Jupiter’s ocean moon Europa most likely glows in the dark

According to, a new study, published on November ninth in the journal Nature Astronomy, suggests the icy Jovian moon Europa glows in the dark due to intense radiation and its chemical composition. The radiation is due to Jupiter’s intense magnetic field which accelerates any charged particles in the space around Jupiter. This likely illuminates Europa’s icy shell, which overlies a huge, potentially habitable, ocean of saltwater.

“If Europa weren’t under this radiation, it would look the way our moon looks to us, dark on the shadowed side,” study lead author Murthy Gudipati, a scientist at NASA’s Jet Propulsion Laboratory (JPL) in Southern California, said in a statement. “But because it’s bombarded by the radiation from Jupiter, it glows in the dark.”

Gudipati and his team built an instrument called Ice Chamber for Europa’s High-Energy Electron and Radiation Environment Testing, which they then took to an electron-beam facility in Maryland. They tested the effects of radiation on simulated Europa surfaces composed of water ice and various salts suspected to be there, including sodium chloride and magnesium sulfate. 

The radiation caused the ice samples to glow. Though this did not come as a surprise to the researchers, the phenomenon is well understood: High-velocity particles penetrate the sample, exciting molecules near the subsurface, and causing a glow. “But we never imagined that we would see what we ended up seeing,” study co-author Bryana Henderson, also of JPL, commented. “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.”

The color variation likely ranges from greenish to bluish to whitish, depending on surface composition, the team members said. Also, because water from Europa’s underground ocean most likely makes its way to the surface in some places, according to Gudipati, “How that composition varies could give us clues about whether Europa harbors conditions suitable for life.”

Scientists might be able to observe the glow up close relatively soon, thanks to NASA’s Europa Clipper Probe, which is scheduled to launch in the mid-2020s. Clipper will orbit Jupiter and scrutinize Europa on dozens of flybys, gathering data that will help researchers assess the habitability of the moon, and plan out a life-hunting Europa Lander Mission. (The lander has been mandated by Congress, but it remains a concept at the moment, not a full-fledged NASA mission. It will launch sometime after Clipper does.)




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