Underwater snow gives clues to Europe’s marine world

Underwater snow gives clues to Europe's marine world
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Underwater snow forms in the global ocean and travels up through the water to cling to submerged canyons and inverted ice peaks, new research finds. The same phenomenon is taking place under ice shelves on Earth – and this is possibly how Europa is building its ice sheet.

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 crucial as engineers work on assembling NASA’s Europa Clipper spacecraft, which is preparing for launch to Europe in October 2024.

Europa Clipper will use ice-penetrating radar to look under the hull and determine if the moon’s ocean is potentially habitable for life. Any salt in the ice shell could affect how deep radar can penetrate through it, so predictions about the composition of the shell are crucial.

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

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

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

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

Europe’s ocean, closest to its bowl, is similar in temperature, pressure, and salinity to the water beneath the ice shelves in Antarctica. previous research has suggested.

Researchers studied the two methods of freezing water beneath ice shelves on Earth: frozen ice and frazil ice.

Jupiter's moon Europa may have a habitable ice shell

What is the difference? Frozen ice actually grows beneath the ice shelf, while frozen ice floats up in flakes through supercooled seawater before settling beneath the ice shelf.

Both types result in ice that is less salty than seawater – and the researchers predicted seawater was even less salty when they applied this data to the age and size of Europe’s ice sheets.

Frazil ice is possibly the most common type in Europe, which would make the ice shell much purer than previously thought. Frazil ice retains only a tiny fraction of the salt found in seawater. The purity of the ice shell can affect its strength, ice tectonics, and heat flow through the shell.

“We can use Earth to assess Europa’s habitability, measure the exchange of contaminants between ice and ocean, and find out where water is in the ice,” said study co-author Donald Blankenship, a senior research scientist at the University of Texas Institute of Geophysics, in a statement. He is the lead investigator for Europa Clipper’s ice-penetrating radar instrument.

The result could suggest that Earth can be used as a model to better understand Europe’s habitability.

Previous missions have spotted clouds of water vapor erupting through the ice sheet, as shown in this figure.

“This paper opens up a whole new set of ways to think about ocean worlds and how they work,” Steve Vance, a research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement. “It forms the basis of how we might prepare for Europa Clipper’s analysis of the ice.” Vance was not involved in the study.

Meanwhile, work is being done on the core of the Europa Clipper spacecraft at NASA’s Jet Propulsion Laboratory’s Spacecraft Assembly Facility.

The core, which is 10 feet (3 meters) high and 5 feet (1.5 meters) wide, was the focal point of the clean room where NASA teams have assembled spacecraft such as Galileo, Cassini and the Mars rovers.

The mission team is currently assembling the Europa Clipper in High Bay 1, a clean room at NASA's Jet Propulsion Laboratory where other historic pre-launch missions have been conducted.

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 pre-launch tests.

Europa Clipper will reach Jupiter’s moon in April 2030. With nearly 50 planned flybys of Europa, the spacecraft will eventually transition from an altitude of 1,700 miles (2,735 kilometers) to just 16 miles (25 kilometers) above the lunar surface.

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