Starship Asterisk*

Finding prompts a rethinking of the icy moon's subsurface ocean

Tara Regio is the yellowish area to left of center, in this NASA Galileo image of Europa’s surface. This region of geologic chaos is the area researchers identified an abundance of sodium chloride. (Credits: NASA/JPL/University of Arizona)

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A familiar ingredient has been hiding in plain sight on the surface of Jupiter's moon Europa. Using a visible-light spectral analysis, planetary scientists at Caltech and NASA's Jet Propulsion Laboratory in Pasadena, California, have discovered that the yellow color visible on portions of the surface of Europa is actually sodium chloride, a compound known on Earth as table salt, which is also the principal component of sea salt.

The discovery suggests that the salty subsurface ocean of Europa may chemically resemble Earth's oceans more than previously thought, challenging decades of supposition about the composition of those waters. ...

Flybys from NASA's Voyager and Galileo spacecraft have led scientists to conclude that Europa is covered by a layer of salty liquid water encased in an icy shell. Galileo carried an infrared spectrometer, an instrument scientists use to examine the composition of a surface they're studying. Galileo's spectrometer found water ice and a substance that appeared to be magnesium sulfate salts (like Epsom salts). 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. ...

• Science Advances 5(6):eaaw7123 (12 Jun 2019) DOI: 10.1126/sciadv.aaw7123