An artist’s rendition depicts the Europa Clipper probe in flight above Europa. (NASA / JPL-Caltech Illustration)
Scientists have confirmed the viability of a technique to search for microbial life on Europa, one of Jupiter’s icy moons. This method is expected to undergo testing in the 2030s when NASA’s probe conducts multiple flybys of the moon.
The approach entails examining ice grains that scientists anticipate will be collected by one of the instruments aboard Europa Clipper, known as the Subsurface Water Ice Mapping Spectrometer (SWIM).
“It’s remarkable how the analysis of these minute ice grains could provide insights into the presence of life on an icy moon. We now understand that SWIM possesses these capabilities,” stated University of Washington planetary scientist, Klenner, the primary author of a recently published research paper available in the open-access journal.
SWIM will possess the capability to analyze the chemical composition of the material it detects using impact ionization mass spectrometry. The unique aspect of the method described by Klenner and team is the examination of individual ice grains rather than a multitude of particles. This targeted approach allows scientists to focus on specific grains that may contain high concentrations of cellular components.
Various moons of Jupiter and Saturn, including Enceladus, are believed to contain subsurface oceans covered by ice. Discoveries from NASA’s Cassini mission at Saturn indicated the presence of plumes of ice grains emerging from Enceladus’ hidden seas through its icy crust. This observation has led scientists to speculate about similar phenomena on Europa.
“There is an abundance of ice grains surrounding Europa due to interplanetary meteoroid impacts on its surface, creating a faint cloud of ice grains around the moon — an ideal scenario for an instrument like SWIM,” explained Klenner.
The concept of detecting chemical traces of life within material originating from Europa dates back to the 1990s when physicist Freeman Dyson proposed the idea. While freeze-dried fish might be a stretch, fragments of cellular life could potentially exist within Europan ice.
To validate SWIM’s capabilities, Klenner and collaborators conducted simulations using comparable equipment in their laboratory. They propelled a mist of water droplets containing bacteria and bacterial fragments through their laser-equipped device, enabling the analysis of individual droplets.
The experimental setup successfully identified the chemical signature of bacteria within the droplets containing cellular material. The cell signature was most distinct in smaller droplets but remained detectable in larger droplets, resembling the range expected during SWIM’s operations.
One operational mode, focusing on positively charged ions, proved effective for detecting amino acids, while the other mode, targeting negatively charged ions, was better suited for identifying fatty acids.
The recent study’s outcomes will inform the preparations for the upcoming Europa Clipper mission. Scheduled for launch in October, the spacecraft is set to enter Jupiter’s orbit in 2030 for a four-year scientific mission. Sascha Kempf, one of the study’s co-authors, serves as the lead for the SWIM instrument.
“Our findings will undoubtedly influence the interpretation of data provided by SWIM and similar instruments,” noted Klenner. “I am particularly intrigued by the anion measurements as fatty acids, present in bacterial lipids, tend to form anions. Our results suggest that fatty acid patterns could indicate the presence of bacterial cells.”
A recent study published in Science Advances revealed that Europa’s ice shell might be extremely dynamic, with layers of ice continuously overturning. Researchers propose the existence of conductive lid layer regions, known as melt pools, which could facilitate material exchange between the surface and the subsurface ocean.
“If Europa Clipper confirms the presence of ice-ocean exchange processes, it implies that the moon possesses a mechanism for transporting material from the ocean to the surface. The instruments aboard Europa Clipper could potentially analyze material that originated from the ocean, including cellular material if present,” Klenner added.
SWIM is not the sole instrument capable of detecting cellular material within ice grains. Klenner and colleagues highlighted that impact ionization mass spectrometers with similar capabilities are under consideration for future missions to Europa, as well as for NASA’s Artemis program and Japan’s mission to the asteroid Phaeton.
Apart from Klenner and Kempf, the study published in Science Advances also credits Janine Bönigk, Maryse Napoleoni, Jon Hillier, Nozair Khawaja, Karen Olsson-Francis, Morgan Cable, Michael Malaska, Bernd Abel, and Frank Postberg as co-authors.