Jupiter’s moon known as Europa is fascinating the scientific field. The moon is the sixth-largest object in the Solar System, but it is the smallest one between the four Galilean moons.
The most fascinating thing is Europa’s subsurface ocean and the chance for livability, though. The scientific conclusion is that the moon has a subsurface ocean below its incredibly smooth, icy surface. The surface is thought to be 10 to 30 kilometers (6 to 19 miles) thick, and the waters beneath it could be approximately 100 kilometers (60 miles) deep. If this proves to be accurate, it means that the mass of Europa’s oceans is roughly two or three times the mass of Earth’s waters.
The inner part of the moon is warmed by tidal heating, and probably by radioactive decomposition of materials in its rocky crust. However, researches have depicted that radioactive decay alone is not sufficient to generate the heat in the moon. Irrespective of the precise source, it is enough to produce the subsurface ocean.
The ocean is most probably holding salt water within, which is crucial for habitability. Initially, researchers have suggested that the saltiness was produced by magnesium chloride, which is essentially Epsom salts. However, a new study from researchers at Caltech and JPL shows that it might not be magnesium chloride, but instead, sodium chloride, the same kind of salt that makes our planet’s oceans salty.
The new research is dubbed ‘Sodium Chloride on the surface of Europa,’ and it has been issued on June the 12th on the journal Science Advances. The authors of the assay are Samantha Trumbo, the lead author, Michael Brown, and Kevin Hand.
The findings are delivered by Hubble Space Telescope’s observations of Europa’s surface. The data gathered depicts yellowish regions on the surface of the moon, which have remained an enigma up until now.
The surface of Europa is a young icy shell, geologically speaking. That means that anything present on its surface is probably produced by the ocean underneath. Also, the rifts and fractures in the crust led scientists to believe that there’s an ocean below, an ocean abundant in sulfate salts.
However, new spectral information from the Keck Observatory implied that the salts on the surface were not magnesium sulfates. Assimilating lines suggesting the presence of magnesium sulfates were utterly absent in the Keck observations. Those kinds of salts have unique absorption lines, and they were missing. Researchers believed they might find sodium chloride on the surface, but the issue is that sodium chloride cannot be observed with infrared.
Which one is it then?
One of the paper authors, Kevin Hand of JPL, which irradiated ocean salts in a lab, under the moon’s similar conditions discovered that after irradiation, sodium chloride appeared in visible light, by changing its color. The color it turned into was yellow, just like in the yellow area on the surface of Europa, named Tara Regio.
Samantha Trumbo, a Caltech graduate student and lead author of the paper said that no scientist had captured visible wavelength spectra of the moon before as the Galileo probe was not equipped with a visible spectrometer, having only a near-infrared spectrometer.
The team of scientists appealed to Hubble’s observations to further examine the idea. They directed the telescope instruments at Europa and discovered an absorption line in the visible spectrum that accurately evened the irradiated salt. This affirmed the existence of irradiated sodium chloride on the moon. And the most likely origin for that is the underneath ocean.
This is robust evidence in support of a subsurface ocean with sodium chloride similar to our planet’s oceans. However, this is not a sure thing, as it can also be proof of different elements in the icy shell.
Scientists say that if the salt in the waters is magnesium sulfate, it could have percolated into the ocean from the rocks on the ocean bottom. However, if it is sodium chloride, it changes the story.
Trumbo explained that magnesium sulfate would just have percolated into the ocean from rocks on the waters’ floor, but sodium chloride could suggest that the ocean floor is hydrothermally active.
Brad is a former Senior Fellow at the Schuster Institute for Investigative Journalism at Brandeis University, is an award-winning travel, culture, and parenting writer. His writing has appeared in many of the Canada’s most respected and credible publications, including the Toronto Star, CBC News and on the cover of Smithsonian Magazine. A meticulous researcher who’s not afraid to be controversial, he is nationally known as a journalist who opens people’s eyes to the realities behind accepted practices in the care of children. Brad is a contributing journalist to Advocator.ca