Surprise methanol found around Enceladus

Methanol has been detected in the plumes of Saturn’s moon Encleadus from the ground for the first time. When the chemical was first spotted by NASA’s Cassini spacecraft, it was hoped they might be signs of life on the moon, but this new finding puts that into doubt.

 
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The plumes of Enceladus feed into Saturn's E-ring, a wide ring made up of tiny particles, rather than larger blocks of ice

Methanol has been detected in the plumes of Saturn’s moon Encleadus from the ground for the first time. When the chemical was first spotted by NASA’s Cassini spacecraft, it was hoped they might be signs of life on the moon, but this new finding puts that into doubt.

Water plumes were first seen by Cassini in 2005, spurting high over the moon’s surface in 2005 before feeding into the planet’s second outermost ring, the E-ring. Later observations found signs of the organic chemical methanol within the jets.

This time however, the molecule was detected using IRAM’s 30m radio telescope in the Spanish Sierra Nevada by Jane Greaves from Cardiff University and Helen Fraser from the Open University. It was a somewhat serendipitous discovery, as the pair were primarily looking for different molecules, but found the methanol signature surprisingly bright as the levels of methanol surrounding the plumes was much higher than that measured by Cassini within the plume.

“Recent discoveries that icy moons in our outer Solar System could host oceans of liquid water and ingredients for life have sparked exciting possibilities for their habitability,” says Emily Drabek-Maunder from Cardiff University who was part of the team and announced the observations on 4 July.

“But in this case, our findings suggest that that methanol is being created by further chemical reactions once the plume is ejected into space, making it unlikely it is an indication for life on Enceladus,” she continues.

Instead it’s suggested that the unexpectedly large amount of methanol was either trapped by Saturn’s magnetic field, or had spread further out into Saturn’s E-ring than expected. In both scenarios, the methanol has been greatly enhanced when compared with what was detected in the plumes.

“Observations aren’t always straightforward. To interpret our results, we needed the wealth of information Cassini gave us about Enceladus’s environment. This study suggests a degree of caution needs to be taken when reporting on the presence of molecules that could be interpreted as evidence for life,” says David Clements from Imperial College, who was also on the team.

As NASA’s Cassini mission is due to end on 15 September, the ability to observe such complex chemistry from Earth will be a boon to astronomers wishing to continue studying the moon. However, to truly understand Enceladus, a more direct approach will be needed.

“To understand the complex chemistry in these subsurface oceans, we will need further direct observations by future spacecraft flying through Enceladus’s plumes,” Drabek-Maunder concludes.


 

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