The sharpest images from Earth of Jupiter’s moons, Europa and Ganymede, reveal their icy landscape

Jupiter’s moon Europa was captured by the Jupiter Orbiter’s Very Large Telescope (VLT). Credit: ESO/King & Fletcher

The most detailed photos ever were captured from two JupiterEarth’s largest telescope moons are revealing the mixture of chemicals that make up their frozen surfaces.

new pictures of Europa And the Ganymedetwo future destinations for exciting new missions to the Jovian system, have been revealed by planetary scientists from the University of Leicester’s School of Physics and Astronomy.

Europa is the name of a woman kidnapped by the god Zeus – Jupiter in Roman mythology in Greek mythology. It may be the most promising place in our solar system to find present-day environments suitable for an extraterrestrial life form. With an equatorial diameter of 1,940 miles, Europa is about 90% the size of Earth’s moon. It orbits Jupiter every 3.5 days.

As some of the sharpest images of Jupiter’s moons obtained from a ground-based observatory, they are revealing new insights into the processes that shape the chemical makeup of these massive moons — including geological features such as the long, rift-like rift that crisscrosses the surface of Europa.

Ganymede and Europa are two of the four largest moons orbiting Jupiter, a quadrilateral group known as the Galilean satellites. While Europa is very similar in size to our own moon, Ganymede is the largest moon in the entire solar system.

Lister’s team, led by doctoral student Oliver King, used the European Southern Observatory very large telescope (VLT) in Chile to monitor and map the surfaces of these two worlds.

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

Pictures and spectra of Europa, published in Planetary Science Journal, It reveals that Europa’s crust consists mainly of frozen water ice with non-ice materials that pollute the surface.

VLT Ganymede

Jupiter’s moon Ganymede was captured by ESO’s Very Large Telescope (VLT). Credit: ESO/King & Fletcher

Oliver King, from the University of Leicester’s School of Physics and Astronomy, said: “We’ve mapped the distributions of different materials on the surface, including sulfur. sour The frost that is mainly on the side of Europe which is heavily bombarded with gases around Jupiter.”

“Modeling found that there could be a variety of different salts present at the surface, but indicated that infrared spectroscopy alone is generally unable to identify specific types of salt present.”

Ganymede is not only the largest moon of Jupiter, but the largest moon in our solar system. In fact, it is larger than the planet Mercury and the dwarf planet Pluto. NASA‘s Hubble Space Telescope He found evidence of an underground saltwater ocean believed to be buried under a thick crust of mostly ice. It orbits Jupiter every 7.2 days.

Ganymede’s notes published in the magazine JGR: Planetsshows how the surface consists of two main types of terrain: small areas with large amounts of water ice, and ancient areas consisting mainly of dark gray matter, the composition of which is unknown.

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The icy regions (blue in images) include Ganymede’s polar caps and craters – where the impact event revealed fresh clean ice of Ganymede’s crust. The team mapped how Ganymede’s ice grain size varies across the surface and the potential distributions of a variety of different salts, some of which may originate from within Ganymede itself.

The Very Large Telescope at very high altitude in northern Chile, with mirrors over 8 meters wide, is one of the most powerful telescope installations in the world.

Oliver King adds: “This has allowed us to perform detailed mapping of Europa and Ganymede, observing features on their surfaces less than 150 km wide – all at distances of more than 600 million km from Earth. Mapping at this precise scale was previously only possible By sending a spacecraft all the way to Jupiter to closely observe the moons.”

Professor Lee Fletcher, who supervised the VLT study, is a member of the science teams on ESA’s Jupiter Icy Moons Explorer (JUICE) and NASA’s Europa Clipper mission, which will explore Ganymede and Europe closely in the early 2030s. JUICE is scheduled to launch in 2023, and University of Leicester scientists play key roles in its proposed study of Jupiter’s atmosphere, magnetism, and moons.

Professor Fletcher said: “These terrestrial observations have fueled the appetite for our future exploration of Jupiter’s moons.”

“Planetary missions operate under strict operational constraints and we simply cannot cover all the terrain we desire, so difficult decisions must be made about areas of the moons surfaces that merit close examination. 150 km-wide observations such as those provided by the VLT, and ultimately its formidable successor, help ELT (Extremely Large Telescope), provides a global context for spacecraft observations.”

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“Global Modeling of Ganymede’s Surface Composition: Near Infrared Mapping of VLT/SPHERE” by Oliver King and Lee N. Fletcher, Accepted, JGR: Planets.
arXiv: 2209.01976

“Typical Mapping of Europa using MCMC Modeling of Near-IR VLT/SPHERE and Galileo/NIMS Observations” by Oliver King, Lee N Fletcher and Nicholas Leger (2022), March 31, 2022, Available here. Planetary Science Journal.
DOI: 10.3847 / PSJ / ac596d

This work was funded by Royal Society Promotion Award No. 180071 to Professor Lee Fletcher in the School of Physics and Astronomy, entitled “Diversity of the Galilean Moons of Jupiter: Earth Explorer Observations in Preparation for JUICE.”

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