September 16, 2003. Copyright 2002. Graphic News. All rights reserved.

Fiery end for Galileo probe

LONDON, September 16, Graphic News: NASA plans to destroy its $1.5 billion Galileo spacecraft orbiting Jupiter to ensure it canÕt accidentally contaminate one of the planetÕs moons, Europa, with bugs from Earth.

On Sunday, as Galileo completes its 35th orbit of the gas giant, the ageing probe will plunge into the planetÕs stormy atmosphere at a speed of nearly 108,000mph (174,000km/h). The heat generated as it streaks through the atmosphere will vaporize the nearly 3,000-lb (1,360-kg) Galileo and the untold millions of microbial stowaways lurking since its 1989 launch.

The crash will ensure Galileo doesnÕt hit Europa, a planet-sized moon which may have warm, salty oceans, and perhaps life, beneath its ice-crusted surface.

Were bugs from Earth to infect Europa -- perhaps in pools of water warmed by the radioactive plutonium the spacecraft uses to generate electricity -- it would compromise future attempts to investigate the moon for indigenous life.

ÒIt seems like a good place where, potentially, you can have life and it also seems like a place where Earth life would find it a nice place to live. So why hit it?Ó said John Rummel, planetary protection officer for NASA.

NASA usually scrubs its spacecraft clean of microbes to prevent contamination of other places in the solar system. But that was not done with Galileo, which was originally intended to remain in orbit around Jupiter.

However, concerns that the gravitational tug of Jupiter could alter the orbit of the spacecraft and cause it to hit Europa or another moon, convinced NASA to destroy the spacecraft. Recent research has revealed the tenacity of microbial life and its ability to resist the extremes of temperature and radiation found in the vacuum of space.

ÒWe in our infinite wisdom thought nothing could survive in those harsh environments, but we are learning every day about things that can,Ó says Claudia Alexander, GalileoÕs latest project manager at NASAÕs Jet Propulsion Laboratory in Pasadena.

The 14-year mission has been among NASAÕs most successful, despite a litany of glitches. Its focus was to have been Jupiter itself, but the planetÕs quirky, diverse moons -- including Io, the solar systemÕs most volcanically active body -- stole the spotlight.

On January 17, 2002, the veteran spacecraft made its last and closest flyby of any of the giant planetÕs 61 known moons. The Galileo flight team used the remaining propellant to skim the orbiter just 62 miles (100km) above IoÕs heaving surface and put Galileo on its collision course with Jupiter this weekend.

NASA hopes to wring some scientific measurements from Galileo before its demise. When the end does come, 1,500 people associated with the mission are expected to gather at the JPL to mark the occasion. ÒIt will have some of the flavour of a wake,Ó Alexander said.
/ENDS

Sources: Associated Press, NASA, JPL