The most important astronomical discoveries in the history of space exploration are associated with the name of Galileo Galilei. It was thanks to this talented and persistent Italian that the world in 1610 first learned about the existence of the four moons of Jupiter. Initially, these celestial objects received a collective name - Galilean satellites. Later, each of them was given a name: Io, Europa, Ganymede and Callisto. Each of the four largest satellites of Jupiter is interesting in its own way, but it is the Io satellite that stands out among the other Galilean satellites. This celestial body is the most exotic and unusual among other objects of the solar system.
What is unusual in the satellite Io?
Already with one observation through a telescope, the satellite Io stands out for its appearance among other satellites of the Solar system. Instead of the usual gray and muddy surface, the heavenly body has a bright yellow disc. For 400 years, man could not find the reason for such an unusual color of the surface of the Jupiter satellite. Only at the end of the 20th century, thanks to the flights of automatic space probes to giant Jupiter, was it possible to obtain information about the Galilean satellites. As it turned out, Io is perhaps the most volcanically active object of the solar system in terms of geology. This was confirmed by the huge number of active volcanoes discovered on the satellite of Jupiter. To date, they identified about 400 and it is on the area, which is 12 times smaller than the area of our planet.
The surface area of the satellite Io is 41.9 square meters. kilometers The Earth has a surface area of 510 million km, and on its surface today there are 522 active volcanoes.
In terms of its size, many Io volcanoes exceed the size of terrestrial volcanoes. According to the intensity of the eruptions, their duration and power, the volcanic activity on the satellite of Jupiter exceeds the similar terrestrial indicators.
Some volcanoes of this satellite emit a huge amount of poisonous gases to an altitude of 300-500 km. At the same time, the surface of the most unusual satellite of the Solar System Io is a vast plain, in the center of which there is a huge mountain range, divided by huge lava flows. The average heights of the mountain formations on Io are 6-6.5 km, but there are also mountain peaks here, more than 10 km high. For example, the mountain South Boosavla has a height of 17-18 km and is the highest peak of the solar system.
Almost the entire surface of the satellite is the result of centuries-old eruptions. According to instrumental studies conducted from the Voyager-1, Voyager-2 space probes and other devices, the main surface material of the Io satellite is frozen sulfur, sulfur dioxide and volcanic ash. Why multi-colored areas on the surface of the satellite so much. This is due to the fact that active volcanism constantly forms the characteristic contrast of the coloring of the surface of the satellite Io. An object can change its bright yellow color to white or black for a short time. The products of volcanic eruptions form a thin and heterogeneous composition of the atmosphere of the satellite.
Such volcanic activity is caused by the peculiarities of the structure of the celestial body, which is constantly exposed to the tidal action of the gravitational field of the mother planet and the effects of other large satellites of Jupiter, Europe and Ganymede. As a result of the influence of cosmic gravity in the depths of the satellite, friction arises between the crust and the inner layers, generating natural heating of matter.
For astronomers and geologists who study the structure of objects in the solar system, Io is a real and active testing ground, where processes characteristic of the early period of the formation of our planet occur. Scientists in many fields of science today carefully study the geology of this celestial body, making the unique satellite of Jupiter Io the object of close attention.
Interesting facts about the satellite Io
The most geologically active celestial body in the solar system has a diameter of 3,630 km. Io's dimensions are not that big compared to other satellites in the solar system. In terms of its parameters, the satellite takes a modest fourth place, passing forward the huge Ganymede, Titan and Callisto. The diameter of Io is only 166 km. exceeds the diameter of the Moon - Earth satellite (3474 km).
The satellite is closest to the mother planet. The distance from Io to Jupiter is only 420 thousand km. The orbit has almost the correct form, the difference between perihelion and apogelium is only 3400 km. The object rushes in a circular orbit around Jupiter with a huge speed of 17 km / s, making a complete rotation around it in 42 Earth hours. Movement in orbit is synchronized with the rotation period of Jupiter, so Io is always turned to him by the same hemisphere.
The main astrophysical parameters of a celestial body are as follows:
- Io's mass is 8.93x1022kg, which is 1.2 times the mass of the Moon;
- the density of the satellite is 3.52 g / cm3;
- the acceleration due to gravity on the surface of Io is 1.79 m / s2.
Observing the position of Io in the night sky, it is easy to determine the swiftness of his movement. The celestial body is constantly changing its position relative to the planetary disk of the mother planet. Despite the satellite’s rather impressive gravitational field, Io is not able to maintain a constantly dense and homogeneous atmosphere. The thin gas envelope around the moon of Jupiter is practically cosmic vacuum, does not prevent the release of eruption products into outer space. This explains the enormous height of the volcanic ejection pillars occurring on Io. In the absence of a normal atmosphere, low temperatures prevail on the satellite's surface, down to -183 ° C. However, this temperature is not uniform for the entire satellite surface. In the infrared images obtained from the Galileo space probe, the heterogeneity of the temperature layer of the Io surface was visible.
Low temperatures prevail on the main area of a celestial body. On the temperature map such areas are colored blue. However, in some places on the satellite surface there are bright orange and red spots. These are the areas of greatest volcanic activity, where eruptions are visible and clearly visible on ordinary images. Pele Volcano and Locke Lava Flow are the hottest areas on the surface of the Io satellite. The temperature in these areas varies from 100-130 ° below zero on the Celsius scale. The small red dots on the temperature map are craters of active volcanoes and fracture sites in the crust. Here the temperature reaches 1200-1300 degrees Celsius.
Satellite structure
Unable to land on the surface, scientists are now actively working on modeling the structure of the Jovian moon. Presumably the satellite consists of silicate rocks diluted with iron, which is characteristic of the structure of the terrestrial planets. This is confirmed by the high density of Io, which is higher than that of its neighbors - Ganymede, Callisto and Europe.
The modern model, based on data obtained by space probes, is as follows:
- in the center of the satellite, the iron core (iron sulfide), constituting 20% of the mass of Io;
- the mantle, consisting of minerals of asteroid nature, is in a semi-liquid state;
- liquid magma subsurface layer 50 km thick;
- The satellite lithosphere consists of sulfur and basalt compounds, reaching a thickness of 12-40 km.
Assessing the data obtained in the simulation, the scientists concluded that the satellite Io core must have a semi-liquid state. If sulfur compounds are present together with iron, its diameter can reach 550-1000 km. If it is a fully metallized substance, the size of the nucleus can vary between 350-600 km.
Due to the fact that no magnetic field was detected during satellite studies, there are no convection processes in the satellite core. Against this background, a natural question arises, what are the true causes of such intense volcanic activity, where do Io volcanoes draw their energy?
The minor size of the satellite does not allow us to say that the heating of the bowels of a celestial body is carried out due to the reaction of radioactive decay. The main source of energy inside the satellite is the tidal effect of its cosmic neighbors. Under the influence of gravity of Jupiter and neighboring satellites, Io oscillates, moving in its own orbit. The satellite seems to be swinging, experiencing a strong libration (uniform rocking) while it is moving. These processes lead to the curvature of the surface of a celestial body, causing thermodynamic heating of the lithosphere. This can be compared with the bend of a metal wire, which at the bend site is very hot. In the case of Io, all these processes occur in the surface layer of the mantle on the border with the lithosphere.
The satellite is covered above by sediments - the results of volcanic activity. Their thickness varies in the range of 5-25 km in places of main localization. In their color, these are dark spots, strongly contrasted with the bright yellow surface of the satellite, caused by the outpourings of silicate magma. Despite the large number of active volcanoes, the total area of volcanic calderas on Io does not exceed 2% of the satellite surface area. The depth of volcanic craters is insignificant and does not exceed 50-150 meters. The relief on most of the celestial body is flat. Only in some areas there are massive mountain ranges, for example, the complex of the Pele volcano. In addition to this volcanic formation on Io, the mountain massif of the Pater Ra volcano, mountain chains and massifs of various lengths are revealed. Most of them have names that are consonant with earth toponyms.
Io's volcanoes and its atmosphere
The most interesting objects on the satellite Io are its volcanoes. The size of areas with increased volcanic activity ranges from 75 to 300 km. Even the first Voyager during its flight recorded the eruption of eight volcanoes at once on Io. A few months later, the pictures taken by the Voyager spacecraft in 1979 confirmed the information that the eruptions at these points are continuing. At the place where the largest volcano Pele is located, the highest surface temperature was recorded, +600 degrees Kelvin.
Subsequent studies of information from space probes allowed astrophysicists and geologists to divide all Io volcanoes into the following types:
- the most numerous volcanoes, which have a temperature of 300-400 K. The gas emission rate is 500 m / s, and the height of the emission column does not exceed 100 km;
- The second type includes the hottest and most powerful volcanoes. Here you can talk about temperatures in 1000K in the caldera of the volcano itself. This type is characterized by a high ejection velocity of 1.5 km / s, the giant height of the gas sultan is 300-500 km.
Pele Volcano belongs to the second type, having a caldera with a diameter of 1000 km. Deposits as a result of the eruptions of this giant occupy a huge area - one million kilometers. Another volcanic object, Pater Ra, looks no less interesting. From orbit, this portion of the satellite’s surface resembles a marine cephalopod. Serpentine lava flows, extending from the site of the eruption, stretched for 200-250 km. Thermal radiometers of space vehicles do not allow to accurately determine the nature of these flows, as is the case with the geological object of Loki. Its diameter is 250 km and in all likelihood this lake is filled with molten sulfur.
The high intensity of the eruptions and the enormous scale of the cataclysms not only constantly change the relief of the satellite and the landscape on its surface, but also form a gas envelope - a kind of atmosphere.
The main component of the atmosphere of the satellite of Jupiter is sulfur dioxide. In nature, it is a sulfur dioxide gas with no color, but with a strong odor. In addition to sulfur dioxide, sulfur monoxide, sodium chloride, sulfur atoms and oxygen atoms were detected in the Io gas interlayer.
Sulfur dioxide on Earth is a common food additive, which is widely used in the food industry as a preservative E220.
The thin atmosphere of the satellite Io is uneven in its density and thickness. The atmospheric pressure of the satellite is also characterized by this inconsistency. The maximum value of atmospheric pressure Io is 3 nbar and is observed in the region of the equator in the hemisphere, facing Jupiter. Minimum values of atmospheric pressure are found on the night side of the satellite.
The sultans of hot gases are not the only visiting card of Jupiter’s satellite. Even with the presence of a strongly dispersed atmosphere, auroras can be observed in the equatorial region above the surface of a celestial body. These atmospheric phenomena are associated with the effect of cosmic radiation on charged particles entering the upper atmosphere during the eruption of Io volcanoes.
Io satellite research
A detailed study of the planets of gas giants and their systems began in 1973-74 with the missions of the Pioner-10 and Pioneer-11 space probes. These expeditions provided scientists with the first images of the Io satellite, on the basis of which more accurate calculations were made of the size of the celestial body and its astrophysical parameters. Behind the Pioneers, two American space probes, Voyager 1 and Voyager 2, set off to Jupiter. The second unit succeeded in getting as close to Io as possible at a distance of 20 thousand km and making better pictures at close range. It was thanks to the work of Voyagers that astronomers and astrophysicists obtained information on the presence of active volcanic activity on this satellite.
The mission of the first space probes, who studied outer space near Jupiter, was continued by the NASA Galileo spacecraft, launched in 1989. After 6 years, the ship reached Jupiter, becoming its artificial satellite. In parallel with the study of the giant planet, the automatic probe Galileo was able to transmit data on the surface of the satellite Io to Earth. During orbital flights from the space probe, terrestrial laboratories received valuable information about the structure of the satellite and data on its internal structure.
After a short break in 2000, the NASA and ESA Cassini-Huygens space probe intercepted the baton in the study of the most unique satellite of the Solar System. The study and examination of the Io apparatus was engaged during his long journey to Titan - the satellite of Saturn. The most recent satellite data was obtained using the New Horizons modern space probe, which flew near Io in February 2007 on the way to the Kuiper belt. A new batch of images presented to scientists ground observatories and the Hubble Space Telescope.
Currently, NASA's Juno spacecraft is operating in Jupiter’s orbit. In addition to the study of Jupiter, its infrared spectrometer continues to study the volcanic activity of the satellite Io. The data transmitted to Earth allows scientists to monitor active volcanoes on the surface of this interesting celestial body.
