Everyone take a deep breath and look at the beauty of Europa. It glows. No, literally, it glows. You see, Jupiter is constantly zapping Europa’s surface night and day with high-energy radiation such as electrons and other particles. And those high-energy particles are making the surface of Europa glow in the dark.

This new research from NASA’s Jet Propulsion Laboratory details what this glow would look like. Per the press release: It could reveal…the composition of ice on Europa’s surface. Different salty compounds react differently to the radiation and emit their own unique glimmer. To the naked eye, this glow would look sometimes slightly green, sometimes slightly blue or white and with varying degrees of brightness, depending on what material it is.

Usually, scientists take spectra of an object to determine its composition. Of course, you need sunlight to use a spectrometer, which means taking the measurements on Europa’s dayside if we want to know what the ice is made of. Now we can talk about how Europa looks in the dark.

JPL’s Murthy Gudipati, lead author of the new paper published just yesterday in Nature Astronomy, explains: We were able to predict that this nightside ice glow could provide additional information on Europa’s surface composition. How that composition varies could give us clues about whether Europa harbors conditions suitable for life.

In case you weren’t aware, Europa is a strong candidate for finding life elsewhere in our solar system because it has a massive interior ocean of liquid water. And scientists are primed to understand that subsurface ocean as much as possible.

Per the press release: Scientists have inferred from prior observations that Europa’s surface could be made of a mix of ice and commonly known salts on Earth, such as magnesium sulfate (Epsom salt) and sodium chloride (table salt). The new research shows that incorporating those salts into water ice under Europa-like conditions and blasting it with radiation produces a glow.

To be honest, that part of the story isn’t a surprise. Where this research broke a little new ground is best explained by co-author Bryana Henderson: When we tried new ice compositions, the glow looked different. And we all just stared at it for a while and then said, ‘This is new, right? This is definitely a different glow?’ So we pointed a spectrometer at it, and each type of ice had a different spectrum.

And here is where a fantastic NASA acronym comes in. The team used a new instrument called Ice Chamber for Europa’s High-Energy Electron and Radiation Environment Testing (ICE-HEART) and did experiments with high-energy electron beams. As co-author Fred Bateman pointed out: Seeing the sodium chloride brine with a significantly lower level of glow was the ‘aha’ moment that changed the course of the research.

So while our Moon glows from sunlight, Europa glows from sunlight AND the radiation of Jupiter. It’s possible that the upcoming Europa Clipper mission could detect this glow, and the instrument team is determining that possibility. If that’s the case, the spacecraft could match its data with the measurements in this research to identify salty components on the moon’s surface and narrow down what they might be.

It will be a bit of a wait, but I think it will be worth it.

More Information

NASA JPL press release 

“Laboratory Predictions for the Night-Side Surface Ice Glow of Europa,” Murthy S. Gudipati, Bryana L. Henderson & Fred B. Bateman, 2020 Nov. 9, Nature Astronomy