Tiger, tiger, burning bright

Saturn’s sixth largest moon, Enceladus, has been found to be warmer than expected.

A recent study published in Nature Astronomy revealed that the first few metres beneath the surface of Enceladus’ icy exterior are up to 250C higher in temperature than scientists first anticipated.

The data were collected from the only high-resolution observations of Enceladus’ southern pole, captured at microwave wavelengths in 2011 by the Cassini mission, a joint project between NASA, the European Space Agency and the Italian Space Agency.

Previous observations made by Cassini in 2005 led to the discovery of the moon’s characteristic ‘tiger stripes’: four enigmatic bluish bands stretching across the south pole region, and which produce geyser-like jets blasting out plumes of chilly vapour and ice particles.

A subsequent Cassini fly-by undertaken a couple of months later used composite infrared spectrometry to reveal that these 130 kilometre-long fractures were up to 95C warmer than predicted.

The finding led some researchers to suggest an internal heat source might be responsible for the discrepancy.

The latest data provide further insight into Enceladus’ unique geology. Although recording a temperature of approximately minus-215C , the first few metres below the surface of the south pole region was “much warmer than we had expected: likely up to 20 Kelvin warmer in some places,” explains Alice Le Gall, associate member of the Cassini Radio Detection and Ranging (RADAR) instrument team, and lead scientist of the study.

These anomalous thermal observations suggest that an ocean of liquid water may in fact be lurking just  three kilometres beneath the moon’s icy surface, much closer than previously anticipated.