Jupiter’s icy moon Europa may give the phrase “moonlight” an entire new that means. New lab experiments counsel the nightside of this moon glows at the hours of darkness.
Europa’s floor, considered mostly water ice laced with various salts, is frequently bombarded with energetic electrons by Jupiter’s intense magnetic subject (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 trusted the sort 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 sort of moonlight, a future mission there, akin to NASA’s planned Europa Clipper spacecraft, might be able to use this ice glow map Europa’s floor composition. That, in flip, may give perception into the salinity of the ocean thought to lurk under 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 one of the most promising places to search for extraterrestrial life within the photo voltaic system (SN: 4/8/20).
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 crew observed 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 those 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 various wavelengths. However the brightness of every ice pattern trusted its composition. Ice containing sodium chloride, also referred to as 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 had been to be standing on it at the hours of darkness,” Gudipati says. “It’s roughly … as shiny as me strolling on the seaside in full moonlight.”
Primarily based on the specs proposed for a digital camera 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 approach on Europa, Hanley cautions. Jupiter’s icy moon has been barraged by high-energy electrons for lots longer than 20 seconds. “Is there ever some extent the place you may break down the salts, and this glow stops taking place?” she wonders.
Different planetary scientists, in the meantime, are usually 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, akin 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.”