Sharpest Earth-based images of Europa and Ganymede reveal their icy landscapes

The cocktail of chemical compounds that make up the frozen surfaces on two of Jupiter’s largest moons are revealed in probably the most detailed photos ever taken of them by a telescope on Earth.

Planetary scientists from the College of Leicester’s College of Physics and Astronomy have unveiled new photos of Europa and Ganymede, two future locations for thrilling new missions to the Jovian system.

Among the sharpest photos of Jupiter’s moons ever acquired from a ground-based observatory, they reveal new insights into the processes shaping the chemical composition of those large moons—together with geological features such because the lengthy rift-like linae chopping throughout Europa’s floor.

Ganymede and Europa are two of the 4 largest moons orbiting Jupiter, often known as the Galilean moons. While Europa is sort of comparable in measurement to our personal Moon, Ganymede is the biggest moon in the entire Photo voltaic System.

The Leicester workforce, led by Ph.D. scholar Oliver King, used the European Southern Observatory’s Very Massive Telescope (VLT) in Chile to look at and map the surfaces of those two worlds.

The brand new observations recorded the quantity daylight mirrored from Europa and Ganymede’s surfaces at completely different infrared wavelengths, producing a reflectance spectrum. These reflectance spectra are analyzed by creating a pc mannequin that compares every noticed spectrum to spectra of various substances which have been measured in laboratories.

The pictures and spectra of Europa, printed within the Planetary Science Journal, reveal that Europa’s crust is especially composed of frozen water ice with non-ice supplies contaminating the floor.

Oliver King from the College of Leicester College of Physics and Astronomy says that they “mapped the distributions of the completely different supplies on the floor, together with sulfuric acid frost which is especially discovered on the aspect of Europa that’s most closely bombarded by the gases surrounding Jupiter.”

“The modeling discovered that there could possibly be a wide range of completely different salts current on the floor, however advised that infrared spectroscopy alone is mostly unable to establish which particular forms of salt are current.”

The observations of Ganymede, printed within the journal JGR: Planets, present how the floor is made as much as two essential forms of terrain: younger areas with giant quantities of water ice, and historical areas primarily consisting of a darkish grey materials, the composition of which is unknown.

The icy areas (blue within the photos) embody Ganymede’s polar caps and craters—the place an affect occasion has uncovered the contemporary clear ice of Ganymede’s crust. The workforce mapped how the dimensions of the grains of ice on Ganymede varies throughout the floor and the attainable distributions of a wide range of completely different salts, a few of which can originate from inside Ganymede itself.

Situated at high altitude in northern Chile, and with mirrors over 8 meters throughout, the Very Massive Telescope is without doubt one of the strongest telescope amenities on the planet.

Oliver King provides that “this has allowed us to hold out detailed mapping of Europa and Ganymede, observing options on their surfaces smaller than 150 km throughout—all at distances over 600 million kilometers from the Earth. Mapping at this positive scale was beforehand solely attainable by sending spacecraft all the best way to Jupiter to look at the moons up-close.”

Professor Leigh Fletcher, who supervised the VLT research, is a member of the science groups for ESA’s Jupiter Icy Moons Explorer (JUICE) and NASA’s Europa Clipper mission, which is able to discover Ganymede and Europa up shut within the early 2030s. JUICE is scheduled to launch in 2023, and College of Leicester scientists play key roles in its proposed research of Jupiter’s ambiance, magnetosphere, and moons.

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

“Planetary missions function below robust working constraints and we merely cannot cowl all of the terrain that we might prefer to, so troublesome selections have to be taken about which areas of the moons’ surfaces deserve the closest scrutiny. Observations at 150-km scale resembling these offered by the VLT, and finally its monumental successor the ELT (Extraordinarily Massive Telescope), assist to supply a world context for the spacecraft observations.”