earth interior

The temperature inside the earth is as high as 5270K(4996.85? Celsius). The heat inside the planet comes from the "accretion" at the beginning of its formation (see gravitational binding energy). The subsequent heat comes from the decay of radioactive elements such as uranium, thorium and potassium. The heat reaching the surface from the interior of the earth is only 1/20000 of the solar energy received by the surface.

Depth? Inner layer?

Kilometers? Miles.

0–60? 0–37? Lithosphere (about 5 or 200 kilometers away)?

0–35? 0–22? Crust (about 5 or 70 kilometers away)?

35–60? 22–37? Outer mantle (magma)?

35–2890? 22– 1790? Manto?

100–700? 62–435? Asthenosphere?

2890–5 100? 1790–3 160? Extraterrestrial nucleus?

5 100–6378? 3 160–3954? The core of the earth?

Earth core

The average density of "Earth" in the profile of the internal structure of the Earth is 55 15kg/m3, which is the planet with the highest density in the solar system. However, the density of materials on the earth's surface is only about 3000kg/m3, so it is generally believed that there are high-density materials in the earth's core-in the early days of the formation of the earth, about 4.5 billion years ago (4.5× 109), the earth was almost composed of molten metal, which led to the process of high-density materials gathering to the center of the earth and low-density materials moving to the surface (see planetary differentiation). The core is mostly composed of iron (80%), and the rest is basically nickel and silicon. High-density elements such as uranium are either rare elements on the earth or exist in the earth's crust in the form of light elements (see Chang Ying Mineral Entry).

The core is located in the Guggenheim discontinuity, and it is divided into two parts: the core with a radius of about 1250km, that is, the G layer, and the liquid outer core outside the core until it is about 3500km away from the center of the earth, that is, the E layer and the F layer. F layer is the transition layer between the core and the mantle.

Generally speaking, people think that the earth's core is a solid core mainly composed of iron and a part of nickel. Another different view is that the inner core may be composed of single iron crystals. The outer core wrapped in the outer layer of the inner core is generally considered to be composed of liquid iron mixed with liquid nickel and other light elements. Usually, people think that the convection of the outer core and the rapid rotation of the earth-with the help of generator theory (see Coriolis force)-are the reasons for the geomagnetic field. The solid core is too hot to produce a permanent magnetic field (see Curie temperature). But the inner core can still maintain the magnetic field generated by the liquid outer core.

Recent observational evidence shows that the rotation speed of the inner core may be a little faster than that of other parts of the earth, with a difference of about 2 degrees every year.

[editor]? Dihan

The area extending from Guggenheim discontinuity with a depth of about 2900 kilometers to Mohs discontinuity with a depth of about 33 kilometers around the core is called the mantle. The pressure at the bottom of the mantle is about 1.40 ATM( 140 GPA). Most of them are composed of substances rich in iron and magnesium. The melting point of a substance depends on the pressure it is under. With the increase of the depth into the mantle, the compressive stress also increases gradually. The lower part of the ground function is generally considered to be solid, while the upper part of the ground function is generally considered to be composed of more plastic solid substances. The viscosity of the substance in the ground function is between 102 1 to1024 pa s, and the specific data changes with depth [2]. The huge compressive stress causes the continuous deformation of the ground functional materials, so the upper part of the ground functional deformation has the ability to flow very slowly.

The inner core of the earth is solid and the outer core is liquid, but the mantle is solid and plastic. The reason is the melting point of different formation materials and the temperature and compressive stress increasing with depth. When the surface temperature is low enough, the main components of nickel-iron alloy and silicate are solids. Silicate in the upper mantle is basically solid and partially melted, but its viscosity is relatively low due to high temperature and low compressive stress. However, due to the huge compressive stress, the viscosity of the lower mantle is much higher than that of the upper mantle. Due to the low melting point of the alloy, the metallic nickel-iron outer core has only a large compressive stress, but it is liquid. Finally, the huge compressive stress keeps the core strong.

[editor]? (Crust)

The crust refers to the underground area with an average depth of about 33km from the ground to Moho. The thin ocean bottom shell is composed of high-density mafic silicate (mafic rock). Magnesite is the basic raw material of ocean basin. The thick continental crust is composed of low density potassium sodium aluminosilicate (felsic mineral). The boundary between the crust and the mantle presents different physical characteristics: First, there is a physical boundary called Mohorovicic interface, which changes the propagation rate of seismic waves. It is generally believed that the reason for the boundary surface is that the upper rock contains plagioclase and the lower rock contains no feldspar. The second difference is that chemical changes have taken place between the crust and the mantle-the difference between ultraalkaline deposits without magnetic field in the deep ocean crust and plagioclase, and the difference between ophiolite produced by the extrusion of the ocean crust on the continental crust.

raw material

4.5 billion years ago, the surface of the moon was still a sea of liquid magma. Scientists believe that the mineral KREEP, which constitutes the moon, shows the chemical clues left by the magma ocean. KREEP is actually a component called "incompatible element" by scientists-substances that cannot enter the crystal structure are left behind and float to the surface of magma. For researchers, KREEP is a convenient clue to understand the volcanic history of the lunar crust and infer the frequency and time of the impact of comets or other celestial bodies.

The lunar crust consists of many major elements, including uranium, thorium, potassium, oxygen, silicon, magnesium, iron, titanium, calcium and aluminum. And hydrogen. When bombarded by cosmic rays, each element emits specific gamma radiation. Some elements, such as uranium, thorium and potassium, are already radioactive, so they can emit gamma rays by themselves. But whatever the reason, the gamma rays emitted by each element are different, and each element has its own unique spectral line characteristics, which can be measured by spectrometer.

Until now, human beings have not made a comprehensive measurement of the abundance of moon elements. At present, the measurement of spacecraft is limited to a part of the moon. For example, in 1992, Galileo once measured the element abundance while flying over the moon. [3]

[editor]? Surface geography

The shape of the moon is a flat ball, with the north and south poles slightly flat and the equator slightly higher. Its average polar radius is 500 meters shorter than the equatorial radius. The polar regions are also asymmetrical, with the Arctic region uplifting and the Antarctic region sinking by about 400 meters. But in general calculation, the moon can still be regarded as a triaxial ellipsoid. The study of physical libration is helpful to solve the problem of moon shape. The study of libration also shows that the center of gravity of the moon does not coincide with the geometric center, and the center of gravity is 2 kilometers away from the earth. This conclusion has been confirmed by the data obtained by Apollo landing on the moon.

There are tens of thousands of craters with a diameter exceeding 1 km on the surface of the moon. Most lunar craters have a history of hundreds of millions of years. The lack of atmospheric and meteorological activities and recent geological activities ensure that most of them remain intact forever.

The Antarctic-Aitoken Basin is the largest known crater in the moon and solar system. This crater is located on the back of the moon, near the south pole, with a diameter of about 2? 240 kilometers, 13 kilometers deep.

Those dark and uncharacteristic moon plains are called "Moon Sea" because ancient astronomers thought it was an ocean. In fact, the Moon Sea was formed by basalt magma that flowed out of the lunar mantle and covered the surface after being hit by a huge meteorite. The lighter highland is called "Moon Land". Almost only the moon facing the earth has a moon sea, and the back of the moon is rare. Astronomers believe that this is because the center of mass of the moon is closer to the earth than the center of mass.

There is a dusty rock layer on the lunar shell, which is called lunar soil, not soil. The lunar crust and lunar soil on the surface of the moon are unevenly distributed. The thickness of the lunar crust varies from 60km (the front of the moon) to 100km (the back of the moon), while the thickness of the lunar soil varies from about 5m (the moon sea) to more than 10m (the land of the moon).

In 2004, Ben of Johns Hopkins University? The team led by Dr. Bussey discovered Peary in the North Pole of the Moon from the photos taken by the Clementine mission. Four areas along the crater are often exposed to sunlight (but no similar areas have been found in Antarctica). These perennial sunshine zones are produced because the inclination of the moon's axis is very small. Similarly, there are many craters at the poles, and there is often no light.

[editor]? The existence of water

Comets and meteorites have been hitting the moon since ancient times. Most of these objects contain water. Energy from sunlight breaks down most water into its constituent elements, hydrogen and oxygen. Both usually fly away from the moon immediately. However, some scientists have put forward the hypothesis that there is still a considerable amount of water on the moon, such as on the surface of the moon or deep in the lunar shell. The Clementine mission of the United States shows that some tiny water ice cubes (fragments after the impact of water-containing comets) may be hidden in a permanently sunless area of the lunar shell and not melted. Although these ice cubes are small, the total amount of water may be considerable (about 1 cubic kilometer).

And some water molecules may also fall into the crater and hide in it when the moon bounces. Because the rotation axis of the moon is slightly inclined to the normal of the ecliptic plane by 65438 0.5 degrees, the bottom of some polar craters has never been exposed to sunlight and is in a permanent shadow. The Clementine mission once measured these craters at the south pole of the moon [1] and drew a map [2]. Scientists hope that water ice can be found in such craters, and solar energy, electricity or nuclear energy can be exploited and used for electrolysis into hydrogen and oxygen. The amount of water available on the moon greatly affects the cost of living on the moon, because it is impractical to transport water (or hydrogen and oxygen) from the earth.

The rocks collected by Apollo astronauts near the equator of the moon do not contain water. Lunar probes and other recent studies (such as the Smithsonian Institution) have found no direct evidence of liquid water, ice or water vapor. However, the results of the lunar probe show that there is hydrogen in the permanently sunless area, which may exist in the form of water ice.

[editor]? magnetic field

Compared with the earth, the magnetic field of the moon is very weak. The magnetic field in some areas is thought to come from the moon itself (for example, the moon shell on the Sirsalis Moon Creek), but the collision with other celestial bodies may also change its magnetic field. Whether a celestial body without an atmosphere can obtain a magnetic field through the collision of comets and asteroids is a long-standing and often new problem in planetary science. Measuring the lunar magnetic field can provide data such as the size and conductivity of the lunar nucleus, which is very helpful for scientists to understand the origin of the moon. If the lunar core contains more magnetic substances (such as iron) than the earth, then the origin theory of lunar impact is not so credible (although scientists have explained the reason why the lunar core contains less iron from other angles)

[editor]? atmosphere

The moon has an extremely thin atmosphere. One of the sources of these atmospheres is degassing-the release of gases, such as radon on the surface of the moon, which was originally hidden in the depths of the moon. Sometimes, the solar wind will be captured by the gravity of the moon and become another important gas source.