Io-moon of Jupiter, summary of findings - part I

Io is the first extraterrestrial body to have real-time volcanic eruptions observed by any spacecraft observing it. An island is a living geological body. Some of the volcanic eruptions were more powerful than any known volcanic eruption on Earth.

Below is the first of the two parts of the article.

to the second part of the article

introduction

Io is the closest moon to Jupiter among the Galilean moons. Its diameter is 3630 km, its distance from Jupiter is 422,000 km, its orbit around Jupiter lasts 1.769 days and its density is 3.55 g/cm1. It is slightly larger than the Earth's moon. Like the other bodies in the solar system, telescopes were pointed at it even before the launch of spacecraft. The infrared spectral tests showed that in terms of water it is completely dry. On the other hand, the visible light tests raised the possibility that there is sulfur on its surface(1). A study published before Voyager 2's arrival at Jupiter showed that the strength of the waves acting on it under the influence of Jupiter's gravity is very strong. On the other hand, the other side of the moon is affected by the gravitational force of the moons Europa and Ganymede. These gravitational forces constantly heat its interior and over geological periods of time they melted and melted parts of the moon's interior. The result is volcanic eruptions that began to be discovered from the time spacecraft began photographing the moon(XNUMX). Io is the first extraterrestrial body to have real-time volcanic eruptions observed by any spacecraft observing it. An island is a living geological body. Some of the volcanic eruptions were more powerful than any known volcanic eruption on Earth.

Parallel observations of the past אYo

Along with the Voyager spacecraft and the Galileo spacecraft that transmitted to Israel an abundance of photographs in very high resolutions, additional observations of this moon were made from Earth and other spacecraft. These photographs could not be compared to the Galileo photographs since they were taken from a distance (Galileo's transit flights from the moons were hundreds of kilometers away from their surface), but they have great value on their own and are a complement to the Galileo photographs. The terrestrial observations were made using terrestrial telescopes and the Hubble Space Telescope. The other spacecraft that measured and photographed Io are the Cassini spacecraft that took advantage of Jupiter's gravity to reach Saturn, the New Horizons performed a similar maneuver to reach Pluto and the Ulysses spacecraft whose orbit was such that it would pass over its north pole and fly towards the Sun to study its poles. The terrestrial observations were made at the same time as the Galileo observations. Examples of the additional observations:

1. On July 24.7.1996, 400, the Hubble telescope observed the eruption of the Pele volcano. It was possible to distinguish his plume that reached a height of 3 km(XNUMX).

2. In June 1977 a plume was seen from both Pillen Patera and Galileo and was from Hubble(4). The plume reached a height of 120 km and the eruption could also be seen from terrestrial telescopes.

3. Observations towards Loki Patera on 25.11.1999 from Galileo and the terrestrial telescopes at Mauna in Hawaii and Wyoming(5).

4. One of the hypotheses that the researchers wanted to test is that the bright material on Io is formed from unstable forms of sulfur that condense from sulfur gas. For this purpose, it was necessary to combine the observations of the Galileo and the Hubble telescope, when the Galileo made 3 flybys, the Hubble telescope was directed towards it(6).

5. In December 2000 and at the beginning of 2001, Io was photographed by Galileo and Hexini(7).

6. On February 28.2.2002, 2.5, New Horizons photographed Io from a distance of 8. million km (XNUMX).

7. Between 10.1991-3.1992 an infrared observation was made from Earth towards Io and on 2.1992 the Ulysses observed Io's torus (9). It turned out that part of the dust from the plumes emitted from the volcanic sources does not return to the ground, but escapes into space at a speed of 300 km/h. Ulysses discovered this when it was 100 million kilometers away from Jupiter. As Galileo approached Jupiter, a connection could be found between Io's volcanic activity and the dust eruptions. It turned out that the dust is affected by Io's movement. The dust is electrically charged and Jupiter's electrical forces accelerate this dust to a speed of 300 km/h. Justice throws this dust in all directions (10).

8. The importance and power of earthly observations of the past can be learned from the fact that in some of these observations it was possible to notice the emission of sodium atoms in the volcanic activity of the moon(11).

atmosphere

Infrared observations made by Voyager 1 showed that the moon has a thin atmosphere of SO2. The atmospheric pressure is 0.1 microbar and it is probably at a balance point with SO2 frost on the ground near the equator(12). Galileo found evidence of the circulation of SO2 in the atmosphere. The amount of this gas in the atmosphere increases due to volcanic eruptions and it decreases when the gas condenses and returns to the ground (13). In addition, sulfur, oxygen, sodium, potassium and chlorine are found in the atmosphere. The relative amount of chlorine in the atmosphere is probably higher than in any other body in the solar system and originates from volcanic activity or the breakdown of salt on the ground by ionized particles from the torus which regularly bombards the ground(14). Volcanic activity is also what supplies gaseous salt to the atmosphere. This discovery answered the observation from 1974 that indicated the presence of clouds of neutral sodium around the moon(15)

When Io enters Jupiter's shadow region, its atmosphere partially collapses. At the same time a bright blue emanation emitted from volcanic plumes becomes brighter. What is actually happening is an aurora and it is similar to the terrestrial aurora created during a collision between electrons and gases of the atmosphere. Io is washed by a swarm of charged particles trapped in Jupiter's magnetic field similar to the Van Allen belts that surround the Earth. In addition, a powerful electric current moves from Io towards the poles of Jupiter. This current is created by a very large electric potential caused by the movement of Jupiter's magnetic field passing near Io. When these electrons collide with Yu's atmosphere they create a dim light that shows red, green and blue emissions bright enough to see with the naked eye. The red light and the green light are probably created by neutral atoms of oxygen and sodium and the light blue light is probably created by the volcanic sources emitting the SO2. The partial collapse of the atmosphere occurs when the Moon enters Jupiter's shadow. It originates from the fact that at that time sunlight does not reach the ground and the components of the atmosphere begin to condense during the eclipse(16).

When Pioneer 10 passed by Io it became clear that the moon has an ionosphere that rises to a height of 700 km. This ionosphere is 20,000 times thinner than Earth's. During Io's nighttime, the ionosphere is further depleted due to the influence of Jupiter's magnetic field. The electron density in the ionosphere at its peak is    ^-410X 6 for 1 cc. Since the ionosphere is within the boundaries of Jupiter's magnetosphere, a scattering of charged particles is created. When Io reaches a certain point relative to Jupiter's magnetic field, an electric current is created. Following this current, a current is created between the ionosphere of Io and the ionosphere of Jupiter, which moves back and forth along the magnetic field lines of Jupiter and creates radio waves tens of meters long associated with Jupiter(17).

dust

In July 1994 Galileo began to feel a strong stream of dust, much stronger than that detected by the Ulysses spacecraft. The strength of the current grew stronger and stronger as it approached Jupiter. The speed of the particles as they move away from Jupiter reaches 48-96 km/h (18). The accumulation of information over the years found a connection between the volcanic activity on Io and the dust currents and that they are modulated by the movement of Io. Io's dust is electrically charged so Jupiter's electrical forces accelerate the speed of the particles. In its movement, the dust leaves the plane of Jupiter's equator and is thrown by the planet in any direction it is(19). The intensity of the dust particles that are a product of Yu's volcanic activity reaches a peak every 42 hours, the period of time the moon orbits Jupiter. In addition, they are also affected by Jupiter's magnetic field in a way that occurs only when Io is the main contributor to the dust streams(20).

gas cloud

In one of the volcanic eruptions, a cloud of gas containing ionized and non-ionized atoms is thrown into space. The distance this cloud reached was 150 million km. A significant part of the atoms are sulfur, SO2 and oxygen. Near Jupiter some atoms become ions, then become atoms and in some cases become ionized again. What happens is that the ions are accelerated to a speed that allows them to escape Jupiter, but due to their electrical charge, they remain inside Jupiter's magnetosphere. They can take electrons from other atoms or molecules and become normal atoms again. These atoms are no longer bound to the atmosphere and can move into interplanetary space. From the moment they reach these distances, through photonization (a process in which electrons are blown off atoms due to the collision of high-energy ultraviolet photons from the sun) they become ions again(21).

Around Io are also clouds made of neutral sodium atoms. They originate from the sodium chloride emitted by the volcanic activity that breaks down into its components. These two components are found in a plasmatic torus that surrounds Jupiter (15,22).

Surface

Io is the reddest body in the solar system. On the surface there are a large number of dark spots that are in most cases adjacent to areas that are red or orange in color. At the equator and mid-latitudes these spots are bright. The polar regions are darker. On the surface there are also large areas that are yellow, white or blue-white in color. Some of the spots are a product of volcanic activity and have low relief (23). The source of the difference in colors is from different forms of sulfur in SO2. The color of the sulfur is temperature dependent and ranges from yellow to black. If the temperature of the sulfur drops suddenly as in many cases where volcanic plumes are blown up the color does not change. A study done in 1980 based on the spectral responses of SO2 frost and alkali sulfides shows that the white areas of Yu are SO2 frost and the red areas are mainly other forms of sulfur. This does not mean that there is no SO2 in the red areas, but that the presence of sulfur is more limited than in other compounds. This research also explains the changes in the white and red coloring patterns observed by the Voyager spacecraft. Since the volcanic eruptions are episodic, the changes in soil coloring are both spatial and temporal(17).

Following Galileo's observations, the changes of light green colored substances on the moon were surprising. In several places it seems that red material sinks into a particularly fresh lava flow, at the bottom of the caldera the color changes to green. It seems that the hot soil accelerates the change of the red sulfur types and the sublimation of SO2. At the end of the process, both the red and dark materials turn into a light yellow characteristic of common yellow sulfur made of rings of 8 sulfur atoms(6).

There are many calderas on the island and the flat areas between them are probably made of volcanic sediments covered by new lava flows, material that returned to the ground from volcanic material that was blown up and material that condensed (condense). Near the North Pole, especially white spots are actually hills that stand out from the gray flat surface of the place. There are places where there are formations of inclined plates protruding above the surface that have undergone breaking (faults) or erosion at their edges. There are notched slabs that are hundreds of meters high. Large plates are found in the South Pole and are bounded and crossed by fault lines. Part of the palette overlaps. Their sharp edges reach a height of 1.7 km. These edges are sometimes jagged and sometimes broken and shaped like table mountains (mesas), which indicates some kind of weathering(24).

Iyo has a number of special morphological formations - pits and domes whose size ranges from tens to hundreds of meters. What their origin is not clear. They may be a product of the interaction between the hot lava and the volatiles on the ground. Such formations are formed on Earth when lava flows come into contact with ground water or ice far from the source of the lava(25). Another configuration is a theater configuration. A place that underwent extensive erosion due to the collapse of rocks under the influence of gravity. The height of the walls is 1-2 km above the ground. The largest rock that collapsed is 4 km long, the location W ° 124.8 S ° 21.45 (26). In Prometheus there are plains covered by hills oriented east-west. It could be that these hills were formed by the folding of the soil or depositions of soil by erosion. Along the hills you can see bright lines coming from the edges of the lava flow. Most likely from where the SO2 evaporates from the lava. The light material was probably thrown at a low angle since it covers only the lava side of the hills(27).

In the 17 years between the passage of the Voyagers near Jupiter and the arrival of Galileo, the moon underwent many changes. The most significant factors that led to this are the volcanoes that worked continuously. It is possible to notice changes in the color of the ground due to this. You can see new frost deposits of sulfur - SO2 from the volcano. The SO2 gas creates a large plume, condenses and paints the ground white (28).

Makhteshim

In the set of photographs broadcast by both the Voyagers and Galileo, no impact craters were found on the moon. The reason for this is the massive volcanic activity that resulted in the erasure of the craters and constant renewal of the surface. According to estimates, a total of thousands of tons per second are emitted in the volcanic activity and the meaning is that at least the upper part of the crust and the mantle have been renewed several times during the geological history of the moon(1).

Mountains

The mountains of the moon rise up to a height of 16 km. According to their shape it is clear that they are not of volcanic origin. The mountains are covered with concentric hills, a phenomenon that is also found in the plateaus, which raises the possibility that the mountains create large rockslides under the influence of gravity(29). In Mo'am the mountains are broken and tilted blocks and it is possible to distinguish a clear line of succession of the stages of the collapse of the mountains - initial collapse, intermediate collapse and final collapse, starting with steep rockslides and ending with the leveling of the surface. The lava flattens one area, its environment begins to heat up, this causes the crust to expand, which results in thermal compression pressures within the crust that cause the crust to break up and create fractures and mountains. This behavior can explain the fact of the concentration of the mountains separated from the concentration of volcanoes(30).

Examples of mountains:

1. Euboea Mons location W ° 336 S ° 47. It has an elliptical shape measuring 240 x 175 km and is surrounded by smooth plains with two escarpments that are 100-300 meters high. The height of the mountain in its center is 1±10.5. This mountain was formed when a large block of the crust rose to a height of 10.5 km and tilted at an angle of about 6°. The lifting created a slope around it on the northwest side(31).

2. Haemus Mons, a location near the South Pole. Dimensions at its base 100-200 km (32).

3. Telegonus Mensaeolido a cluster of several ridges parallel to its margin. Location W ° 117.1 S ° 53.8 for (33).

4. Tohils Mons rises to a height of 5.4 km. Location W ° 161 S ° 28 ( 34).

Volcanic sources

All the spacecraft that imaged Io from the Voyagers to the New Horizons that passed by Jupiter on its way to Pluto including terrestrial observations showed that Io is very volcanically active. Some of the outbreaks were short-lived and some continued for a long time. Until 28.12.2000, 120 volcanic sources were counted on the moon(35). A small part of the volcanic foci are in the familiar configuration of terrestrial volcanoes with a caldera at their summit and the majority in the form of ground calderas(2), depressions in the surface from which the lava erupts in full force. Due to this they received the overall name Patera such as Loki Patera. The lava erupts from the volcanic sources and can rise to heights of hundreds of kilometers. Due to its configuration, it received the name plumes. For illustration several volcanic sources will be described in detail.

1. Prometheus Volcano - This volcano is of the type of volcanoes called Shield Volcano. It is the most active volcano in the solar system. Its activity continues since it was first photographed by the Voyager spacecraft and in its morphological characteristics it is similar to the Kilawa volcano in Hawaii, although it is larger. Two hot spots were observed in it, one large in the west and the other colder in the east. Many lava flows were observed in the hot spot(36).

A comparison of the eruptions observed by the Voyager and Galileo spacecraft revealed several differences. In the eruptions observed by Galileo the lava flows are darker. The opening from which they flowed out is located in another place 75 km to the west and the plumes reach a height of 100 km (37). Its plumes are long-lived and require large amounts of volatile substances, probably silica, which is a product of the interaction of the hot lava with the SO2 snow that covers large areas(38).

2. Pele volcano - active for at least 4 years and until the year 2000 it had the largest plume on the moon. In the observation made by the Cassini spacecraft, the height of the plume above the ground was 390 km. Although the temperature was very high, the presence of silicate lava cannot explain this high heat, as it was observed in ultraviolet(7). Pele is probably an area where the temperature is consistently high. Probably an active lava lake regularly exposing fresh lava. In infrared photographs taken by Galileo, part of the volcano glows in a thin, dark, curving line. The length of this line is more than 10 km and its width is 50 meters. It is estimated that this line or rather this path is a cave of exposed lava when the crust breaks along the caldera lines (29).

3. Loki Patera - this volcanic source is the most powerful place in the solar system. It regularly emits more heat than all the active volcanoes on Earth(29). The area of ​​the caldera is more than 10,000 square kilometers (39) and its diameter is 150 kilometers. Its bottom is dark and in the center an "island" with a darker albedo. The amount of heat emitted is 25% of the total heat of an island. The intensity of volcanic explosions can be learned from the fact that they can be seen from the Earth. These are outbreaks that occur once a year and last for several months. In the 24th flyby of the Galileo, a heat source was detected at the western end of the caldera and a more or less constant temperature in the rest of it. On the 27th transit flight, most of the bottom of the caldera was changed and the temperature increased by 40°(40).

4. Chaac Patera - a volcanic source that is 100 km long and 30 km wide. The height of the sides of the caldera is 2.8 km. The lava flows are similar to the caldera of the Kilawa volcano in Hawaii. It is estimated that the bottom of the caldera was covered by a combination of lava flows and lava lakes(41). This caldera contains areas known as the Gulf Stream of Yu due to their green color(42).

5. Ra Patera - a caldera filled with black material that sends out winding arms with lava flows up to a distance of 200 km. The black material is probably a later stage of sulfur and the currents represent colder and less viscous stages(1). Photographs taken by Galileo show a fiery plume in the dark, probably due to the careful release of sulfur and oxygen ions formed by the breaking of SO2 molecules by energetic particles in Jupiter's atmosphere. In one of the photos, you can see changes that took place near the caldera compared to the Voyager photos. The plume that erupted is similar to a new type of activity that was discovered during the Voyager flyby in 1979. Probably a geyser-like eruption fueled by SO2 and sulfur gases that froze in the moon's atmosphere. An area near the caldera with an area of ​​40,000 square kilometers was covered by new lava flows(37).

6. Tvashtar Patera - on 26.11.1999 when Galileo passed within 300 km of the moon, a strong volcanic eruption was observed from this source. The length of the fissure from which the lava erupted is 40 km and the location is W ° 119 N ° 61. A trend cloud with a height of 1.5 was formed. km. This type of lava is not common on the moon. Infrared measurements made a few hours later from both the spacecraft and the Earth raised the possibility that the temperature was higher than 1327°C (43). In the observation made on Yu in 2.2000, the intensity of the volcanic eruption was less in another part of this volcanic source. In the photographs taken on 30.12.2000 from the Galileo and Cassini that was on its way to Saturn, a sulfur plume was discovered at a height of 385 km and a diameter of 1392 km (44). For two years between 2000 and 2002, this volcanic source had 3 types of volcanic eruptions. A 50 km long lava screen in the center of Patera, a very large lava flow at the left end and a very large plume eruption(45). In the eruption observed by New Horizons, the plume reached a height of 330 km (46).

7. Zamama - This volcanic source was formed in the period between the Voyager flyby in 1979 and the first photographs taken by Galileo in 1996. Location W ° 173 N ° 17. Between 1998-1999 there were changes in this area. It is believed that the dark lava erupted from a crack in the ground. The temperature is higher than 830 °C. Since this temperature is too high for sulphur, it is believed that the lava is made of silica. From a comparison between two photographs, it is estimated that the volcanic plume was active in March 3.1998 and stopped in July 1999. In the photograph from 1998, the center of the plume is blue and surrounded by dark lava. From the center onwards light and dark materials fall to the ground. During the fall, they create white circular spots on the ground and yellow deposits around the mouth of the crater. It is estimated that the white precipitate is mainly made of SO2. This material burst out during the volcanic eruption as steam and condensed to frost when the gases spread in the atmosphere (47).

8. Amirani-Maui - photograph from July 3.7.1999, 118. Location W ° 23 N ° 250. It was estimated that the Amirani and Maui formations are of two volcanic origins. It turned out that it was one source. Maui is the active front of a lava flow that has turned westward from the Amirani vent for a distance of more than 2 km. Infrared imaging showed a hot spot on Maui, which means the lava continued to flow. The white deposits around Amirani are probably made from SO250 vapor that came out of the vent, froze and returned to the ground in the form of snow. The red sediment originates from a dark spot southwest of Amirani. They were diverted from the stronger Amirani plume. The red material is probably made of sulfur. The length of Amirani-Maui is more than 48 km (XNUMX).

9. Emakong Patera - a dark caldera from which bright streams come out in all directions. Unlike other volcanic sources, high temperatures were not measured here. A bright stream emerges from the southeast side of the caldera. A dark channel ran along the stream and apparently fed her heart as it grew. The bright, interlocking margins of this flow show that the lava could have moved through narrow topographic areas or that it passed through many rock paths. The observations are consistent with low liquid viscosity, it may be sulfur (49).

10. Camaxtli Patera – location W ° 136 N ° 15. The caldera is active. On the floor of the caldera there are light and dark currents. The dark lava flows have cooled and probably contain magnesium-rich silica. The bright currents are much colder and are probably richer in sulfur. Light dark spots can also be seen outside the caldera and around it there is a dark "halo" that reaches a distance of 30 km from its rim. This "halo" is probably made of frozen drops of lava that returned to the ground after being blown up by a volcanic eruption (50).

11. Culann Patera - one of the most colorful volcanic sources on the moon. It is located north of Tohil Mons mountain. In its eruptions, it created black and red lava flows and around it diffuse rings made of red and yellow sulfur particles, a product of the plumes. Silicic rocks within Culann Pataera mixed with underground reservoirs of sulfur - SO2 and formed plume deposits. The green color in the center of Culann and within Tohil Patera was formed when sediments of plumes made of sulfur reached the ground and the dark siliceous lava flows. The combination between the two materials created a green veneer. The white bright spot southwest of Tohil Patera is rich in SO2 and is probably an area of ​​cold SO2 currents. The small white spots on the peaks of Tohil Patera are probably SO2 deposits that have accumulated in the crevices and bases of the steep slopes in various colder areas of the mountain(51).

According to the estimate made in 2000, the distribution of the volcanic sources on the island is uniform and there are probably 300 active sources. In the 3 months of the Galileo transits near the moon on 10.1999, 11.1999 and 2.2000 volcanic activity was noticed. Some of the small ones "turn on and off" and go from a warm and hot state to a cold and dim state. in a matter of weeks. The large volcanic sources are active for months and even years. The evidence for this is the examination of a continuum line of activity observed by the Voyager and Galileo spacecrafts(39).

In a comparison made between two photographs, one taken by Galileo on October 10.1999 and the other taken by New Horizons on February 2.2007, little changes were found in the surface at the global level, despite the intense activity of the volcanic sources. The volcanic source Dazhbog is very prominent in the New Horizons photograph, but less prominent in the Galileo photograph. In the southern hemisphere at W ° 290 S ° 55 in a photo from New Horizons you see a volcanic eruption that created a circular deposit on the ground with a diameter of 500 km that was not observed by the Galileo. In other photographs from New Horizons it is also possible to distinguish the plume created by this sediment (52).

The caldera structure

There are many calderas across the island. The number of calderas with a diameter greater than 20 square kilometers is greater than 200 and they cover 5% of the surface of the moon whether they are active or dormant. They lack outer edges. in their general configuration. These are depressions in the ground whose sides are steep and the bottom is relatively flat. Although they are usually circular, there are some whose shape is less circular. Some of them have curled sides, which indicates different stages of collapse. There are calderas whose contours are linear and others are elongated and groove-like. In the calderas photographed at high resolutions, ridges can be seen on their bottom. The bottom of most of them is very dark. Although most of the calderas are dark around them, there is a small group whose bottom is lighter. Io's calderas are similar to large terrestrial calderas such as Velles in New Mexico and Aira in Japan, which have low relief and are associated with vents that emit large amounts of ash(53).