Jupiter’s intriguing moons shine in the most detailed images ever taken from Earth

Jupiter’s giant moon Ganymede and icy moon Europa posed for the most detailed images ever taken of them from Earth. Planetary scientists from the University of Leicester used the European Southern Observatory’s Very Large Telescope in Chile to capture the images and study the surfaces of the moons.

This chart shows the sizes of Jupiter’s moon. The inset shows different views of the VLT’s Sphere instrument over time.

ESO/King & Fletcher. Background image of Jupiter: NASA, ESA, A. Simon (Goddard Space Flight Center) and MH Wong (University of California, Berkeley) and the OPAL team

You might be looking at these images and thinking “this looks a little fuzzy”, and you’d be right. Compared to what NASA’s Juno spacecraft saw as you get closer to these moons, terrestrial images appear blurry. But that’s okay because it’s not a beauty contest.

The researchers basically performed a cosmic fingerprint scan.

“The new observations recorded the amount of sunlight reflected from the surfaces of Europa and Ganymede at different infrared wavelengths, producing a reflectance spectrum,” the university said in a statement Monday. “These reflectance spectra are analyzed by developing a computer model that compares each observed spectrum to the spectra of different substances that have been measured in the laboratory.” This reveals the chemical compositions of the moons by matching reflectance data to known substances such as water and minerals.

The research team published a study of Europa in The Planetary Science Journal earlier this year and had a study of Ganymede accepted for publication in the journal JGR:Planets.

Jupiter’s moons are a challenge for terrestrial telescopes because they are far away and relatively small. The VLT’s Sphere instrument was able to image the moons in infrared and compensate for distortions caused by our planet’s atmosphere. “Mapping at this fine scale was previously only possible by sending a spacecraft up to Jupiter to observe the moons up close,” said planetary scientist Oliver King.

Some interesting details emerged in the data. Ganymede is largely made up of two types of terrain, with young areas consisting of water ice and older areas consisting of as yet unknown dark gray material.

Europa will be at the center of NASA’s next mission European Clipper assignment. Scientists believe the moon hides a liquid ocean below the surface and is a good place to look for signs of extraterrestrial life. “We mapped the distributions of the different materials on the surface, including the sulfuric acid frost that is mostly on the side of Europa that is most heavily bombarded by gases surrounding Jupiter,” King said. The lunar crust is mainly composed of water ice.

NASA’s Jupiter Study The Juno spacecraft performed close flybys of the two moons and provided incredibly detailed surface views. The new VLT studies show the benefits of using different types of observations to build a more complete picture of what is happening with these mysterious moons.

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