The best images of Europa and Ganymede from Earth

Oct. 10 () –

The chemical cocktail that makes up the frozen surfaces of two of Jupiter’s largest moons is revealed in the most detailed images ever taken by a telescope on Earth.

Planetary scientists from the University of Leicester’s School of Physics and Astronomy have released new images of Europa and Ganymede, two destinations for future missions to the Jovian system.

Some of the sharpest images of Jupiter’s moons ever acquired from a ground-based observatory reveal new insights into the processes that shape the chemical composition of these massive moons, including geological features such as long rift lines. that cross the surface of Europe.

Ganymede and Europa are two of the four largest moons orbiting Jupiter, known as the Galilean moons. While Europa is fairly similar in size to our own Moon, Ganymede is the largest moon in the entire Solar System.

The Leicester team, led by PhD student Oliver King, used the European Southern Observatory’s Very Large Telescope (VLT) in Chile. to observe and map the surfaces of these two worlds.

The new observations recorded the amount of sunlight reflected off the surfaces of Europa and Ganymede at different infrared wavelengths, producing a reflectance spectrum. These reflectance spectra are analyzed by developing a computer model that compares each observed spectrum with spectra of different substances that have been measured in laboratories.

The images and spectra of Europe, published in Planetary Science Journal, reveal that Europa’s crust is composed primarily of frozen water ice with non-ice materials contaminating the surface.

Oliver King, from the University of Leicester’s School of Physics and Astronomy, says it’s a statement who “mapped the distributions of the different materials on the surface, including the sulfuric acid frost found mainly on the Europa side which is most heavily bombarded by the gases surrounding Jupiter”.

“The model found that there could be a variety of different salts present on the surface, but suggested that infrared spectroscopy alone cannot generally identify which specific types of salt are present.”

The Ganymede observations, published in the journal JGR: Planets, show how the surface is made up of two main types of terrain: young areas with large amounts of water ice and old areas that they consist mainly of a dark gray material, the composition of which is unknown.

The icy areas (blue in the images) include Ganymede’s ice caps and craters, where an impact event has exposed the fresh, clean ice of Ganymede’s crust. The team mapped how the size of ice grains on Ganymede varies across the surface and the possible distributions of a variety of different salts. some of which may originate from Ganymede itself.

Located high in northern Chile, and with mirrors more than 8 meters wide, the Very Large Telescope is one of the most powerful telescope facilities in the world.

Oliver King adds: “This has enabled us to carry out detailed mapping of Europa and Ganymede, looking at features on their surfaces less than 150 km wide, all at distances of more than 600 million km from Earth. Mapping at this fine scale was previously only possible by sending spacecraft to Jupiter to observe the moons up close.”

Professor Leigh Fletcher, who supervised the VLT study, is a member of the science teams for ESA’s Jupiter Icy Moons Explorer (JUICE) and NASA’s Europa Clipper mission, which will explore Ganymede and Europa up close early in the decade. 2030. JUICE is scheduled to launch in 2023, and scientists at the University of Leicester they play a key role in his proposed study of Jupiter’s atmosphere, magnetosphere, and moons.

Professor Fletcher says that “these ground-based observations whet the appetite for our future exploration of Jupiter’s moons.”

“Planetary missions operate under tight operational constraints and we simply can’t cover as much ground as we’d like, so tough decisions have to be made about which areas of the moons’ surface deserve the closest scrutiny. 150 km-scale observations such as those provided by the VLT and, ultimately, its huge successor, the ELT (Extremely Large Telescope), They help provide a global context for observations from a spacecraft.”