[ad_1]
A familiar ingredient is hidden from view on the surface of Jupiter's moon, Europa. Using spectral analysis of visible light, Caltech's planetary scientists and the Jet Propulsion Laboratory, which Caltech manages for NASA, have discovered that the visible yellow color on some parts of the surface Europa was actually sodium chloride, a compound known on Earth as table salt. , which is also the main component of sea salt.
The discovery suggests that Europe's salt-water ocean could look more like Earth's oceans than previously thought, challenging decades of assumptions about the composition of these waters. and making them potentially more interesting to study. The discovery was published in Progress of science June 12th.
The flybys of Voyager and Galileo spacecraft led scientists to conclude that the Europa was covered with a layer of salty liquid water covered with an icy shell. Galileo was wearing an infrared spectrometer, an instrument used by scientists to examine the composition of the surface being examined. The Galileo spectrometer detected ice with water and a substance that appeared to be magnesium sulfate, such as Epsom salt, which are used in soaking baths. Because the ice shell is geologically young and contains a lot of evidence of past geological activity, it has been suspected that the surface salts could come from the ocean. As such, scientists have long suspected an oceanic composition rich in sulphate salts.
All this changed when new spectral resolution data from the W. Keck Observatory on Maunakea suggested that scientists did not actually see magnesium sulphates on Europa. Most of the sulfate salts previously considered actually have distinct absorptions that should have been visible in the higher quality Keck data. However, the spectrum of regions believed to reflect the internal composition did not exhibit any of the characteristic sulfate uptakes.
"We thought we might be seeing sodium chlorides, but they are essentially devoid of any functions in the infrared spectrum," says Mike Brown, Richard and Barbara Rosenberg, a professor of planetary astronomy in Caltech and co-author of the Progress of science paper.
However, Kevin Hand of JPL had irradiated sea salts in a laboratory under conditions similar to those of Europe and discovered that several new and distinct features appeared after irradiation, but in the visible part of the spectrum. He found that the salts changed color so that they could be identified by a visible spectrum analysis. Sodium chloride, for example, has taken a yellow hue similar to that seen in a geologically young European region called Tara Regio.
"Sodium chloride is a bit like invisible ink on the Europa surface." Before the irradiation, one can not know it, but after irradiation, the color you is obvious, "says Hand, JPL scientist and co-author of the book Progress of science paper.
"No one had ever used visible wavelength spectra from Europe before such a spatial and spectral resolution.The Galileo spacecraft had no visible spectrometer. A near-infrared spectrometer, "says Samantha Trumbo, a graduate student at Caltech. main author of the article.
"People traditionally assumed that the full spectrum of spectroscopy is in the infrared on planetary surfaces because it is there that most molecules researched by scientists have their fundamental characteristics," says Brown. .
By closely examining the Hubble Space Telescope, Brown and Trumbo were able to identify a distinct absorption in the visible spectrum at 450 nanometers, corresponding exactly to the irradiated salt, confirming that the yellow color of Tara Regio reflected the presence of irradiated sodium. chloride on the surface.
"We've had the ability to do this analysis with the Hubble Space Telescope for 20 years," said Brown. "It's just that no one has thought of looking."
Although the discovery does not guarantee that this sodium chloride is derived from the ocean underwater (this could actually simply be evidence of different types of layered materials in the moon's icy shell), the authors of The study propose that this warrants a reassessment of the geochemistry of Europe.
"Magnesium sulphate would have simply infiltrated into the ocean rocks from the bottom of the ocean, but sodium chloride could indicate that the bottom of the ocean is hydrothermally active", said Trumbo. "This would mean that Europa is a planetary body more geologically interesting than previously thought."
This research was funded by the NASA Space and Space Science Scholarship Program, Space Telescope Science Institute and JPL.
[ad_2]
Source link