Hua Feng understands that unlike many moons of the outer solar system, Europa has many similarities with terrestrial planets, its surface is composed of silicate lava, and according to Galileo's observations, its core may be composed of iron sulfide, and its radius is estimated to be at least 900 kilometers.

It was previously thought that Europa must have had a number of craters on the surface. However, from the photographs that Voyager 1 sent back to Earth in 1979, there are not many craters on the surface of Io, not as one might think, because its volcanic activity has changed its topography.

As a result, people regard its constantly renewing surface as "young" because the terrain is newly formed, and on the contrary, the surface of the moon is full of craters and has been retained for billions of years, and the surface of the moon is considered "old".

Outside of volcanoes, Io's other landscapes are just ordinary mountains, lakes of melting sulfur, caldas hundreds of kilometers deep, and hundreds of kilometers of low-viscosity liquids, which may be liquid sulfur or silicates. In addition, Io's sulfur and its compounds come in a variety of colors, giving it a unique and varied appearance.

Scientists analyzed multiple photographs sent back from the two Voyagers and believed that the lava flow on Europa's surface was mainly composed of melted sulfides.

However, from the results of infrared studies on the ground, the temperature of the Io hot spot can be as high as 2000 K, which is 1300 K higher than the boiling point of sulfur, so it is unlikely that these lava rocks are sulfur, and the overall average temperature of Io is 130 K, which is much lower than the hot spot temperature, and the latest theory also points out that those lava flows are composed of silicates. According to observations from the Hubble Space Telescope, these substances may be rich in the metallic element sodium, and may also contain different substances in different places.

Europa's atmosphere is extremely thin, only one billionth of the Earth's atmospheric pressure, and its main component is sulfur dioxide, but also small amounts of sodium chloride, sulfur monoxide and oxygen.

While the other Galilean moons have solid water, Io contains very little water, and it is thought that early Jupiter was so hot that its heat could evaporate water from Europa, but not enough for other large moons.

All of its energy may come from its interactions with Europa, Europa, and Jupiter

Tidal force. The co-motion of these three moons is fixed, and the orbital period of Europa is half that of Europa, which is half that of Europa. Although Europa, like Earth's moon moon, only has a fixed side facing its host star, Europa and Europto make it a little unstable. It causes Europa to twist and bend, about 100 meters long, and generates energy in a cycle of healing twists.

Io also cuts Jupiter's magnetic field lines, generating an electric current. The resulting energy is not much for the gravitational force, but the power of the current is still 1 megawatt. It also strips away some of Io's material and produces intense convex-like radiation around Jupiter. The particles that detach from the bulge partially create Jupiter's massive magnetosphere.

The Moon, the Earth's moon, is slightly larger, with an average radius of 1,821.3 kilometers (about 5% more than the Moon) and a mass of 8.9319×10 kilograms (about 21% more than the Moon). It is slightly ellipsoidal in shape, and its longest axis is directed towards Jupiter. In the Galileo moons, Io is smaller in mass and volume than Gaymede and Carristo, but larger than Europa.

Composed mainly of silicate rocks and iron, Io is closer to the structural body of terrestrial planets than any other moon in the outer solar system, and the others are mostly composed of a mixture of crushed ice and silicate. With a density of 3.5275 g/cm, Io is the densest of the solar system's moons, significantly higher than the other Galilean moons, and higher than the Earth's Moon.

Based on the mass, radius and quadrupole gravitational coefficient (a numerical value on how the mass is distributed internally) measured by Voyager and Galileo, it is suggested that there is a difference between its interior and exterior, with a silicate-rich shell and an inner mantle, iron or iron sulfide - rich in the core, and the mass of the metal core accounts for about 20% of the mass of Io. Depending on the sulfur content in the core, the radius of the core is between 350 and 650 km (220 to 400 mi) if it is composed entirely of iron, and 550 to 900 km (310 to 560 mi) if it is composed of a mixture of iron and sulphur. Galileo's magnetometer did not detect the magnetic field inside Io, so it is believed that there is no convection in the core.

The model also suggests the composition of the Io's interior, where the mantle is at least 75% composed of the magnesium-rich mineral olivine, and that there are a large number of meteorites similar to the L chondrite and the LL chondrite, and that there is a higher iron content (compared to the silicon of the Earth's moon moon, but still lower than that of Mars) to maintain the heat flux observed on the Io, where 10-20% of the mantle may be dissolved, but the volcanic areas where high temperatures are observed, perhaps have a higher proportion of being melted. Due to extensive volcanism, the lithosphere of Io, composed mainly of sulfur and basalt, is at least 12 kilometers (7 miles) thick, but not more than 40 kilometers (25 miles).

Unlike the Earth and the Moon, the heat sources inside Io come mainly from tidal dissipation rather than the decay of radioactive isotopes, which is the result of the resonance of Io's orbit with Europa and Gaymede. Such heating is related to the distance between Jupiter and Io, the eccentricity of the orbit, its internal structure and physical state. It resonates with Europa and Gaymede's Laplace, maintaining Io's eccentricity and preventing it from rounding its orbit due to tidal escape.

Orbital resonance also helps Io maintain a distance from Jupiter, which would otherwise cause Io's orbit to spiral from the outside to the inside towards the parent planet. The tidal uplift of Io has a vertical variation of 100 m (330 ft) between the near and far timber points in the orbit.

As a result of this tidal pulling, friction or tidal dissipation in the interior of Io, if there is no orbital resonance, these will make Io's orbit more rounded, creating greater tidal heating in Io's interior, causing more of the moon's mantle and core to melt. The resulting energy is greater than 200 times that of radioactive decay, and this heat is released in the form of volcanic activity, resulting in high heat flows observed (global total: 0.6 to 1.6×10 watts). Its orbital model suggests that tidal heating inside Io changes over time, and that the current heat flow is not representative of long-term averages.

Based on their experience with ancient surfaces such as the Moon, Mars, and Mercury, scientists expect to see many impact craters on the first image of Io sent back by Voyager 1. The density of craters across the surface could have given Io's age, but they were surprised to find that there were almost no craters on the surface, instead there were smooth plains and craters and lava flows of all sizes.

Compared to the points that have been observed in various places, the surface of Io has a variety of materials composed of different sulfur (compared to the color of Io's leading hemispheres with rotten oranges or pizza). The lack of impact craters indicates that Io's surface is young, like the surface of the Earth, and that the crater has been buried by the endless volcanic material they have created. A brief observation by Voyager 1 confirmed this spectacular scenario, with at least 9 active volcanoes present.

The colorful surface of Io is the result of its extensive volcanism resulting in a wide variety of materials, including silicates (e.g., rhodoxoxene), sulphur and sulphur dioxide frosts that span and are ubiquitous on the surface of Io, forming vast areas of white or grey material. Sulfur, which is scattered in the mid-latitudes and polar regions, is often damaged by radiation, resulting in the destruction of stable 8-chain sulfur. This radiation damage causes the polar regions of Io to take on a reddish-brown color.

Erupting volcanoes, often producing umbrella-shaped streams that coat the surface with sulfur and silicate materials. The sediment on the surface of the stream beam will be white or red, depending on the amount of sulphur and sulphur dioxide in the beam. Typically, the formation of flow beams from volcanoes containing large amounts of S2 results in red fan-shaped deposits or, in extreme cases, large red rings (in the main cases of heights up to 450 km (280 mi)).

A clear example of a red ring of flow beams is the Perei volcano, which is dominated by sulfur (usually a 3- or 4-chain sulfur molecule), sulfur dioxide, or Cl2SO2. Streams that form at the edge of the silicate lava (through the lava and previously deposited sulphur and sulphur dioxide) cause grey or white deposits.

Based on the structural diagram and high density of Io, it is believed that there is no or only a small amount of water in Io, although small caverns containing ice chips or water-bearing minerals have been detected, most notably in Gish Ba

Mo

s). The lack of water can be attributed to Jupiter's high enough heat in the early days that volatile substances near Io, like water, evaporated during the evolution of the solar system, but not enough heat to affect further afield.

Tidal heat triggered by Io's orbital eccentricity has forced the moon to become the most volcanically active body in the solar system, with hundreds of volcanic centers and scurrying lava flows. When a major eruption occurs, the main component is the silicate of basalt and the lava flow of iron-magnesian or ultra-iron-magnesian rocks ten times longer than usual and can be hundreds of kilometers long.

As a byproduct of these activities, materials such as sulfur, dioxide, and silicate debris (such as ash) can be blown up to 500 kilometers (310 miles) into the air, forming huge fan-shaped streams that provide red, black, and white to the surrounding terrain and a wide range of materials to complement the Io-Io atmosphere and Jupiter's vast magnetosphere.

The surface of Io, which is made up of sediment and has many points known as craters, which generally have high walls and a certain amount of flat surface. These features resemble caldas on Earth, and if they were cousins on Earth, they collapsed and caused the formation of some lava tubes, but these are still unknown.

There is a hypothesis that these features can be identified by the rock layers formed by the excavation of volcanoes, and the materials that have been superimposed on or excluded from the rock layers. Unlike the characteristics of Earth and Mars, these sediments do not have pinnacles at the center of shield volcanoes and are much larger, with an average diameter of 41 kilometers (25 miles) and the largest Rocky crater reaching 202 kilometers (126 miles) in diameter. Regardless of the mechanism of formation, the morphology and distribution of many craters suggest that these features are structurally controlled, or at least half are related to mountains or faults.

These features are usually the hallmarks of volcanic eruptions, which may be lava flows across the plains within the crater, such as the eruption of Mount Jixiba in 2001, or the formation of lava lakes. In Io's lava lake, there is a lava crust that constantly flips, such as the Peret volcano, or a crust with a flipping plot, such as the Loki crater.