Titan's tropical lake hints at hydrocarbon wells

THE Caribbean it ain't, but the "tropical" regions of Saturn's moon Titan seem to harbour lakes of liquid methane. The pools are surprisingly long-lasting, suggesting that they may be replenished by underground wells of hydrocarbons.

The Cassini spacecraft confirmed the presence of liquid-hydrocarbon lakes in Titan's polar regions in 2004, but it was unclear whether similar pools could survive in the moon's marginally warmer lower latitudes - its "tropics" - without evaporating.

Caitlin Griffith and colleagues at the University of Arizona in Tucson analysed the sunlight reflected from Titan's tropical regions, recorded by Cassini. They found a highly reflective oval-shaped black feature, 2400 square kilometres in size. They say the combination of shape and colour is consistent with a liquid methane lake (Nature, DOI: 10.1038/nature11165). If it is a lake, it is long-lived, persisting since at least 2004, through both rainy and dry seasons. This means it's unlikely to be a big rain puddle and could be fed by hydrocarbon wells, say the researchers.

Jonathan Lunine, a planetary scientist at Cornell University in Ithaca, New York, says such lakes might be good habitats for simple life, but that Titan's larger polar lakes are better candidates.