The James Webb Space Telescope (JWST) spotted Saturn‘s moon Enceladus spewing out a huge plume of water vapor much larger than anything seen there before. This huge cloud may contain the chemical components of life that escape from beneath the moon’s icy surface.
In 2005, NASA’s Cassini probe discovered icy particles spewing from Enceladus’ subsurface ocean through cracks in the lunar surface. However, JWST shows that the material is spraying much further than previously thought – many times deeper into space than the size of Enceladus itself.
“It’s tremendous,” Sara Faggi, a planetary astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said May 17 at a conference at the Space Telescope Science Institute in Baltimore, Maryland. She declined to provide further details, citing a scientific paper that will be published soon.
A rare ocean world
Enceladus excites astrobiologists because it is one of the few “ocean worlds” in the Solar System, making it one of the best places to look for extraterrestrial life. The salty ocean that lies beneath the outer ice shell of Enceladus is a possible refuge for living organisms that could be sustained by chemical energy in hydrothermal vents on the ocean floor.
The material spewing from Enceladus, primarily through fractures known as tiger stripes around the moon’s south pole, is a direct link to this potential alien ecosystem. The plumes seen by Cassini contained particles of silica that were likely carried up from the seafloor by swirling fluids1.
But it took the JWST telescope, located 1.5 million kilometers from Earth, to discover something Cassini couldn’t see from its ringside seat.
Enceladus at first glance
On November 9, 2022, JWST took a brief look at Enceladus. In just 4.5 minutes, the data revealed a huge, very cold cloud of water vapor. The upcoming paper will quantify how much water is spraying out and its temperature, Faggi said. But the plume is likely to be low-density, more like a diffuse, cold cloud than a moist spray. This is not great news for anyone looking to sample the cloud and hope to find life, as signs of life may be too rare to detect2.
The ice grains that Cassini saw much closer to Enceladus are more likely to have high concentrations of organic particles, says Shannon MacKenzie, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
JWST also analyzed the spectrum of sunlight reflected from Enceladus and found evidence of many chemicals, including water and possibly other compounds, that could indicate geological or biological activity in the moon’s ocean. “We have many more surprises,” Faggi said.
Scientists are already planning how to follow up on the discovery. Last week, JWST organizers released a list of observations to be made in the telescope’s second round of operations and it includes another project to study Enceladus.
This work will explore Enceladus six times longer than the first JWST study and will focus on finding chemical compounds associated with habitability, such as organic compounds and hydrogen peroxide.
“The new observation will give us our best chance yet to look for indicators of habitability on the surface,” says project leader Christopher Glein, a geochemist at the Southwest Research Institute in San Antonio, Texas.
A snake robot exploring the moon
The JWST findings provide further evidence for a possible NASA mission to Enceladus to search for signs of life there. Proposals under consideration include an “orbilander” mission that would orbit the moon for a year and a half before landing at its south pole.
Another proposal calls for the development of an autonomous snake robot that could crawl beneath the ice of Enceladus to explore the ocean.
Other icy moons in the Solar System are also attracting JWST’s attention. At the conference, Geronimo Villanueva, a planetary scientist at Goddard, said the telescope detected carbon dioxide on Jupiter’s moon Europa.
This excites scientists because carbon and oxygen are the key building blocks for life on Earth. NASA will launch a mission to Europa next year to explore this oceanic world in more detail. “This is definitely a new era in solar system exploration,” Villanueva said.
Written by: Vaishali Verma
Reference: https://www.nature.com/articles/d41586-023-01666-x
