Hua Feng is clear that Europa is made up of Galileo and Ma

Discovered in 1610, the IUS is Jupiter's sixth known moon, the fourth largest of Jupiter, and the second closest to Jupiter among the moons discovered by Galileo. Europa is slightly smaller than Earth's moon, the moon.

Europa and Europa are similar in composition to terrestrial planets: mostly composed of silicate rocks. But unlike Europa, Europa has a thin crust of ice. Recent data from Galileo suggests Europa has an internal layered structure and may have a small metal core.

But Europa's surface doesn't resemble something from the inner solar system, it's extremely smooth: only a handful of terrain hundreds of meters high can be seen. The protruding marks appear to be only albedo characteristics or minor fluctuations. There are very few craters on Europa, and only three craters with a diameter of more than 5 km have been found. This surface has a youthful and active surface. However, Voyager made a small section of the surface high-definition map. Europa's apparent precise age is an open question.

Photos of Europa's surface are similar to those of ice in Earth's oceans. This may be due to a layer of liquid water beneath the ice on Europa's surface, perhaps 50 kilometers deep, and the heat from the gravitational forces remains liquid. If this were the case, it would be the only place in the solar system other than Earth where there is a large amount of liquid water.

Europa's most striking appearance is the strings of cross stripes that can be found all over the world. The larger one spreads outwards into a zone of pale material, nearly 20 kilometers long. The most recent theory of their origin is that they are produced by a series of volcanic ejections or fountains.

Recent observations from the Harbour Telescope have revealed that Europa has an oxygen-containing rarefied atmosphere (1e-11 bar). Only 4 of the 63 moons in the solar system (Io, Callisto, Titan, and Triton) are known to have atmospheres. Unlike oxygen in Earth's atmosphere, Europa is not biologically formed. It is most likely due to the production of water vapor from charge particles in sunlight hitting Europa's icy surface, which however splits into hydrogen and oxygen. The hydrogen detached, leaving behind oxygen.

Europa was replaced by Galileo and Ma

The IUS was discovered in 1610. It is the largest known moon of Jupiter and the seventh moon of Jupiter to be discovered, and the third closest to Jupiter among the moons discovered by Galileo.

Ganymede is the largest moon in the solar system, larger in diameter than Mercury but half as massive. Europa is much larger than Pluto.

Prior to Galileo's contact with Callisto, it was generally believed to be a stony mass with Europa encased in a large mixture of water or ice-water as a mantle, and to have an ice crust (similar to Titan and Triton).

Preliminary data from Galileo suggest that Europa has a unique composition, while Europa has three layers: a small core of iron or iron sulphides with a silicate rock mantle on the outside and an ice crust on the outside. In fact, Europa is extremely similar to Europa except for an ice shell.

The surface of Ganymede is rough, with a mix of two types of terrain: very old, dark areas full of craters, and relatively young, brighter areas with large grooves and ridges. Their origin is apparently due to natural formation, but the details are not clear. In this respect, Ganymede may be similar to Earth, as well as to Venus or Mars (although there is no recent evidence of crustal activity).

The Hubble telescope has found evidence that Europa has a thin oxygenated atmosphere, very similar to that found on Europa. (This is definitely not evidence of life). Similar grooves with ridge topography are also visible in Titan, Enceladus and Enceladus. The Dark Zone is similar to the surface of Callisto.

Both terrains have extended craters, and the density of craters reflects that it is 30-3.5 billion years old, not much like the Moon. The crater is sometimes cut off by grooves, indicating that the grooves are also ancient. The rather young crater can also be seen through the light emitted. But unlike the Moon, the craters are flat, lacking a ring of mountains, and the central depression is usually the same as on the Moon and Mercury. This may be due to the fragile ice crust of Ganymede, which allows the ground to flow and lack undulations. Ancient craters are gradually erased and are often referred to as "overpaintings".

When the Galileo spacecraft first flew by Ganymede, it discovered that it had its own magnetic field, contained in Jupiter's giant magnetic field. This may be similar to the reason for the formation of the Earth: the interior of the stars

It was created by Galileo and Ma

The IUS was discovered in 1610. It is the eighth closest known moon to Jupiter and the second largest in diameter. Of the moons discovered by Galileo, it is the farthest from Jupiter.

Calmede is slightly smaller than Mercury, but only a third of its mass. Unlike Callisto, Callisto's internal structure is almost non-existent, and it is always composed of more or less 40% ice and 60% rock or iron. This may be similar to Titan and Triton.

Callisto's surface is full of craters, and the surface is very old, like the plateaus on the Moon and Mars. Calmede has the surface with the most craters of the oldest surface observed in the solar system, with only minor changes in the long 4 billion years, except for occasional impacts.

Some of the larger craters are surrounded by a string of concentric rings, like cracks, but the slow movement of the ice has smoothed it out over the years. The largest of these, known as Valhalla, is 4,000 kilometers in diameter and is a prime example of a multi-ring basin that results from a violent impact. Other examples are Ganymede's Asga

d), O in the shadowy part of the lunar surface

ie

Tale and Calo on Mercury

IS Basin.

Similar to Ganymede, Callisto's ancient crater has collapsed. They lack all the tall rings of mountains, radial rays, and central depressions on the Moon and Mercury. Clear pictures from the Galileo show that, at least in some areas, small craters have disappeared. This suggests that some movements are underway, whether others are in decline or not.

Another peculiar topographical phenomenon is the Gipul Cate

a, a series of striking craters arranged in a straight line. This may be caused by the gravitational pull of an object that breaks off (very similar to Comet Shoemaker Levi 9) as it approaches Jupiter and then crashes into Callisto.

Unlike Ganymede, it has complex terrain, but there is little evidence of crustal movement on Callisto. Most of its properties are the same as those of Ganymede, so it should have a similar geographical history to Ganymede. The different geographical histories of these two moons are an important puzzle for planetary science. (This may have something to do with Callisto's orbit and changes in gravitational forces) Taken "simply", Europa is an ideal reference when comparing other complex planets, and it may also tell us about the early history of other moons discovered by Galileo.

Beijing time, February 5, 2008 According to foreign media reports, there may not be a few celestial bodies in the universe that have life. Some scientists believe that in the solar system alone, it is possible that life exists not only on Mars, but also on other celestial bodies. And Mikhail Marov, an academician of the Russian Academy of Sciences, even believes that life may exist on such celestial bodies as Europa, the moon of Jupiter.

"Flying to those distant planets is of high scientific value," Marov said. From the point of view of the search for life, Mars is not the only planet to choose from. Scientists believe that there is an ocean under the thick ice on the surface of Europa, and at the same time do not rule out the possibility of some kind of life activity there. ”

Marov said that humanity now has the technical ability to fly to distant planets, but the reliability of existing technical equipment must also be improved to effectively support long interstellar travel.

"To get to Jupiter, for example, would require a probe to go on a long four-year flight," he said. In this way, a high level of reliability must be ensured for the various instruments. ”

In addition, Vladimir Shokovich, president of the Russian Academy of Space Sciences, also announced to reporters that Russia is indeed developing a new manned spacecraft.

"The 'Power' Rocket-Space Technology Corporation is developing a new spacecraft that can carry six astronauts - the 'Three-masted Sailing'. The spacecraft can be used to transport people and supplies to the space station, and can also operate in orbit for long periods of time. ”

He declared that Russia's new generation of domestically produced space station is also under development, and it will be put into operation when the current ISS expires.

Lavochkin is Russia's leading enterprise for designing, manufacturing and testing interplanetary automatic probes and various earth satellites.

At a time when the development of a series of launch vehicles is in full swing, the Institute of Medicine and Biology of the Russian Academy of Sciences will also carry out experimental activities on the topic of training astronauts for long space flights. According to the institute's staff, cosmonaut Valery Polyakov, "the Russian Institute of Medicine and Biology has begun to conduct experimental topics related to long space flights. ”

Astronomy is often understood simply as the application of existing laws of physics to explain observed astronomical phenomena.

In fact, because the various strange states in which celestial bodies are located provide a large number of physical states that cannot be realized on the ground, a large number of astronomical observations actually provide observational facts for the establishment of new physical laws, such as the establishment of Newton's formula of universal gravitation, which is based on Kepler's three laws of planetary motion. The phenomenon of optical travel related to the establishment of the theory of relativity was also first discovered in astronomical observations.

An important constant in modern physics was also obtained in 1676 by the French astronomer Romer from his observations of Europa. From all the observations made of light propagation, we know that the speed of light is enormous, and Galileo tried to measure this speed with light signals, but was unsuccessful, because it only took a very short time for light to pass a distance on the ground. Therefore, the only way to make such a successful measurement is to make use of the enormous distances between celestial bodies in astronomical space.