NASA aims to unveil biosignatures of life from Europa and Enceladus’s icy shells

Europa and Enceladus are considered the most promising moons in our solar system for harboring life. Astronomers believe that these moons might possess complex organic molecules such as amino acids and nucleic acids—biosignatures of life—just below their icy surfaces. Enceladus, one of Saturn’s 146 known moons, and Europa, one of Jupiter’s four large Galilean moons among its 95 moons, are believed to have vast subsurface oceans that could support life.

Researchers hope that future robotic missions will be able to dig into the surfaces of these moons to release these potential biosignatures, as a study suggests these molecules could be trapped within the moons’ icy shells. However, the harsh radiation from the sun that constantly bombards Europa and Enceladus would destroy these complex organic molecules if they were exposed on the surface.

The study indicates that on Enceladus, it might not even be necessary to dig deep to find these biosignatures, as they likely exist closer to the surface than on Europa. According to Alexander Pavlov from NASA’s Goddard Space Flight Center, “Based on our experiments, the ‘safe’ sampling depth for amino acids on Europa is almost 8 inches (20 centimeters) at high latitudes of the trailing hemisphere, the hemisphere opposite to the direction of Europa’s motion around Jupiter, in areas less disturbed by meteorite impacts.”

Pavlov added, “Subsurface sampling is not required for the detection of amino acids on Enceladus—these molecules will survive radiolysis, or radiation breakdown, at any location on Enceladus’ surface less than a tenth of an inch (a few millimeters) from the surface.”

Remarkably, scientists might not even need to land a rover on Enceladus to detect these biosignatures. The moon’s icy crust periodically ejects dramatic plumes, which an orbiting mission could capture directly.

 

Challenges on the Moons

The potential for life on Europa and Enceladus is tempered by the extreme conditions they endure. These moons are incredibly cold, lack atmospheres, and are continuously bombarded by energetic particles and radiation from the sun. Additionally, supernovas beyond the solar system emit powerful cosmic rays that also reach these moons.

Despite these harsh conditions, the likelihood of liquid water oceans beneath the thick icy shells of Europa and Enceladus has long excited scientists. These icy layers protect the oceans from the harmful particles and radiation, while geothermal heat generated by the gravitational pull of their planets helps keep the water in a liquid state. This combination of protective ice and internal heat has fueled hopes about the potential for life on these distant moons.