Jupiter's watery moon, Europa, is covered in table salt

Rodiano Bonacci
Giugno 14, 2019

Europa, one of Jupiter's moons, might be a site for a major cooking essential found on Earth: table salt. Previous observations made by the Near-Infrared Mapping Spectrometer aboard the Galileo spacecraft pointed to sulfate salts on the surface of Europa, but there was no evidence that this salt originated from the giant ocean underneath. It seems that the moon is hiding a salty, liquid ocean underneath its icy shell. This is potential evidence that sodium chloride, otherwise known as table salt, exists within Europa's subsurface ocean-yet another indication of this moon's potential to support alien life.

The data collected by Galileo of Europa's surface indicated the presence of a salt known as magnesium sulfate, thus researchers initially thought that this is what the ocean below contained. "It just had a near-infrared spectrometer, and in the near-infrared, chlorides are featureless". Crucially, this salt was detected around young chaos regions-geological features in which the moon's surface ice is heavily disrupted and where blocks of ice can be seen drifting apart.

"People have traditionally assumed that all of the interesting spectroscopy is in the infrared on planetary surfaces, because that's where most of the molecules that scientists are looking for have their fundamental features", said Mike Brown, study co-author and the Richard and Barbara Rosenberg Professor of Planetary Astronomy at the California Institute of Technology, in a statement. "The spectra showed a distinct absorption feature in the sunlight reflected off of Europa's surface, near a wavelength of 450 nm, which indicates the presence of irradiated NaCl". "The Galileo spacecraft didn't have a visible spectrometer", Samantha Trumbo, Caltech graduate student and lead author of the paper, said in the press release.

Now, a new research paper reveals that the colossal ocean isn't just liquid water, it's salty liquid water, making it potentially even more like Earth's oceans than we originally thought. But, the spectra of these areas "expected to reflect the internal composition lacked any of the characteristic sulfate absorptions", according to the study.

"This changes our picture of Europa in the following way: what kind of salts are on the surface, and therefore what kind of salts are in the ocean", Jonathan Lunine, a planetary scientist from Cornell University who's not affiliated with the new study, said in an email to Gizmodo. The sea salt changed color and could be identified in the visible light spectrum as yellow.

In a laboratory that resembled Europa's conditions, plain white table salt (sodium chloride) turned yellow.

This was similar to an area on Europa called Tara Regio, which has a distinct yellow color. "Before irradiation, you can't tell it's there, but after irradiation, the color jumps right out at you", Hand said.

"We've had the capacity to do this analysis with the Hubble Space Telescope for the past 20 years", Brown said.

This also concludes that the hidden ocean that's underneath the Europa's ice may be more similar to the oceans that are on our planet, at least definitely more similar than it has previously been believed.

With these findings, the researchers say they're confident that sodium chloride is present in Europa's oceans, but it's unclear whether it dominates the subterranean waters, or if sulfate salts reside there as well.

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