Saturn's smog-ridden moon Titan bears a striking resemblance to Earth despite its alien environment, a study has revealed.
Scientists have now mapped a third of Titan's surface using radar to pierce the planet-sized moon's thick atmosphere.
The probe has revealed mountain ranges, dunes, numerous lakes and suspected volcanoes.
Just as on Earth, the weather on Titan appears to have erased most evidence of meteorite craters.
US planetary geologist Dr Rosaly Lopes, from the Jet Propulsion Laboratory in Pasadena, California, said: "It really is surprising how closely titan's surface resembles Earth's.
"In fact, Titan looks more like the Earth than any other body in the Solar System, despite the huge differences in temperature and other environmental conditions."
Titan is a supercooled world with average surface temperatures of around minus 180C, where water cannot exist except as deep-frozen, rock-hard ice.
Methane and ethane take the place of water in Titan's hydrological cycle, falling as rain or snow, and forming lakes and drainage channels.
Titan is the only moon known to possess a thick atmosphere, and the only celestial body other than the Earth to have stable pools of liquid on its surface.
The American space agency Nasa's Cassini probe has been investigating Saturn and its moons for the past five years.
It acted as "mothership" to the European Space Agency probe Huygens which landed on the surface of Titan in 2005.
Dr Lopes presented the latest results from the mission today at the International Astronomical Union (IAU) General Assembly in Rio de Janeiro, Brazil.
Other findings presented at the meeting showed evidence of water-ice and ammonia "cryovolcanoes" on Titan.
New infrared images obtained by Cassini suggest that the volcanoes have deposited ammonia on the moon's surface.
The chemical environment on Titan closely resembles that of the early Earth around the time life first emerged.
Dr Robert Nelson, a senior Jet Propulsion Laboratory research scientist who also addressed the meeting, said: "One exciting question is whether Titan's chemical processes today support a pre-biotic chemistry similar to that under which life evolved on Earth."
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