Six months after NASA's Cassini spacecraft reaches Saturn in July 2004, it will deploy the European Space Agency's Huygens probe to Saturn's largest moon, Titan. A cold, dark, smog-shrouded world nearly half the size of Earth, Titan the only moon in the solar system with a thick atmosphere.

Even the most advanced telescopes have been able to glimpse only vague light and dark patches through Titan's haze. So until the NASA/ESA Cassini-Huygens mission delivers the Huygens probe by parachute to Titan's surface in January 2005, scientists can only guess what its surface might be like.

"This is our chance to test the predictive power of scientific principles," says Ralph Lorenz, a senior research associate at the University of Arizona Lunar and Planetary Laboratory.

Lorenz, a member of both the Cassini spacecraft's radar mapping team and a co-investigator of the Surface Science Package on the Huygens probe, has developed a new perspective on how planetary landscapes are shaped. He talked about it in a press conference at the 34th annual meeting of the American Astronomical Society's Division of Planetary Sciences in Birmingham, Ala.

Lorenz' idea is that Titan's landscape will show the effects of such mechanical processes as impact cratering, erosion by the atmosphere, and tectonics.

The amount of impact cratering on Titan can be estimated from the cratering record elsewhere in the Saturnian system, he said. Heat drives the other two processes, he added. Estimates of heat flow in the atmosphere and interior can be based on knowing how much sunlight reaches Titan and guessing at how much radioactive material is present in Titan's interior.

The rate at which heat drives Titan geology is confined by a well-known theoretical limit called the Carnot limit, he added. "In essence, the atmosphere and interior are assumed to work as heat engines operating at their maximum power output."

Lorenz calculates that erosion caused by wind-blown sand, wind-driven waves and other atmospheric forces is 400 times weaker on Titan than on Earth. Such tectonic forces as earthquakes, mountain building and other outputs of Titan's mantle heat engine are only 50 times weaker on Titan than on Earth. Tides and cratering are broadly comparable on the two bodies, he adds.

"These considerations suggest that Titan's landscape will have bizarre complexity, with craters and tectonics featuring prominently. These features will be comparably much less eroded than on Earth or Mars."

Lorenz, who began working on the Huygens project as an engineering for the European Space Agency in 1990, is a co-author of the book, "Lifting Titan's Veil."