Tidal waves may rock Saturn moon
By Robert Roy Britt
SPACE.com
SPACE.com -- Saturn's moon Titan might be one of the most out-of-this world places to hang ten, according to new computer modeling that suggests wind could generate waves there that are seven times taller than on Earth.
Scientists aren't sure if Titan has seas, but they suspect it does based on hard-to-interpret telescopic observations. The oceans would be made mostly of ethane and methane, studies show.
Because Titan's gravity is about one-seventh that of Earth, any wind-driven waves would behave differently than they do here.
"Big-wave riding could take on a whole new meaning on Titan," says Nadeem Ghafoor of Surrey Satellite Technology in the UK.
Ghafoor and colleagues considered several factors -- Titan's gravity, the likely composition and density of the atmosphere and any possible seas, and probable wind speeds -- to generate wave scenarios using modified version of terrestrial ocean computer models.
The development of waves depends on wind speed and how long and over what distance it blows in one direction, called the "fetch." The Titan model incorporates wind speeds up to a modest 12.5 mph.
"We do not know much about the surface winds on Titan, although early models suggest the sustained wind speed at the surface is likely to be low," Ghafoor explained. The model includes fetches up to 1,000 kilometers.
"Much of the Titan wave growth happens before 100 kilometers (62 miles) is reached, however," said Ghafoor."Waves grow to be up to seven times higher and longer than those on Earth. However because of the lower gravity on Titan, waves on Titan will generally appear to move in slow motion."
Ghafoor is slated to present the results on Tuesday at a meeting of the Royal Astronomical Society. He said the computer model is sound, but he allows that the make-up of Titan's surface -- liquid or solid -- involves speculation at this point.
"Something weird is happening down there, however, and it seems that we may only truly know when Cassini-Huygens arrives in January 2005," Ghafoor said, referring to the Cassini mission to Saturn. The craft carries the Huygens probe, which will plunge through the atmosphere and land on Titan's surface -- whatever it's made of -- early next year. If Huygens lands in a sea, it could float and transmit data for up to two hours.
The probe has instruments that could measure the height and frequency of any waves and the liquid's composition. With sonar, it could measure the sea's depth. Its camera might even return the first pictures of an extraterrestrial sea.
Open University professor John Zarnecki, a participant in the new study and leader of Huygens' Surface Science Package experiment, speculated on what Titan's seas might look like.
"Well, the waves would be more widely dispersed than on Earth but they will be very much higher," Zarnecki said. "So the surface around us would probably appear flat and deceptively calm, but in the distance we might see a rather tall, slow-moving wave advancing towards us -- a wave that could overwhelm or sink us."
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