Hua Feng knows that just like Europa and Europa, some people believe that there may be extraterrestrial life in the saltwater ocean beneath the surface of Callisto. However, the environment on Europa and Europa is relatively harsh, mainly due to the lack of accessible rocky material and the low heat flux from the inner core of the star.

Scientist Terence Johansen discusses the possibility of life on Callisto and other Galileo moons: "The basic materials that make up life – what we call 'pre-life matter' – are abundant in many solar system bodies, such as comets, asteroids, and ice moons.

Biologists believe that liquid water and heat are essential to support life, so it is exciting to be able to find liquid water on another celestial body. However, for Callisto, at least for the time being, heat is a big problem, and the oceans above it are mainly heated by the decay of radioactive elements, while Europa, which is relatively close to Jupiter, is able to rely on gravitational tides to generate more heat. ”

Spanish scientists have provided a new explanation for the ocean inside Europto in the British journal Nature, published on the 26th. Calculations have shown that Callisto's temperature and pressure conditions make the ice on its surface less heat-transferable, preventing internal heat loss and keeping it warmer than previously thought.

According to calculations, a huge ocean 20 kilometers deep may exist at a depth of 150 kilometers below the surface of Callisto. Jupiter's other two large moons, Europa and Europa, may also have subsurface oceans for similar reasons.

Europa is Jupiter's second largest moon, with a diameter of 4,800 kilometers. In 1998, data sent back by the Galileo probe showed that Callisto's magnetic field fluctuated as Jupiter rotated. The most likely explanation for this situation is that Callisto has a large salty ocean beneath its surface. Salty water conducts electricity, causing the magnetic field of Ganymede and the magnetic field of Jupiter to interact to produce these fluctuations. New results from Spanish scientists provide further support for this hypothesis.

It is often assumed that where there is water, there is the possibility of life. But scientists say the depths of the ocean inside Callisto are filled with dense ice and rocks. These ice blocks and rocks block the flow of heat energy, making the possibility of life on Callisto very slim.

Based on the above considerations and other scientific observations, Europa is considered to be the most likely to harbor life in the Galilean moons.

In 2003, NASA conducted a project called "Human Outer Planet Exploration" (Huma) for the future exploration of the outer solar system by mankind

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, HOPE). In the detailed deliberations, it will be targeted at Ganymede. Scientists believe it is possible to build a base on the surface of Europa that would fuel exploration deeper into the solar system.

The benefits of having a base on Callisto are its lower radiation (Calymede is farther away from Jupiter) and its geological stability. It also facilitates further exploration of Europa, and is an ideal location for a repair station in Jupiter's system to travel farther afield to outer solar spacecraft, which can gain gravitational boost by flying by Jupiter at close range.

Ganymede is the third closest known natural satellite to Jupiter, discovered by Edward Emmerson Barnard on September 9, 1892 with a 36-inch (91 cm) refracting telescope at the Lick Observatory, the last moon to be discovered directly with the naked eye (later discoveries are usually made by photographs or other means), and the first Jupiter moon to be discovered after Galileo Galilei discovered four Jupiter moons in 1610.

In March 1979, the Voyager 1 space probe found that Calliste was light gray, with a reddish area about 130 kilometers long and 200~220 kilometers wide. Ganymede is in the same family as the other three inner moons of Jupiter. Ganymede is the largest of them.

The International Astronomical Association named it Amalthea. In Greek mythology, Amalse was a nymph who raised Zeus (Jupiter) with the milk of a goat. Note that in addition to Ganymede, Ospin (asteroid 113) is also known as Amalthea.

Calliste's shape is irregular, its three axes are 250×146×128 kilometers long, and its long axis points to Jupiter. It has craters on its surface, the largest of which is 100 km in diameter and 8 km deep compared to its size, and the other crater (Gaia) is 80 km in diameter and twice as deep as Pan can be. There are also two mountains on Callisto, which are 20 kilometers higher than the others.

Ganymede is the reddest object in the solar system, even redder than Mars. Its red color comes from sulfur from volcanic eruptions on Europa. There are also patches of green on the main slopes of Callisto, the origin of which is unknown. In March 1979, the Voyager 1 space probe found that Calliste was light gray, with a reddish area about 130 kilometers long and 200~220 kilometers wide.

Callisto emits more heat than it receives from the sun's rays, possibly due to the current it induces inside Jupiter's magnetic field. Ganymede is in the same family as the other three inner moons of Jupiter. Ganymede is the largest of them. Calliste's revolution and rotation period are the same. Like most of Jupiter's moons, Ganymede rotates synchronously, with its long axis pointing directly at Jupiter.

Europa has a particularly small density – roughly as dense as ice, although it doesn't have a lot of ice in its composition. Therefore, scientists believe that Callisto is not a monolithic structure, but a large pile of space pebbles that are gathered together by gravity. In some cases, adjacent pebbles will only gently collide with each other, and there will still be a vacuum between them. In all likelihood, Europto was originally a monolithic structure, but was later shattered into a pile of pebbles due to an impact with an asteroid.

The Galileo probe, which began its journey to Jupiter in October 1989, flew its first flight to Europa in 2011, completing a scientific exploration of Jupiter's high-radiation inner magnetosphere. Europa's gravitational pull may interfere with the spacecraft's radio emissions, which may help scientists understand Callisto's mass and structure. It was also Galileo's last scientific exploration activity.

However, due to the intense radiation interference it encountered as it approached Jupiter's surface, Galileo stopped all normal operation and the system went into "safe" mode. All data collected by the probe must wait for the technician to restart the system before it can be sent back to the ground remote control center.

Galileo flew over Europto at a distance of 160 km. Galileo has approached Jupiter's other moons 30 times, but this is the first time it has reached the orbit of Ganymede.

When Galileo flew to Callisto, a few seconds after flying over Callisto, Galileo entered Callisto's "Spider Web Ring" (Gossame).

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g)。 The spacecraft then passes through Jupiter's inner magnetosphere, which is filled with all kinds of charged particles and the radiation is very intense. Scientists point out that the data collected by the spacecraft will help reveal more deeply the "secrets" of Jupiter's magnetosphere, and that studying Jupiter's "mysterious" rings can help explain why Jupiter did not become a star, and that engineers will help design more powerful spacecraft.

Ganymede is the reddest object in the solar system, even redder than Mars. Its red color comes from sulfur from volcanic eruptions on Europa. There are also patches of green on the main slopes of Callisto, the origin of which is still unclear.

Calliste's shape is irregular, its three axes are 250×146×128 kilometers long, and its long axis points to Jupiter. It has many impact craters on its surface, and they are somewhat very large compared to its size. The largest of these is Pan crater 100 km in diameter and 8 km deep, and the other crater (Gaia crater) is 80 km in diameter and is probably twice as deep as Pan. There are also two mountains on Callisto, which are 20 kilometers higher than the others.

Callisto's size and irregular shape may indicate that it is a very sturdy object, otherwise its shape would have become more rounded over time. It could be an asteroid captured by Jupiter. Like Jupiter's other moons, Ganymede has the same period of revolution and rotation. Like Io, Calmede emits more heat than it receives from sunlight, possibly due to the current it induces in Jupiter's magnetic field.

After Hua Feng and Yun Meng briefly remembered the situation of Guardian, they began to understand Guardian, and at this moment, the world outside the dungeon was quietly changing.

Enceladus is named after a titan giant from Greek mythology. At that time, William Herschel's son, John Herschel, in his 1847 book "Results of Astronomical Observations at the Cape of Good Hope", named seven known moons of Saturn, including Enceladus, after the Titans, on the grounds that Saturnus (the god of agriculture in Roman mythology, equivalent to Cronus in Greek mythology) was the leader of the Titans.

According to Riddle and Scott's Greek-English lexicon, Enceladus is used as an adjective for Mima

tea

(The possessive case is Mima in Latin.)

tis, Μῑμάντος in Greek). In practice, English adjectives are like Mima

sia

or Mimia

is very common, and the phrase "of Mimas" is used more often.