Galileo returns closeups of volcanic Io
A color mosaic of Io produced by using near-infrared, green and violet filters. This false color image is provided to show subtle color variations.
Click here to see how Io would appear to the human eye|
August 27, 1999
Web posted at: 1:02 p.m. EDT (1702 GMT)
By Robin Lloyd
CNN Interactive Senior Writer
(CNN) -- The latest data returned by NASA's Jupiter orbiter show the surface of the highly volcanic jovian moon Io looking more than ever like a cosmic pizza.
The pictures were taken by the Galileo spacecraft on July 3 as it passed closer to Io than it has since the orbiter reached Jupiter in 1995. They show a side of Io that has never been photographed at a relatively close distance -- 130,000 kilometers (81,000 miles) in this case.
"These are our best pictures of the side of Io that always faces away from Jupiter," said project scientist Torrence Johnson. Voyager passed by the Jupiter side of Io in 1979 and took high-resolution pictures.
Io's surface facing away from Jupiter appeared mottled in earlier Galileo pictures, but now it looks even more blotchy, especially around Io's active volcanoes. Io is the most volcanic object in our solar system, giving it a relatively smooth surface covered with molten material, scientists say.
Scientists are especially interested in a volcano called Prometheus just left of center close to the equator in the main image. The volcano shoots up snow and small particles of dust in a plume that rises up 75 to 100 km (about 60 miles) above the surface, Johnson said.
Prometheus was discovered by Voyager during its 1979 pass and has been erupting ever since, he said, producing a "sprinkler-head effect."
Oddly, its center has moved 75 km to the west since it was discovered.
Some of the images show shades of lemon yellow, light greens and auburn as they would appear in space, while others have been enhanced.
Radiation risk increasing
Flight engineers are trimming Galileo's orbit by making it pass repeatedly by Jupiter's moon Callisto to bring its orbit closer to Io. The spacecraft is being prepared for even closer encounters with Io, as close as 500 km (300 miles), in October and November.
Scientists are anxious about the Io encounters because intense radiation belts that surround Jupiter could damage the aging spacecraft. Galileo currently is enduring the most radiation it has encountered since it arrived at Jupiter, Johnson said.
The radiation dose now faced by Galileo increases with each of its orbits as it is pulled closer and closer to Jupiter and Io, the inner-most of Jupiter's four largest moons.
Flight engineers have noticed some trouble in recent weeks with the spacecraft's operations due to the increased radiation, but so far they have been able to make corrections.
The flight team has contingency plans in case the radiation interrupts future efforts to collect data at Io.
"We'll have to deal with noise in the pictures due to radiation," Johnson said. "That's why we're doing a couple of passes."
With the upcoming Io passes this fall, scientists also hope to make up for a lost opportunity in December 1995 when the spacecraft passed directly by Io, within 900 km, but failed to collect data because of a broken tape recorder that has since been fixed.
Galileo could get third life
The main mission for Galileo, managed by NASA's Jet Propulsion Laboratory, ended two years ago. Since then the orbiter has been conducting a two-year extended study of Jupiter's largest moons -- Ganymede, Callisto, Europa and Io.
That funding, about $30 million, will run out at the end of the year, but NASA managers are working on another possible extension, Johnson said. More funding would make it so Galileo could return observations of Jupiter simultaneously with NASA's Saturn-bound Cassini spacecraft during its jovian fly-by in December 2000.
Scientists discover key to Io light show
August 5, 1999
Dusty Jupiter moon gives clues to interplanetary rings
June 16, 1999
Oh, Io! Hubble views volatile moon
April 20, 1999
Jupiter's moon Callisto may hide underground sea
October 22, 1998
Galileo sends back details of Jupiter's rings
September 15, 1998
Galileo Project Information
Note: Pages will open in a new browser window
External sites are not endorsed by CNN Interactive.