Jupiter's icy moon Europa may have snow 'floating up'

Credit image: NASA
Credit image: NASA

Article by: Andacs Robert Eugen, on 29 August 2022, at 08:53 am Los Angeles time

The mantle of Jupiter's famous icy moon may be made, in part, of pure snow that "floats up" instead of falling to the ground. A new study, published in the August issue of the journal Astrobiology, shows that the icy crust of the moon Europa may be built in part from a fluffy accumulation of ice crystals that also form beneath Earth's ice sheets. 

For astrobiologists, Europa is one of the most intriguing objects in the solar system. The moon is covered by an ocean between 60 and 150 kilometers deep, covered by an icy crust between 15 and 25 kilometers thick, according to NASA. 

Europa is a quarter the size of Earth, but its surface ocean could contain about twice as much water as all of Earth's oceans, according to the space agency, making this Jupiter moon an intriguing place to search for life extraterrestrials. 

A new NASA mission, Europa Clipper, is due to launch in October 2024 to fly by the icy moon and see if it could be a suitable habitat for life. Scientists at the University of Texas at Austin are leading the development of the ice analysis radar instrument that will be deployed on the Europa Clipper, which will survey the ice sheet and the ocean just below it. 

As part of this effort, the researchers wanted to understand how the ice sheet might be structured. They turned to Earth as an analogy, examining the two main modes of ice formation under the Antarctic ice sheet. 

One form, freeze-thaw ice, grows from the surface of the ice shelf, and the other forms in cold seawater and rises in flakes like "reverse" snow, eventually becoming trapped beneath the ice sheet. 

Europa, like Antarctica, probably has a low temperature, meaning it changes with depth. While frozen ice might contain 10% of the salt in the surrounding seawater, ice in the form of snow is much purer, containing only 0.1% of the salt in the seawater from which it forms. 

This low-salt ice could not only affect the structure and strength of Europa's ice crust but also impact how well Clipper's radar can penetrate the icy surface. 

"This work opens up a new horizon of possibilities for looking at ocean worlds and how they work," said Steve Vance, a scientist at NASA's Jet Propulsion Laboratory (JPL).

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