Pasadena, Calif. ? Scientists on Saturday released what they called the best pictures yet of the frozen surface of Saturn’s enormous moon Titan 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.

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 was 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.

This image of Saturn's moon Titan, taken by the Cassini spacecraft, shows the southern hemisphere of the moon in near-infrared colors.

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.