Io (satellite)
Io is the closest Galilean satellite to Jupiter. It is the third largest satellite, has the highest density among all satellites and, proportionally, the least amount of water among all known objects in the solar system. It was discovered by Galileo Galilei in 1610. It gets its name from Io, one of the many maidens Zeus fell in love with in Greek mythology, although it was initially named Jupiter I because it was Jupiter's first satellite based on its proximity to the planet..
With a diameter of 3,600 kilometers, it is the third largest of Jupiter's moons. On Io there are very extensive plains and also mountain ranges, but the absence of impact craters suggests the geological youth of its surface. With more than 400 active volcanoes, it is the most geologically active object in the solar system. This high activity is due to due to tidal heating, which is the response to the dissipation of enormous amounts of energy from the friction caused inside the satellite. Several volcanoes produce clouds of sulfur and sulfur dioxide, which rise up to 500 km. Its surface also has more than a hundred mountains that have been raised by extreme compression at the base of the satellite's silicate crust. Some of these mountains are higher than Mount Everest.
Unlike most of the outer satellites of the solar system, which are covered in thick layers of ice, Io is composed primarily of a molten iron core encased in silicate rock.
Io played an important role in the development of astronomy during the 17th and 18th centuries, helping to adopt Copernicus' heliocentric model of the solar system and Kepler's Laws of planetary motion. The first measurement of the speed of light was made by Ole Rømer by measuring Io's period of translation.
History
Io was discovered by Galileo on January 7, 1610, the date on which he found next to Jupiter "three fixed stars, totally invisible due to their small size", as he noted in his diary. The next night he discovered a fourth star, and on subsequent nights he found that they orbited the planet, from which he deduced that they were satellites. They were Io, Europa, Ganymede and Callisto. Galileo initially called these moons "Medicean stars", in honor of his patron, Cosimo II de' Medici, but other astronomers did not like the proposal, who sought alternatives; Thus, the German Simon Marius, who claimed to have also discovered the moons even before Galileo, proposed names based on Greek mythology, which are known today. Galileo countered by proposing that they be called Jupiter I, II, III, and IV, names that were used until the early XX century, in that the names proposed by Marius were recovered. Jupiter's four moons are also known as the "Galilean satellites".
Physical characteristics
Unlike most satellites in the solar system, Io may have a chemical composition similar to that of telluric planets, mainly composed of silicate rocks. Recent data from the Galileo mission indicates that it may have an iron core with a radius of about 900 km.
When Voyager 1 returned the first close-up images of Io in 1979, scientists expected to find numerous craters whose density would provide insight into the satellite's age. Contrary to expectations, Io did not have craters. The satellite is subjected to such intense volcanic activity that it has completely obliterated signs of past impact craters on its surface. In addition to the volcanoes, the surface has the presence of non-volcanic mountains, molten sulfur lakes, volcanic calderas several kilometers deep, and extensive flows several hundred kilometers long, composed of very low viscous fluid material (possibly some type of compound of molten sulfur and silicates). Sulfur and its compounds take on a wide variety of colors, responsible for the surface appearance of the satellite. Infrared studies from the Earth's surface show that some of the hottest regions of the satellite, covered by lava flows, reach temperatures of up to 2 000 K (although average temperatures are much colder, closer to 130 K).
Io could have a thin atmosphere made up of sulfur dioxide and a few other gases. Unlike the other Galilean satellites, it is almost completely devoid of water. This is probably due to the fact that in the formation of the Galilean satellites, Jupiter was so hot that it did not allow the most volatile elements to condense in the region near the planet. However, these volatiles could condense further away, giving rise to the other satellites, which show a significant presence of ice.
As for the interior of the satellite, its composition can be intuited by studying its density, which is approximately 3.5 g/cm³. The density of iron is about 5, and that of silicate is 3, so the interior of Io must be made of rock material and sulfur.
In the depths of Io is possibly a core composed of heavier metallic elements such as iron. This nucleus is what gives rise to the magnetosphere of this satellite. This "pizza" it resembles a pizza due to its colors.
Volcanism
Io is the body in the solar system with the most volcanic activity. Its volcanoes, unlike the terrestrial ones, expel sulfur dioxide. The energy necessary to maintain this volcanic activity comes from the dissipation of the heat generated by the tidal effects produced by Jupiter, Europa and Ganymede, since the three satellites are in a particular case of orbital resonance called the Laplace resonance. Io's solid rock tides are eight times higher than those caused in Earth's oceans by gravitational interaction with the Moon.
Some of Io's eruptions emit material over 300 km high. The satellite's low gravity allows some of this material to be permanently ejected from the surface, distributing itself in a ring of material that covers its orbit. Subsequently, some of this material can be ionized and trapped by Jupiter's strong magnetic field. Ionized particles from Io's orbital ring are dragged by magnetic field lines to Jupiter's upper atmosphere where their impact with the atmosphere at ultraviolet wavelengths can be seen, taking part in the formation of Jovian auroras. Io's position relative to Earth and Jupiter also has a strong influence on Jovian radio emissions, which are much more intense when Io is visible.[citation needed]
The features on the surface of Io obey a strict nomenclature by the International Astronomical Union. Therefore, the active eruptive centers are named in particular for the deities and heroes of fire, lightning and sun in various mythologies such as Prometheus, Hephaestus, Loki, Maui, Inti or Amaterasu. Other features such as mountains, valleys or regions are named after places associated with the myth of Io or Dante Alighieri's Divine Comedy
Observation and exploration
For the next two and a half centuries after its discovery, Io remained a fifth-magnitude point impossible to resolve with a telescope. Even so, during the 17th century the Galilean satellites were used for various purposes such as determining longitude, validating Kepler's third law for planetary motion or the measurement of the time it takes light to cross the space that separates Jupiter from Earth. From the ephemeris calculated by astronomers such as Giovanni Cassini, Pierre-Simon Laplace developed a mathematical theory to explain the resonant orbits of Io, Europa, and Ganymede. This resonance is the cause of the various geological characteristics of these three satellites.
Io's location in one of Jupiter's most intense radiation belts precludes a prolonged flyby of the satellite, but the "Galileo" flies by it quickly before orbiting Jupiter two years ago, on December 7, 1995. Although no image is taken during this first approach, the encounter yields significant results such as the discovery of its large iron core, similar to that found on the terrestrial planets. of the Solar System. Since then, further observations have been made by other probes, as well as from Earth via ground-based telescopes or the Hubble Space Telescope.
Pop Culture
Due to its already estimated size at that time, there was speculation, for example, about possible life on its surface during the first half of the century XX being Ío always a propitious setting for science fiction among others such as "The Mad Moon" (1935) by Stanley G, Weinbaum written in the Fantastic Adventures pulp magazine. Or in films of this type such as 2010: The Year We Make Contact (1984) directed by Peter Hyams and sequel to 2001: A Space Odyssey (1968) directed by Stanley Kubrick. In fact in this movie the spaceship Discovery One is in orbit at the Lagrange Points between Jupiter and Io during the film.