Man has always been interested in what is happening in the sky. The planets of the solar system seem especially attractive because they are relatively close to us. Now, when the Juno research apparatus has gone to Jupiter, the world community is looking forward to the results of its observations. At first, the device sent clear pictures of Io, Europe and Ganymede. Callisto, satellite number two from the Galilean group, did not enter the field of view of the device. In anticipation of new data about the planet and its moons, it is worth recalling what we know about them at the moment.
Satellites
Currently, about a hundred satellites of this giant are open. Four of them are quite large, the rest are much smaller.
All moons of Jupiter are divided into inner and outer groups.
A group of internal satellites includes eight objects. All of them rotate in the plane of the planet, their orbits are circular. These satellites, in turn, are divided into subgroups:
- One of them includes Metis, Adrastea, Amalthea and Theba. These bodies of small size, from 20 to 250 km in diameter, call them the "Amalthea group."
- The second subgroup includes four Galilean satellites.
External satellites are bodies that do not exceed several kilometers. The largest of these objects is the Himalia. Its diameter is only 170 km. They are called external for the reason that they rotate at a considerable distance from the planet, their orbits are elliptical and are located at a large angle to Jupiter. Interestingly, unlike the satellites of the internal group, these rotate in the direction opposite to the rotation of the giant. This orbit is called retrograde. In science, it is customary to give such bodies names that end in "e", regardless of whose honor the name is given. External satellites are so small that they can only be viewed with the most powerful telescopes.
Most satellites have been discovered in the last couple of decades, since their size did not allow them to be observed with the help of devices of previous years. However, scientists do not exclude the possibility that in the coming years some more satellites of this giant planet will be discovered.
Galilean satellites
This group was opened in 1610 by Galileo Galilei. He watched them at one of the first telescopes. These moons are so large that you can even see them through a telescope.
Ganymede
The largest not only among objects near Jupiter, but also among all the satellites of the solar system. Yes there satellites - its dimensions exceed the diameter of Mercury. So that there is no doubt, it’s worth turning to the numbers: the diameter of Ganymede is 5262 km, the Moon is 3474.2, Mercury is 4880. Thus, if this object independently revolved around our star, it would be considered a planet! However, despite its impressive size, the mass of Ganymede is half that of Mercury. Which nonetheless makes it the heaviest satellite in the solar system. The core of Ganymede is molten, it has a magnetosphere, a kind of atmosphere with residual traces of oxygen. The planet is covered with a thickness of water ice. Presumably, this layer hides the ocean of water. If not for the incredible fluxes of radiation from Jupiter, scientists would have made every effort to study this satellite.
Callisto
A little less in diameter - 4820.6 km - Callisto. The satellite, a photo of which the Juno apparatus has already sent, is covered in ice. The thickness of this layer is about 200 km. In the size range of moons in our stellar system, Callisto (satellite) takes third place. There is no mercury in this ranking, since it is a planet. Nevertheless, their sizes are quite comparable, although in weight the moon of the giant planet loses much.
The tidal forces of Jupiter are so great that Callisto is a satellite that revolves around itself as much as around the planet.
This object is of particular interest to scientists for the reason that it seems most suitable for equipping a base on it in the future. This seems possible for the following reasons:
- Callisto is a satellite whose orbit passes beyond the boundaries of the strong radiation of Jupiter.
- Its surface is water ice, which means that there will not be a lack of water there.
- Jupiter’s satellite Callisto formed about 4 billion years ago, which almost guarantees its geological stability.
Europe
It is the smallest of this group of satellites. Its size is 3138 km. The core of the planet is metallic. Like Ganymede and Callisto, the Europa satellite is covered in water ice. Scientists believe that oceans also hide under it. It is likely salty. It is these expanses of water that attract the attention of scientists. The fact is that the ice here is the thinnest - only 10-30 kilometers. This is very small in order to create high pressure. Therefore, experts suggest that water is a liquid due to the positive temperature. Why is this so important? Scientists hope that warm water can be a source of life. These facts make Europe such a desirable subject to study in a variety of space agencies. The only negative is radiation, because Europe is located inside the radiation field of Jupiter.
And about
The satellite closest to the planet. Metal core, liquid mantle and bark. The main feature is geological instability. This satellite contains more than 400 volcanoes, each of which is active.
The moons of Jupiter Io, Europe, Ganymede and Callisto in the next twenty months will be carefully studied along with the planet itself. Scientists hope that by the end of this period they will have a lot of new information, thanks to which they will be able to realize their long-held dream - to begin a closer examination of satellites to detect life in any form.