Those four moons are likely about the same age as the rest of the solar system — about 4. 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. Astronomer Galileo Galilei gets the credit for discovering these moons, among the largest in the solar system.
Europa is the smallest of the four but it is one of the more intriguing satellites. The surface of Europa is frozen, covered with a layer of ice, but scientists think there is an ocean beneath the surface. The icy surface also makes the moon one of the most reflective in the solar system.
Researchers using the Hubble Space Telescope spotted a possible water plume jetting from Europa's south polar region in A different research team, after repeated attempts to confirm the observations, saw apparent plumes in and The researchers cautioned that the plumes haven't yet been fully confirmed, but they do provide a suggestion that there is water in Europa's ocean jetting to the surface.
Several spacecraft have done flybys of Europa including Pioneers 10 and 11 and Voyagers 1 and 2 in the s. The Galileo spacecraft did a long-term mission at Jupiter and its moons between and Age : Europa is estimated to be about 4. Distance from the sun : On average, Europa's distance from the sun is about million miles or million kilometers. Distance from Jupiter : Europa is Jupiter's sixth satellite. Its orbital distance from Jupiter is , miles , km. It takes Europa three and a half Earth-days to orbit Jupiter.
Europa is tidally locked, so the same side faces Jupiter at all times. Size : Europa is 1, miles 3, km in diameter, making it smaller than Earth's moon , but larger than Pluto. It is the smallest of the Galilean moons. Temperature : Europa's surface temperature at the equator never rises above minus degrees Fahrenheit minus degrees Celsius.
At the poles of the moon, the temperature never rises above minus F minus C. Galileo Galilei discovered Europa on Jan. It is possible that German astronomer Simon Marius also discovered the moon at the same time. However, he did not publish his observations, so it is Galileo who is most often credited with the discovery. For this reason, Europa and Jupiter's other three largest moons are often called the Galilean moons. Galileo, however, called the moons the Medicean planets in honor of the Medici family.
It is possible Galileo actually observed Europa a day earlier, on Jan. However, because he was using a low-powered telescope, he couldn't differentiate Europa from Io, another of Jupiter's moons. It wasn't until later that Galileo realized they were two separate bodies. The discovery not only had astronomical, but also religious implications. 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. Due to powerful push-and-pull gravitational forces, Europa's orbit is exceptionally oblong. This exaggerated ellipse is caused by a unique occurrence between Europa and its neighboring satellites Io and Ganymede.
With nearly clock-like precision, Europa makes one trip around Jupiter while Europa's inner neighbor Io makes two trips around Jupiter. For every two trips Europa makes around Jupiter, Europa's outer neighbor Ganymede makes only one trip.
0コメント