US researchers said Wednesday they have created the first global topographic map of Saturn's largest moon Titan, one of the most Earth-like in the solar system.

Titan is the only moon in the solar system known to have clouds, surface liquids and a thick atmosphere. The cold atmosphere is mostly nitrogen, like Earth's, but the organic compound methane on Titan acts the way water vapor does on Earth, forming clouds and falling as rain and carving the surface with rivers.

"Titan has so much interesting activity -- like flowing liquids and moving sand dunes -- but to understand these processes it's useful to know how the terrain slopes," Ralph Lorenz, a researcher from US space agency NASA who led the map-design team, said in a press release.

"It's especially helpful to those studying hydrology and modeling Titan's climate and weather, who need to know whether there is high ground or low ground driving their models."

The researchers said almost all the data used to compile the map comes from NASA's Saturn-orbiting Cassini spacecraft, which has flown past the moon nearly 100 times over the past decade.

On many of those flybys, Cassini has used a radar imager, which can peer through Titan's thick haze, and the radar data can be used to estimate the surface height, they said.

The researchers described the map, published as part of a paper in the journal Icarus, as "an interim product" as Cassini has only imaged about half of Titan's surface and more observations are still needed.

Lorenz said it could be worth revising when the Cassini mission ends in 2017, when more data will have accumulated, filling some of the gaps in present coverage.

"We felt we couldn't wait and should release an interim product, " he said. "The community has been hoping to get this for a while. I think it will stimulate a lot of interesting work."