Using the IRAM radio telescope, astronomers have observed an extended gas cloud around Saturn’s moon Enceladus and detected the signature of the organic molecule methanol (CH3OH). This is the first time that a molecule from Enceladus has been detected with a ground-based telescope. This surprising detection suggests that material spewed from the icy moon undertakes a complex chemical journey once vented into space.
Enceladus’ plumes are thought to originate in water escaping from a subsurface ocean through cracks in the moon’s icy surface.
Eventually these plumes feed into Saturn’s second-outermost ring, the E ring.
“Recent discoveries that icy moons in the outer Solar System could host oceans of liquid water and ingredients for life have sparked exciting possibilities for their habitability,” said Dr. Emily Drabek-Maunder, an astronomer at Cardiff University.
“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.”
Past studies of Enceladus have involved NASA’s Cassini spacecraft, which has detected molecules like methanol by directly flying into the plumes.
In the new study, Dr. Drabek-Maunder and her colleagues from Imperial College London, the Open University and Cardiff University detected the bright methanol signature using the IRAM 30-m radio telescope on Pico Veleta in the Spanish Sierra Nevada.
“This finding shows that detections of molecules at Enceladus are possible using ground-based facilities,” Dr. Drabek-Maunder said.
“However, to understand the complex chemistry in these subsurface oceans, we will need further direct observations by future spacecraft flying through Enceladus’ plumes.”
“This observation was very surprising since it was not the main molecule we were originally looking for in Enceladus’ plumes,” added Dr. Jane Greaves, also of Cardiff University.
The astronomers suggest the unexpectedly large quantity of methanol may have two possible origins: either a cloud of gas expelled from Enceladus has been trapped by Saturn’s magnetic field, or gas has spread further out into Saturn’s E ring.
In either case, the methanol has been greatly enhanced compared to detections in the plumes.
“Observations aren’t always straightforward,” said Dr. Dave Clements, of Imperial College London.
“To interpret our results, we needed the wealth of information Cassini gave us about Enceladus’ 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.”
The researchers will present their work today at the UK National Astronomy Meeting in Hull, the United Kingdom.
Emily Drabek-Maunder et al. Ground-based detection of a cloud of methanol from Enceladus: When is a biomarker not a biomarker? National Astronomy Meeting 2017