The Jupiter’s tiniest satellite goes by the name

The discovery of the first four satellites of Jupiter (Io, Europa, Ganymede, Callisto) took place in 1610. These satellites are commonly referred to as the Galilean satellites, in honor of Galileo. Two of these satellites are larger in size compared to the Moon, while the other two are slightly smaller. By the middle of the 20th century, a total of 12 satellites had been identified, but as of 1989, the number had increased to 16. However, it is worth noting that all of these satellites are significantly smaller in size compared to the Galilean satellites. Now, let’s examine the available data on these satellites, starting with the one that is closest to Jupiter.

The two nearest satellites are located approximately 1.8 radii away from the planet’s center, and their orbits serve as an outer boundary for Jupiter’s thin and transparent ring (at distances of 128 and 129 thousand km from the planet’s center). Closer to Jupiter, there is an even more sparse outer halo of small particles. It seems that these satellites are nearing Jupiter’s gravitational forces, where they could potentially be torn apart and form rings (at the boundary of the Roche zone). They act as “shepherds” for the ring particles, preventing them from straying beyond their designated orbits. The sizes of these objects are estimated to be around 40 and 25-15 km respectively, although these figures are only rough approximations. These satellites complete one revolution around Jupiter in less than a third of an Earth day. They were discovered in 1979.

AMALTHEA

Located at a distance of 2.5 radii from the center of the planet (131,200 km from the surface of the planet), AMALTHEA was discovered in 1892 by Barnard. However, there is still limited information available about this moon. Its diameter is estimated to be around 270 km, although some sources suggest it could be between 270-150 km. AMALTHEA completes a full orbit around Jupiter in just half a day.

FEBA (or Teba).

FEBA (also known as Teba) is situated at a distance of 3.1 radii from the planet. It was discovered in 1979, but precise data regarding its diameter are not currently available. Estimates suggest that it could have a diameter of approximately 100 km.

Emotional Intelligence

Revolve around the planet’s center at a distance of 5.9 radii (422,000 km from the surface), with a period of 1.8 Earth days, an inclination of 3 degrees to the planet’s orbit, a diameter of 3460 km (3630 km according to recent data), and a mass 1/83 of that of Earth. The strong tidal forces from Jupiter cause the nearest large satellite to experience continuous volcanic activity, with eruptions of sulfuric gas and sulfuric acid lava (reaching heights of up to 30 km in fountains, and gases reaching up to 300 km). “During the Voyager 1 mission, 8 active volcanoes were discovered, and subsequent reports from Voyager 2 confirmed that 6 of them were still erupting. In total, 12 active volcanoes were initially reported, but by 1998, observations from the Galileo spacecraft revealed the presence of 32 active volcanoes. Due to the abundance of lava, meteorite craters are rare on the surface. The volcanic activity is so intense that it can cover the entire satellite with a layer of 1.5 centimeters of lava in a year. The surface of Io is characterized by a variety of colors, representing fresh or darkened lava (as observed by the Voyager spacecraft). Over a period of 17 years, certain areas of Io have changed color from bright red to pale yellow (with spots the size of Belgium). The eruptions bring sulfur of different colors to the surface. The largest lava sea, near the volcano Loki, has a width of 200 km. Io’s orbit is surrounded by a hydrogen torus, which is a result of volcanic emissions. The volcanically active regions of Io are heated to temperatures of at least 300 degrees Celsius. Measurements from the Galileo spacecraft indicate that the surface temperature in the cratered areas can reach 1800 degrees Kelvin, suggesting that the interior temperatures could reach 2000 degrees Kelvin. On Earth, the corresponding temperature is only 1600 degrees Kelvin. Io experiences tidal forces from Jupiter, resulting in two tidal humps that slightly shift across its surface due to its elongated orbit, resembling a wiggling motion that helps maintain the interior’s heat (similar to the phenomenon observed with the Moon). As mentioned in a 1999 post (What’s New in the Jupiter Family), the volcanoes and volcanic fissures on Io are concentrated in these tidal humps, both at the closest and farthest points from Jupiter. Recent reports indicate that Io also has its own magnetic field;

The heating of the interior of Io causes the metals to flow towards the center, creating a core. A rocky mantle, devoid of surface ice, surrounds the core. It is worth noting that one of the volcanoes on Io has undergone an impressive displacement of 80 kilometers in just 17 years. Connecting Io to Jupiter are two bright bands, where an electrical discharge occurs between their atmospheres, generating a current of up to 1 million amperes. The auroras on Io exhibit a striking blue hue, while certain volcanoes also display luminous or bluish electric arcs. These arcs are produced by voltages exceeding 400 kV and are a result of the interaction between electric fields and sulfur dioxide gas. Additionally, there are areas on Io that emit a red or green glow, caused by the excitation of oxygen and hydrogen by Jupiter’s magnetic field’s charged particles.

EUROPE.

Located 9.4 radii away from the planet’s core (approximately 671,000 km from its surface), Europe completes a full revolution around the planet every 3.6 Earth days. It follows a path that is inclined at an angle of 3 degrees to the planet’s orbit. With a diameter of 3050 km (or 3140 km according to recent data), Europe has a mass that is approximately 1/125 of Earth’s mass. The proximity to Jupiter results in tidal forces that generate enough heat to prevent Europe from being as cold as other small celestial bodies in our solar system. The absence of visible craters leads scientists to believe that the entire surface of Europe is covered by a vast ocean, with an estimated depth of around 100 km of unfrozen water. This ocean is believed to be covered by a layer of ice that is approximately 30 km thick, according to information gathered by the Voyager missions.

Based on more recent and refined data obtained from the Galileo flyby at 205 km, it is believed that the entire icy shell of Europa has a thickness ranging from 80 to 170 km, with a most likely thickness of 100 km. Additionally, it has been discovered that the metallic core of Europa is larger than previously thought and occupies up to 50% of the moon’s radius. The perturbation of Jupiter’s magnetic field near Europa also indirectly suggests the presence of an ocean containing salt water, as the field is distorted by eddy currents, which can only occur in a conducting liquid. The presence of chemosynthetic life beneath the icy surface is theoretically possible, as life on Earth was once only possible in the ocean. The images obtained by Galileo reveal numerous craters, but there is still a lack of sufficient craters, with only one three-kilometer crater discovered so far. There are also five craters with diameters ranging from 10 to 30 kilometers. However, the entire surface is marked by long, branching, and intersecting furrows, which are believed to be manifestations of ice volcanism. This phenomenon occurs when water periodically flows to the surface from cracks and other formations. In our country, this phenomenon is referred to as “ice”. Recent findings from Galileo indicate the presence of magnesium sulfate on Europa, similar to the salt marshes found on Earth, along with fractures and cracks nearby. It is likely that water flows out of these cracks onto the surface and evaporates, leaving behind salt deposits. Europa has also been found to have its own magnetic field, indicating differentiation in its interior and the presence of a metallic core. During the Galileo mission in December 1996 and February 1997, the spacecraft passed behind Europa six times, and although radio signals were received with interference, they still reached Earth. Analysis of these interferences revealed the presence of an ionosphere around Europa, with a density of no more than 10,000 electrons per cubic centimeter. This ionosphere is believed to have formed when charged particles from Jupiter’s magnetosphere collided with individual nuclei and atoms in the ice. Consequently, Europa possesses a thin atmosphere. The Americans plan to send the “Europa Observer” spacecraft to Europa in 2003, equipped with the same radar that discovered subglacial lakes in Antarctica. The mission aims to locate the thinnest ice on Europa’s surface and melt through it to collect water samples for the detection of life.

CALLISTO.

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CALLISTO.

Located 26.5 radii away from the center of the planet (1,884,000 km from its surface), Callisto completes one revolution in 16.7 Earth days. It is inclined at an angle of 3 degrees to the planet’s orbit and has a diameter of 4,750 km (recent data suggests it may actually be 4,800 km). Callisto is about 1/67th the mass of Earth and is slightly more massive than the Moon. Despite this, Jupiter’s tidal forces have minimal impact on Callisto. Callisto has a typical lunar appearance, but unlike the Moon, it lacks any “seas” formed by solidified lava. Instead, it has a single continent with meteoric craters, ridges, and crevasses that were created through catastrophic events. The craters on Callisto are composed of ice. The largest ring structure on Callisto is known as Valhalla, which features a central crater of the same name measuring 350 km in diameter. Around this central crater, there are concentric circles of mountain ranges and cracks spanning a radius of 2000 km. These details have mainly been obtained from the Voyager and Galileo missions. Recent photographs from the Galileo mission have revealed a significant number of large meteorite craters on Callisto. However, it is puzzling that there are hardly any craters less than 100 meters in diameter visible in these images. According to scientists, these craters should have been visible with the surveying techniques employed. Furthermore, displaced blocks of matter have been discovered on Callisto, which is difficult to explain as plate tectonics are not expected to occur on this moon. As a result, the Galileo mission, which was initially planned to conclude in December 1997, was extended for another two years. The displaced blocks of matter are now believed to be evidence of avalanches and landslides. The latest data from the Galileo mission, obtained in September 1997, indicates that Callisto does not possess its own magnetic field. However, it does have a thin atmosphere that becomes ionized by the solar wind and Jupiter’s magnetic field. This atmosphere is primarily composed of hydrogen and carbon dioxide. Due to the absence of a magnetic field, it is likely that Callisto does not have an iron core and instead consists of undifferentiated matter, with rocks and ice covered by a layer of ice. This is because Callisto orbits at a considerable distance from Jupiter and has not been subject to the tidal forces that could have caused the interior to melt and separate into different layers based on density. However, subsequent research has partially refuted or at least provided further clarification on these findings. It is now understood that Callisto is partially differentiated, with a small core (no more than a quarter the size of Io’s radius) composed of iron-stone. Above the core, there is a mixture of ice and rocks, and the outermost layer consists primarily of ice, which is no more than 350 km thick.

ICE

An ice block that has been preserved since Jupiter’s formation was discovered approximately 155 radii away from the planet. It has a diameter of about 16 kilometers and was first found in 1974.

HIMALIA.

Himalia is the largest of Jupiter’s outer minor satellites (non-Galilean) and is located approximately 161 radii away from the planet (11,452,000 km from the planet). It has a diameter of at least 100 km and takes 250 Earth days to complete one orbit. Perrin discovered it in 1905. Is there an ice block that has been preserved since the formation of Jupiter on Himalia?

LYSITEA.

Located at a distance of 164 radii from the planet (equivalent to 11,700,000 km). Its discovery dates back to 1938. This moon has an orbital period of 260 Earth days and a diameter of approximately 40 kilometers. Is it possible that this celestial body is an icy mass that has been preserved since Jupiter’s formation?

ELARA

Situated at a distance of 165 radii from the planet (equivalent to 11,700,000 km). It was first discovered in 1905 by Perrin. Elara has a circulation period of 260 Earth days and a diameter of around 80 kilometers. Could it be that this moon is a frozen block that has been preserved since Jupiter’s formation?

ANANKE.

Located at a distance of 297 radii from the planet (equivalent to 21,000,000 km). This moon orbits in the opposite direction to the Galilean satellites and other inner satellites, completing one revolution around the planet in 620 Earth days. With a diameter estimated to be around 30 kilometers, Ananke is considered a captured asteroid. It was first discovered by Nicolson in 1951.

KARME

Positioned at a distance of 317 planetary radii (equivalent to 22,560,000 km), Karme is another moon that orbits in the opposite direction to the Galilean satellites. It completes one revolution around the planet in approximately 692.5 Earth days. With a diameter estimated to be around 45 km, Karme is also considered a captured asteroid. It was first discovered by Nicolson in 1938.

PACIFE.

Located at a distance of approximately 23,000,000 km from the planet, PACIFE orbits in the opposite direction to the Galilean satellites and completes one revolution in 738.9 Earth days. It has a diameter of around 70 kilometers and is classified as a captured asteroid. This celestial body was first discovered by Melott in 1908.

SYNOPE.

Situated at a distance of about 23,700,000 km from the planet, SYNOPE also orbits in the opposite direction to the Galilean satellites and completes one revolution in 745 Earth days. It has a diameter of approximately 40 kilometers and is classified as a captured asteroid. Notably, SYNOPE holds the distinction of being the farthest satellite from a planet in the entire solar system. It was discovered by Nicolson in 1914. On the sides of the large satellites facing Jupiter, there are catenas – chains of meteorite craters.

The groups of satellites around Jupiter can be clearly distinguished from each other:

1) The first group consists of four small satellites that are closest to the planet. If it weren’t for Adrastea and Metida, which are practically in the same orbit, this group could be considered analogous to the terrestrial planets. The distances between these satellites follow Bode’s rule, with all of them being small. The first two are smaller than the next one, Amalthea, which is the largest and similar to Earth. The last one, Theba, is smaller than the others and can be compared to Mars;

2) Following this group, there is a gap that is somewhat similar to the asteroid belt;

3) The second group consists of four Galilean satellites that are similar to the giant planets, with the only difference being that the largest of them are farther away from Jupiter. The distances between these satellites also follow Bode’s rule, with all of them being large.

3) There are 4 additional satellites that are distinctly separated from the rest. These satellites have close orbits and are all small in size. They move in the standard direction.

This group of satellites is similar to the second asteroid belt or the inner part of the Oort cloud.

4) The remaining 4 satellites are located farthest away. They also have close orbits, but they move in the opposite direction. This group is comparable to the outer part of the Oort cloud.

The four largest satellites of Jupiter were first observed by Italian astronomer Galileo Galilei in 1610. These satellites have since been named Galileo’s satellites in his honor. Initially, Galileo could only see three of the four satellites, as he mistook Io and Europa for a single celestial body. He also mistakenly believed that he had discovered fixed stars, but later realized that they were actually orbiting Jupiter.

Galileo’s finding caused a sensation. It demonstrated that not all heavenly bodies orbit the Earth, which went against the prevailing geocentric theory. Additionally, it highlighted the significant role that telescopes could have in studying the stars: Galileo was only able to observe Jupiter’s satellites after enhancing his telescope.

When Galileo first discovered them, he initially referred to the satellites as “Cosimo’s stars” (later known as “Medicean stars”) after his patron, Cosimo de’ Medici. In his records, he labeled them as Jupiter I (Io), Jupiter II (Europa), Jupiter III (Ganymede), and Jupiter IV (Callisto). However, the names by which we now know these satellites were actually given by astronomer Simon Marius, who made his own discovery of them around the same time as Galileo. Marius chose to name the satellites after characters from Greek mythology. Now, let’s delve deeper into the first satellites ever detected around Jupiter.

Movement

Jupiter possesses not only an immense size but also a substantial atmosphere. Comprising 90 percent hydrogen and 10 percent helium, this gas giant’s atmosphere seamlessly blends with the rest of the planet. As it descends towards the core, the temperature and density of the hydrogen and helium undergo changes, causing Jupiter’s atmosphere to divide into four distinct regions:

Due to the absence of a solid surface, scientists deem the lower atmospheric boundary to be the point where the pressure reaches one bar. As the altitude decreases, the atmosphere’s temperature also decreases, eventually reaching a minimum. Jupiter’s troposphere and stratosphere are demarcated by the tropopause, which lies approximately 50 kilometers above the planet’s so-called “surface”.

Within the vast expanse of Jupiter’s atmosphere, traces of methane, ammonia, water, and hydrogen sulfide can be found. These chemical components contribute to the creation of truly captivating clouds, observable through telescopes from Earth’s surface. Precisely defining Jupiter’s color proves to be a challenge, yet from an artistic perspective, it appears as a blend of red and white, adorned with alternating light and dark stripes.

The visible bands on Jupiter are, in fact, ammonia clouds. Scientists classify the dark stripes as poles and the light stripes as zones, with a continuous interchange between the two. It is only the dark stripes that consist entirely of ammonia. The specific substance or compound responsible for the lighter tone has yet to be identified.

The Great Red Spot on Jupiter is the most magnificent storm in the entire universe. It has been ongoing for hundreds of Earth years without any signs of stopping. With winds reaching speeds of 432 kilometers per hour, it is truly a force to be reckoned with. The size of the storm is so immense that it could easily fit three Earths within its boundaries.

Classifications

Jupiter’s satellites can be categorized into various groups. The inner groups are particularly distinguishable:

Jupiter’s irregular satellites fall into this category:

• Themisto, which is spatially isolated;
• Himalia Group, a dense cluster with a major semi-axis of approximately 11.86 ± 0.695 Gm and an inclination of 27.5 ± 0.8 degrees; the eccentricity ranges from 0.11 to 0.25;
• Carpo and S / 2003 J 12, two other isolated satellites.

The initial diagram depicts the paths followed by Jupiter’s irregular moons. The shape of the paths is represented by segments inclined on the vertical axis, from the point closest to Jupiter to the farthest point. Moons located above the horizontal axis move in a direct motion, while those below it move in a retrograde motion. The size of the paths is measured in gigameters (millions of kilometers) and in fractions of the radius of the Hill sphere. The second diagram displays the distribution of inclination and eccentricity, specifically for moons with reduced transmission, allowing for easier identification of the various groups.

It appears that the majority of Jupiter’s irregular outer moons that move in a retrograde motion can be classified into three main families. These families are characterized by similar orbital properties and are named after their largest member. The classification is based on the major semi-axis, as well as the inclination and eccentricity of the moons’ paths.

• The Carmé Group
• The Ananke Group
• The Pasiphae Group
• The Carmé Group is located at a major semi-axis of 23.404 Gm, with an inclination of 165.2 ± 0.3 degrees and an eccentricity between 0.238 and 0.272. Only S / 2003 J 10 deviates slightly due to its high similarity.
• The Ananke Group is centered around a large semi-major axis of 21.276 Gm, with an inclination of 149 ± 0.5 degrees and an eccentricity between 0.216 and 0.244. However, its boundaries are more ambiguous. The central eight moons of the group (S / 2003 J 16, S / 2003 J 21, Euanthe, Orthosie, Harpalyke, Praxidike, Thyone, S / 2003 J 22, Ananke, Jocaste) are well grouped, but the classification of another eight moons as part of the group is more or less questionable.
• S / 2003 J 2, the most remote moon in the entire system, is in solitude.

Features

The initial satellite exhibits a spherical structure. The celestial body has a radius of 1817 km at the poles and 1830 km at the equator. The smaller circumference is accounted for by the flattening of the sphere at the poles. The peculiar shape of Io is a result of the gravitational forces exerted by the parent planet, as well as the neighboring moons Europa and Ganymede.

The density of the initial satellite is slightly lower than that of Mars and is 3.55 g/m3. The density values of the other moons of the gas giant decrease as they get farther from it. For instance, the most remote satellite Callisto has a density of 1.83 g/m3.

Io shares the same period as Jupiter. Its orbital period around Jupiter and its own axis are synchronized. As a result, Io always faces one side of the gas giant. At perihelion, the moon approaches the parent planet at 422,000 kilometers and moves away at 423,000 kilometers. It completes a full revolution around Jupiter in 42 Earth hours.

The initial Trojan asteroid was found in 1904 at Jupiter’s L4 point in its orbit. In keeping with tradition, it was given a name from ancient Greek mythology. This particular celestial object was named after the hero of the legendary city of Troy – “Achilles”. Subsequently, twenty additional asteroids were discovered in the orbit of this massive planet.

This discovery did not come as a surprise to scientists, as many astronomers had been attempting to confirm Lagrange’s theory. The only question was whether they had the necessary technical capabilities. As anticipated, all of the newly discovered objects were situated at Jupiter’s L4 and L5 points in its orbit.

For a considerable period of time, the majority of scientists held reservations regarding the plausibility of small planets like Earth or Mars hosting Trojans. This skepticism stemmed from the fact that such an asteroid, alongside the planet itself and the celestial body, would exert a substantial gravitational force on other massive entities within the solar system, thereby raising doubts about the stability of the object at the Lagrangian points of a small planet. Nevertheless, in 1990, a discovery was made of an asteroid located at the L5 point of Mars, which was subsequently named “Eureka”.

Trojan asteroids of Earth

For a long time, it was challenging to detect Trojan asteroids near our planet. The reason for this difficulty is that the L4 and L5 Lagrangian points of Earth are typically situated on the sunlit side, making observations challenging for observers on the planet’s surface.

In 2010, the situation changed when the space telescope “Wise” was launched into orbit. It successfully discovered the first and only known Trojan asteroid of Earth, named 2010TK7. This asteroid is located at the Lagrangian point L4. 2010TC7 is an ordinary irregularly shaped rock with a diameter of approximately 300 meters, orbiting in outer space among a vast number of other asteroids.

Scientists propose various uses for Trojan asteroids in the future. For instance, one idea is to utilize the L2 point in the Sun-Earth system as a placement for an orbiting telescope. This observation station, constantly in the shadow of the planet, would have a more advantageous position compared to an orbital one. Without the Earth’s rotation, it would be easier to conduct long-term observations of a specific area of the sky.

The L1 point could serve as an ideal location for continuous monitoring of the Sun. It could promptly detect any increase in solar activity and alert ground services about approaching solar plasma ejections. All of this could be accomplished in a timely manner with the help of scientific instruments situated on the first “frontier”.

The planet that holds multiple records

In conclusion, it can be confidently stated that Jupiter is the biggest, heaviest, most rapidly spinning, and most hazardous planet in our solar system. It possesses the most powerful magnetic field and boasts the greatest number of identified satellites. Moreover, it is theorized that Jupiter managed to capture pristine gas from the interstellar cloud, which ultimately led to the formation of our Sun.

Jupiter, in comparison to the other planets in our solar system, plays a significant role in the movement of materials. Its strong gravitational pull attracts ice, water, and organic molecules from the outer regions of the solar system, allowing them to be captured by Earth’s gravitational field. This phenomenon is supported by the discovery of hot Jupiters in the orbits of other stars, which are exoplanets with similar masses to Jupiter and close proximity to their respective stars, resulting in high surface temperatures.

With the Juno spacecraft currently in orbit around Jupiter, there is a unique opportunity for the scientific community to unravel the enigmas surrounding the formation of this magnificent gas giant. Could it be that Jupiter’s origins lie in a rocky core that gradually accumulated a massive atmosphere? Or is it more akin to the genesis of a star, born from a swirling cloud of gas and dust? These are just a few of the pressing questions that scientists aim to address during Juno’s upcoming 18-month mission, which is solely dedicated to a comprehensive investigation of the King of the Planets.

Population explosion

But then came along Scott Sheppard. A group of astronomers hailing from the Carnegie Institution stumbled upon 60 out of the 79 known satellites of Jupiter. Although all of them are irregular, it is still a remarkable achievement. Since 2000, Sheppard’s team has been uncovering satellites orbiting Jupiter. In just the previous year, they managed to include around twelve new ones on the inventory. These fresh satellites contribute to our comprehension of Jupiter’s vicinity and aid astronomers in unraveling the mysteries of the planet’s formation dating back to ancient times.

Sedna

It appears that there are certain anomalies in the movement of Pluto. These deviations cannot be fully explained by the influence of the known planets alone. This implies the existence of another significant celestial body in the outer regions of our solar system. However, this body remains elusive and carefully concealed from human detection. Based on the impact it has on Pluto’s motion, it is believed that this mysterious body has an incredibly large orbit. Experts propose that it completes a full revolution around the Sun every 10,500 years. Furthermore, its trajectory follows a highly elongated path, unlike any other planet in our solar system.

It has been discovered that Sedna is positioned three times further away from the Sun than Pluto, and 97 times further than the Earth. The planet rotates around its axis every 20 Earth days. This extraordinary celestial object appears to be of diminutive size. Experts estimate that the planet’s diameter does not exceed 2250 kilometers. Over the course of the next 72 years, Sedna will gradually approach the Earth. Afterward, the enigmatic goddess will once again begin to move away. It will embark on an incredible journey, distancing itself from the Sun. Ultimately, it will become nearly impossible to study Sedna. Due to its minuscule size, Sedna can hardly be classified as a genuine planet.

Explosive Eruptions

Io’s volcanic eruptions as seen in the infrared spectrum.

Jupiter’s enigmatic moon is home to approximately 400 volcanoes, some of which produce such powerful eruptions that they can be observed from Earth using a telescope.

Occasionally, massive plumes of sulfur, rocks, and particles shoot up from Io’s crust, creating rivers of lava that span hundreds of kilometers across its surface.

This intense geologic activity distinguishes Io from other natural satellites in the solar system. Most moons of this size have either entered a stable phase or ceased tectonic activity millions of years ago.

• Earth and Io are the only two celestial bodies in the solar system with active volcanoes.

Europa is situated in the section. It is the tiniest of Galileo’s moons with a metallic central part and a rocky covering. They are bordered by a layer of water (potentially in a liquid state) and concealed beneath an external layer of ice.

Due to the fact that water has the ability to conduct electricity, Europa’s motion through the massive planet’s magnetosphere is expected to cause alterations in its magnetic field and clusters of particles around the planet. These effects were identified by the Galileo spacecraft.

Life is inevitably brought into question by the discovery of comparable aqueous structures on numerous other moons of Jupiter, notably Callisto and Ganymede, as well as on various moons of Saturn.

An artificial color image of Europa, one of Jupiter’s moons, reveals that its icy surface is tainted with foreign matter (indicated in red) brought in from elsewhere. The frozen plains are depicted in blue.

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Friday, January 20, 2012.

JUPITER SATELLITES (IO, EUROPA)

Total number: 65;
Galileo group: Io, Europa, Ganymede, Callisto;
Amalthea group: Metida, Adrastea, Amalthea, Phoebe;
Other satellites: Small asteroids, with a diameter ranging from 1 to 100 km.

All of Jupiter’s satellites revolve around it due to the immense gravitational pull of the planet, much like the moon revolves around the Earth. Each individual “moon” has its own unique orbit, varying in distance from the gas giant. The closest satellite to Jupiter is Metide, located 128,000 kilometers away, while the farthest ones are situated 20-30 million kilometers from their host planet. Currently, scientists and astronomers are particularly interested in studying the four Galilean satellites (Io, Europa, Ganymede, and Callisto), as they are the largest and most unpredictable moons orbiting Jupiter. Each of these moons is a captivating new world, with its own intriguing history, enigmas, and phenomena.

The volume of the satellite is 2.53×10^10 km³;
The mass of the satellite is 8.93×10^22 kg;
The density of the satellite is 3530 kg/m³;
The rotation period of the satellite is 1.77 days;
The period of rotation of the satellite is 1.77 days;
The distance of the satellite from Jupiter is 350,000 km;
The orbital velocity of the satellite is 17.33 km/s;
The equatorial length of the satellite is 11,500 km;
The orbital inclination of the satellite is 2.21°;
The free-fall acceleration of the satellite is 1.8 m/s²;
The satellite is called Jupiter

Volcanic eruptions are a relatively frequent phenomenon on Io. Sulfur emissions can reach heights of up to 300 kilometers, with some of them descending to the surface and creating vast oceans of molten lava. Meanwhile, others escape into the outer reaches of space.

The initial four satellites were discovered by Galileo in January 1610 (New Style) when he directed his own telescope, or rather, telescope tube, towards the night sky. He attributed this discovery to the family of the Duke of Tuscany, Cosimo II de’ Medici, whom he served as the court mathematician. The satellites were given the names Io, Europa, Ganymede, and Callisto. These satellites are still recognized as “Galileo’s satellites” and were previously referred to as “Galileo’s moons”.

Galileo observed the satellites using a telescope that had a magnification of 32 times. With modern binoculars, you can observe these satellites near Jupiter as tiny radiant specks.

Until 1892, only these four satellites were known. In 1892, Bernard, a French astronomer, made a significant discovery by visually identifying another satellite of Jupiter called Amalthea using a telescope. This marked the last time a satellite of Jupiter was found through visual observation. However, with the advent of automatic probes equipped with photography equipment, more satellites were discovered in the vicinity of Jupiter. As of now, 16 satellites of Jupiter have been identified and studied to some extent, but this number is not final. The presence of additional, smaller celestial bodies orbiting the planet is being recorded by automated interplanetary stations.

The table provides information on the key features of the Jupiter’s satellites discovered by Galileo, including their Distance to Jupiter, Orbital Period, Radius, Mass, and Average Density.

Now we will provide you with the fundamental details regarding the Jupiter satellites, which have been acquired through the examination conducted by automatic interplanetary stations.

The Satellite Io

Based on the images received from the Voyager 1 probe in 1979, and later from the Galileo probe (which began in October 1989 and reached Jupiter’s orbit), it was discovered that there is active volcanic activity on Io. In one of the photos, there is a volcanic depression measuring approximately 50 km in diameter, containing evidence of solidified lava. This large crater with a flat bottom could have been formed by a volcanic collapse or eruption. Over a hundred similar formations, each with a diameter of over 25 km, have been identified on Io’s surface.

The lava flowing from the satellite’s interior exhibits a wide range of colors, including black, yellow, red, orange, and brown. It is believed that the lava is composed of molten basalt mixed with sulfur, or possibly pure sulfur.

Io possesses a magnetic field that is generated by its core, consisting of liquid metal. The presence of active volcanoes has resulted in the formation of a thin atmosphere around the moon, with minimal amounts of free oxygen. As a result, the liquid sulfur released from the volcanoes accumulates on the surface, as there is insufficient oxygen for it to undergo combustion. This is the primary reason behind the distinct orange hue of Io’s surface.

The ionosphere of Io is profoundly impacted by charged particles from the surrounding space, which become energized by Jupiter’s magnetic field. This energization of the ionospheric atoms gives rise to vibrant auroras, visible in the imagery captured by the Galileo probe.

There is a belief that Europa possesses a metallic core, with a radius that can be as much as half the radius of the satellite itself, which is approximately 790 kilometers. Different calculations suggest that the water-ice shell of Europa may have a thickness ranging from 80 to 170 kilometers, while the ice cover may vary in thickness from 2 to 20 kilometers.

The theory regarding the potential existence of simple life forms on Europa can only be proven or disproven through a comprehensive examination of this moon using descent probes, assuming that such an exploration is ever feasible.

Ganymede: The Satellite of Jupiter

Ganymede, the largest moon of Jupiter, is bigger than Mercury and ranks as the third largest moon in the Solar System, surpassed only by Titan (Saturn’s moon) and Triton (Neptune’s moon). If Ganymede were to orbit the Sun instead of Jupiter, it could easily be classified as a planet in its own right.

Underneath the layer of ice, there is a combination of liquid water and soil fragments on Ganymede. This mixture makes up most of the moon’s mass, resulting in a low average density of 1.93 (g/cm³). To put it in perspective, Europa has an average density of 2.97 (g/cm³) and Io has an average density of 3.57 (g/cm³). The pattern is evident: the farther a satellite is from the central luminary, the less heavy elements are present in its composition. This distribution of matter is believed to have occurred during the formation of Jupiter and its satellites. In this case, we refer to Jupiter as the “luminary”.

Ganymede possesses a highly rarefied atmosphere, similar to Io and Europa. The upper layers of its atmosphere consist of charged particles, forming an ionosphere. One atmospheric phenomenon observed on Ganymede is the formation of frost. It is still uncertain whether this frost is composed of water, carbon dioxide, or a combination of both.

Callisto: The Satellite

Moons of Jupiter

In addition to the moons discovered by Galileo, Jupiter is also surrounded by a number of smaller moons. In total, over sixty of these moons have been found. These moons have varying distances from Jupiter, with their orbits ranging from several hundred thousand to several tens of millions of kilometers.

The table below presents the main characteristics of the 12 small moons that have been discovered and to some extent studied.

The table includes the date of discovery, the semi-major axis of the orbit, the orbital period, the radius or size, and the mass and density of each moon. To see the full table, please visit the website page –>

The innermost moons of Jupiter, known as Jupiter’s inner satellites, are of great interest to astronomers. These satellites, namely Metidea, Adrastea, Amalthea, and Teba, have orbits that lie within the orbit of Io. The largest of these satellites, Amalthea, is an irregularly shaped stone block with impressive dimensions of 250x146x128 km (by Earth standards). In 1892, astronomer Bernard visually discovered this satellite, which appeared to him as a tiny luminous dot next to Jupiter through his telescope. Some physical characteristics of Amalthea were later obtained by the automatic probes “Voyager 1 and 2.” The satellite’s surface is dark and brownish-yellow in color, and it is covered with craters, two of which are particularly large for Amalthea’s size. One crater has a diameter of 100 km, while the other measures about 80 km. The color of the satellite is believed to be caused by the deposition of sulfur ejected by the volcanoes on Jupiter’s moon, Io.