Mounds of snow-like frazil ice under the Antarctic ice shelf. According to research from UT Austin, Europa’s ice shell could be made of the same stuff. Credit: © Helen Glazer 2015, from the project "Walking in Antarctica" (helenglazer.com)
Key Points:
- Scientists believe Europa’s ice shell is being thickened by the presence of underwater snow.
- Ice formed by underwater snow is less saline, which affects how far into the ice shell the Europa Clipper will be able to see.
- The “purer” ice also plays a factor in whether or not Europa is a hospitable environment that can sustain life.
Europa, the smallest of Jupiter’s four moons, is ensconced in a thick layer of ice. Researchers now believe that an unusual phenomenon in the ocean beneath that crust might be responsible for how the moon’s ice shell is created. The event causes an “inverted snowfall,” with currents pushing particles of ice up from the ocean that then attach to the ice shell above.
Scientists believe the underwater snow may be a factor that affects whether or not Europa is capable of sustaining life, since the salinity of water crystallized this way is lower than that of ice formed via other methods.
NASA is preparing to launch the Europa Clipper in October 2024 to study, among other things, the likelihood of life on the moon. Salt levels in the ice shell are critically important as levels determine how deeply scientists can peer inside using radar.
“When we're exploring Europa, we’re interested in the salinity and composition of the ocean,” said researcher Natalie Wolfenbarger, “because that's one of the things that will govern its potential habitability or even the type of life that might live there.”
The researchers examined the two processes by which ice is formed beneath Europa’s ice shell. Congelation ice is different from frazil ice, which is responsible for the underwater snowfall that drifts up from icy waters. Congelation ice, on the other hand, forms right beneath the shell. The study, published in Astrobiology, concluded that frazil ice, which is less saline than congelation ice, may be more prevalent on the moon than previously thought.
The team says those implications are profound and affect the ice shell’s physical properties.
Frazile ice is not unique to Europa, though. It occurs in Earth’s oceans, too, which has allowed researchers to use the Earth as a sort of reference point. The team hopes that in continuing to do so, it can better equip the Europa Clipper to extract useful information from the moon’s ice shell.