How weird can nature get?

Try Titan, Saturn’s largest moon, almost 900 million cold miles from the sun and even further, perhaps, from the feeble limits of human imagination.

This is a world where it rains gasoline. Soot drifts down like snow and is mounded into dunes by nitrogen winds. Rivers have carved canyons through mountains of frozen hydrocarbons, and layers of ice float on subsurface oceans of ammonia. A chemical sludge that optimistic astronomers call “prebiotic” creeps along under an oppressive brown sky. Besides Earth, Titan is the only world in the universe that is known to harbor liquid on its surface — and everything that could imply.

For almost four centuries, Titan was just a mysterious brown dot in the sky. Then, in 1980, Voyager 1 swerved by the moon on the way out of the solar system and radioed back evidence of a smoggy atmosphere four times denser than Earth’s. Time, technology and human ingenuity have since revealed that dot, Titan, to be a natural wonderland. Last month in Nature Astronomy, planetary scientists and geologists from NASA’s Jet Propulsion Laboratory and Arizona State University, led by Rosaly Lopes of J.P.L., published what they called the first geologic map of the distant, frigid world.