AS THE Huygens probe slips beneath the clouds covering Saturn鈥檚 giant moon Titan in January 2005, it should see a sweeping panorama of mountains and giant craters filled with lakes of dark liquid methane and ethane. That鈥檚 the prediction of astronomer Ralph Lorenz, based on the moon鈥檚 bizarre geology.
Titan is larger than the planet Mercury, and the only moon in the Solar System with an obvious atmosphere. The opaque, smoggy blend of nitrogen, hydrogen, and methane is 50 per cent thicker than the Earth鈥檚 atmosphere and blocks our view of the moon鈥檚 surface, which astronomers believe is made of solid water ice. The atmosphere is thought to resemble that of the very early Earth, so NASA鈥檚 Cassini mission to Saturn will carry the European Space Agency鈥檚 Huygens probe to study it.
To predict what Huygens will see below the clouds, Lorenz, who is based at the University of Arizona, studied its geology and has come up with a vision of a truly alien world (see Graphic). 鈥淭itan鈥檚 landscape will have bizarre complexity, with craters and tectonics featuring prominently,鈥� he told 快猫短视频.
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Titan is 9.5 times as far from the Sun as the Earth is, and since winds are driven by solar energy, Lorenz estimates that wind erosion on Titan is 400 times weaker than on Earth. So Titan will be covered with relatively pristine impact craters, he says, all larger than about 10 kilometres across, as small asteroids would have exploded in Titan鈥檚 thick atmosphere. Liquid hydrocarbons will fill some of the craters, forming glossy black lakes.
And instead of having tectonic plates like Earth鈥檚, a layer of liquid water mixed with ammonia may lie below Titan鈥檚 icy crust. Convection currents deep within the moon will still create 鈥渋cequakes鈥� and mountains, but Lorenz estimates these forces are 50 times weaker than on Earth.
Even so, Titan鈥檚 tectonic movements are likely to be relatively large compared with the rate of erosion, so mountains will grow much faster than on Earth. But although peaks on Titan are probably common, they won鈥檛 be tall, as ice is too weak to support massive ranges.
