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Intense radiation from the giant planet Jupiter causes the night side of its moon Europa to visibly glow in the dark, a phenomenon that could help scientists figure out whether it can support simple life forms, according to a new study.
The findings, published Monday in the journal Nature Astronomy, were the result of experiments conducted by NASA scientists to study how Jupiter’s radiation affects the chemistry of Europa, which is believed to host an underground water ocean.
And although telescopes have not yet observed the glow, the possibility of Europa glowing in the dark could be verified by two probes that will study the moon in the coming years.
The researchers built a sub-zero “ice chamber” at NASA’s Jet Propulsion Laboratory in Pasadena, California to contain chemicals believed to be on Europa’s icy surface and exposed it to a beam of electrons. high energy to simulate the radiation of Jupiter.
“We saw that every time we shot with the electron beam, it glowed,” said Murthy Gudipati, an astrophysicist at the Jet Propulsion Laboratory and lead author of the study. “And when the electrons were turned off, the glow went out.”
The radiation hitting Europa is caused by Jupiter’s vast magnetosphere, the most powerful magnetic field anywhere in the solar system, apart from the sun. It is thought to be generated by metallic hydrogen in the giant planet’s highly pressurized core.
Jupiter’s magnetosphere forms an invisible flat disk up to 12 million miles wide, much larger than Europa’s roughly one million mile orbit. Its radiation would kill a human on the surface of Europa in seconds.
Since the simulated radiation in the experiments is also intense, the researchers studied its remote interactions with cameras, according to Gudipati.
In addition to seeing evidence of major chemical and physical changes in Europa’s crust, Jupiter’s radiation breaks the water ice into oxygen and hydrogen, increasing the chances of oxygen seeping into the liquid ocean below – the researchers noted. the ice shone visibly.
The scientists then changed the chemicals thought to be mixed with the ice on Europa’s surface – such as sodium chloride “table salt” and magnesium sulfate “Epsom salt” – and found that the ice so salted different shines with different intensities and sometimes different colors: greenish, bluish or white.
It was a moment of serendipity, Gudipati said.
“We realized that this ice glow can be controlled by the type of material present,” he said.
Calculations indicate that Europa’s glow would be similar to the light of a full moon on a beach on Earth, he said.
This means that it could be bright enough to be detected on the night side of the moon by nearby spacecraft, such as the Europa Clipper spacecraft which is expected to arrive there before the end of this decade, and that its measurements could distinguish surface areas with different chemistry. Gudipati said.
Europa Clipper project scientist Bob Pappalardo, a planetary geologist at the Jet Propulsion Laboratory, said the spacecraft’s main purpose will be to confirm Europa’s subterranean ocean and evaluate the possibilities that microbes might live there.
Only fossils of any life that evolved on Mars or Venus billions of years ago are expected to remain, he said. And while other gas giant moons, such as Saturn’s Enceladus, are also thought to have groundwater, they don’t have the intense radiation thought to create the chemicals necessary for life in the ocean of Europa.
But the radiation that makes life on Europa more likely could also damage Europa Clipper, which means the spacecraft will dive fairly close – between 15 and 60 miles above its surface – for short periods and spend most of its orbit a lot. farther.
“We call it toe-dip,” Pappalardo said. “It’s like running down and sticking your big toe in the water, and then running away because it’s cold.”
Planetary scientist Andrew Coates of University College London, who has worked on several space probes, said the glow of Europa could also be visible at the European Space Agency’s JUICE mission – Jupiter Icy Moons Explorer – due to arrive in 2029. .
“The specter of the glow would give more clues to the oceanic subsurface,” he said in an email.
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