Charon can also take credit for some of its awesome features.
Like its gigantic canyon system that’s 1800 kilometers long and up to 7.5 kilometers deep.
That’s four times as long and four times as deep as the Grand Canyon,
even though Charon’s diameter is less than 10% of Earth’s.
The canyon probably stretches around most of Charon’s surface, and there are also
plenty of mountains on what we thought was going to be a boring, little moon.
Charon might have ended up with that weirdly uneven geology because of a subsurface ocean
that froze a few hundred million years after the moon formed.
Most of Charon’s surface is made up of water ice, but astronomers think that right after
Charon formed, it might have been hot enough to melt some of the ice underground.
Then, over time, the underground ocean could have frozen, expanded,
and created that huge fracture in Charon’s surface.
We’re not positive that’s exactly what happened, but the possibility of another ocean
in the solar system is just plain awesome.
So from the tip top of ice volcanoes to the bottom of super canyons,
New Horizons has shown us that the Kuiper Belt is way more fascinating than we thought.
And two years later, scientists still have plenty of data to analyze,
so we’ll be learning a lot more about Pluto and its moons in the future.
Meanwhile, New Horizons is on track to visit another object in the Kuiper Belt,
called 2014 MU69, on New Year’s Day, 2019.
So this little spacecraft isn’t done teaching us about the solar system yet.
And neither are we!
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[OUTRO ♪]