Jupiter’s icy moon Europa may give the phrase “moonlight” a complete new that means. New lab experiments counsel the nightside of this moon glows at the hours of darkness.
Europa’s floor, considered largely water ice laced with varied salts, is regularly bombarded with energetic electrons by Jupiter’s intense magnetic area (SN: 5/19/15). When researchers simulated that interplay within the lab by taking pictures electrons at salty ice samples, the ice glowed. The brightness of that glow relied on the form of salt within the ice, researchers report on-line November 9 in Nature Astronomy.
If the identical interplay on Europa creates this never-before-seen form of moonlight, a future mission there, equivalent to NASA’s deliberate Europa Clipper spacecraft, could possibly use this ice glow map Europa’s floor composition. That, in flip, may give perception into the salinity of the ocean thought to lurk below Europa’s icy crust (SN: 6/14/19).
“That has implications for the temperature of that liquid water — the freezing level; it has implications for the thickness of the ice shell; it has implications for the habitability of that liquid water,” says Jennifer Hanley, a planetary scientist at Lowell Observatory in Flagstaff, Ariz. not concerned within the new work. Europa’s subsurface ocean is taken into account some of the promising locations to search for extraterrestrial life within the photo voltaic system (SN: 4/8/20).
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The invention of Europa’s potential ice glow “was serendipity,” says Murthy Gudipati, who research the physics and chemistry of ices at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Gudipati and colleagues initially got down to examine how electron bombardment may change the chemistry of Europa’s floor ice. However in video footage of their preliminary experiments, the staff seen that ice samples pelted with electrons gave off an sudden glow.
Intrigued, the researchers turned their electron beam on samples of pure water ice, in addition to water ice combined with completely different salts. Every ice core was cooled to the floor temperature of Europa (about –173° Celsius) and showered with electrons that had the identical energies as people who strike Europa. Over 20 seconds of irradiation, a spectrometer measured the wavelengths of sunshine, or spectrum, given off by the ice.
The ice samples all gave off a whitish glow, as a result of they emitted gentle at many alternative wavelengths. However the brightness of every ice pattern relied on its composition. Ice containing sodium chloride, also called desk salt, or sodium carbonate appeared dimmer than pure water ice. Ice combined with magnesium sulfate, alternatively, was brighter.
“I used to be performing some again of the envelope calculations [of] what could be the brightness of Europa, if we have been to be standing on it at the hours of darkness,” Gudipati says. “It’s roughly … as brilliant as me strolling on the seaside in full moonlight.”
Primarily based on the specs proposed for a digicam to fly on the Europa Clipper mission, Gudipati and colleagues estimate that the spacecraft may see Europa’s ice glow throughout a flyby of the darkish aspect of the moon. Darkish patches of Europa may reveal sodium-rich areas, whereas brighter areas could also be wealthy in magnesium.
However seeing ice glow within the lab doesn’t essentially imply it occurs the identical manner on Europa, Hanley cautions. Jupiter’s icy moon has been barraged by high-energy electrons for lots longer than 20 seconds. “Is there ever a degree the place you may break down the salts, and this glow stops occurring?” she wonders.
Different planetary scientists, in the meantime, usually are not satisfied that Europa’s floor is extremely salted. These researchers, together with Roger Clark of the Planetary Science Institute in Lakewood, Colo., suppose the obvious hints of salts on Europa are literally created by acids, equivalent to sulfuric acid. Europa’s floor could also be coated in each salts and acids, Clark says. “What [the researchers] must do subsequent is irradiate acids … to see if they will inform the distinction between salt with water ice and acids with water ice.”