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Jupiter’s icy moon Europa is bombarded by a constant and intense burst of radiation from the gas giant. Different saline compounds on the lunar surface react differently to radiation and emit their unique glow. To the naked eye, this glow would sometimes appear slightly green, sometimes slightly blue or white, and with varying degrees of brightness, depending on the material.
This illustration of Jupiter’s moon Europa shows how its icy surface can glow on the night side. Image credit: NASA / JPL-Caltech.
“We were able to predict that this nocturnal ice glow could provide additional information on the composition of Europa’s surface,” said lead author Dr. Murthy Gudipati, a researcher at NASA’s Jet Propulsion Laboratory.
“The way this composition varies could give us clues as to whether Europe offers conditions suitable for life.”
“This is because Europe has a huge global internal ocean that could seep through the moon’s thick ice crust to the surface. By analyzing the surface, we can learn more about what lies beneath. “
Europa’s surface is likely made up of a mixture of ice and salts commonly known on Earth, such as magnesium sulfate and sodium chloride.
The new research shows that incorporating these salts into water ice under conditions similar to those of Europe and detonating it with radiation produces a glow.
“We never imagined we would see what we ended up seeing,” said co-author Dr. Bryana Henderson, also of NASA’s Jet Propulsion Laboratory.
“When we tried new ice compositions, the glow looked different. And we just stared at it for a while and then we said, ‘This is new, right? Is this definitely a different glow? ‘So we put a spectrometer on it and each type of ice had a different spectrum.’
For the study, the researchers built a unique instrument called the Ice Chamber for Europe’s High-Energy Electron and Radiation Environment Testing (ICE-HEART).
They brought ICE-HEART into a high-energy electron beam structure and began the experiments with a completely different study in mind: to see how organic material under the Europa ice would react to the radiation bursts.
They did not expect to see variations in the glow itself related to different ice compositions.
“Seeing the sodium chloride brine with a significantly lower glow level was the ‘aha’ moment that changed the course of research,” said co-author Dr. Fred Bateman, researcher at the National Institute of Standards and Technology. .
“A moon visible in a dark sky may not seem unusual; we see our Moon because it reflects sunlight. But the glow of Europa is caused by a completely different mechanism, “the scientists said.
“Imagine a moon that shines continuously, even on the night side, the side facing the sun.”
“If Europa weren’t under this radiation, it would have the appearance of our moon to us – dark on the shadow side,” said Dr. Gudipati.
“But since it is bombarded with radiation from Jupiter, it glows in the dark.”
The study appears in the journal Nature Astronomy.
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MS Gudipati et al. Laboratory predictions for Europa’s night surface ice glow. Nat Astron, published online on November 9, 2020; doi: 10.1038 / s41550-020-01248-1
This article is based on a press release provided by the National Aeronautics and Space Administration.
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