Underwater snow revealed the secrets of Jupiter’s moon Europa

Jupiter’s icy moon Europa is an ocean world trapped under a thick crust of ice – the place where the snow floats up.

Underwater snow forms in the world’s oceans and rises through the water to attach itself to flooded ravines and inverted ice caps, according to a new study. The same thing happens under ice shelves on Earth — and perhaps this is how Europe builds its ice shell.

The discovery, published Monday in the journal Astrobiology, suggests Europa’s icy shell may not be as salty as scientists thought. Understanding the salt content of the ice crust is critical as engineers work to assemble NASA’s Europa Clipper spacecraft, which is preparing to launch to Europa in October 2024.

This illustration shows the Europa Clipper flying around an icy moon with Jupiter in the background.

Europa Clipper will use ice-penetrating radar to look under the shell and determine if the moon’s ocean is potentially habitable. Any salt inside an ice shell can affect how deep a radar can penetrate through it, so predictions about the shell’s composition are key.

Clues about the icy shell could also help scientists learn more about Europa’s ocean, its salinity and potential for life.

Europa’s ice sheet is between 15 and 25 kilometers thick and is likely at the top of an ocean estimated to be between 60 and 150 kilometers deep.

“When we explore Europe, we are interested in the salinity and composition of the ocean, because this is one of the things that will determine its potential habitability or even the type of life that can live there,” said study lead author Natalie. Wolfenbarger, a research graduate student at the University of Texas Institute of Geophysics at the Jackson School of Geosciences, Utah, in a statement.

Wolfenbarger is also a PhD student member of the Europa Clipper Science Group. Researchers at the University of Texas at Austin are developing an ice-penetrating radar for the spacecraft.

The ocean of Europa closest to its shell has temperature, pressure and salinity similar to the water under the ice shelves in Antarctica, previous studies have shown.

Researchers have studied two methods of freezing water under ice shelves on Earth: ice freezing and rock ice.

Who cares? Congelation ice actually grows from under the ice shelf, while fine-grained ice drifts through supercooled seawater as flakes before settling under the ice shelf.

Both of these types result in ice having less salinity than seawater, and the researchers predicted that seawater was even less saline when they applied this data to the age and extent of the Europa ice sheet.

Phrazil ice may be the most common type on Europa, making the ice shell much cleaner than previously thought. Crushed ice retains only a small fraction of the salt found in sea water. The purity of an ice shell can affect its strength, the tectonics of the ice, and how heat travels through the shell.

“We can use the Earth to assess the habitability of Europa, measure the exchange of impurities between ice and the ocean, and figure out where water is in the ice,” said study co-author Donald Blankenship, senior research fellow at the University of Texas Institute of Geophysics.

This discovery may suggest that the Earth can be used as a model for a better understanding of Europa’s habitability.