Jupiter's Month Europa is an intriguing world. It is the weakest body in the solar system, and the sixth largest month in the solar system, although it is the smallest of the four Galilean months. The most intriguing of all is the underground ocean of Europe and the potential for housing.
Scientific consensus is that Europe has an underground ocean under its extremely smooth, icy surface. It is estimated that the crust between 10 and 30 km (6-19 miles) is thick, and the ocean below it could be about 100 km deep. If it is true, then the extent of the European ocean is about two or three times the size of the Earth's oceans.
The interior of Europe remains warm due to tidal warming, and possibly by the radioactive decomposition of elements in its stone mantle. But studies show that radioactive decay is not sufficient to produce heat in Europe. Whatever the exact source of heat, it's enough to create an underground ocean.
It's probably an ocean with salt water, which is important for housing. Initially, scientists thought that salinity was the result of magnesium chloride, which is basically Epsom's salt. However, a new study by Caltech / JPL scientists suggests that it may not be magnesium chloride, but sodium chloride, the same type of salt that makes the oceans on Earth salty.
The new study is called "Sodium chloride on the surface of Europe" and was published in Science Advances of June 12th. The authors are Samantha Trumbo, Michael Brown and Kevin Hand. Trumbo is the lead author.
The discovery comes from Hubble's observations of the surface of Europe. On the surface of the moon there are yellowish surfaces that have remained so mysterious so far.
The surface of Europe is a geologically young ice shell. So, everything on the surface is probably from the ocean below. That, and cracks and cracks in the icy shell, is what led scientists to think that there is an ocean below it. Ocean rich in sulphate salts.
But new spectral data from the Keck Observatory suggest that surface salts are not magnesium sulphates. Absorption lines indicating the presence of magnesium sulphate were not present in Kecko's data. These types of salts have very pronounced absorption lines and they are simply not there. Scientists thought they could see sodium chloride on the surface, but the problem is that sodium chloride does not detect its presence in the infrared spectrum.
"We thought we might see sodium chloride, but they are essentially useless in the infrared spectrum," says Mike Brown, Richard and Barbara Rosenberg, a planetary astronomy professor at Caltech and a co-author Science Advances paper.
However, his colleague Brauna and possibly co-author of the new work had insight into the problem.
His name is Kevin Hand, JPL. He had irradiated ocean salt in the laboratory, under conditions similar to Europe. He discovered that after radiation, sodium chloride was detected in visible light, changing color. The color in which it changed? You hit: yellow. Just like in a yellow region on the surface of Europe, it is called Tara Regio.
"Sodium chloride is a bit like an invisible ink on the surface of Europe. Before irradiation, you can not say that there, but after irradiation, the color jumps right, "says Hand, a JPL scientist and co-author Science Advances paper.
"No one had taken the visible spectra of the wave length of Europe before which he had this spatial and spectral resolution. The Galileo the aircraft did not have a visible spectrometer. He just had an infrared spectrometer, "says Caltech graduate student Samantha Trumbo, lead author of the paper.
Three scientists then turned to the Hubble Space Telescope to advance this idea. They showed Hubble to Europe and found the absorption line in a visible spectrum that perfectly corresponds to the irradiated salt. This confirmed the presence of sodium chloride in Europe. And the probable source for this is the underground ocean.
"We had the capacity to carry out this analysis with the Hubble Space Telescope for 20 years," Brown said. "Only no one thought to look."
This is a strong evidence of the underground ocean with sodium chloride like the Earth's ocean. But it's not dying. It can be evidence of various materials in the ice sheet.
In any case, the study presents more intricacies around Europe.
As the authors say at the end of their work, "Whether the observed NaCl is directly related to the composition of the ocean, its presence justifies rethinking our understanding of the geochemistry of Europe."
If the salt in the ocean is magnesium sulfate, it could be washed into the ocean of stones at the bottom of the ocean. But if it's sodium chloride, that's another story.
"Magnesium sulphate would simply be washed into the ocean from the walls at the bottom of the ocean, but sodium chloride may indicate that the ocean floor is hydrothermal," Trumbo says. "It would mean that Europe is a more geologically more interesting planetary body than previously thought."
Hit the rockets. Let's find out!