Europa

## General Information

Europa, also known as Jupiter II, is the sixth-closest known moon of Jupiter out of the 95 known moons orbiting the planet. It is the smallest of the four Galilean moons. In the Solar System, it is also the sixth-largest moon. Simon Marius and Galileo Galilei made separate discoveries of Europa, and Marius named it after Europa, the Phoenician mother of King Minos of Crete and a lover of Zeus.

Europa is a silicate rock moon that is somewhat smaller than the moon. It likely has an iron-nickel core and a water-ice crust. Its atmosphere, which is mostly made of oxygen, is extremely thin. There are a few craters compared to the light tan fractures and streaks that striate its white-beige surface. Europa has been studied by a series of space probe flybys, the first of which took place in the early 1970s, in addition to telescopic views from Earth. For a closer look at Europa, the Juno spacecraft traveled within 320 kilometers (200 miles) of the planet in September 2022.

Of all the known solid objects in the Solar System, Europa has the smoothest surface. The idea that a water ocean exists beneath the surface and may potentially contain extraterrestrial life is based on the surface's youthful appearance and smoothness. The most widely accepted theory contends that heat from tidal flexing keeps the ocean liquid and propels plate tectonic-like ice movement, drawing chemicals from the surface into the ocean bottom.  Certain geological structures on Europa may be covered in sea salt from a subterranean ocean, indicating that the ocean and sea floor are interacting.

Furthermore, water vapor plumes resembling those seen on Saturn's moon Enceladus were picked up by the Hubble Space Telescope. These plumes are believed to be the result of erupting cryogeysers. Based on a revised review of data from the Galileo space mission, which circled Jupiter from 1995 to 2003, astronomers presented proof of water plume activity on Europa in May 2018. Without going to the moon, such plume activity could aid scientists in their quest for life in the subterranean Europan Ocean.

### History

Galileo Galilei made the discovery of Europa on January 8, 1610, along with the discovery of Jupiter's other three big moons, Io, Ganymede, and Callisto. Simon Marius may have made the discovery on his own. Galileo made the first known observation of Io and Europa on January 7, 1610, at the University of Padua, using a 20× refracting telescope. However, because of the poor magnification of his telescope, Galileo was unable to distinguish between Io and Europa during that observation, and as a result, they were both recorded as a single point of light. Io and Europa were originally observed as distinct bodies on January 8, 1610, the day after Galileo made his observations of the Jupiter system.

### Properties

Compared to the Moon, Europa is somewhat smaller. With a diameter of little more than 3,100 kilometers, it ranks as the fifteenth largest object in the Solar System and the sixth largest moon. Even though it is the least massive of the Galilean satellites by a significant margin, it is nevertheless larger than all of the known moons in the Solar System that are smaller than it put together. Because silicate rock makes up the majority of its composition, its bulk density indicates that it is similar in composition to terrestrial planets.

According to estimates, Europa has a liquid ocean beneath its ice and an exterior layer of water that is around 100 kilometers thick. Recent Galileo orbiter magnetic-field data revealed that Europa interacts with Jupiter's magnetic field to produce its own, indicating the possibility of a subsurface conductive layer. This stratum is probably an ocean of liquid salt water. It is predicted that portions of the crust have rotated almost 80 degrees, almost to the point of tipping over, which is improbable if the ice were firmly affixed to the mantle. There is most likely a metallic iron core inside Europa.

Europa lacks large-scale features like mountains and craters, making it the smoothest known object in the Solar System. However, one study claims that because of direct sunlight falling on the equator, which causes the ice to sublime and produce vertical fissures, the equator of Europa may be covered in icy spikes called penitentes that might reach heights of up to 15 meters. Radar and temperature data are compatible with this theory, even if the imaging available from the Galileo orbiter lacks the resolution for confirmation. The notable features that transverse Europe seem to be primarily low topography-emphasizing albedo structures. Europa has very few craters.

The most remarkable surface features of Europa are its lineae, or black striations that crisscross the whole planet. Upon closer inspection, it is evident that the crustal borders of Europa have shifted in relation to one another on either side of the fissures. The bigger bands have a diameter of more than 20 kilometers and frequently include a central ring of lighter material, regular striations, and dark, diffuse outside margins.

There are also elliptical and round lenticulae on Europa. Numerous are smooth, dark patches, a few are pits, and many are domes. Some have a rough, disorganized texture. It is possible that the domes arose when the plains were pushed up from below since the dome tops resemble fragments of the earlier plains surrounding them.

## Appearance

Europa has many craters with a slightly red color around it.