Saturn's planet-size moon Titan has some familiar features, but it still remains one of the strangest worlds, according to data being returned by the Cassini spacecraft.

"In this short time, we are beginning to see a few things that we recognize, but most of what we see is very alien," Laurence Soderblom, a geophysicist with the U.S. Geological Survey said Friday of the data from Titan.

Cassini reached Saturn this summer on a $3.3 billion international mission to study the planet's system for four years.

Unlike the airless moons and space rocks that NASA can photograph with startling clarity, Titan, hundreds of millions of miles from Earth, has long stymied scientists because its surface is shrouded by a thick atmosphere of nitrogen and methane.

That has forced scientists to create theories about the surface from observations of the hydrocarbon-laced atmosphere. Scientists believe seas or lakes of methane could form as organic compounds fall from Titan's atmosphere and collect on the surface.

Last week, Cassini sent back radar images that revealed such surface details as a round basin, narrow miles-long linear "streaks," and a cat-shaped region of what could be the moon's theorized lakes of liquid methane and ethane.

Soderblom said streaks roughly parallel to the equator resemble features seen on Mars and could be produced by fluids flowing over the surface or by winds. Groove patterns also have been seen in the pictures, perhaps indicating tectonic processes.

Soderblom said some patterns are beginning to resemble those on Jupiter's moon Ganymede, Saturn's satellite Enceladus and Neptune's moon Triton.

"It's still early yet, but things are starting to emerge and make just a minute amount of sense," Soderblom said.