Europa: Underwater snow reveals clues about the icy moon’s ocean world

The finding, published Monday in the journal Astrobiology, suggested Europa’s ice shell may not be as salty as scientists first thought. Understanding the salt content of the ice crust is crucial as engineers work on assembling NASA’s Europa Clipper spacecraft, which is preparing to launch to Europa in October 2024.

Clues about the ice shell could also help scientists determine more about Europa’s ocean, its salinity and its potential to harbor life.

Europa’s ice shell is between 10 and 15.5 miles (15 and 25 kilometers) thick, and it likely sits on top of an ocean that’s estimated to be 40 to 90 miles (60 to 150 kilometers) deep.

“When we’re exploring Europa, we’re interested in the salinity and composition of the ocean, because that’s one of the things that will govern its potential habitability or even the type of life that might live there,” said lead study author Natalie Wolfenbarger, a doctoral student researcher at the University of Texas Institute for Geophysics in the UT Jackson School of Geosciences, in a statement.

Wolfenbarger is also a graduate student affiliate member of the Europa Clipper science team. Researchers at The University of Texas at Austin are developing the spacecraft’s ice penetrating radar.

The researchers studied the two methods of water freezing beneath ice shelves on Earth: congelation ice and frazil ice.

What’s the difference? Congelation ice actually grows from beneath the ice shelf, while frazil ice drifts up through superchilled seawater in flakes before settling beneath the ice shelf.

Both of these types result in ice that has less salinity than seawater — and according to the researchers’ projections, seawater was even less salty when they applied this data to the age and scale of Europa’s ice shell.

Frazil ice may be the most common type on Europa, which would make the ice shell much more pure than previously believed. Frazil ice only preserves a tiny fraction of the salt that exists in seawater. The purity of the ice shell can impact its strength, ice tectonics and how heat flows through the shell.

“We can use Earth to evaluate Europa’s habitability, measure the exchange of impurities between the ice and ocean, and figure out where water is in the ice,” said study coauthor Donald Blankenship, a senior research scientist at the University of Texas Institute for Geophysics, in a statement. He is the principal investigator for Europa Clipper’s ice penetrating radar instrument.

The finding may suggest that…