The satellite Ganymede is the most outstanding object from Jupiter's suite. A gas giant among the planets, it stands out among the moons of the solar system in size. In terms of 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 exceptionally interesting object for astrophysicists: magnetic field, topography, internal structure. In addition, Ganymede is a moon on which life could theoretically exist.
Opening
The official opening date is January 7, 1610. On this day, Galileo Galilei directed his telescope (the first in history) to Jupiter. He discovered four satellites of the gas giant: Io, Europa, Ganymede and Calisto. Simon Marius, an astronomer from Germany, had observed the same objects about a year earlier. However, he did not release the data in time.
It was Simon Marius who gave the familiar names to cosmic bodies. Galileo, however, designated them as "Medici planets" and assigned a serial number to each. To call the satellites of Jupiter after the names of the heroes of Greek myths have actually becomeonly since the middle of the last century.
All four cosmic bodies are also referred to as "Galilean satellites". A feature of Io, Europa and Ganymede is that they rotate with an orbital resonance of 4:2:1. During the time that the largest of the four circles 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). It is twice as heavy as the Moon. At the same time, the mass of Ganymede is less than two times that of the Mercury. The reason for this lies in the low density of the object. It is only twice the value of the same characteristic of water. And this is one of the reasons to believe that the substance necessary for the origin of life is present on Ganymede, and in a fairly large amount.
Surface
Ganymede is a satellite of Jupiter, with some of its features reminiscent of the Moon. For example, there are craters left 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.
There are two types of relief on Ganymede. Dark areas, richly covered with craters, are considered to be more ancient. They are adjacent to "young" areas of the surface, light and dotted with ridges and recesses. The latter, according to scientists, were formedas a result of tectonic processes.
The structure of the crust of the satellite may resemble a similar structure on Earth. Tectonic plates, which are large chunks of ice on Ganymede, may have moved and collided in the past, forming faults and mountains. This assumption is confirmed by the discovered frozen flows of ancient lava.
Probably the light furrows of the younger portions of the satellite were formed as a result of the divergence of the plates, filling the faults with viscous substance under the crust, and further restoration of surface ice.
Dark areas are covered with a substance that is of meteorite origin or formed as a result of the evaporation of water molecules. Under its thin cover is, according to researchers, pure ice.
Recently opened
In April of this year, information about the discovery of two scientists from the United States was made public. At the equator of the moon Ganymede, they found a large bulge. The formation is comparable in size to Ecuador and is half as high as Mount Kilimanjaro.
A possible reason for the occurrence of such a relief feature is the drift of surface ice from one of the poles to the equator. Such a movement can occur if there is an ocean under the crust of Ganymede. 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 abundance inbowels, is another feature that characterizes Ganymede. Jupiter's largest moon has three inner layers:
- molten core, consisting either of metal only, or of metal and sulfur impurities;
- mantle composed of rocks;
- a layer of ice 900-950 km thick.
Perhaps there is a layer of liquid water between the ice and the mantle. In this case, it is characterized by a temperature below zero, but does not freeze due to high pressure. The thickness of the layer is estimated at several kilometers, it lies at a depth of 170 km.
Magnetic field
The satellite Ganymede not only resembles the Earth in tectonics. Another notable characteristic of it is a powerful magnetic field, comparable to the similar formation of our planet. Scientists suggest that such a phenomenon in the case of Ganymede can have only two reasons. The first is the molten core. The second is a layer of s alty liquid, a good conductor of electricity, under the ice crust of the satellite.
The data of the Galileo apparatus, as well as recent studies of the Ganymede aurora, speak in favor of the latter assumption. Jupiter brings discord in the satellite's magnetic field. As it was established during the study of the aurora, their magnitude is much lower than expected. The probable cause of the deviations is the liquid subsurface ocean. Its thickness can be up to 100 km. In suchthe interlayer should contain more water than the entire surface of the Earth.
Such theories make it possible to seriously consider the possibility that Ganymede is a life-bearing moon. The possibility of this indirectly confirms the discovery of organisms on Earth under conditions that seem to be unsuitable for it: in thermal springs, at the depths of the ocean with an almost complete absence of oxygen, and so on. So far, the satellite Ganymede is recognized as a likely candidate for the possession of extraterrestrial life. Is this so, only new flights of interplanetary stations will be able to establish.
