Jupiter’s moon Europa has ice that may glow green in the dark

Jupiter’s moon Europa may glow in the dark. Lab experiments have shown that the type of ice that covers the moon’s surface glows under radiation, which could help us figure out the composition of its frozen plains and subsurface oceans.

Because of the way Jupiter’s powerful magnetic field accelerates charged particles, Europa is constantly bombarded by high-energy electrons. Murthy Gudipati at NASA’s Jet Propulsion Laboratory in California and his colleagues investigated how Europa’s icy surface might react to that bombardment by blasting electrons at samples of ice enriched with molecules that may be found on Europa.

When the electrons hit molecules in the ice, the molecules fell apart and their constituent atoms absorbed some energy. The atoms then re-emitted that energy as light, causing an eerie, green-tinged glow. This was brighter or dimmer depending on the type of molecule – for example, adding sodium chloride decreased the glow.

“If you imagine that you are standing on Europa and looking at the glow under your feet, the brightness would be similar to if you were to stand outside under full moonlight and then look at the ground,” says Gudipati. “But Europa’s surface is a very dangerous environment, so while we can imagine standing on it, a few seconds standing on Europa would probably kill a person.”

Although visiting Europa in person may be a non-starter, NASA already has a spacecraft in the works, the Europa Clipper mission that is planned to launch in 2024 and study the moon while orbiting Jupiter. It could potentially observe the glowing ice and use its brightness to help determine its composition.

“There is some evidence that there are oceans beneath the ice on Europa which could be habitable, and if that is the case, the minerals and salts that are in that ocean should be exchanging with the surface,” says Gudipati. Figuring out what the surface is made of could help us understand whether Europa’s seas have the necessary ingredients for life.

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