Ice from the snow from below

A mysterious world of water and ice on the horizon: Researchers report that the icy crust of Jupiter’s moon Europa could partly consist of so-called frasile ice – “snowflakes” that “fall” from below on deck hulls. This arises from comparisons with ground observations of this process. The special thing about it is that Frizzle ice cream is relatively low in salt. According to this, the ice crust could be “purer” than previously thought, which scientists say is of great interest to research into a possible living environment.

Europa has it all, according to various studies in recent years: it is now assumed that the icy companion of Jupiter has a huge ocean of liquid salt water under the ice crust one kilometer thick. This orb, about the size of the moon, has been put at the center of the search for extraterrestrial life forms in our solar system. Given the amazing adaptation of life on Earth, it seems possible that living things also evolved in the hidden underwater world of Europe. NASA’s planned “Europa Clipper” mission will soon provide more information about the mysterious icy moon: the probe is set to swing in orbit around Europe in order to collect various data.

Antarctica as a model

Among other things, it is also planned to analyze the crust with ice-penetrating radar in order to examine its structure and possibly look under it. Scientists at the University of Texas at Austin are busy developing the radar equivalent to the Europa Clipper. Advance basic information about what shape the ice sheet might look like is useful for performance. In order to obtain clues, scientists use structures and processes on Earth that can correspond to those on Europe. “We can certainly use the Earth to draw conclusions about Europe,” says senior author Donald Blankenship. Specifically, the focus is on Antarctica: Previous studies indicate that the temperature, pressure, and salinity of the water under the ice are similar to those of Jupiter’s moon.

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As part of their study, the scientists examined the two most important types of growth from below in the Antarctic ice shelf. One form is based on the so-called frozen ice. It is the increase in the existing icy surfaces. The other version is based on the accumulation of so-called frasile ice. These flakes form from ice needles or scales in cold sea water and then float upward. Like snow from below, it rests on the surface of the ice and then integrates.

Mounds of snow-like Fraselle ice beneath the Antarctic ice shelf. © Helen Glazer 2015, from the “Walking in Antarctica” project (helenglazer.com)

There may be less salt in the ice

As the scientists reported, there is probably only a small temperature gradient under the ice of Europe – the values ​​change little at depth. Under these conditions, in the case of the Antarctic, the formation of Fraselle ice occurs particularly intensely, investigations show. According to the calculations of researchers, a significant part of the ice cover in Europe could be the result of the accumulation of snowflakes under water.

The study showed that this, in turn, would be related to an important aspect. Because while frozen ice contains 10 percent of the salt of the surrounding sea water, frasile ice is much purer and will only contain 0.1 percent of the salt of the European waters that it’s made of. This means that the ice sheet could be much purer in size than previously thought. “When researching in Europe, we are very interested in salinity because it is a polyamorous factor,” says lead author Natalie Wolfenberger. It affects many aspects – from force to thermal motion to forces that can drive a type of ice tectonics. Salinity also has practical implications: It affects how Clipper’s radar penetrates the ice, the scientists note.

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“This work opens a whole new dimension in looking at distant ocean worlds and the processes that occur within them,” comments Steve Vance of NASA’s Jet Propulsion Laboratory in Pasadena, who was not involved in the study. “It sets the conditions for how to prepare for ice analysis by Europa Clipper,” says the scientist.

Source: University of Texas at Austin, professional article: Astrobiology, doi: 10.1089/ast.2021.0044

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