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>> Narrator:
Approaching Neptune.

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After 12 years on the road,
and another billion miles,

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Voyager 2 was an
exhausted traveler.

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By August of 1989,
Voyager 2 was speeding

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more than 40,000 miles per hour

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toward its rendezvous
with Neptune.

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The last stop on a
spectacular grand tour

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of the four outer planets.

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Discovered in 1846,

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Neptune was named after the
mythical Roman God of the Sea.

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The planet appears blue,
because its methane

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absorbs most of the
red in the spectrum,

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leaving mostly green and blue.

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Voyager 2 flew by
Neptune only 22 miles

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off its charted course,
and only one second

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off its scheduled flyby time.

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Skimming only 3,000 miles
over the planet's North Pole,

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Voyager found Neptune
to be a giant ball

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of melted rock and ice,
cloaked in hydrogen, helium,

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and methane gasses,
its atmosphere whipped

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by winds of up to
700 miles per hour.

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Voyager flew the closest
that any spacecraft

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has come to one of
the outer planets,

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discovering at least four
complete rings of ice and rock,

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six new moons, and
a great dark spot,

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a hurricane the size of Earth

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raging in Neptune's
southern hemisphere.

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Doctor Andrew Ingersoll:

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>> Ingersoll: The storm revolves

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around the planet
every 18 hours,

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and then it rotates
around its own axis

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like a big glob of pizza
dough every 16 days.

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>> Narrator: Largest of
Neptune's eight moons,

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Triton orbits in an opposite
rotation from the planet.

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Triton was once probably
an independent object

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in orbit around the sun, until
it collided with the moon

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and was captured by
Neptune's gravity.

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Pock marked by impact
craters and glazed pink

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by a radiation blitz of
methane and nitrogen ices

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and atmosphere, Triton is
the coldest known object

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in the solar system, and
one of the most reflective.

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Utilizing Voyage's digitized
photographs of this icy moon,

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scientists saw jagged mountains,

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high cliffs,

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and frozen lakes.

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The most bizarre discovery
on Triton was the presence

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of icy geysers, some of
which are still active,

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spewing organic particles
a hundred miles downwind.

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Doctor Edward Stone:

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>> Stone: The Voyager
mission of the outer planets

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has certainly been the
journey of a lifetime.

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Having encountered
Triton as the last world

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we would visit, I
don't see how any

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of the scientists could
have been happier.

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>> Narrator: Voyager
2 has set its course

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for southwest of the
constellation Sagittarius.

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Traveling at 10 miles per
second, it is expected

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to pass four light
years from Sirius;