Satellites also have magnetic fields! The only satellite in the solar system with a magnetosphere is bigger than mercury

As we all know, in the beautiful solar system, in addition to the sun, Jupiter is the largest, and it has a lot of satellites. So far, mankind has found a total of 79 natural satellites! And the following small series will tell you about one of Jupiter’s moons.

The size of this satellite has surpassed that of a planet in the solar system. If it does not revolve around Jupiter, but around the sun, it may become another planet.

It is also the only satellite in the solar system with a magnetosphere. At the same time, there are some things that make people feel very suitable for life on this satellite. It is the mysterious Ganymede.

Discovery process

On January 11, 1610, Galileo Galilei observed three stars near Jupiter. The next night, he noticed that the three stars had shifted. Then he launched the fourth star and later Ganymede. On the evening of January 15, 1610, Galileo determined that these stars were orbiting Jupiter.

However, Gande in the Warring States period discovered Ganymede about 364 BC, which is more than 2000 years earlier than Galileo. According to what gander said when he talked about Jupiter in Tang Kaiyuan ZHANJING: if there is a small red star attached to its side. Xi Zezong, a famous astronomy historian, pointed out that gander had observed the largest moon of Jupiter in the middle of the 4th century BC.

body size

The diameter of Ganymede is 5262 kilometers, and that of mercury is only 4878 kilometers. Its size is 8% larger than that of mercury and only slightly smaller than that of Mars. Its orbit is about 1.04 million kilometers away from Jupiter, and it takes seven days to orbit around Jupiter.

The structure of Ganymede

It is mainly composed of silicate rock and water ice

1. Inside, there is a dense and iron rich core with a radius of 500 km and a temperature between 1500 and 1700K.

2. There is a mantle composed of silicates.

3. There’s a shell of ice.

There are two types of terrain on the surface of Titan

1. Dark terrain covers about 1 / 3 of the surface of Ganymede. Although the surface of Ganymede is full of impact craters, dark areas are more common. The reason why the terrain presents dark shadows is that the ice on the surface contains clay and organic matter. Scientists believe that the clay and organic matter of these objects came from the fall.

2. The other topography is composed of long and narrow depressions, most of which are arranged in parallel, 5-10 km apart from each other, but the depth can reach hundreds of kilometers. This terrain may be formed by the tectonic activity of Ganymede.

Have a magnetic field

In 1996, shortly after arriving at Jupiter, Galileo made an amazing discovery: Ganymede has its own magnetic field, and most of the planets in the system, including the earth, have a magnetic environment called “magnetosphere”.

No one thought that satellites would have magnetic fields. Galileo made six fixed-point leaps to Ganymede from 1996 to 2000, and collected the data of Ganymede’s magnetosphere with several instruments, including the plasma subsystem ppls. PLS is used to measure the density, temperature and direction of the plasma passing through the environment around Galileo. The plasma is the excited ionized gas.

The new research results reveal interesting details of the unique structure of Ganymede’s magnetosphere. The research paper was published in geophysical research letters. We know that the earth’s magnetosphere can not only make the compass work and perform brilliant Aurora, but also protect the earth from space radiation. Therefore, it is the key to the reproduction of life on earth.

Some scientists believe that the earth’s magnetosphere is also indispensable for the initial evolution of life. Because harmful space radiation can corrode our atmosphere, the study of porcelain circles in the solar system can not only help scientists understand the physical processes that affect the magnetic environment around the earth, but also help us to explore the atmosphere of other potentially habitable planets in and outside the solar system.

Xiao Bian believes that Ganymede’s magnetosphere provides an opportunity for scientists to explore the unique magnetic environment in Jupiter’s magnetosphere, which is larger in scale. The magnetosphere protects Ganymede from solar wind erosion. Its shape is different from other magnetospheres in the solar system. Like the earth, Ganymede can also perform brilliant Aurora shows. The difference is that the particles that cause the aurora on Ganymede come from the plasma around Jupiter, not from the solar wind.

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