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How scientists plan to find alien life on Saturn's moon Enceladus

Astrophysics and space research have long been intrigued by one persisting question: Is there life beyond Earth? Saturn’s icy moon, Enceladus, emerges as a prime candidate in this search.

Enceladus is known as an ‘ocean world‘ and possesses all three key essential elements for life as we know it — water, energy, and organic material.

Ice plumes on Saturn’s moon Enceladus

NASA’s Cassini spacecraft, during its remarkable 20-year mission, uncovered that Enceladus ejects ice plumes at a staggering speed of approximately 800 miles per hour.

These plumes are not only fascinating but also offer a unique opportunity to study the composition of Enceladus’ oceans and their potential to harbor life. The main challenge, however, was the uncertainty of whether organic compounds within these ice grains could survive the high-speed ejection without degradation.

In a significant development, researchers from the University of California, San Diego, have provided clear laboratory evidence that amino acids in these ice plumes can withstand impact speeds of up to 4.2 km/s. This research supports the possibility of detecting such compounds during space missions.

Aerosol impact spectrometer

Led by Distinguished Professor of Chemistry and Biochemistry Robert Continetti, the team at UC San Diego developed a custom-built aerosol impact spectrometer.

This apparatus, unique in its ability to handle single particles at high velocities, was initially not intended for studying ice grain impacts but proved to be exceptionally suited for this purpose.

Continetti explains, “This apparatus is the only one of its kind in the world that can select single particles and accelerate or decelerate them to chosen final velocities.”

The spectrometer’s versatility in examining particles of various sizes and materials adds to its significance in understanding particle behavior upon high-speed impact.

In 2024, NASA plans to launch the Europa Clipper, aiming for Jupiter’s moon Europa. Similar to Enceladus, Europa is another ‘ocean world’ with icy composition. This mission, along with any future probes to Saturn, holds the promise of identifying molecules in ice grains that could indicate life in the subsurface oceans of these moons.

Finding life in the Enceladus ice

Continetti’s team is the first to measure the effects of single ice grain impacts, a crucial step in understanding the survivability of organic molecules during high-speed ejections from moons like Enceladus and Europa.

The team generated ice grains using electrospray ionization and observed their behavior in a vacuum. They meticulously measured the mass, charge, and impact timing of these grains, providing insights into the survivability of amino acids at high velocities.

Their research bolsters the possibility of detecting extraterrestrial life and opens new avenues in chemistry. The presence of salt in Enceladus’ oceans, believed to be more than Earth’s, could affect the detectability of amino acids. This aspect of salt altering water’s properties and solubility of molecules could lead to more efficient detection methods.

“To get an idea of what kind of life may be possible in the solar system, you want to know there hasn’t been a lot of molecular fragmentation in the sampled ice grains, so you can get that fingerprint of whatever it is that makes it a self-contained life form,” said Continetti. “Our work shows that this is possible with the ice plumes of Enceladus.”

Beyond biosignatures

Continetti expresses excitement about the broader implications of their work, stating, “The implications this has for detecting life elsewhere in the solar system without missions to the surface of these ocean-world moons is very exciting, but our work goes beyond biosignatures in ice grains.”

He emphasizes the potential contributions to fundamental chemistry and the continuation of pioneering research in the field.

“It has implications for fundamental chemistry as well. We are excited by the prospect of following in the footsteps of Harold Urey and Stanley Miller, founding faculty at UC San Diego in looking at the formation of the building blocks of life from chemical reactions activated by ice grain impact,” Continetti concluded.

The research by Continetti and his team at UC San Diego marks a significant step in the ongoing quest to understand the potential for life beyond Earth. As space missions continue to explore the icy moons of our solar system, this research paves the way for new discoveries and a deeper understanding of the universe we inhabit.

The full study was published in The Proceedings of the National Academy of Sciences (PNAS).

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