Overview of Mercury

Mercury or Mercury is the smallest and closest Sun planet among the eight Solar System planets, with an orbital cycle of 88 Earth days.

Viewed from Earth, the planet appears with orbital cycles of approximately 116 days, and faster than other planets. This fast movement made the Romans name the planet Mercurius, the god of communication and reporting quickly.

Since the planet has almost no atmosphere to retain heat, Mercury's surface experiences the largest temperature change among planets, ranging from 100 K (−173 ° C; −280 ° F). at night to 700 K (427 ° C; 800 ° F) during the day. Mercury's rotating axis has the smallest inclination in the Solar System (about 1⁄30 degrees), but the planet has the largest orbital eccentricity.

Mercury color photos taken by MESSENGER.

The structure of Mercury

Mercury is one of four Earth-like planets in the Solar System, and is a planet made of rock like Earth. This is the smallest planet in the solar system with an equatorial radius of 2,439.7km.

Mercury has a composition of about 70% of metal and 30% of silicate. The average density of Mercury is 5,427 g / cm ³ , the second highest in the Solar System, only slightly smaller than the Earth's own mass (5,515 g / cm ³ ). If the effect of gravitational compression pressure is ignored, the materials on Mercury may be denser with a specific mass of about 5.3 g / cm ³ in this case, 4.4 g / cm ³ .

The average density of Mercury can be used to conjecture its internal detailed structure. While the Earth's large density due to the significant contribution of gravitational compression, especially at the core, Mercury has a smaller volume and the core area is not as strongly compressed as Earth's. Therefore, because the planet has a high density, its core must be larger in size and contain more iron.

Geologists estimate that Mercury's core accounts for about 42% of its volume compared to Earth's by 17%. Recent research suggests that Mercury has a molten core.

Mercury's core contains more iron than any other planet in the Solar System, and many theories have been proposed to explain this. The most widely accepted hypothesis is that Mercury initially had the same silicate-metal ratio as the common chondrit meteorite, believed to be the typical ice-forming material of the Solar System, and has about a mass of about 2.25 times its current volume.

Mercury's orbit

Mercury orbit (yellow, brown) in 2006.

Mercury orbits its axis three times in the orbital cycle around the Sun, when it takes fixed stars as a frame of reference. If viewed from the Sun, in the frame of rotation in orbit, Mercury only rotates one round in two orbits of the planet. This exact ratio is due to the influence of the tide lock phenomenon. If a person stands on Mercury, they will only see the Sun move once in the sky, or only a "day" in 2 "five" Mercury.

Terrain on Mercury

The surface of Mercury has many large and jagged holes like the surface of the Moon, consisting of large plains and collisions, showing that it has experienced a quiet geological time of billions of years.

Mercury has been bombarded by comets and meteors for a short time after it formed 4.6 billion years ago, and in another phase 3.8 billion years ago. During the second bombardment, there were a lot of collisions across the planet's surface.

"Strange terrain" formed at the opposite point of the Caloris impact crater.

Craters and sinks collide

Mercury craters have diameters from small recesses to hundreds of kilometers wide. They are in a "weathered" state gradually, from relatively new radiations to long-existing pits that remain only faint traces. Collisions on Mercury are significantly different from the craters on the Moon because of the smaller range of materials fired after meteor hits, which is the result of Mercury's stronger gravitational field. compared to the Moon.

Plain on Mercury

There are two geologically different plains on Mercury.

1. 1 The craters / craters are the oldest features on the surface, [40] before the planet's surface is bombarded by meteors. The inter-crater plains appear to be blurred by impact craters earlier than before, and often only pits with a diameter of less than 30 km.
2. 2. Smooth flat plains are large areas with low altitudes and similar shapes to the "sea" on the Moon.

An unusual feature on the surface of Mercury is the appearance of many cliffs cutting through the plains. As the planet's core cools, its crust shrinks and leads to a distorted surface topography, which collapses to create these cliffs.

Surface environment and atmosphere of Mercury

Despite its small size and slow axial velocity, Mercury has a remarkable and seemingly distributed magnetic field across the entire planet.

Mercury's magnetic field is strong enough to deflect the solar wind around this planet, creating a magnetosphere.

Mercury probe

Two Earth spacecraft used to visit Mercury: Mariner 10 flew in 1974 and 1975; and MESSENGER, launched in 2004, turned around Mercury more than 4,000 times in four years. The ship ran out of fuel and fell on the planet's surface on April 30, 2015.