The Ganymede satellite is the most outstanding object from the Jupiter retinue. The gas giant among the planets, it stands out among the moons of the solar system in size. In diameter, Ganymede is even ahead of Mercury and Pluto. However, not only because of its size, the satellite of Jupiter attracts the eyes of researchers. Many parameters make it an extremely interesting object for astrophysicists: magnetic field, relief, internal structure. In addition, Ganymede is a satellite on which life can theoretically exist.
Opening
The official opening date is January 7, 1610. On this day, Galileo Galilei sent his telescope (first in history) to Jupiter. He discovered four satellites in the gas giant: Io, Europe, Ganymede and Calisto. About a year before, the same objects were observed by Simon Marius, an astronomer from Germany. However, he did not release the data on time.
It was Simon Marius who gave the usual names to cosmic bodies. Galileo designated them as āthe planets of the Mediciā and assigned a serial number to each. Jupiterās moons were named after the heroes of Greek myths in fact only from the middle of the last century.
All four cosmic bodies are also designated as āGalilean satellitesā. The peculiarity of Io, Europe and Ganymede is that they rotate with an orbital resonance of 4: 2: 1. While the largest of the four flies around Jupiter, Europe manages to make 2, and Io - four turns.
Features
The Ganymede satellite is truly amazing in its size. Its diameter is 5262 km (for comparison: a similar parameter of Mercury is estimated at 4879.7 km). In severity, it is twice the size of the moon. Moreover, the mass of Ganymede is inferior to the Mercury more than twice. The reason for this lies in the low density of the object. It is only twice the magnitude of the same characteristic of water. And this is one of the reasons to believe that the substance necessary for the birth of life is present in Ganymede, and in large enough quantity.
Surface
Ganymede is the satellite of Jupiter, with some of its features resembling the moon. For example, there are craters left over from fallen meteorites. Their age is estimated at about 3-3.5 billion years. Similar traces of the past are abundant on the lunar surface.
In Ganymede, two types of relief can be distinguished. Dark areas abundantly covered with craters are considered more ancient. Next to them are āyoungā sections of the surface, bright and dotted with ridges and grooves. The latter, according to scientists, were formed as a result of tectonic processes.
The satelliteās crust structure may resemble a similar structure on Earth. Tectonic plates, which are large pieces of ice on Ganymede, could in the past move and collide, forming faults and mountains. This assumption is confirmed by the discovered frozen flows of ancient lava.
Most likely, light furrows of the younger sections of the satellite were formed as a result of plate divergence, filling of faults with viscous material under the crust, and further restoration of surface ice.
Dark areas are covered with a substance of meteor origin or formed as a result of the evaporation of water molecules. According to the researchers, pure ice is located under its thin cover.
Recent discovery
In April this year, information was released on the discovery of two scientists from the United States. At the equator of the Ganymede satellite, they found a large bulge. The formation is comparable in size to Ecuador and reaches half of Mount Kilimanjaro in height .
A possible reason for the occurrence of such a feature of the relief is considered to be the drift of surface ice from one of the poles to the equator. Such a movement can occur if an ocean is located under the Ganymede crust. Its existence has long been discussed in the scientific world, and a new discovery can serve as additional proof of the theory.
Internal structure
Water ice, according to astrophysicists, is found in large quantities in the bowels, is another feature that characterizes Ganymede. The largest of the moons of Jupiter has three inner layers:
a molten core consisting either of metal alone or of metal and sulfur impurities;
mantle consisting of rocks;
a layer of ice 900-950 km thick.
Perhaps between the ice and the mantle is a layer of liquid water. In this case, it is characterized by a temperature below zero, but does not freeze due to the high pressure. The layer thickness is estimated at several kilometers; it lies at a depth of 170 km.
A magnetic field
The Ganymede satellite is not only tectonically reminiscent of the Earth. Another notable characteristic of it is a powerful magnetic field, comparable to the similar formation of our planet. Scientists suggest that this phenomenon in the case of Ganymede can have only two reasons. The first is the molten core. The second is a layer of salt liquid that conducts electricity well, under the satelliteās ice crust.
The last assumption is supported by the data of the Galileo apparatus, as well as recent studies of Ganymedeās aurora . Jupiter introduces discord into the satelliteās magnetic field . As it was possible to establish during the study of the aurora, their value is much lower than expected. The probable cause of the deviations is the liquid subsurface ocean. Its thickness can be up to 100 km. Such a layer should contain more water than on the entire surface of the Earth.
Such theories provide an opportunity to seriously consider the likelihood that Ganymede is a satellite where there is life. The possibility of this indirectly confirms the discovery of organisms on Earth in conditions that would seem to be of little use: in thermal springs, deep in the ocean with an almost complete absence of oxygen, and so on. So far, the Ganymede satellite is recognized as a probable candidate for the possession of extraterrestrial life. Is it so, they can only establish new flights of interplanetary stations.