Chapter 1639: Crater ocean

The first thousand eight hundred and twenty-seven chapters
There are currently two theories explaining the formation of the polar cap. One is believed to be caused by the diffusion of ice at high latitudes, and the other is believed to be caused by the bombardment of plasma ice from outer space. Galileo’s observations are more inclined to the latter theory.
Ganymede may have been produced by the accretion of Jupiter’s sub-nebula, a disk of gas and dust that surrounds Jupiter after it was formed. Ganymede’s accretion process lasted about 10,000 years. There is a clear distinction between the darker Nicholson area and the brighter Harpagia trough.
This is much shorter than Callisto's 100,000 years. When the Galileo moons began to form, the gas content in the Jupiter sub-nebula was already relatively small; this resulted in a longer accretion time for Callisto. On the contrary, since Ganymede was formed immediately after Jupiter, the secondary nebula at this time is still denser, so its accretion takes less time.
The relatively short formation time makes the heat generated in the accretion process less escape. This unescaped heat leads to the melting of the ice body and the differentiation of the internal structure of Ganymede: the rock and the ice body separate from each other, and the rock sinks into the star The center forms the inner core. In this respect, Ganymede is different from Callisto, the latter being able to melt away the ice and differentiate the internal structure due to its long formation time, which leads to the escape of accretion heat. This hypothesis reveals why two satellites with such close masses and constituent substances look so different.
After its formation, Ganymede's inner core still retains most of the heat formed during the accretion and differentiation process. It only slowly releases a small amount of heat into the icy mantle, just like the operation of a thermal battery. Then, the mantle conducts heat to the surface of the star through convection. Soon the radioactive elements contained in the rock began to decay, and the heat generated further heated the inner core, which intensified the differentiation of its internal structure, and finally formed an iron-ferrous sulfide core and a silicate mantle. So far, Ganymede's internal structure has completely differentiated.
In contrast, the radioactive heat generated by Callisto without internal structural differentiation can only cause convection within its ice, which effectively cools the stars and prevents large-scale ice melting and internal structure. At the same time, it can only cause partial differentiation between ice and rocks. Today, Ganymede’s cooling process is still very slow. The heat released from the inner core and the silicate mantle allowed the underground ocean on Ganymede to exist, while the slow-cooling flowing iron-ferrous sulfide core still promotes the thermal convection in the star and maintains its magnetism. The existence of the circle. Europa’s external heat flux is likely to be higher than that of Europa.
After Zhao Zhongyao talked to Feifei some knowledge about Ganymede. Their spacecraft had already flown over Ganymede.
Now their spacecraft is more than 100 kilometers away from Ganymede. From this height, you can see the entire surface of Ganymede. Ganymede is also a planet full of craters. After all, in the entire solar system, with the exception of the terrain on the earth, there are not many craters in sight due to the changes in the vicissitudes of life. On other planets in the solar system, there are almost all large and small craters.
After all, after these planets have experienced billions of years of history, no matter which planet they are, there will be many craters left behind. After all, there are many small celestial bodies in the entire solar system. The number of these small celestial bodies can be said to be countless.
After a long history of several billion years, Ganymede has naturally suffered numerous meteorite impact accidents. Of course, most meteorites are very small. Only a few meteorites are very large.
Feifei looked at Ganymede close in front of him and said, ‘Dad, then we should go there to find the sixth amethyst gem. Do you feel that this sixth amethyst gem will be somewhere on this planet. ’
After hearing Feifei’s words, Zhao Zhongyao said, ‘According to past experience, wherever amethyst gems exist, they should be places with life. And, most of them are in huge craters on some planets.
There are also many craters on this Ganymede. If we are looking for amethyst gems, we should also look for a huge crater. I feel that the sixth amethyst gem is in a very huge crater. ’
‘What Dad said is, can we now look for a huge crater. Said Feifei.
‘Yes, we just need to find a huge crater now. Zhao Zhongyao said so too.
So, Zhao Zhongyao took Feifei on the spacecraft, and could search for the huge crater on Ganymede.
But after they searched for a while, Feifei looked at Zhao Zhongyao again and said, ‘Dad, then we should go to that crater to find amethyst gems. You feel that this amethyst gem will be in that crater. ’
Zhao Zhongyao thought for a while and said, ‘On this Ganymede, there is a very famous crater. This crater is called Galileo Crater. We, we can first take a look at this crater. ’
‘Okay, let’s take a look in this crater first! Feifei said after hearing what his father said.
Therefore, Zhao Zhongyao flew to Galileo Crater again in his spacecraft. Soon, they flew over this huge crater.
After reaching the sky above this huge crater, Zhao Zhongyao was surprised to see that there was a huge ocean at the bottom of this huge crater.
As soon as he saw this huge ocean, Zhao Zhongyao felt that the amethyst gems they were looking for must be in this ocean.
Feifei also said very happily, ‘Dad, there is an ocean in this crater. In this way, the amethyst gem we are looking for must be in this ocean. ’
‘Yes, let’s start landing in this Galileo crater now! We will soon find the sixth amethyst gem. Feifei said happily.
So, Zhao Zhongyao flew into this Galileo crater again with his spacecraft.
This Galileo crater reaches hundreds of kilometers in diameter and is the largest crater on Ganymede. May be formed two billion years ago. It was formed by the impact of an asteroid about ten kilometers in diameter.
It is precisely because of the large size of this asteroid that when it hit Ganymede, it hit a very huge crater.
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