Yellow expanse of table salt spotted on the surface of Jupiter's Moon Europa

Europa's surface appears to be in covered in a layer of salty liquid water under its icy shell.

Researchers have discovered that the visible yellow pattern on the surface of Jupiter's moon — Europa — is actually sodium chloride, an ingredient we use on a daily basis.

Using a visible light spectral analysis, planetary scientists have discovered that the yellow colour visible on portions of the surface of Europa is table salt, which is also the principal component of sea salt.

Flybys from the Voyager and Galileo spacecraft have led scientists to conclude that Europa is covered by a layer of salty liquid water encased by an icy shell, according to the study published in the Journal of Science Advances.

Yellow expanse of table salt spotted on the surface of Jupiters Moon Europa

Table Salt Compound Spotted on Europa. Tara Regio is the yellowish area to the left of centre, in this NASA Galileo image of Europa's surface. This region of geologic chaos is the area researchers identified an abundance of sodium chloride. Credit: NASA/JPL/University of Arizona

Galileo carried an infrared spectrometer, instrument scientists use to examine the composition of the surface they are examining. Galileo's spectrometer found water ice and a substance that appeared to be magnesium sulfate salts like Epsom salts, which are used in soaking baths.

Since the icy shell is geologically young and features abundant evidence of past geologic activity, it was suspected that whatever salts exist on the surface may derive from the ocean below. As such, scientists have long suspected an ocean composition rich in sulfate salts.

That all changed when new, higher spectral resolution data suggested that the scientists weren't actually seeing magnesium sulfates on Europa.

This artist's concept shows a simulated view from the surface of Jupiter's moon Europa. Europa's potentially rough, icy surface, tinged with reddish areas that scientists hope to learn more about. Image courtesy: NASA/JPL

This artist's concept shows a simulated view from the surface of Jupiter's moon Europa. Europa's potentially rough, icy surface, tinged with reddish areas that scientists hope to learn more about. Image courtesy: NASA/JPL

"We thought that we might be seeing sodium chlorides, but they are essentially featureless in an infrared spectrum," said Mike Brown, co-author of the Science Advances paper.

However, "sodium chloride is a bit like invisible ink on Europa's surface. Before irradiation, you can't tell it's there, but after irradiation, the colour jumps right out at you," said Hand, a scientist and co-author of the Science Advances paper.

"No one has taken visible wavelength spectra of Europa before that had this sort of spatial and spectral resolution. The Galileo spacecraft didn't have a visible spectrometer. It just had a near-infrared spectrometer," said Samantha Trumbo, the lead author of the paper.

While the finding does not guarantee that this sodium chloride is derived from the subsurface ocean (this could, in fact, simply be evidence of different types of materials stratified in the moon's icy shell), the study's authors propose that it warrants a reevaluation of the geochemistry of Europa.

 

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