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.