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Voyager Set to Enter the Milky Way - presented by Science@NASA
More than 30 years after they left Earth, NASA's twin Voyager probes are
now at the edge of the solar system.
Not only that, they're still working.
And with each passing day they are beaming back a message that, to
scientists, is both unsettling and thrilling.
The message is, "Expect the unexpected.".
"It's uncanny," says Ed Stone of JPL, Voyager Project Scientist since 1972.
"Voyager 1 and 2 seem to have a knack for making discoveries."
On April,28, 2011, NASA held a press conference to reflect on what
the Voyager mission has accomplished - and to preview what lies ahead
as the probes prepare to enter the realm of the Milky Way itself.
The Voyager-adventure began in the late 1970's and 80's when the
probes took a Grand Tour of the outer planets.
Voyager 1 visited Jupiter and Saturn, while Voyager 2 flew past
Jupiter, Saturn, Uranus and Neptune.
Voyager 2 is still the only probe to visit Uranus and Neptune.
When pressed to name the top discoveries from those encounters, Stone
pauses, not for lack of material, but rather an embarrassment of riches.
"It's so hard to choose," he says.
There was the discovery of volcanoes on Jupiter's moon Io, evidence
for an underground ocean on Europa, hints of methane rain on Saturn's
moon Titan, the crazily-tipped magnetic poles of Uranus and Neptune,
planetary winds that blow faster and faster with increasing distance
from the sun.
"Each of these discoveries changed the way we thought of other
worlds," says Stone.
In 1980, Voyager 1 used the gravity of Saturn to fling itself
slingshot-style out of the plane of the Solar System.
In 1989, Voyager 2 got a similar assist from Neptune.
Both probes set sail into the void.
Sailing into the void sounds like a quiet time, but the discoveries
have continued.
Voyager 1 and 2 are now at the edge of the solar system, in a place
called the "heliosheath," where the solar wind meets interstellar gas
for the first time.
This is a very strange place, filled with a magnetic froth no
spacecraft has ever encountered before, echoing with low-frequency
radio bursts heard only in the outer reaches of the solar system, so
far from home that the sun is a mere pinprick of light.
"In many ways, the heliosheath is not like our models predicted,"
says Stone.
Soon, in a matter of years, the two probes will leave the solar
system altogether and enter the realm of the stars,
interstellar space, the Milky Way itself.
Then they will have a new job: Ambassador.
Each probe is famously equipped with a Golden Record, literally, a
gold-coated copper phonograph record.
It contains more than 100 photographs of Earth; 90 minutes of the
world's greatest music; an audio essay entitled Sounds of
Earth, featuring everything from burbling mud pots to barking dogs to
a roaring Saturn 5 liftoff; greetings in 60 human languages and one
whale language; and the brain waves of a young woman in love.
A team led by Carl Sagan assembled the record as a message to
possible extraterrestrial civilizations that might encounter the spacecraft.
Some people say that the chance of aliens finding the Golden Record
is fantastically remote.
The Voyager probes won't come within a few light years of another
star for some 40,000 years.
What are the odds of making contact under such circumstances?
On the other hand, what are the odds of a race of primates evolving
to sentience, developing spaceflight, and sending the sound of
barking dogs into the cosmos?
Expect the unexpected, indeed.
For more information about Voyager and other mind-blowing NASA
missions, please visit Science.nasa.gov