Glaciers made of acetylene 鈥� on Earth, a gas used in welder鈥檚 torches 鈥� may tower over the polar regions of Saturn鈥檚 moon, Titan, according to a new analysis. The region near Titan鈥檚 north pole also appears to harbour huge hydrocarbon seas, new radar observations reveal.
Jeffrey Kargel of the University of Arizona in Tucson, US, led a team that surveyed the zoo of organic chemicals known or suspected of being present on Titan. Then, the team analysed what form they might take in the ultra-cold, hydrocarbon-rich environment of the enigmatic moon.
At the -180潞 Celsius temperatures on Titan, it is cold enough for acetylene, which is a gas on Earth, to freeze solid, the researchers say.
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Because the poles are a little colder than the rest of the moon, the acetylene may have accumulated there, forming kilometre-thick glaciers. Vapour could rise like steam from the glaciers, perhaps accounting for the acetylene observed in Titan鈥檚 atmosphere.
Other strange things may burble up from Titan鈥檚 interior from time to time. These include volcanic eruptions of liquid polyethylene, which in its solid form is used to make plastic bags on Earth.
Blobs of plastic
鈥淢asses of polyethylene might be exuded in the liquid state to the top of the core,鈥� says Kargel, who presented the results on Tuesday at the Lunar and Planetary Science Conference in Houston, Texas, US. 鈥淎nd if it accumulates, big blobs of plastic could come floating up.鈥�
Icy moon expert Jeff Moore of NASA鈥檚 Ames Research Center in Moffett Field, California, US, says these bizarre scenarios are possible. 鈥淥ur understanding of Titan is so unconstrained that there is nothing [Kargel] said that is ruled out,鈥� Moore told New 杏吧原创.
Ralph Lorenz of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, US, agrees that future observations are likely to reveal unexpected features on the moon.
鈥淲e do have to keep an open mind because we don鈥檛 understand all the material properties,鈥� he told New 杏吧原创. But as exciting as it would be to find something like an acetylene glacier, nothing like this has been seen so far, he adds.
Giant seas
There do appear to be plenty of liquid hydrocarbons on Titan, however. Recent observations have revealed the largest lake-like features ever seen on the moon (see Titan鈥檚 largest lake rivals Earth鈥檚 Caspian Sea). One of these is about as big as the Caspian Sea on Earth. Watch an (large file, 28 MB).
Now, scientists studying recent radar observations by the Cassini spacecraft have turned up what appear to be even more large seas, with the largest measuring at least 100,000 square kilometres.
鈥淲e鈥檝e long hypothesised about oceans on Titan and now with multiple instruments we have a first indication of seas that dwarf the lakes seen previously,鈥� says Jonathan Lunine of the University of Arizona.
Missing ethane
Oceans of liquid methane were once suggested to explain why Titan鈥檚 atmosphere contains so much of the hydrocarbon, but Cassini and ground-based observatories failed to find the large bodies of liquid, instead discovering disconnected lakes and now apparent seas.
Recently, however, scientists have recalculated how much liquid methane would have to lie on the surface to account for the atmospheric observations. 鈥淟ooking at what we鈥檝e seen of Titan so far, there is easily that much,鈥� Lorenz says.
Still missing is a global ocean of ethane. The lakes may be a mixture of methane and ethane, but the breakdown of methane in the atmosphere over Titan鈥檚 lifetime should have produced a global ocean of ethane by now.
This might be an indication that the rate of ethane production is much lower than believed, or that there is extra ethane hidden underground, Lorenz says.
