Astronomers have spotted an enormous plume of water vapour blasting out of Enceladus, a tiny moon of Saturn that is considered one of the most promising places to find life beyond Earth.
The record-breaking plume reached nearly 6,000 miles into space – covering the distance between Ireland and Japan – and poured water into the void at an estimated rate of 300 litres a second.
Enceladus, which harbours a deep saltwater ocean beneath an icy outer crust, is known to vent water vapour into space, but this is the first time such a massive ejection has been seen erupting from the 300-mile-wide moon.
“We were really impressed [by] how big and extended it was,” said Geronimo Villanueva, first author on the study and a planetary scientist at Nasa’s Goddard Space Flight Center in Maryland. “We were not sure what to expect.”
Researchers observed Enceladus, the sixth largest moon of Saturn, with the James Webb space telescope (JWST) last November. Images captured with the telescope’s near infrared spectrograph instrument captured what the scientists described as “an extraordinarily extensive plume”.
Measurements taken by the telescope show that Enceladus was losing 300kg of water a second in the plume, enough to fill an Olympic-sized swimming pool in a couple of hours.
The observations demonstrate the power of the JWST to understand the ocean world in detail, the researchers write in a paper accepted for publication in Nature Astronomy. They add that the telescope opens “a new window into the exploration of Enceladus … while preparing for future missions”.
Enceladus is described as an ocean world because astronomers believe that a global ocean lies beneath its icy terrain. Previous observations of the Saturnian moon have spotted water vapour plumes, carrying ice particles and organic chemicals, erupting geyser-like through surface cracks known as tiger stripes.
Because Enceladus whips around Saturn so fast, completing an orbit of the planet in little more than a single Earth day, the water vapour streams into the moon’s orbit where it forms a giant doughnut-like ring called a torus. According to the astronomer’s data from the telescope, about 30% of the water venting from Enceladus feeds the torus with the rest wafting out into Saturn’s surroundings.
The observations build on those of the highly successful Cassini mission which spent a decade exploring Saturn and its dozens of moons. The probe became the first to image the plumes erupting from Enceladus and flew through the streams of vapour to sample their constituents.
In 2017, Nasa scientists reported that Enceladus has nearly all of the ingredients needed for life as we know it, including water, energy and relevant chemistry. The energy source is believed to be similar to hot undersea vents that are teeming with life on Earth. Future missions to the frigid ocean world aim to explore the thickness of the icy outer crust and the depth of the subterranean ocean.
