Astro-boffinry breakthrough: Loads of ingredients for life found on Saturn's Enceladus
And Jupiter's Europa is looking sweet, too
Pics Tantalizing new evidence of hydrothermal vents on Enceladus and liquid water on Europa have reignited hopes that alien life may exist in our Solar System, NASA announced today.
First, some quick facts: Enceladus is Saturn’s sixth largest moon – smaller than Europa and easily identifiable by a bright surface riddled with craters and a series of streaks. Europa is Jupiter’s fourth largest moon – slightly smaller than our own moon. It’s very smooth, white and covered in red patches.
Both moons have been objects of intense interest for astrobiologists for quite some time. Data taken during flybys from the Galileo and Cassini spacecrafts hinted at liquid oceans and rocky cores hidden beneath icy crusts on Europa and Enceladus.
Now, after digging through 12 years of data from the Cassini probe, scientists have uncovered the best evidence yet that life could exist somewhere beyond Earth. The Ion and Neutral Mass Spectrometer on the spacecraft has detected a whiff of hydrogen in the gassy plumes belching out from Enceladus.
Observations show the spray is made up of about 98 per cent water vapor, one per cent hydrogen, and the rest is a mixture of carbon dioxide, methane and ammonia. The tiny presence of hydrogen is a big find. It suggests that the gas is being produced in a series of complex chemical reactions happening in hydrothermal vents on the bottom of the moon's ocean.
Hydrothermal vents may have been the source of life on Earth. The warm environments provide the right conditions for simple microbes to exist. But they need energy to survive. On Enceladus, hydrogen could be the food source for alien microbes.
“Although we can’t detect life, we’ve found that there’s a food source there for it. It would be like a candy store for microbes,” said Hunter Waite, lead author of the Cassini study.
A chemical reaction known as “methanogenesis” converts carbon dioxide and hydrogen into methane and water, a process that may be happening on Enceladus. Methane contains some of the critical elements needed to form amino acids – the building blocks of protein.
Mary Voytek, a senior astrobiologist at NASA, said there were roughly four main ingredients for life: water, time, energy and the right chemical elements – including carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur.
Scientists predict Enceladus has most of these boxes ticked. There is no clear indication that it harbors phosphorus or sulfur, but they suspect they might be contained in its rocky core. Now we need to see if enough time has passed for life to exist, she added.
More details on Enceladus can be found in a paper published in Science.
Diagram of hypothetical hydrothermal vents on Enceladus (Image credit: NASA/JPL-Caltech)
A similar situation is unfolding on Europa. New snapshots taken from the Hubble Space Telescope reveals cracks in the surface where water vapor is sprayed out.
William Sparks, a researcher at NASA’s Space Telescope Science Institute, said the showers were spotted in 2014. Two years later, scientists found a second plume erupting from the same place.
A thermal map of Europa reveals the sweet spot to be unusually hot – it was considered a thermal anomaly at the time. But now, if the temperature is connected to the plumes – just like on Enceladus – it suggests that cryovolcanism is also happening on Europa.
“Repeatability gives us a lot more faith,” Sparks said. “The pendulum has swung from caution to optimism.”
Possible plume activity spotted on Europa (Image credit: NASA/ESA/STScI/USGS)
Water vapor may be warming the surrounding surface from below the surface, and after it is ejected, from above, when it rains back down as a fine mist. Both possibilities are explored in a paper published in The Astrophysical Journal.
Scientists will have a chance to explore Europa’s watery world as NASA prepares for the Europa Clipper mission.
“If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them,” said Jim Green, Director of Planetary Science at NASA.
The hotspot will be a target area for the powerful ultraviolet camera onboard the Europa Clipper spacecraft. It will provide measurements a thousand times closer than the Hubble Space Telescope. A separate lander robot will assess the possibility of life on the moon by searching for key elements on its surface. The mission is expected to launch in the early 2020s.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at headquarters in Washington.
“These results demonstrate the interconnected nature of NASA’s science missions that are getting us closer to answering whether we are indeed alone or not.” ®