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Salt water similar to Earth's oceans is seen in Europe. Another good reason why we really have to visit this place



Jupiter's moon Europa is an intriguing world. It is the smallest body in the solar system and the sixth-largest moon in the solar system, although it is the smallest of the four Galilean moons. The most intriguing is the subsurface ocean of Europe and the possibility of living.

The scientific consensus is that Europe has a subsurface ocean under its exceptionally smooth ice surface. The crust is estimated to be 10-30 km thick, and the ocean under it can be about 100 km deep. If this is true, then the volume of the ocean of Europe is about two or three times the size of Earth's oceans.

Two models of the interior of Europe. Most of the scientists who have studied Europe favor the model of a liquid ocean over a model of convective ice. Photo: NASA / JPL.
Two models of the interior of Europe. Most of the scientists who have studied Europe favor the model of a liquid ocean over a model of convective ice. Photo: NASA / JPL.

The interior of Europe is kept warm by tidal heating and probably by the radioactive decay of the elements in its rocky cloak. However, research shows that radioactive decay alone is not enough to generate heat in Europe. Regardless of the exact source of heat, it is enough to create a subsurface ocean.

It is probably an ocean of salt water that is important for life. Initially, the researchers thought that saltiness comes from magnesium chloride, which is basically Epsom salts. But a new study by scientists at Caltech / JPL shows that it may not be magnesium chloride, but rather sodium chloride, the same type of salt that makes the Earth's oceans salty.

The new study is called "Sodium chloride on the surface of Europe" and was published in the Science Advances of June 12. The authors are Samantha Trumbo, Michael Brown and Kevin Hand. Trumbo is the main author of the article.

The discovery stems from Hubble's observation on the surface of Europe. On the surface of the moon are yellowish areas that have remained somewhat mysterious until now.

A colorful view of Europe. On the left is a natural colored image, and on the right - a colorfully improved image used to highlight the differences on the surface of the moon. White and blue areas are water ice, brown-red areas are hydrated salts, and in 1997, when the Galileo spacecraft intercepted these images, the yellow areas were unidentified. The new study says that the yellow areas are sodium chloride, which comes from the subsurface ocean. Image source: NASA / JPL / University of Arizona - http://photojournal.jpl.nasa.gov/catalog/PIA01295 (link to the photo), Public Domain, https://commons.wikimedia.org/w/index.php ? curid = 10705462
A colorful view of Europe. On the left is a natural colored image, and on the right – a colorfully improved image used to highlight the differences on the surface of the moon. White and blue areas are water ice, brown-red areas are hydrated salts, and in 1997, when the Galileo spacecraft intercepted these images, the yellow areas were unidentified. The new study says that the yellow areas are sodium chloride, which comes from the subsurface ocean. Image source: NASA / JPL / University of Arizona – http://photojournal.jpl.nasa.gov/catalog/PIA01295 (link to the photo), Public Domain, https://commons.wikimedia.org/w/index.php ? curid = 10705462

The surface of Europe is a geologically young ice crust. So everything on the surface probably comes from the ocean below. This, as well as cracks and cracks in the icy shell, led the scientists to the conclusion that there is an ocean there. Ocean rich in sulphate salts.

However, new spectral data from the Keck Observatory suggest that the surface salts are not magnesium sulphates. There were no absorption lines in Keck's data indicating the presence of magnesium sulphates. These types of salt have very distinct absorption lines and they simply were not there. Scientists thought they could see sodium chloride on the surface, but the problem is that sodium chloride is not known in the infrared.

"We thought we could see sodium chlorides, but they're essentially devoid of infrared spectrum features," says Mike Brown, Richard and Barbara Rosenberg, professor of planetary astronomy at Caltech and co-author Scientific progress paper.

But Brown's colleague and possible co-author of the new article had an insight into this problem.

"Sodium chloride is a bit like invisible ink …"

Kevin Hand, JPL, co-author.

His name is Kevin Hand from JPL. He irradiated ocean salts in a laboratory in conditions similar to Europe. He discovered that after irradiation, sodium chloride was revealed in visible light, changing color. What color has changed? You guessed it: yellow. As in the yellow region on the surface of Europe, called Tara Regio.

"Sodium chloride is a bit like invisible ink on the surface of Europe. You can not say this before irradiation, but after irradiation the color skips over you – says Hand, a scientist at JPL and co-author Scientific progress paper.

"No one has ever seen spectral wavelengths of Europe that would have such spatial and spectral resolution. The Galileo the spacecraft did not have a visible spectrometer. He just had a near-infrared spectrometer, "says Samantha Trumbo, a Caltech graduate, the lead author of the article.

Images from the NASA Galileo probe show the intricate details of the ice surface of Europe. Dark streaks on the surface of the moon are called Linae. Their most probable explanation is that the shell is active like the Earth, and when the shell sections move, the warmer ice and water flow out of the subsurface. Photo: NASA / JPL-Caltech

The three scientists then turned to the Hubble Space Telescope to develop this idea. They pointed to Hubble & # 39; and Europe and found the absorption line in the visible spectrum that perfectly matched the irradiated salt. This confirmed the presence of irradiated sodium chloride on Europe. The most likely source is the subsurface ocean.

"We had the opportunity to conduct this analysis using the Hubble Space Telescope for the last 20 years," says Brown. "Just nobody wanted to look."

This is a strong proof of the subsurface ocean's support with sodium chloride, such as the Earth's oceans. But this is not slam dunk. This may indicate different materials in the ice crust.

Europe is a tempting goal in the search for life. His subsurface ocean is begging for investigation. There were many suggestions on how to do it. It is an artistic representation of the Tunnelbot tunnel in Europe, a conceptual nuclear-powered ship capable of penetrating the moon's ice shell. (Source: Alexander Pawlusik, LERCIP NASA Glenn Research Center internship program)
Europe is a tempting goal in the search for life. His subsurface ocean is begging for investigation. There were many suggestions on how to do it. This is an artistic performance of Tunelbot Europa, a conceptual nuclear-powered ship capable of penetrating the moon's ice shell. (Source: Alexander Pawlusik, LERCIP NASA Glenn Research Center internship program)

In any case, the survey presents more intrigues surrounding Europe.

According to the authors at the end of the article: "Regardless of whether the NaCl observed is directly related to the oceanic composition, its presence guarantees a reassessment of our understanding of the geochemistry of Europe."

If the salt in the ocean is magnesium sulphate, it could get into the ocean from rocks on the ocean floor. But if it's sodium chloride, it's a different story.

"Magnesium sulphate would simply get into the ocean from rocks on the ocean floor, but sodium chloride may indicate that the ocean floor is hydrothermal active," says Trumbo. "It would mean that Europe is a more geologically interesting planetary organism than previously thought."

Fire up the rocket. Let's go and find out!

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