Aug 18, 2022 06:00:00

Jupiter's moon Europa's ice sheet is made of 'upward snow'

Jupiter's second moon,

Europa , is thought to have an ocean beneath its water-ice surface, raising hopes that extraterrestrial life might exist. A research team that investigated how Europa's ice sheet is formed claims that 'Europa's ice sheet may be formed of'upward snow'.'

Ice Shell Structure and Composition of Ocean Worlds: Insights from Accreted Ice on Earth | Astrobiology
https://doi.org/10.1089/ast.2021.0044

Underwater Snow Gives Clues About Europa's Icy Shell - UT News
https://news.utexas.edu/2022/08/15/underwater-snow-gives-clues-about-europas-icy-shell/

Europa's icy shell may be made from pure underwater snow | Live Science
https://www.livescience.com/europa-ice-snow

The exploration ship `` Europa Clipper '' used by NASA to investigate Europa has been announced to be completed in June 2022 and is scheduled to be launched in 2024. A research team at the University of Texas at Austin, which is leading the development of the radar equipment to be mounted on the Europa Clipper, said, 'Europa's ice sheet is How is it formed?' I turned my attention to the mystery.

Europa is about one-fourth the size of Earth, with a surface ice sheet about 15-25 km thick and an ocean beneath it that is thought to be about 60-150 km deep. Previous studies have suggested that the temperature, pressure, and salinity of the Europa sea are relatively close to those of Antarctica's subglacial lake, Lake Vostok .

The research team extrapolated how the Europa ice sheet formed from the dominant ways in which the Antarctic ice sheet formed. One of the main methods of forming the Antarctic ice sheet is '

congelation ice ', a type of ice that grows from the surface of already existing ice sheets. Another major method is ' Frazil ice ', which is fine needle-like and plate-like ice that forms on the surface layer of the ocean below freezing temperatures. Since the density of the crystal ice is smaller than the surrounding seawater, the crystal ice formed floats upward in the sea and settles at the bottom of the ice sheet.

A review of these two methods suggests that fringe ice is common in environments such as Europa, where temperature gradients are low and there is little temperature variation with depth, especially where the ice is thin or cracked. I understand. In other words, most of Europa's ice sheet is likely to be formed by 'snow in water' that floats upward from the sea.

The salinity contained in congelation ice is about 10% of the surrounding seawater, but the salinity of fragile ice is only about 0.1%. Therefore, the findings that Europa's ice sheet is generally made up of large portions of fragile ice suggest that the salinity of the ice sheet may be orders of magnitude lower than previously estimated. thing. This finding is important for future Europa exploration, as ice sheet salinity affects ice sheet strength and structure, as well as radar observations.

'When we explore Europa, we are interested in the salinity and composition of the ocean,' said lead author Natalie Wolfenberger, a researcher at the University of Texas Geophysical Laboratory. 'It's one of the factors that determines its habitability, or the types of life that might live there.'

by Kevin Gill