Scientists released what they called the best pictures yet of the frozen surface of Saturn's enormous moon Titan Saturday, but said they were puzzled that the Cassini spacecraft hadn't glimpsed any evidence of liquids.
The latest images of Titan revealed a single set of clouds about the size of Arizona and dark and light shapes across the moon that the imaging team continued to analyze.
The shots of the moon's surface features were taken during Cassini's first pass Friday at a distance of about 200,000 miles.
"It's different from anything we've ever seen before," imaging scientist Elizabeth Turtle said. "We're still trying to understand the surface of Titan."
Scientists believe the moon could have chemical compounds much like those that existed on Earth billions of years ago before life appeared.
"Scientists think it might mirror in microcosm conditions that existed on earth, in earth's atmosphere 4 billion years ago at the dawn of the solar system," said CBS News Space Consultant Bill Harwood. "By studying Titan, they hope to get some insight into how earth itself evolved."
Big enough to be a planet in its own right, Titan has an atmosphere 1 1/2 times as dense as Earth's, containing organic -meaning carbon-based - compounds. Scientists believe there could be hydrocarbon seas or lakes.
Turtle said initial data analysis suggested the moon is the site of some type of geologic activity that could include wind and erosion and development of the lakes or rivers.
Kevin Baines, a member of the visual and infrared spectrometer team, said scientists were disappointed that they hadn't seen evidence of liquids.
"We thought we'd see some flashes, and we haven't seen any. So we're a little perplexed," he said after a news conference at NASA's Jet Propulsion Laboratory in Pasadena.
Among the new pictures released were four images of a cluster of clouds near Titan's south pole that are believed to be composed of methane. They were the only brightly distinct spots on otherwise fuzzy images of Titan.
"Someone likened it to a melting ice cream sundae," Turtle said.
There will be many more chances to uncover the face of Titan during Cassini's planned four-year tour. The spacecraft will make 45 more flybys of the moon and then send a probe into its atmosphere in January. The closest flyby comes in October.
The probe, named Huygens, will send pictures back to Cassini as it makes a 2 1/2-hour descent by parachute through the atmosphere.
Titan was Cassini's first encounter since the spacecraft began orbiting Saturn earlier this week.
The $3.3 billion mission, funded by NASA, the European Space Agency and the Italian Space Agency, was launched in 1997. The spacecraft flew 2.2 billion miles on a roundabout route to Saturn.
CBS News Space Consultant William Harwood has covered America's space program full time for nearly 20 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.