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In
Search of Alien Oceans
by Patrick L. Barry and Dr. Tony Phillips
A
robotic submarine plunges into the dark ocean of a distant world,
beaming back humanity's first views from an alien ocean. The craft's
floodlights pierce the silty water, searching for the first, historic
sign of extraterrestrial life.
Such a scenario may not be as fantastic as it sounds. Many scientists
believe that Jupiter's moon Europa conceals a vast ocean under its icy
crust. If so, heat from the moon's interior-which would keep the
ocean from freezing solid-may also drive subaquatic volcanoes and
hydrothermal vents. On Earth, such deep-sea vents provide chemical
energy for ecosystems that thrive without sunlight, and some
scientists even suggest that Earthly life first got started around
these vents.
So a warm Europan ocean spotted with thermal vents could be a natural
incubator for life. That's why some scientists hope that someday we
will send a probe to Europa that could bore through the ice and
explore the ocean below like a submarine.
To plan for such a mission, scientists would first need to put a
camera in orbit around Europa. By looking for places where water has
welled up to fill the spindly cracks that riddle Europa's surface,
scientists can estimate where the ice is thinnest-and thus easiest
to bore through.
That mission scenario presents a problem, though. Europa orbits
Jupiter inside the giant planet's punishing radiation belts.
Continuous exposure to such high radiation would damage today's
scientific cameras, making the information they gather less reliable
and perhaps ruining them completely.
That's why NASA is designing a more radiation-tolerant CCD that could
be used on a mapping mission to Europa. A CCD (short for
"charge-coupled device") is a digital camera's chip-like
core, which converts light into electric signals.
"We've seen the effects of this radiation during the Galileo
mission to Jupiter," says JPL's Andy Collins, principal
investigator for the Planetary Imager Project. "Galileo has orbited
Jupiter for many years, dipping inside the radiation belts only for
brief intervals. Even so," he says, "we've seen clear
signs of damage to its instruments."
By using the hardier CCD's developed by the Planetary Imager Project,
a future probe could remain in Jupiter's radiation belts for many
months, gathering the maps scientists will need to finally get a peek
behind Europa's icy veil. And who knows, maybe there will be something
peeking back!
To learn more about the Galileo mission to the Jupiter system, visit
http://www.jpl.nasa.gov/galileo/ . For children, a fun,
interactive "Pixel This!" game at
http://spaceplace.nasa.gov/p_imager/pixel_this.htm introduces CCDs and
how a really tough one will be needed for a future mission to
Europa.
This
article was provided by the Jet Propulsion Laboratory, California
Institute of Technology, under a contract with the National
Aeronautics and Space Administration.
Cracks
on the icy surface of Jupiter's moon Europa give evidence of a
liquid ocean below.
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