Cassini spots ethane clouds on Titan
Snowing at the poles
Scientists suspect that ethane falls as rain or snow on Saturn's moon Titan, after the Cassini spacecraft identified a huge cloud of the hydrocarbon in its atmosphere.
Researchers had expected to find lakes of ethane on the moon, but now suspect the substance is all frozen solid at the poles. The discovery of the ethane cloud has added weight to that hypothesis, since it was identified at the very edges of the moon's arctic circle at altitudes between 29km and 60km.
Dr Caitlin Griffith, from the University of Arizona, told the BBC: "We think that ethane is raining or, if temperatures are cool enough, snowing on the north pole right now. When the seasons switch, we expect ethane to condense at the south pole during its winter."
She added that if the polar conditions are as cold as scientists expect, the ethane could easily accumulate as ice.
The research team says the craft will now be instructed to look for evidence of polar caps on the moon. By the end of next year, it will have recorded a profile of temperature conditions at the moon's poles.
The observations were made with the craft's infrared mapping spectrometer, and the research published in the journal Science. ®