The Sciences

Galileo Makes Its Last Stand

Even as its fuel dwindles and instruments fail, Galileo continues to surprise scientists.

By Maia WeinstockMar 1, 2003 6:00 AM


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The Galileo spacecraft, which has been diligently orbiting Jupiter for seven years, will soon meet a fiery demise. Yet even as its fuel dwindles and its instruments begin to fail, Galileo continues to surprise scientists.

In November Galileo made its closest pass yet to Jupiter, skimming 89,000 miles above the planet's upper cloud layer. This approach—the 34th loop around Jupiter—sent the probe deep inside the planet's powerful radiation belts. A barrage of protons temporarily immobilized Galileo's tape recorder, but engineers managed to recover data about Jupiter's magnetic field and its thin rings.

During that same orbit, Galileo made a close flyby of Amalthea, a ruddy, potato-shaped moon. Amalthea's gravitational tug on the spacecraft was far weaker than expected. Torrence Johnson, Galileo project scientist at NASA's Jet Propulsion Laboratory, says the 170-mile-wide body is probably "a very porous rubble pile, made of light rock mixed with ice and a fair amount of empty space." NASA has also just released five new images of giant red-and-black volcanoes and lakes of sulfurous lava on Io, a hellish satellite the size of Earth's moon.

In September Galileo will plunge into Jupiter's atmosphere, a strategy devised to prevent the spacecraft from contaminating Europa, the icy satellite that some scientists say could harbor life. But the probe will keep working to the end, gathering data about Jupiter's magnetosphere before burning up like a shooting star.

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