Moon of Saturn Is Unveiled
The closest images ever of Saturn’s moon Titan began arriving from the Cassini spacecraft late Tuesday at the Jet Propulsion Laboratory in Pasadena, presenting scientists with as many new questions as insights into the makeup of one of the solar system’s strangest objects.
Despite concerns over rainy weather locally that threatened to disrupt the data signal, startling images of the second-largest moon in the solar system -- and the only one known to have an atmosphere -- flashed up on video screens shortly before 7 p.m., just as planned.
Piercing Titan’s thick atmosphere for the first time, the much-anticipated fly-by revealed the brilliant white surface of a continent-sized landmass that scientists quickly named Xanadu. Next to it lay an undefined dark mass that some scientists speculated could be a hydrocarbon slush, along with wispy clouds at the south polar region.
“This is utterly spectacular,” Cassini mission scientist Carolyn Porco said. “This is the last, greatest expanse of unexplored terrain in the solar system. Once we figure it out, the solar system is going to become a very much smaller place.”
Scientists gathered at JPL oohed and aahed as the images came in from Cassini, which passed over the surface of Titan at an altitude of 745 miles.
But as much as the pictures offered clues to the makeup of the moon, they raised new questions that scientists could be struggling to answer for years.
“We’re awash in multiple hypotheses,” Cassini scientist Torrence Johnson said. Referring to the strange dark area north of Xanadu, discovered by Cassini scientists in the last few days, he wondered: “Is that liquid? Is it hard, like tar?”
Xanadu itself might be covered in ice, Johnson said.
One of the most intriguing early images focused on the dark mass, in the midst of which were several shining tendrils. Speculation was that they could be ice patches on a raised landform.
“It’s pretty bizarre-looking. I’m not sure how to interpret it,” said Robert H. Brown, the leader of Cassini’s Visual and Infrared Mapping Spectrometer team.
“Some of it looks like icy stuff,” Brown said. “And the dark places look like something that has been filled in.”
Though much of the solar system has been revealed during the last five decades of space exploration, Titan, with its dense orange covering of methane gas, has remained a mystery. Cassini carried an array of instruments designed to part those clouds.
The imaging instruments, including several infrared cameras and radar, were expected to yield images with 100 times more precision than any previous spacecraft or Earth-based telescope. Features as small as a football field should appear, scientists said.
Titan has long interested scientists because they believe it to be a kind of time machine. In Titan, investigators think they could be looking at what Earth was like billions of years ago, before life developed.
The difference is that Titan is far too cold, at minus 290 degrees Fahrenheit, for any chemical interactions to produce life.
Essentially, the Saturnian moon might represent young Earth if it had been placed in a deep freeze.
Some of the best data from Tuesday’s fly-by were expected to be assembled overnight for distribution today. One of the things scientists will continue to look for is evidence of volcanism on the moon, as well as any sign that precipitation falls from its methane clouds. If so, the rain would not be water, but more likely a gasoline-type substance, scientists said.
The $3.2-billion Cassini mission is a collaboration among NASA, the European Space Agency and the Italian Space Agency. The biggest and most ambitious interplanetary probe ever launched, the 6-ton spacecraft lifted off Oct. 15, 1997. The mission has involved 260 scientists from 17 nations.
“This mission could not have been done if we didn’t have our international colleagues,” said Charles Elachi, director of JPL and a member of the radar-imaging team.
Cassini has flown through Saturn’s rings and snapped images of moons such as the misshapen rock Phoebe. Its first pass by Titan came in July. But that was at a distance of 210,000 miles, 300 times farther away than Tuesday’s pass.
This fly-by is the first of 45 close passes Cassini will make during its four-year Saturn mission. The portion of the moon its cameras are zeroing in on is the same place where, in January, Cassini is scheduled to send a probe, named Huygens, to Titan’s surface.
The 700-pound Huygens, a 9-foot-diameter, hubcap-shaped collection of scientific instruments built by the European Space Agency, will be ejected by the spacecraft on Christmas Eve. During its parachute descent to the surface weeks later, the probe will take more pictures and sample the atmosphere.
Huygens will not survive long after its landing. If it falls in a methane lake or sea, the cold will finish it. If it lands on solid ground, it will take measurements and transmit data, but only for 30 minutes, before its batteries run out.
