科学美国人60秒:Enceladus Might Be a Methane Hotspot

Enceladus. It’s one of Saturn’s moons. It’s one of the strangest places in the solar system. It’s also one of the most likely places to host extraterrestrial life. Powerful plumes of water vapor erupt from its poles—which proves that a liquid water ocean lies hidden beneath its icy surface. And a new analysis suggests that this buried ocean has striking similarities to the deep oceans here on Earth—at least when it comes to methane. The study is in the journal Geophysical Research Letters. [Alexis Bouquet et al, Possible evidence for a methane source in Enceladus' ocean]

NASA’s Cassini spacecraft in orbit around Saturn recently spotted a surprising amount of methane in the geysers. The simple hydrocarbon compound was expected to exist on Enceladus, but to mostly stay trapped in the moon’s underground ocean by the high pressure there. 

The abundance of methane in Enceladus’ plumes, however, means that the moon might actively produce more methane than had been thought. One explanation for the methane levels is that the compound forms through geological processes at the boundary where Enceladus’ core meets the water. The same thing happens in Earth’s hydrothermal vents—a hotspot for life. Another explanation is that methane locked in primordial ice gets released as the ice melts into the underground ocean. Either way, Enceladus keeps getting more interesting. And, just maybe, its deep water is home to our extraterrestrial cousins.

—Clara Moskowitz