Organic molecules near Saturn’s moon Enceladus not a sign of life


Methanol spotted in plumes from Saturn’s icy moon does not indicate the presence of life, astronomers say. Michael Lucy explains.


A photo taken by Cassini of plumes near the south pole of Enceladus.
A photo taken by Cassini of plumes near the south pole of Enceladus.
NASA / JPL / Space Science Institute

If you’re looking for life elsewhere in the solar system, you could do worse than look to the icy moons of Jupiter and Saturn. Although they don’t have much in the way of atmosphere, several have liquid oceans sealed inside their frozen crusts.

Jupiter’s moons Europa and Ganymede, for example, may hold saltwater oceans under kilometres-deep crust, and conditions inside might be similar to those in underground lakes in Antarctica.

Saturn’s moon Enceladus, with its cryovolcanoes spraying hot water into space, is also worth a look.

Two British astronomers, Jane Greaves of Cardiff University and Helen Fraser of the Open University, recently made a surprising discovery while observing Enceladus via the IRAM 30-metre radio telescope in the Spanish Sierra Nevada. They found the tell-tale signature of the organic molecule methanol in the spray plumes. This is the first observation of Enceladus’ chemistry with a ground-based telescope.

The observation accords with earlier discoveries by NASA’s Cassini spacecraft, which flew directly through the plumes of Enceladus to study their composition. Those results had indicated the methanol levels were similar to those in Earth’s oceans, which raised hopes of finding life on Enceladus.

However, the new result – analysing the plume at greater distances from its source – indicates the methanol is a product of chemical reactions that occur in space, rather than inside the moon.

According to Emily Drabek-Maunder, also of the University of Cardiff, who presented the results to the National Astronomy Meeting at the University of Hull this week, the methanol is “unlikely to be an indication for life on Enceladus”.

The search for signs of life will, as ever, continue.

Michael Lucy is features editor of Cosmos.
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