Dieses Portal bietet Basiswissen zum Thema Astronomie und zeigt aktuelle Forschungsarbeiten und -kooperationen in der Schweiz auf.

Image: ESO

Jupiter - Io, Europa, Ganymed, Kallisto

The four Galilean moons of Jupiter shown to scale – from left to right: Io, Europa, Ganymede, Callisto.
Image: NASA/JPL/DLR

Jupiter has over 60 known moons, but four of them stand out due to their exceptional size and the fact that they have been studied extensively: Io, Europa, Ganymede, and Callisto. These moons were first discovered in 1610 by Galileo Galilei, thanks to their size, and are therefore known as the Galilean moons.
The smallest of the four is Europa, which is slightly smaller than Earth's Moon. The largest is Ganymede, with a diameter slightly greater than that of Mercury. As their distance from Jupiter increases (from Io to Europa, Ganymede, and Callisto), their density decreases from 3.56 grams per cubic centimeter to 1.851 grams per cubic centimeter. Callisto, the farthest, is composed almost entirely of ice rather than rock.
All four moons were photographed by the Voyager 1 probe, which revealed that Io has active volcanoes—an extraordinary feature unique to a moon in our solar system.

Bearbeitete Aufnahme von Io am 30. Dezember 2023
Image: NASA / JPL / SwRI / MSSS / Gerald Eichstädt / Thomas Thomopoulos

Am 30. Dezember 2023 flog die Raumsonde Juno in 1500km Abstand an Io vorbei und schoss neue Bilder. So nah war noch nie eine Sonde am Jupitermond.

Juno ist seit 2011 unterwegs. Ziel der Mission ist es, mehr über die Entstehung und Zusammensetzung von Jupiter herauszufinden. Da die Kamera auf Juno etwas älter ist, und die Qualität der Bilder nicht mehr so gut ist,hat die Nasa die Rohbilder zur Bearbeitung freigegeben. Ein bearbeitete Version ist oben zu sehen.