The underwater snow forms in the global ocean and travels up through the water to attach to submerged canyons and inverted ice peaks, according to new research. This same phenomenon is happening under Earth’s ice shelves — and it may be how Europa builds its ice shell.
The finding, published Monday in the journal Astrobiology, suggested Europa’s ice shell may not be as salty as scientists first thought. Understanding the salinity of the ice crust is critical as engineers work to assemble NASA’s Europa Clipper spacecraft, which prepares to launch to Europa in October 2024.
Europa Clipper will use ice-penetrating radar to look under the shell and determine if the moon’s ocean is potentially habitable for life. Any salt in the ice shell can affect how deep the radar can penetrate through it, so predictions about the shell’s composition are essential.
Clues about the ice shell could also help scientists learn more about Europa’s ocean, its salinity and its potential to host life.
Europa’s ice shell is between 10 and 15.5 miles (15 and 25 kilometers) thick and likely lies on top of an ocean estimated to be 40 to 90 miles (60 to 150 kilometers) deep.
“When we explore Europe, we’re interested in the salinity and composition of the ocean, because that’s one of the things that determines its potential habitability or even the kind of life that could live there,” said lead study author Natalie Wolfenbarger, a researcher. doctoral 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.
Europa’s ocean closest to its shell has a temperature, pressure and salinity comparable to the water under ice shelves in Antarctica, previous research has suggested.
The researchers studied the two methods of freezing water under Earth’s ice shelves: congelation ice and frazil ice.
What is the difference? Congelation ice actually grows from beneath the ice shelf, while fragile ice floats up in flakes through supercooled seawater before settling beneath the ice shelf.
Both types result in ice with a lower salinity than seawater — and according to the researchers’ projections, seawater was even less saline when they applied this data to the age and scale of Europe’s ice shell.
Frazil ice is perhaps the most common type on Europe, which would make the ice shell much purer than previously believed. Frazil ice stores only a small portion of the salt present in seawater. The purity of the ice shell can affect its strength, ice tectonics, and how heat flows through the shell.
“We can use the Earth to evaluate the habitability of Europa, measure the exchange of impurities between the ice and the ocean, and find out where water is in the ice,” said study co-author Donald Blankenship, a senior researcher at the University of Texas Institute for Geophysics, in a statement. He is the principal investigator of Europa Clipper’s ice-penetrating radar instrument.
The finding may suggest that Earth could be used as a model to better understand Europe’s habitability.
“This article opens up a whole new set of possibilities for thinking about ocean worlds and how they work,” Steve Vance, a research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. “It sets the tone for how we can prepare for Europa Clipper’s ice analysis.” Vance was not involved in the investigation.
Meanwhile, work is underway on the core of the Europa Clipper spacecraft at the Spacecraft Assembly Facility at NASA’s Jet Propulsion Laboratory.
The core, which is 3 meters high and 1.5 meters wide, is central to the cleanroom, where NASA teams have assembled spacecraft such as Galileo, Cassini and the Mars rovers.
The flight hardware and scientific instruments will be installed on the spacecraft by the end of the year. Engineers will then put the spacecraft through a series of tests leading up to launch.
Europa Clipper will arrive at the Jovian moon in April 2030. Over nearly 50 scheduled flybys of Europa, the spacecraft will eventually move from an altitude of 1,700 miles (2,735 kilometers) to just 16 miles (25 kilometers) above the moon’s surface.