Fluorescent Amino Acids on Europa: A Search for Life in the Ice
Europa, one of Jupiter’s largest moons, is an exciting target in the search for extraterrestrial life. Beneath its thick ice shell, a global ocean is thought to be in direct contact with a rocky mantle, possibly supporting hydrothermal activity. This environment might resemble deep-sea vents on Earth, where heat and chemical reactions provide energy for life. If life exists in Europa’s ocean, some of its chemical building blocks—such as amino acids—could be transported to the surface, offering a chance for detection by future spacecraft.
Searching for Signs of Life
Amino acids are the building blocks of proteins, essential to all known life. While some simple amino acids, like glycine and alanine, can form through non-biological processes, complex ones such as phenylalanine, tyrosine, and tryptophan are much harder to produce without life. These “aromatic” amino acids absorb ultraviolet (UV) light and fluoresce, meaning they emit light at specific wavelengths when excited by a laser. This property has been used to detect organic molecules on Mars, and it could be applied to Europa as well.
If these molecules exist in Europa’s ice, they are most likely to be found in areas where material from the subsurface ocean has recently surfaced. Scientists believe this could happen through cryovolcanism (ice volcanoes), tectonic shifts, or plumes—jets of water vapor similar to those seen on Saturn’s moon Enceladus. However, Europa’s surface is a harsh place. It is constantly bombarded by charged particles from Jupiter’s magnetic field, as well as intense UV radiation from the Sun. These processes can break down organic molecules over time, reducing the chances of detecting them.
Modeling the Breakdown of Organic Molecules
To determine whether aromatic amino acids could survive long enough to be detected, the researchers modeled two key degradation processes: radiolysis, caused by high-energy particles from Jupiter, and photolysis, caused by UV radiation from the Sun. Their model considered how these processes vary across Europa’s surface, accounting for factors such as ice composition and temperature.
They found that radiation is strongest on Europa’s trailing hemisphere (the side facing backward in its orbit), where charged particles from Jupiter’s magnetosphere hit the surface more directly. Photolysis, on the other hand, is more effective in regions with clearer ice, as UV light can penetrate deeper. Interestingly, high-latitude regions (near the poles) provide the best conditions for preservation, as they are shielded from intense radiation and contain ice that absorbs UV light more efficiently.
Can We Detect These Molecules?
The researchers estimated how long aromatic amino acids could survive in Europa’s near-surface ice and whether their fluorescence could be detected by a future spacecraft. They found that these molecules could persist for hundreds of years in high-latitude regions, particularly in recently resurfaced ice. A laser-based instrument, similar to those used on Mars, could potentially detect fluorescence from these compounds even from orbit, though a lander would provide a much stronger signal.
Importantly, they found that Europa’s plumes, if they exist, might be ideal places to search for biosignatures. If material ejected from the ocean contains amino acids, detecting them before they degrade could be a major step toward answering the question of whether life exists beyond Earth.
What’s Next?
The findings of this study suggest that Europa’s ice could preserve chemical signs of life long enough for future missions to detect them. NASA’s upcoming Europa Clipper mission will explore the moon’s surface and atmosphere, searching for signs of ocean material and potential biosignatures. If fluorescence spectroscopy is used in future missions, it could help reveal whether complex organic molecules—and perhaps even life—exist beneath Europa’s icy shell.
Source: Yoffe
