Facts about Ganymede

• Jupiter's moon Ganymede is the largest moon in the solar system. It is larger than Mercury and Pluto, and only slightly smaller than Mars. It would easily be classified as a planet if it orbited the Sun rather than Jupiter.
• Ganymede is about 4.5 billion years old, about the same age as Jupiter.
• Distance from Jupiter: Ganymede is the seventh moon and third Galilean from Jupiter's surface, orbiting at a distance of approximately 665,000 miles (1.070 million km).
• Size: The average radius of Ganymede is 1,635 miles (2,631.2 km). Due to its size, the satellite Ganymede can be seen with the naked eye. Early Chinese astronomical records show the discovery of a moon of Jupiter, likely the first observation of Ganymede. Although Ganymede is larger than Mercury, it has only half its mass, which is characterized by its low density.
• Temperature: Daytime surface temperatures average 171F to 297F, with nighttime temperatures dropping to -193C. It is unlikely that any living organisms inhabit the moon Ganymede.
• Ganymede's surface consists of two types of terrain: 40 percent littered with numerous craters and 60 percent light-colored grooves that form a complex pattern that gives the moon its characteristic appearance. The grooves, which were likely formed by tectonic activity or when water was released from the surface, are so high that they are 2,000 feet high and stretch for thousands of miles.
• The moon Ganymede is believed to have a marine ocean that is located 124 miles below the surface, unlike the moon Europa, which has a large ocean closer to the surface.
• Ganymede has a thin atmosphere of oxygen - too thin to support life. It is the only satellite in the solar system that has a magnetosphere. Ganymede's magnetosphere is completely embedded in Jupiter's magnetosphere. Discovery of the satellite Ganymede
• Galileo named this moon Jupiter III. But the numerical naming system was abandoned in the mid-1800s and so the moon was named after Ganymede, a Trojan prince in Greek mythology. Zeus, the counterpart of Jupiter in Roman mythology, brought Ganymede to Olympus, who took the form of an eagle, and made him the cupbearer of the Olympian gods and one of Zeus' favorites.

Exploration of Ganymede by interplanetary stations

Jupiter (like all other gas planets) was purposefully studied exclusively by interplanetary stations. Several spacecraft have explored Ganymede up close, including four flybys in the 1970s and multiple flybys from the 1990s to the 2000s. The first photographs of Ganymede from space were taken by Pioneer 10, which flew past Jupiter in December 1973, and by Pioneer 11, which flew by in 1974. Thanks to them, more accurate information was obtained about the physical characteristics of the satellite (for example, Pioneer-10 clarified its dimensions and density). Their images show features as small as 400 km. The closest approach of Pioneer 10 was 446,250 kilometers. In March 1979, Voyager 1 passed by Ganymede at a distance of 112 thousand km, and in July, Voyager 2 passed by at a distance of 50 thousand km. They transmitted high-quality images of the satellite’s surface and carried out a number of measurements. In particular, they clarified its size, and it turned out that it is the largest satellite in the solar system (previously, the largest satellite of Saturn, Titan, was considered the largest. Current hypotheses about the geology of the satellite appeared thanks to Voyager data. From December 1995 to September 2003, the Jupiter system was studied "Galileo". During this time, he approached Ganymede six times. Names of flybys - G1, G2, G7, G8, G28 and G29. During the closest flight (G2), "Galileo" passed 264 kilometers from its surface. a lot of valuable information, including detailed photographs. During the G1 flyby in 1996, Galileo discovered a magnetosphere near Ganymede, and in 2001, an underground ocean. Thanks to Galileo data, it was possible to construct a relatively accurate model of the internal structure of the satellite. a large number of spectra and discovered several non-ice substances on the surface of Ganymede. The New Horizons apparatus on its way to Pluto in 2007 sent photographs of Ganymede in the visible and infrared ranges, and also provided topographic information and a composition map.

Prospective Studies

Proposed for launch in 2020, the Europa Jupiter System Mission (EJSM) is a joint program between NASA, ESA and Roscosmos to study the satellites of Jupiter. In February 2009, it was announced that ESA and NASA had given it higher priority than the Titan Saturn System Mission. For ESA, financing this mission is complicated by the agency's other projects requiring funding. The number of vehicles that will be launched varies from two to four: Jupiter Europa Orbiter (NASA), Jupiter Ganymede Orbiter (ESA), Jupiter Magnetospheric Orbiter (JAXA) and Jupiter Europa Lander (Roscosmos). On May 2, 2012, the European Space Agency (ESA) announced the launch of the Jupiter Icy Moons Explorer (JUICE) mission in 2022 with an arrival in the Jupiter system in 2030. One of the main goals of the mission will be the exploration of Ganymede, which will begin in 2033. Russia, through the involvement of ESA, also intends to send a lander to Ganymede to search for signs of life and to conduct comprehensive studies of the Jupiter system as a representative representative of the gas giants.

Jupiter's moon Ganymede was discovered by Galileo Galilei on January 7, 1610, using his first ever telescope. On this day, Galileo saw 3 “stars” near Jupiter: Ganymede, Callisto and a “star”, which later turned out to be two satellites - Europa and Io (only the next night the angular distance between them increased enough for separate observation). On January 15, Galileo concluded that all of these objects were in fact celestial bodies orbiting Jupiter. Galileo called the four satellites he discovered “Medici planets” and assigned them serial numbers.
French astronomer Nicolas-Claude Fabry de Peyresc proposed giving the satellites separate names after the four members of the Medici family, but his proposal was not accepted. The discovery of the satellite was also claimed by the German astronomer Simon Marius, who observed Ganymede in 1609, but did not publish data about it in time. Marius tried to name the moons "Saturn Jupiter", "Jupiter Jupiter" (this was Ganymede), "Venus Jupiter" and "Mercury Jupiter", which also did not gain popularity. In 1614, he, following Johannes Kepler, proposed new names for them after the names of those close to Zeus.
However, the name "Ganymede", like the names proposed by Marius for other Galilean satellites, was practically not used until the mid-20th century, when it became generally used. In much of the earlier astronomical literature, Ganymede is designated (in the system introduced by Galileo) as Jupiter III or the "third moon of Jupiter." After the discovery of the moons of Saturn, a naming system based on the proposals of Kepler and Marius began to be used for the moons of Jupiter.
Ganymede is now known to be the largest moon in the Jupiter system, as well as the largest moon in the Solar System. Its diameter is 5262 km, which exceeds the size of the planet Mercury by 8%. Its mass is 1.482 * 10 23 kg - more than three times the mass of Europa and twice the mass of the Moon, but it is only 45% of the mass of Mercury. The average density of Ganymede is less than that of Io and Europa - 1.94 g/cm 3 (only twice that of water), which indicates an increased ice content in this celestial body. According to calculations, water ice makes up at least 50% of the total mass of the satellite.

Orbital resonance occurs when forces prevent an object from locking into a stable orbit. Europa and Io regularly resonate with each other's orbits to this day, and something similar appears to have happened to Ganymede in the past. It currently takes Europa twice as long to orbit Jupiter, and Ganymede four times as long.
The closest approach between Io and Europa occurs when Io is at periapsis and Europa is at apocenter. Europa is approaching Ganymede, being at its periapsis. Thus, lining up all these three satellites in one line is impossible. This resonance is called Laplace resonance.
Modern Laplace resonance is unable to increase the eccentricity of Ganymede's orbit. The current value of eccentricity is about 0.0013, which may be a consequence of its increase due to resonance in past eras. But if it is not increasing at the present time, then the question arises as to why it did not go to zero due to tidal dissipation of energy in the bowels of Ganymede. Perhaps the last increase in eccentricity occurred recently - several hundred million years ago. Because the eccentricity of Ganymede's orbit is relatively low, tidal heating of this satellite is currently negligible. However, in the past, Ganymede may have gone through a Laplace-like resonance one or more times, which was capable of increasing the orbital eccentricity to values ​​of 0.01-0.02. This likely caused significant tidal heating of Ganymede's interior, which could have caused tectonic activity that formed the rugged landscape.
There are two hypotheses for the origin of the Laplace resonance of Io, Europa and Ganymede: that it existed since the appearance of the Solar system or that it appeared later. In the second case, the following development of events is likely: Io raised tides on Jupiter, which led to its moving away from it until it entered into a 2:1 resonance with Europa; after this, the radius of Io's orbit continued to increase, but part of the angular momentum was transferred to Europa and it also moved away from Jupiter; the process continued until Europa entered into a 2:1 resonance with Ganymede. Ultimately, the orbital radii of these three satellites reached values ​​​​corresponding to the Laplace resonance.

The current model of Ganymede suggests that a silicate-ice mantle extends beneath the icy crust down to a small metallic core with a size of the order of 0.2 Ganymede radii. According to data from the Galileo spacecraft, a huge ocean of liquid water may exist in the depths of Ganymede between layers of ice. The conclusion about the existence of an iron core was made on the basis of the discovery of the magnetosphere of Ganymede by the Galileo equipment in 1996-1997. It turned out that the satellite's own dipole magnetic field has a strength of about 750 nT, which exceeds the strength of Mercury's magnetic field. Thus, after the Earth and Mercury, Ganymede is the third solid body in the Solar System that has its own magnetic field. Ganymede's small magnetosphere is contained within the much larger magnetosphere of Jupiter and only slightly deforms its field lines.
There are two types of terrain observed on the surface of Ganymede. A third of the satellite's surface is occupied by dark areas dotted with impact craters. Their age reaches four billion years. The remaining area is occupied by younger, lighter areas covered with furrows and ridges. The reasons for the complex geology of the light areas are not fully understood. It is likely related to tectonic activity caused by tidal heating.
On the brown surface there are a large number of light impact craters, surrounded by halos of light rays of material ejected during impacts. Two large dark regions on the surface of Ganymede are named Galilean and Simon Marius (in honor of the researchers who independently and almost simultaneously discovered the Galilean moons of Jupiter). The age of the surface of celestial bodies is determined by the number of impact craters that were intensively formed in the Solar System 2...3 billion years ago. The absolute age scale is built on the Moon, where direct dating (based on the results of radioisotope studies of soil samples delivered to Earth from lava areas) was carried out. Judging by the number of meteorite craters, the most ancient parts of the surface of Ganymede are 3...4 billion years old.
On the lighter icy surface of Ganymede, rows of numerous subparallel grooves and ridges are observed, somewhat reminiscent of the surface of Europa. The depth of the light furrows is several hundred meters, the width is tens of kilometers, and the length reaches thousands of kilometers. Furrows are observed in some relatively young local areas of the surface. Apparently, the grooves were formed as a result of stretching of the bark. The features of some areas of the surface resemble traces of rotation of its large blocks, similar to tectonic processes on Earth.

To designate formations on Ganymede, terrestrial geographical names are used, as well as the names of characters in the ancient Greek myth of Ganymede and characters from the myths of the Ancient East.
An analysis of the features of the ancient surface of Ganymede that has survived to this day allows us to assume that at the initial stage of its existence, young Jupiter radiated much more energy into the surrounding space than it does now. Jupiter's radiation could lead to partial melting of surface ice on nearby moons, including Ganymede. The morphology of some areas of the satellite's crust can be interpreted as traces of melting. Such dark areas (peculiar seas) are apparently formed by the products of water eruptions.
The satellite has a thin atmosphere, which contains allotropes of oxygen such as O (atomic oxygen), O 2 (oxygen) and possibly O 3 (ozone). The amount of atomic hydrogen (H) in the atmosphere is negligible. Whether Ganymede has an ionosphere is unclear.
The first spacecraft to study Ganymede was Pioneer 10 in 1973. Much more detailed research was carried out by the Voyager program in 1979. The Galileo spacecraft, which has been studying the Jupiter system since 1995, discovered the underground ocean and magnetic field of Ganymede.

Evolution of Ganymede

physical characteristics

Internal structure
Presumably, Ganymede consists of three layers: a molten iron or iron sulfide core, a silicate mantle and an outer layer of ice 900-950 kilometers thick. This model is confirmed by the small moment of inertia that was measured during the Galileo flyby of Ganymede - (0.3105 +/- 0.0028)*mr 2 (the moment of inertia of a homogeneous ball is 0.4*mr 2). Ganymede has the lowest coefficient in this formula among the solid bodies of the Solar System. The existence of a molten iron-rich core provides a natural explanation for Ganymede's own magnetic field, which was discovered by Galileo. Convection in molten iron, which has high electrical conductivity, is the most reasonable explanation for the origin of the magnetic field.
The exact thickness of the various layers in the depths of Ganymede depends on the assumed composition of the silicates (the proportion of olivine and pyroxenes), as well as on the amount of sulfur in the core. The most likely value for the radius of the core is 700-900 km, and the thickness of the outer ice mantle is 800-1000 km. The remainder of the radius falls on the silicate mantle. The density of the core is presumably 5.5-6 g/cm 3 , and that of the silicate mantle is 3.4-3.6 g/cm 3 . Some models of Ganymede's magnetic field generation require a solid core of pure iron within a liquid core of Fe and FeS, similar to the structure of the Earth's core. The radius of this core can reach 500 kilometers. The temperature in the core of Ganymede is supposed to be 1500-1700 K, and the pressure is up to 10 GPa.

Studies of Ganymede's magnetic field indicate that there may be an ocean of liquid water beneath its surface.

Evidence for an ocean on Ganymede The diagram shows a pair of auroral belts on Jupiter's moon Ganymede. Their displacement/movement gives an idea of ​​the internal structure of Ganymede. Ganymede has a magnetic field created by its iron core. Since the satellite is located close to Jupiter, it is completely included in the magnetic field of the giant planet. Under the influence of Jupiter's magnetic field, the aurora belts on Ganymede shift. The fluctuations are less pronounced if there is a liquid ocean beneath the surface. Numerous observations have confirmed the existence of a large amount of salty water under the icy crust of Ganymede, which affects its magnetic field.

Space Telescope named after. Hubble, observing the aurora belts on Ganymede in ultraviolet light, confirmed the existence of an ocean on Ganymede. The location of the belts is determined by Ganymede's magnetic field, and their displacement is due to interaction with Jupiter's huge magnetosphere.

SC "GALILEO": GANYMED

Sandwich model of the structure of Ganymede (2014) Previous models of Ganymede's structure showed an ocean sandwiched between an upper and lower layer of ice. The new model, based on laboratory experiments simulating salty seas and liquids, shows that Ganymede's oceans and ice may form multiple layers. The ice in these layers depends on pressure. That. "Ice I" is the least dense form of ice and can be compared to the ice mixture in chilled drinks. As the pressure increases, the ice molecules are located closer to each other and, therefore, the density increases. The oceans of Ganymede reach a depth of 800 km, so they experience much greater pressure than on Earth. The deepest and densest layer of ice is called "Ice VI". Given enough salts, the liquid can be dense enough to sink to the very bottom and even below the Ice VI level. Moreover, the model shows that quite strange phenomena can occur in the uppermost liquid layer. The liquid, cooling from the upper ice layer (crust), falls down in the form of cold currents, which form the “Ice III” layer. In this case, upon cooling, the salt precipitates and then sinks down, while at the Ice III level an ice/snow slurry forms. According to another group of scientists, such a structure of Ganymede cannot be stable, but it could well precede the model with one huge ocean.

SC "GALILEO": GANYMED

Jupiter's moon Ganymede is the largest moon in the solar system. Ganymede satellite larger than Mercury and Pluto, and only slightly smaller than Mars. And much less than that. It would easily be classified as a planet if it orbited the Sun rather than Jupiter.

Ganymede satellite: facts

The moon Ganymede is about 4.5 billion years old, about the same age as Jupiter.

Distance from Jupiter: Ganymede is the seventh moon and third Galilean from Jupiter's surface, orbiting at a distance of approximately 665,000 miles (1.070 million km).
Size: The average radius of Ganymede is 1,635 miles (2,631.2 km). Due to its size, it can be seen with the naked eye. Early Chinese astronomical records show the discovery of a moon of Jupiter, likely the first observation of Ganymede. Although Ganymede is larger than Mercury, it has only half its mass, which is characterized by its low density.

Temperature: Daytime surface temperatures average 171F to 297F, with nighttime temperatures dropping to -193C. It is unlikely that any living organisms inhabit the moon Ganymede.

Several spacecraft have flown around Jupiter and its moons. Pioneer 10 arrived first, in 1973, followed by Pioneer 11 in 1974. Voyager 1 and Voyager 2 returned with stunning photographs of these worlds. The Galileo spacecraft passed just 162 miles (261 km) above the surface of the Galilean moons and produced detailed images.
The moon Ganymede has a core of metallic iron, followed by a layer of rock topped by a crust of ice that is for the most part very thick. There are also a number of irregularities on the surface of Ganymede that could be rocks.

Ganymede's surface consists of two types of terrain: 40 percent littered with numerous craters and 60 percent light-colored grooves that form a complex pattern that gives the moon its characteristic appearance. The grooves, which were likely formed by tectonic activity or when water was released from the surface, are so high that they are 2,000 feet high and stretch for thousands of miles.

It is believed to have a marine ocean that is located 124 miles below the surface, unlike the moon Europa, which has a large ocean closer to the surface.
Close-up photo of the Nicholson region and Arbela Sulcus, further demonstrating the diversity of Ganymede's surface

Close-up photo of the Nicholson region and Arbela Sulcus, further demonstrating the diversity of the surface of the moon Ganymede

Ganymede has a thin atmosphere of oxygen - too thin to support life. It is the only satellite in the solar system that has a magnetosphere. Ganymede's magnetosphere is completely embedded in Jupiter's magnetosphere.

Jupiter's moon Ganymede: history of discovery

Ganymede satellite was discovered by Galileo Galilei on January 7, 1610. It was discovered along with three other moons of Jupiter and was the first time a satellite orbiting a planet other than Earth had been discovered. Galileo's discoveries eventually led to the understanding that the planets revolve around the Sun, rather than our solar system revolving around the Earth.

Galileo named this moon Jupiter III. But the numerical naming system was abandoned in the mid-1800s and so the moon was named after Ganymede, a Trojan prince in Greek mythology. Zeus, the counterpart of Jupiter in Roman mythology, brought Ganymede to Olympus, who took the form of an eagle, and made him the cupbearer of the Olympian gods and one of Zeus' favorites.

The Ganymede satellite, being the largest known in our solar system, is larger in size than the planets Mercury and Pluto. If it revolved around the Sun, and not in the orbit of Jupiter, then it could well be classified as a full-fledged planet.

Basic physical characteristics

The Ganymede satellite includes three main layers:

• A sphere of metallic iron in the center (a core that is capable of generating a magnetic field)
• Rocky shell (mantle)
• Spherical ice shell.

The outer shell has an impressive depth, which can reach 800 km. The surface of the top is called the ice shell because it is mostly ice. In addition, the shell may contain some mixed breeds. The magnetic field of such a celestial body as the satellite Ganymede has a closed system inside the massive magnetosphere of Jupiter. In 1996, astronomers using the Hubble Space Telescope found evidence of a thin oxygen atmosphere, not enough to support life.

Complex geological history

Images from spacecraft reveal a complex geological history. The surface of the Ganymede satellite is represented by two types of landscape. Forty percent are cratered in very dark areas, while the remaining sixty have light striations that form intricate patterns. The large craters on Ganymede are quite flat. They do not have a central depression. This is probably due to the slow and gradual adaptation to the soft ice surface.

Satellite Ganymede: history of discovery

This discovery, made by the great scientist of his time Galileo Galilei on January 7, 1610, along with the discovery of three other moons of Jupiter, eventually led to the acceptance that the planets orbit the Sun in a special way. Initially, Galileo called them the Medici planets, numerically I, II, III and IV. This naming system was used for several centuries, until the mid-19th century. The new names of the satellites were Io, Europa, Ganymede and Callisto. The numeric names became irrelevant as new additional satellites were discovered.

Ganymede in mythology

In mythology, he was a handsome young boy who was created on Olympus by Zeus (the Greek equivalent of the Roman god Jupiter) disguised as an eagle. Ganymede became the symbol of the cupbearer among the Olympian gods.

Jupiter - a giant planet and its "moons"

The planet is surrounded by 53 confirmed moons, as well as 14 temporary ones, for a total of 67 moons. Jupiter also has three rings, but they are very difficult to see and are not as elegant as Saturn's. Jupiter is named after the king of the Roman gods. Scientists are most interested in the four largest ones, discovered by Galileo. These are Europa, Callisto, Ganymede and Io.

Key Facts

• Ganymede (a moon of Jupiter) is about the same age as the planet itself, about 4.5 billion years old.
• The distance from Jupiter to its natural satellite is more than 1 million kilometers.
• Ganymede is larger than some known planets, such as Mercury.
• Daytime surface temperatures average minus 171 degrees Fahrenheit, while at night this figure reaches minus 297 (down to -193 Celsius).

Magnetosphere of the largest satellite

Ganymede, a moon of Jupiter, is unique in that it is the only natural satellite to have its own magnetosphere. As a rule, this characteristic is characteristic of planets. Ganymede's magnetosphere is shaped like a comet, in which charged particles are captured or deflected.

Composition and surface characteristics

Jupiter's moon Ganymede, with an average density of 1.936 g/cm 3 , most likely consists of equal parts rocky material and water ice. Spectral and ultraviolet studies also showed the presence of carbon dioxide, sulfur and possibly cyanogen, hydrogen sulfate and various organic compounds. Later evidence showed the presence of salts such as magnesium sulfate and possibly sodium sulfate, which may have originated from the underground ocean. The satellite of the planet Jupiter has a solid inner core with a radius of 50 km, a mantle and a spherical shell. The mantle is composed of silicate materials, most likely chondrites and iron. The outer shell is ice and rocks.

What other interesting facts can you tell about the satellite Ganymede? Scientists believe that somewhere in the ice there is a frozen ocean. Its presence has been confirmed by readings taken by orbiters and by studying how auroras behave. Dark areas of the surface comprise about one-third of the surface due to the clay and organic materials contained in the ice. Although craters are more common in dark areas, they are found almost everywhere. The moon Ganymede, whose surface characteristics are associated with ancient crater formation, has a diameter of 5268 kilometers.

Is there life on Ganymede?

Who knows for sure whether there are signs of life under the thick ice shell? Nevertheless, there are still remote prerequisites for considering this issue. The moon has a frozen ocean and a hot core, meaning Ganymede has the potential to develop marine life similar to that found on Earth's ocean floor, such as in thermal springs or in the absence of air. If this is possible, then this nucleation will develop without the need for sunlight, since no one or nothing will be able to penetrate through the thick ice.

Exploring Ganymede

Jupiter was purposefully studied by NASA interplanetary stations. The first images were obtained thanks to the Pioneer 10 expedition (December 1973), as well as Pioneer 11 (1974). More detailed information about its geophysical characteristics, its size and density has become known. In 1979, the Voyager 1 and 2 spacecraft passed by the giant satellite. As a result, better photographs were taken, and various additional measurements were taken. For example, it was confirmed that Ganymede is the largest satellite in the Solar System, although previously this big title belonged to another giant, Saturn’s satellite Titan.

Ganymede is truly one of the outstanding objects in Jupiter space. It stands out from the general cosmic mass not only by its size; geophysical characteristics are of great interest to astrophysicists and researchers: magnetic field, topography, internal structure. Just look at the fact that life is potentially possible on the satellite. To study Jupiter and its moons, a specially equipped spacecraft will be launched in June 2022 with an 11-year mission. An interplanetary spacecraft is already under development.