Name: 土星の不思議な月（V1 (Saturn's Mysterious Moons (V1))
Uploaded: 2021-01-14T04:59:14.000Z
Duration: 18 min 41 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Some 900 million miles from the Sun... in the outer regions of our Solar System... orbiting

Enceladus is enveloped in ice. Because nearly all of the sunlight that manages to hit its

surface is reflected back into space, it's one of the brightest objects in the solar

At its equator, the temperature is -315 degrees Fahrenheit.

But, at the poles, the temperature is at least 15 degrees warmer... and as much as 65 degrees

warmer in grooves that stretch across the south like tiger stripes.

In 2005, the Cassini spacecraft spotted a complex plume of water vapor shooting out

into space from several locations near the south pole.

That may mean that Enceladus harbors a remarkable secret below its frigid surface:

A liquid ocean... and maybe... some forms of life.

This discovery was the culmination of a search that began over three decades ago. .

Back in 1979, the outer planets of the solar system lined up in such a way that mission

planners were able to dispatch the Voyager spacecraft to fly past each of them ...

The two Voyagers sent back tens of thousands of images... of planetary realms more diverse

These long-distance marathon flyers - both now headed out towards interstellar space

- made discoveries about the planetary chemistry that make these gas giants appear to us as

The Voyagers disclosed new details about their magnetic fields, atmospheres, ring systems,

and even the nature of their inner cores.

Voyager turned up some surprising new mysteries too:

a huge dark spot - a storm in fact - on Neptune...

They found that Uranus is tipped 90 degrees to one side...

That Saturn is less dense than water; if you had a bathtub big enough, Saturn would float!

...And that you'd need the mass of three Saturns to make just one Jupiter!

But what really knocked the scientists' socks off were the moons that orbit these gas giants.

All of them have been pummeled over the millennia by wayward asteroids and comets...

But a few appear to also be sculpted by forces below their icy surfaces.

Neptune's largest moon Triton has few craters. It's marked with circular depressions bounded

by rugged ridges that may mean the icy surface is collapsing.

There are also grooves and folds in the land that stretch for dozens of miles, a sign of

Triton has geysers too. But these are not spurts of water. On frigid Triton - so far

from the Sun - the liquid that spouts some five miles above the planet is nitrogen. No

Tiny Miranda... one of 27 known moons that orbit Uranus... wears a jumbled skin that's

been shaped and reshaped. Most likely, its outer crust is slipping and sliding on a molten

The moon called Io - orbiting perilously close to giant Jupiter is literally turning itself

inside out! Rivers of sulfurous lava roll down from open craters that are constantly

What was causing these tiny moons to generate so much energy from within? The answer may

well be here... on Jupiter's Europa - just slightly smaller than Earth's Moon.

Voyager saw no signs of volcanic activity, but -but instead documented a complex network

In the 1990s, the Galileo spacecraft was sent back to get a closer look at Europa and its

It found that Europa's surface is a crazy quilt of fractured plates, cliff faces and

gullies... amid long grooves like a network of superhighways.

Well, as it orbits around Jupiter in a nearly circular ellipse, the massive planet's gravity

The friction of rock rubbing on rock causes that core to heat up.

That heat rises up through an ocean of liquid water... then cracks and spreads the icy surface

Callisto and Ganymede also show such features... suggesting they have - or perhaps once had

Crossing outward to the Saturn system, Voyager's images from the late 1970's showed that the

The same was presumed of Saturn's by far largest moon, Titan... enshrouded in heavy clouds.

So when the Cassini spacecraft arrived in 2004 to scrutinize the kingdom of Saturn,

it came ready to answer a range of burning questions...

Can such moons really have liquid oceans beneath their surfaces... and do those oceans have

the ability to cook up and then support life?

After a year in orbit, Cassini let go of its traveling companion, the Huygens probe...

and sent it parachuting down towards the surface of Titan.

It's the largest moon in the solar system, larger in size - in fact - than the planet

Mercury... and massive enough to hold an atmosphere.

Unexpected crosswinds buffeted Huygens' parachute... but the probe was able to snatch a wealth

During Huygens' descent, its on-board radar showed a complex topography... with ridges,

rivers, and lakes... and even individual rocks on the ground.

Titan's atmosphere is thick and cold, the thermometer hovering just above minus 300

Fahrenheit. Like Earth, the air here is mostly nitrogen gas.

And like Earth in its very early years, Titan's muddy, wet terrain is a stew of organic compounds.

But while the liquid that cycles from ice to steam here on Earth is water, Titan's ever-changing

On Titan, methane gurgles up from the ground in liquid form and flows into lakes...freezes

into hydrocarbon icebergs ... and puffs off as gas in orange clouds and pinkish fog.

It may not be completely crazy to imagine a primitive form of life arising out of this

Once again, the evidence points toward a moon with a rocky core, heated by the tidal gravity

of a massive planet... and layers of liquid and ice near the surface that burst forth

All this activity has left a profound imprint upon the landscape.

Repeated radar passes by Cassini reveal expansive dune fields of methane mud... wetlands...

structures that look like volcanic vents... and the occasional crater.

And there's at least one continent... now known as Xanadu.

To reach us, these images had to travel nearly a billion miles. At the end of the journey...

...they were picked up by the Deep Space Network... think of the DSN as the early prototype for

Within just a few years, Cassini had transmitted one of the most impressive photographic records

Of a fascinating ringed planet... a turbulent gas giant.

It saw a storm that raged across Saturn's southern hemisphere for months - generating

lightning strikes thousands of times more powerful than those on Earth.

Cassini witnessed a giant cyclone larger than Earth ... spinning around at Saturn's south