Scientists taking a peek under the clouds of ammonia gas that blanket Jupiter have found that the giant planet has wet and dry areas like the deserts and tropics on Earth.
When the unmanned Galileo spacecraft's atmospheric probe plunged through the outer layers of Jupiter's bottomless atmosphere on December 7, 1995, scientists expected to detect lots of water. Instead, they found dryness.
But now, new data from telescopes on Earth and on Galileo show other areas on Jupiter with clouds of water and perhaps even rain.
"We had suspected that the probe landed in the Sahara Desert of Jupiter," Andrew Ingersoll, a planetary science professor at the California Institute of Technology, told reporters Thursday at NASA's Jet Propulsion Laboratory.
Now that additional analysis has revealed moisture surrounding such dry spots, Ingersoll happily proclaimed: "Jupiter is wet."
But although Jupiter's weather may be more Earth-like than first believed, the planet lacks a solid surface, making it "highly unlikely" it could sustain life, Ingersoll said.
Robert Carlson, an investigator for Galileo's Near Infrared Mapping Spectrometer, showed a water map of a South America-sized expanse. It included bone-dry areas with 1 percent humidity, akin to Death Valley in California, and other places so wet, "It's either going to rain or is raining right now."
Astronomers hope to learn more about the way the oceans and atmosphere formed on Earth by studying the weather on Jupiter.
Tobias Owen, a University of Hawaii planetary scientist, explained that the abundance of elements found in Jupiter's atmosphere suggests it was seeded by comets.
"We think the same bombardment ... also brought the same important elements to Earth," he said.
NASA also released Galileo's images of Jupiter's very thin auroras, which glow in a narrow ring around the poles like the Northern Lights and Southern Lights above Earth's poles.
Auroras occur when electrically charged particles crash into Jupiter's atmosphere, but "where these charged particles come from is a mystery," Ingersoll said.
Galileo, launched in 1989 aboard a space shuttle, is more than halfway through a two-year orbital tour of Jupiter and its four major moons: Io, Europa, Callisto and Ganymede.