Liquid levels in the lakes on Saturn’s biggest moon Titan are falling fast, space scientists have discovered. It means that if there were any alien Titanites (which sadly is not terribly likely), they might be facing a hosepipe ban.
The lakes, discovered by NASA’s orbiting Cassini spaceprobe, are dropping by around a meter a year in its southern hemisphere.
Titan is the most-Earthlike body in the solar system, with lakes, rivers, seasons and rainfall. But it is too cold for water with temperatures as low as -300F (149C) at the poles, and the liquid on Titan is a mix of methane, ethane and propane. Some scientists reckon the chemistry is right for alien life to develop in the future.
Scientists at the California Insitute of Technology studied data gathered by Cassini over four years. They blame the observed drop in lake levels on seasonal evaporation as Titan’s lake district enjoys what amounts to midsummer 890 million miles out from the Sun.
Caltech student Alexander Hayes said: “It’s really exciting because, on this distant object, we’re able to see this meter-scale drop in lake depth. We didn’t know Cassini would even be able to see these things.”
One of the lakes, Ontario Lacus – named after North America’s Lake Ontario – is the largest lake in Titan’s southern hemisphere’s. Hayes, Caltech associate professor of planetary science Oded Aharonson and colleagues report that its shoreline receded by about six miles from June 2005 to July 2009. A year on Titan lasts 29.5 Earth years so summer is a long time coming.
Cassini used a form of radar to produce images of Titan’s lakes. The results suggest that the liquid in the lakes is transparent, like liquid gas sold on Earth, rather than dark like tar.
The radar was able to penetrate the liquid to a depth of several meters. Hayes said: “Then the radar hits the floor, and bounces back. Or, if the lake is deeper than a few meters, the radar is completely absorbed, producing a ‘black’ signature.” Noting changes in how far offshore they could “see” the lakebeds allowed their slopes to be measured and liquid loss to be gauged.
Space scientists from the UK and US have proposed that NASA send a new probe to land a “boat” in one of Titan’s lakes to tell us more about their properties. In January 2005, as it arrived at Saturn, Cassini landed a European probe called Huygens on Titan. It landed on a slushy surface that UK scientists suggest could be a lake bed where the liquid has evaporated.
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