Europa (moon)

Galileo Galilei

Europe ( Jupiter II) with a diameter of 3121 km the second innermost and smallest of the four large moons of Jupiter and the sixth largest in the solar system. Although the temperature on the surface of Europa reach a maximum of -150 ° C, it is assumed that a up to 100 km deep ocean could be located from water with a crust of water ice.

• 7.1 Planned missions

Discovery

Europe's discovery is the Italian scholar Galileo Galilei awarded -with its simple telescope at Jupiter in 1610. The four large moons Io, Europa, Ganymede and Callisto are also referred to as the Galilean moons.

Was named the moon to Europe, a lover of Zeus in Greek mythology. Although the name of Europe has already been proposed shortly after his discovery by Simon Marius, he could not prevail over time. Only in the middle of the 20th century he came again into use. Previously, the Galilean moons were commonly referred to by Roman numerals and Europe was Jupiter II

The Galilean moons are so bright that they can already be observed with binoculars or small telescopes.

Orbit and rotation

Europe orbiting the prograde Jupiter at an average distance of 670 900 kilometers in 3 days, 13 hours and 14.6 minutes. Your orbit is almost circular with a numerical eccentricity of 0.0101. Your jupiter Next and the most distant point on the path - Perijovum and Apojovum - soft each from only 1.01 % of the semi-major axis. The orbital plane is inclined only 0.470 ° with respect to Jupiter's equatorial plane.

The orbital period of Europe stands by its inner and outer neighboring moon in an orbital resonance of 2:1 or 1:2; that is, during two rounds of Europe is exactly four times Io and Ganymede exactly once around Jupiter.

Europe has, as the Earth's Moon and the other inner moons of Jupiter, synchronous rotation, and always shows the same side to the planet.

Structure and physical data

Europe has an average diameter of 3,121.6 miles and an average density of 3.01 g / cm ³. Although the smallest of the four Galilean moons clearly, their mass is greater than that of all the smaller moons of the solar system combined.

The temperature on Europa's surface is only 110 K (about -160 ° C) at the equator and 50 K (about -220 ° C) at the poles.

Surface

The surface of Europa includes 30.6 million km ², which is about the size of Africa. With an albedo of 0.64, it is one of the brightest surfaces of all known moons in the solar system: 64 % of the incident sunlight is reflected. The surface is composed of ice. The reddish stains are the result of deposited minerals. The surface is extremely flat. It is covered by grooves, but having a small depth. Only a few structures that are more than a few hundred meters rise above the environment, have been identified.

Crater

In Europe, very few impact craters are visible, only three of which have a diameter of more than 5 kilometers. The second largest crater Pwyll, has a diameter of 26 kilometers. Pwyll is one of the youngest geological structures on Europe. In the felling bright material was ejected from the ground for thousands of kilometers away.

The low cratering is an indication that Europa's surface is geologically very young. Estimates of the impact frequency of comets and asteroids yield an age of 30 million years ago.

Phyllosilicates were detected on Europe's crust. It is believed that they are derived from impacts at a shallow angle to the surface.

Furrows and ditches

Europe's most striking feature is a network of criss-crossing trenches and furrows lineae called ( singular: Linea ), which cover the entire surface. The linea have a strong similarity with cracks and distortions on terrestrial ice fields. The larger ones are about 20 kilometers wide and have indistinct outer edges and an inner area of bright material. The lineae could have originated from warm water by Kryovulkanismus ( Kältevulkanismus ) or the eruption of geysers, so that the ice crust was pushed apart.

This lineae also include for the most part at other locations than you would expect. This can possibly be explained that there is an ocean between ice crust and the lunar surface. This could have arisen because due to the eccentric orbit of the moon around Jupiter continuously its gravitational effect on Europe is changing, so that it is permanently deformed. As a result, Europe is warming and the ice melts in part.

If Europe is in its orbit by the largest Jupiter ran away, repeatedly hydrogen and oxygen atoms over the South Pole could be detected. It is believed that they originated from the splitting of water molecules that are released as open columns and shoots water into space, which falls back to 200 kilometers to the ascent to the surface.

Other structures

Another type of surface structures are called circular and elliptical structures, Lenticulae (lat. spots). Many are surveys (german cathedral ), other depressions or flat dark spots. The Lenticulae emerged apparently by rising warmer ice, similar to magma chambers in the crust. The domes were thereby pushed up, the flat dark spots could be frozen meltwater. Chaotic zones as Conomara chaos are like a jigsaw puzzle of fragments formed, which are surrounded by smooth ice. They have the look of icebergs in a frozen lake.

Ice deposits and ocean

The smooth surface and the structures are strongly reminiscent of ice sheets in polar regions on Earth. It is thought that an ocean is among Europe's icy crust of liquid water, which is heated by tidal forces. At the very low surface temperatures of water ice is as hard as rock. The largest visible crater were obviously filled with fresh ice and leveled. This mechanism, as well as calculations of the tidal forces caused by the warming suggest that Europe's crust of water ice is about 10 to 15 kilometers thick. The ocean underneath may have a depth of up to 100 kilometers. The amount of liquid water would be more than twice as large as that of the terrestrial oceans. From about 3 kilometers below the surface, however, there could be trapped in the ice water bubbles.

Detailed photographs show that parts of the ice crust have shifted against each other and are broken, wherein a pattern of ice fields emerged. The movement of the crust caused by tidal forces, the lifting and lowering of the surface to 30 m. The ice fields would have to have a certain, predictable pattern due to the bound rotation. Other images show instead that only the geologically recent areas have such a pattern. Other countries differ with age of this pattern. This can be explained that Europa's surface moves slightly faster than their intrinsic mantle and the core. The icy crust is mechanically decoupled from the lunar interior through the intervening ocean and is influenced by Jupiter's gravitational forces. Comparisons of images of space probes Galileo and Voyager 2 show that Europe's icy crust would have to move once completely around the Moon in about 10,000 years.

Internal construction

The moon is similar in structure to the terrestrial ( Earth-like ) planets as it is composed mainly of silicate rock. Its outer layer is composed of water, with an estimated thickness of 100 kilometers. Furthermore, it should have a relatively small core of iron.

Atmosphere

Images from the Hubble Space Telescope have shown evidence for the presence of an extremely thin atmosphere of oxygen, at a pressure of 10-11 bar. It is believed that the oxygen produced by the effect of solar radiation on the icy crust, where the water is split into hydrogen and oxygen. The volatile hydrogen escapes to space, the more massive oxygen is held by Europe's gravity.

Magnetic field

In flybys of the Galileo probe, a weak magnetic field was measured ( its thickness is approximately ¼ of Ganymede ). The magnetic field varies, while Europe moved by the extremely strong magnetosphere of Jupiter. The data from Galileo indicate that an electrically conductive liquid is under Europa's surface, such as an ocean of salt water. In addition, spectroscopic studies show that the reddish lines and structures on the surface are rich in salts such as magnesium oxide. The salt deposits could be retarded, had evaporated as leaked salt water. Since the observed salts are usually colorless, should other elements such as iron or sulfur be responsible for the reddish color.

Speculation about life on Europa

The possible presence of liquid water could rise to speculation about whether can exist forms of life in Europe's oceans. On Earth, life forms have been discovered that may exist under extreme conditions even without the presence of sunlight, such as in the hydrothermal vents ( black smokers ) or in the deep sea.

According to a report of the science magazine New Scientist NASA scientist who planned the Painted Nasa Mission Jupiter Icy Moons Orbiter came after reports of previous missions in the spring of 2004 to the conclusion that the moon Europa could be far more hostile to life than previously thought.

As hydrogen peroxide and concentrated sulfuric acid covered surfaces were found on the surface. Here, it is assumed that the acid derived from the assumed under ice ocean. The concentration is explained by unterseeischem volcanism, which may be responsible for the sulfur.

It is quite possible that the sulfur comes from Jupiter 's moon Io. Meanwhile, there are also indications that the suspected ocean under Europa's surface has an appreciable salt concentration. So epsomite was detected on the surface ( a magnesium sulfate compound). Epsomite could have originated with magnesium chloride to radiation exposure by reaction of sulfur from Jupiter 's moon Io. The magnesium chloride comes with high probability from within Europe. Epsomite is much easier to prove than sodium or potassium chloride which would rather suggest to Europe.

To avoid contamination of Europe with earthly microorganisms were allowed to Galileo spacecraft, which most recently Europe watched burn up in the atmosphere of Jupiter.

Exploration by special missions

After flying past the probes Pioneer 10 and Pioneer 11 in the years 1973 and 1974 there were of the largest moons of Jupiter at least blurred photographs. Voyager 1 and Voyager 2 flew past when delivered in 1979 substantially more accurate images and data. In 1995, the Galileo spacecraft began eight years to circle Jupiter. She led here by also detailed investigations and measurements on the Galilean satellites, upon which most of our present knowledge of these celestial bodies.

Planned missions

So far there is no evidence for life, but later missions should clarify this. The look is of an unmanned Cryobot spacecraft landing on the surface, by melt through the ice crust and a "mini - submarine" ( Hydrobot ) to drain in Europe Ocean. Before this mission can become a reality at all, a Europe Orbiter spacecraft could be launched in the next decade, which is scheduled to enter orbit around Europe and study the moon comprehensively. The outcome will be to gather more knowledge about Europe and to find suitable landing sites for future missions.

For 2020, the space agencies NASA and ESA planned the start of the European Jovian System Mission / Laplace mission which two orbiter Compromise ( JEO - Jupiter Europa Orbiter and JGO - Jupiter Ganymede Orbiter ), which should occur each in an orbit around Europa and Ganymede and the entire Jupiter system should explore with a revolutionary draft. The JEO (Jupiter Europa Orbiter ) should swing in orbit around Europe after 2028 and planning for several years with various on-board instruments, inter alia, data collect on morphology, temperature and gravity of the moon. In addition, to be studied by Ice Penetrating Radar properties of water ice in order to shed light on the consistency or the extent of the ice mantle and a possible liquid ocean can.

NASA, who wanted to build the JEO, but got out of the project. However, the ESA realized the JGO with a slightly different mission planning as JUICE. JUICE is in the year to perform and clarify whether Europe has the suspected ocean under its icy crust 2030 two flybys of Europe after their arrival at Jupiter.