MESSENGER Update - December 5, 2003

For JPL internal use only.

http://www.bayarea.com/mld/mercuryne...al/7445519.htm

Nuclear-powered spacecraft to explore Jupiter's moons
ANDREW BRIDGES
Associated Press
December 8, 2003

SAN FRANCISCO - NASA plans to dispatch a hulking nuclear-powered
spacecraft to determine whether three of Jupiter's icy, planet-sized moons have the
potential to harbor life.

The Jupiter Icy Moons Orbiter, or Jimo, would spend monthlong stints circling the
moons Callisto, Europa and Ganymede, which are believed to have vast oceans
tucked beneath thick covers of ice.

The unmanned craft, far larger and more powerful than any other sent to explore the
outer solar system, would spend years studying the moons' makeup, geologic
history and potential for sustaining life as well as Jupiter itself.

Besides water, the moons appear to contain two other ingredients necessary for life:
energy and the right chemicals. Along with Mars, they are considered the most likely
places to find extraterrestrial life within our solar system.

"It's not guaranteed to find life. We don't know if life is there. But this mission will
allow to ask that question with some pretty sound tools," said Christopher McKay of
the National Aeronautics and Space Administration's Ames Research Center.

Jimo won't launch until at least 2011. On Monday, scientists at the fall meeting of
the American Geophysical Union briefed reporters on the mission's progress.

The spacecraft would be the first in a series of robotic NASA probes that rely on
uranium-fueled fission reactors to generate large amounts of electricity. While
probes such as Galileo and Cassini have made do with hundreds of watts of
electricity, Jimo might have thousands of watts to power its thrusters and
instruments, said Torrence Johnson of NASA's Jet Propulsion Laboratory.

The reactor conceivably could produce enough electricity to power several U.S.
homes. That could provide Jimo a hundredfold boost over previous missions in the
amount of data it would be able to beam back to Earth.

Jimo would carry high-resolution cameras and other instruments, including radar and
lasers to map the thickness and elevation of the ice that envelops each moon.

Scientists are keen to study the Jovian system because of its complexity. The planet
and its stable of moons represent, in many ways, a miniature solar system.

"These are worlds in their own right," said Ron Greeley, of Arizona State University,
Tempe.

The spacecraft is envisioned as being 60 to 100 feet in length. Early conceptions
place its nuclear reactor at the end of a boom to shield the scientific instruments from
radiation.

Jimo also would bristle with fins to dissipate the intense heat from its reactor.

NASA is expected to begin stepping up use of nuclear power in its exploration of the
solar system, including Mars. There, it could power rovers capable of roaming the
planet for years at a time.

"It just opens up a whole new vista of things you can do," said Jay Bergstralh,
associate director of NASA's solar system exploration division.

Scientists allayed potential concerns about sending a nuclear reactor into space. The
reactor would be launched "cold" and powered up only once the spacecraft was safely
on its way to Jupiter, Bergstralh said.

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Scientists allayed potential concerns about sending a nuclear reactor into space. The
reactor would be launched "cold" and powered up only once the spacecraft was safely
on its way to Jupiter, Bergstralh said.

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Even so, the environuts will still freak out on this. Better not do any
Earth flybys. Or Mars.
I don't think anyone will worry about hitting Venus, as it's way too hot
for its real estate
to be worth anything......