The U.S. space agency has released the first close-up pictures of Titan, Saturn's secretive, giant moon. Photos from the international Cassini spacecraft show the orbiting object shrouded in haze, and astronomers say the new images do not answer many questions surrounding the mysterious moon.

The images of Titan's hazy atmosphere are part of the four-year Cassini mission to Saturn. Initial images taken from a distance of 1,200 kilometers, the closest any spacecraft has ever gotten to Titan, show smog shrouding the moon's surface.

The new images, while clearer than those of the past, still don't reveal much more about Saturn's biggest moon than was previously known. Scientists believe Titan's atmosphere is similar to that of early Earth, and they want to study it to learn about the sort of chemistry that might have existed just before life on Earth began.

The leader of the Cassini imaging team, Carolyn Porco, says astronomers still have a long way to go to learn what's beneath Titan's haze.

"I'm not surprised we're having such a difficult time interpreting what's on the surface because remember this is an environment that we've never seen before," said Carolyn Porco. "It's not like we're visiting another airless body, and we have a lot of experience in interpreting airless bodies, all those methods of examining solid surfaces from planetary spacecraft that we have learned over the last half century. We can't use that on Titan because it's a very different environment. The materials it's made of are alien."

Ms. Porco says there are several surface features that appear to have sharp boundaries, but scientists can't distinguish them and they can't tell whether the surface is rugged or smooth.

Also, astronomers saw clouds moving very slowly over the moon's southern pole at the same time that it appears winds whip quickly across Titan's surface.

The mission is one of 45 planned flybys of Titan - some even closer - during Cassini's four-year tour of Saturn and its moons and rings. Later this year Cassini will deploy a European Space Agency probe, named Huygens, that will descend to the surface of Titan in January.