Titan in View
A successful test of the camera on NASA’s Cassini spacecraft has produced images of Saturn 20 months before the spacecraft arrives at that planet. Dr. Dennis Matson, Cassini project scientist at JPL in Pasadena, Calif., said, "This is an emotional event for the mission. We now have Saturn in our sights."
|Red line points to the Saturnian moon, Titan. The planet was 285 million kilometers (177 million miles) from the spacecraft when the images were taken last week, nearly twice the distance between Earth and the Sun. Titan’s haze was breached by the Hubble telescope, scanning in the near infrared wavelengths, in 1994. Surface features included a bright spot the size of Australia. The ESA’s Huygens probe will descend through Titan’s atmosphere, settling on the moon’s surface. It will provide researchers with chemical analysis, spectra and images. Image Credit: NASA/JPL/Southwest Research Institute|
The image shows the shadow of the planet falling across its famous rings and includes Saturn’s largest moon, Titan.
Titan, Saturn’s largest moon, appears in the upper left of the Cassini image. It is the only moon resolved from this distance. This composite uses a threefold enhancement in the brightness of Titan relative to the brightness of Saturn. Saturn’s giant moon Titan, cloaked in a thick nitrogen atmosphere laced with hydrocarbons, could provide a laboratory in the sky for scientists seeking insight into the origins of life.
Titan is a Mercury-sized world comprised of a 50-50 mix of ices and rock. The chemical composition of its environment resembles that of early Earth but it is far colder and lacks liquid water. Scientists think Titan may have carbon- and nitrogen-containing molecules accumulated on its surface.
It is summer in Saturn’s southern hemisphere. The Sun is a lofty 27 degrees below the equator and casts a semi-circular shadow of the planet on the rings. The shadow extends partway across the rings, leaving the outer A ring in sunlight. The last Saturn-bound spacecraft, Voyager 2, arrived in early northern spring. Many features seen in Voyager images — spoke-like markings on the rings, clouds and eddies in the hazy atmosphere, ring-shepherding moons — are not yet visible to Cassini.
"Cassini has sighted the ringed planet looking distant, mysterious and serene," said Dr. Carolyn Porco, a planetary scentist at Southwest Research Institute in Boulder, Colo., and leader of the science team using the Cassini camera. "Our anticipation has been building for years, so it’s good to know our destination is in view."
|Huygens parachutes onto Titan. ESA’s Huygens probe descends through Titan’s mysterious atmosphere to unveil the hidden surface (artist’s impression) Credit: ESA|
Cassini camera-team member Dr. Alfred McEwen at the University of Arizona, Tucson, added, "Seeing the picture makes our science-planning work suddenly seem more real. Now we can see Saturn and we’ll watch it get bigger as a visual cue that we’re approaching fast. It’s good to see the camera is working well."
Fourteen camera-team scientists selected by NASA will use the camera to investigate many features of Saturn, its moons and its rings. Cassini will begin a four-year prime mission in orbit around Saturn when it arrives on July 1, 2004. It will release a piggybacked probe, Huygens, to descend through the thick atmosphere of Titan on Jan. 14, 2005.
Titan, with a diameter about two-fifths that of Earth, ranks second largest of all the solar system’s moons. Only Jupiter’s moon Ganymede is larger. The atmospheric pressure near its surface is 60 percent greater than on Earth at sea level. The dense Titan atmosphere is ten times as thick as Earth’s gaseous covering. Unlike Earth’s atmosphere, however, Titan’s bears mostly nitrogen, with methane and other trace hydrocarbons a mix that resembles the smog over Earth’s most polluted cities.
Titan is a major attraction for scientists of the Cassini-Huygens mission. They will study its haze-enshrouded atmosphere and peer down, with special instrumentation, to its surface to look for evidence of organic processes similar to those that might have occurred on the early Earth, prior to the emergence of life.
Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. Additional information about it is available online. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Office of Space Science, Washington, D.C.
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