Each planet in the inner solar system is less dense than their inner neighbor — Mars is less dense than Earth, which is less dense than Venus, which is less dense than Mercury. The Galilean moons follow the same principle, being less dense the farther they are from Jupiter. The reduced density at greater distances is likely due to temperature: denser, rocky, and metal material condenses out first, close to Jupiter or the Sun, while lighter-weight icy material only condenses out at larger distances where it is colder.
Distance from Jupiter also determines how much tidal heating the Galilean satellites experience — Io, closest to Jupiter, is heated so much that it is the most volcanically active body in the solar system, and it likely long ago drove off any water it had when it formed. Europa has a layer of ice and water on top of a rocky and metal interior, while Ganymede and Callisto actually have higher proportions of water ice and so lower densities.
Like our planet, Europa is thought to have an iron core, a rocky mantle, and an ocean of salty water. While evidence for an internal ocean is strong, its presence awaits confirmation by a future mission. All along Europa's many fractures, and in splotchy patterns across its surface, is a reddish-brown material whose composition is not known for certain, but likely contains salts and sulfur compounds that have been mixed with the water ice and modified by radiation. This surface composition may hold clues to the moon's potential as a habitable world.
Some of these fractures have built up into ridges hundreds of meters tall, while others appear to have pulled apart into wide bands of multiple parallel fractures. Galileo also found regions called "chaos terrain," where broken, blocky landscapes were covered in mysterious reddish material. In , scientists studying Galileo data proposed that chaos terrains could be places where the surface collapsed above lens-shaped lakes embedded within the ice. Europa has only a tenuous atmosphere of oxygen, but in , NASA announced that researchers using the Hubble Space Telescope found evidence that Europa might be actively venting water into space.
This would mean the moon is geologically active in the present day. One of the most important measurements made by the Galileo mission showed how Jupiter's magnetic field was disrupted in the space around Europa. The measurement strongly implied that a special type of magnetic field is being created induced within Europa by a deep layer of some electrically conductive fluid beneath the surface.
Based on Europa's icy composition, scientists think the most likely material to create this magnetic signature is a global ocean of salty water, and this magnetic field result is still the best evidence we have for the existence of an ocean on Europa.
Resource Packages. A 3D model of Jupiter's moon Europa, an icy moon with a hidden subsurface ocean. A 3D model of Europa Clipper, a future mission to Jupiter's ocean moon. The next full Moon is the Beaver Moon, and there will be a near-total lunar eclipse. Europa could have all three of these ingredients, and its ocean may have existed for the whole age of the solar system, long enough for life to begin and evolve there. Go farther. Europa orbits Jupiter, the fifth planet from the Sun.
Jupiter orbits the Sun at a distance of about million miles million kilometers. Europa rotates once on its axis and completes one orbit of Jupiter every 3. Abundant liquid water, energy and the right chemical elements make Europa one of the best places in the solar system to seek present day life beyond Earth. Europa has been featured in short stories, comics, and novels, with perhaps the best-known being the Arthur C.
The Latest. Full Moon Guide: November - December Reddish Bands on Europa. Europa's surface is mostly solid water ice. It is crisscrossed by fractures. Europa has an extremely thin oxygen atmosphere — far too thin for humans to breathe. The lack of craters and the surface ice cracks some of which are more than nine miles wide indicate that something is constantly fracturing and replacing the ice.
Probably an ocean below. Could an Europan ocean contain living things? For example, it is quite possible that the ocean, warmed by Europa's molten core, contains deep-sea vents like Earth's "black smokers.
Discovery: Europa was discovered on January 7, by Galileo Galilei. Exploration: Early spacecraft missions to Jupiter began in the s with Pioneer 10 and Pioneer 11, which were sent to photograph Jupiter and its moon system. Several years later, Europa came into focus when in the twin Voyager captured images of a pale-yellow sphere, covered in a thick layer of cracked ice. Improved technology aboard the Galileo spacecraft gave us a closer look at Europa, and close-up images indicated that Europa's huge fissures were being "repaired" in a sense by an upward flow of new material from below the surface.
Orbit: Europa orbits Jupiter at an approximate , kilometer distance.
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