Io, also known as Io, is covered with active volcanoes on its surface, and is the celestial body with the most frequent volcanic activity in the solar system,[30]Four of JupiterGalileo satelliteMiddle closestJupiterA satellite of.Its diameter is 3642 kilometerssolar systemThe surface environment of the fourth largest satellite is extremely harsh, with more than 400 active volcanoes scattered all over its surface, and the surface shape shaping cycle is relatively short.Its name comes from the king of godsZeusOne of our lovers:Ao, YesHeraOfPriests。[1]
People used to think that Io must have manyCrater。But fromVoyager 1In the picture sent back to Earth in 1979CraterNot much, not as people think, because its volcanic activity makes its terrain constantly changing.Therefore, people regard its constantly updated surface as "young", because these terrains are newly formed;contrary,MoonThe surface is covered with meteorite craters and has been preserved for billions of yearsMoonThe surface of is regarded as "old".
Io
exceptvolcanoIn addition, there are only some ordinary landscapes in Iomountain range, dissolved sulfur lakeCaldera, and low viscosity liquid flowing for hundreds of kilometers, which may be liquid sulfur orsilicate。In addition, Io'ssulfurIts compounds have many different colors, forming its unique and changeable appearance.
Scientists from two shipsVoyagerAccording to the analysis of many photos sent back, it is believed that the lava flow on the surface of Io is mainly caused by meltingsulfurChemicalsConsists of.But according to the infrared research results on the ground, the temperature of Io hot spot can be as high as 2000K, which is higher thansulfurThe boiling point of is 1300K higher, so it is pointed out that these lavas are unlikely to besulfurThe overall average temperature of Io is 130K,[3]The temperature is much lower than that of hot spots, and the latest theory also points out that those lava flows are caused bysilicateform.according toHubble Space TelescopeThe observation result that these substances may be rich inmetallic elementsodiumIt may contain different substances in different places.
otherGalileo satelliteBoth have solid water, but Io contains very little water. It is believed that the early Jupiter was very hot, and its heat could evaporate the water on Io, but the water of other large satellites was not enough to evaporate.
The energy required for all its activities may come from its interaction withEuropa、GanymedeandJupiterThe interactive tidal generating force between.The co motion of the three satellites is fixed, and the revolution period of Io isEuropaHalf ofGanymedeHalf of.Although Io is like Earth's satelliteMoonGenerally, only the fixed side faces its main star, and Europa and Ganymede make it slightly unstable.It twists and bends Io, about 100 meters long, and generates energy in the cycle of restoring the distortion.
Io in celestia (map replaced)
Io is also cutJupiterOfmagnetic fieldLines, generatingelectric current。The resulting energy is not much for the tidal force, but the power of the current is still 1 megawatt.It also stripped some of the material of Io, andJupiterStrong convex radiation is generated around.Partially, the particles separated from the convex surfaceJupiterThe giant magnetosphere.
Io is slightly larger than the Earth's satellite moon, its average radius is 1821.3 km (about 5% more than the moon), and its mass is 8.9319 × 10 kg (about 21% more than the moon).Its shape is slightly ellipsoid, and its longest axis points to Jupiter.In Galileo's satellite, Io's mass and volume are smaller than those of Ganymede and Callisto, but larger than Europa's.
inside
Inside Io
It is mainly composed of silicate rocks and iron. Io is closer to the main structure of earth like planets than other satellites in the outer solar system, and other satellites are mainly composed of crushed ice and silicate.The density of Io is 3.5275 g/cm, which is the highest among the satellites in the solar system;It is obviously higher than other Galileo satellites, and also higher than the Earth's moon.According to the model established based on the satellite mass, radius and quadrupole gravitational coefficient (the numerical value about how the mass is distributed inside) measured by Voyager and Galileo, it is suggested that there are differences between the inside and outside of it. The silicate rich crust and the inner mantle, iron or iron sulfide rich in the core, and the mass of the metal core accounts for about 20% of the Io mass.According to the sulfur content in the core, if it is completely composed of iron, the radius of the core is between 350 and 650 kilometers (220 and 400 miles);If it is composed of iron and sulfur, the radius of the core is 550 to 900 km (310 to 560 miles).Galileo's magnetometer did not measure the magnetic field inside Io, so it believed that there was no convection in the core.
The model also suggests that the composition of Io's interior, the mantle is at least 75% composed of magnesium rich mineral olivine, and there are a large number of L chondrites andLL chondriteAnd higher iron content (compared with the silicon of the Earth's satellite moon, but still lower than that of Mars) to maintain the heat flow observed on Io, 10-20% of the mantle may be dissolved, but it is observed that high temperature volcanism areas may have a higher melting ratio.Due to extensive volcanism, Io's lithosphere is mainly composed of sulfur and basalt. Its thickness is at least 12 kilometers (7 miles), but not more than 40 kilometers (25 miles).[6]
tidal heating
Unlike the Earth and the Moon, Io's internal heat source mainly comes from tidal dissipation rather thanradio isotopeThis is the result of the resonance of Io's orbit with Europa and Ganymede.Such heating is related to the distance between Jupiter and Io, the eccentricity of its orbit, its internal structure and physical state.It resonates with the Laplacian of Europa and Ganymede, maintaining the eccentricity of Io and preventing its orbit from becoming round due to tidal dissipation.Orbital resonance also helps Io maintain the distance from Jupiter, otherwise the rising tide of Jupiter will cause Io's orbit to spiral and gradually approach the parent planet from outside to inside.The Io tidal bulge has a vertical variation of 100 meters (330 feet) between the near and far wooden points in the orbit.Because this tidal pull produces friction or tidal dissipation inside Io, if there is no orbital resonance, these will make Io's orbit more round;Create greater tidal heating in Io's interior, so that more mantle and core inside the satellite are melted.The energy generated in this way is 200 times greater than that of radioactive decay, and these heat is released in the form of volcanic activity, resulting in the high heat flow observed (global total: 0.6 to 1.6 × 10 watts).Its orbital model believes that the tidal heating in Io will change with time, and the current heat flow is not representative of the long-term average.
surface
Based on their experience of ancient surfaces such as the moon, Mars and Mercury, scientists expect to see many impact craters in the first image of Io sent back by Voyager 1.The density of impact craters across the surface can provide Io's age, but they were surprised to find that there were almost no impact craters on the surface, instead of smooth plains and lava flows with various sizes of craters and volcanoes on the surface.Compared with the spots observed everywhere, Io's surface has colorful materials from different sulfur compositions (compared with the leading hemisphere of Io, there are rotten oranges or pizza colors).The lack of impact craters indicates that Io's surface is very young, like the surface of the earth;The crater is buried by the continuous volcanic material they produce.stayVoyager 1A brief observation confirmed this spectacular scene, at least 9 active volcanoes exist.
Surface composition
The colorful surface of Io is the result of its extensive volcanism leading to a variety of materials. These materials include silicate (such as orthopyroxene), sulfur, sulfur dioxide and sulfur dioxide. The frost of sulfur dioxide spans and generally exists on the surface of Io, forming a vast area of white or gray materials.Sulfur scattered in mid latitude and polar regions is often damaged by radiation, resulting in the destruction of stable 8-chain sulfur.This radiation destruction makes Ao's polar region reddish brown.
The erupting volcano often produces an umbrella shaped stream beam, coating the surface with sulfur and silicate materials.The sediment on the surface of Io beam will be white or red according to the amount of sulfur and sulfur dioxide in the beam.Usually, fromtwoThe current beam formed by the volcano will lead to red fan-shaped sedimentation, or in extreme cases, form a large red ring (in major cases with a height of 450 km (280 miles)).An obvious example of red ring deposits formed by a stream beam is Peilei Volcano. The red deposits are mainly sulfur (usually 3 or 4 chain sulfur molecules), sulfur dioxide, or CltwoSOtwo。The stream beam formed at the edge of silicate lava (through lava and sulfur and sulfur dioxide deposited previously) will cause gray or white deposition.
According to the structural map and high density of Io, Io has no or only a small amount of water. Although small cavities containing ice chips or water bearing minerals have been detected, the most famous is on the northwest side of Gish Bar Mons.The lack of water can be attributed to the fact that Jupiter had enough heat in its early days. During the evolution of the solar system, volatile substances near Io, such as water, evaporated, but the heat was not enough to affect farther away.
Volcanism
By IoEccentricity of trackThe resulting tidal heat forced the satellite to become the most active volcano in the solar system, with hundreds of volcanic centers and lava flows flowing everywhere.When the main eruption occurs, the main components are silicate of basalt and lava flow rich in ferromagnesian or ultramafic rocks, which is ten times longer than usual, and can be hundreds of kilometers long.As a by-product of these activities, sulfur, dioxide flow, silicate debris and other materials (such as ash) can be blown to a height of 500 kilometers (310 miles) to form a huge fan-shaped stream beam, providing red, black and white materials for the surrounding terrain, and providing a wide range of materials to supplement the Io atmosphere and Jupiter's vast magnetosphere.
Io's surface is composed of many sediment points called craters, which generally have high walls and a certain number of flat surfaces.These features are similar to the caldera on the earth;If they are like cousins on the earth, it is through collapse that some lava tubes are formed, but these are still unknown.There is a hypothesis that these characteristics can be identified by the rock strata formed by the excavation of volcanoes and the materials superimposed into or excluded from the rock strata.Different from the characteristics of the Earth and Mars, these sediments do not have a peak in the center of the shield volcano, and they are larger. Their average diameter is 41 kilometers (25 miles), and the diameter of the largest Rocky crater is 202 kilometers (126 miles).Regardless of the formation mechanism, the morphology and distribution of many craters suggest that these characteristics are controlled by the structure, or at least half of them are related to mountains or faults.These characteristics are usually the characteristics of volcanic eruptions, which may be the lava flows across the plains in the crater, such as the eruption of Mount Xiba in 2001, or the formation of lava lakes.In Io's lava lake, there is a lava crust that will continue to flip, such as Mount Perry, or a crust with a flip plot, such as the Rocky Crater.
Lava flows represent another major volcanic terrain in Io.Magma erupts from the vent hole or crack on the surface of the crater to produce expansion, and the lava flow formed is similar to the Kilauea volcano on the earth in Hawaii.The image from Galileo shows that the main lava flows of Io, such as Prometheus and Amirani, are the accumulation of new lava flows above the small fractures on the old lava flows.Enough lava eruptions have also been observed on Io, for example, since 1979VoyagerBy 1996GalileoFor the first time, the lava on the front of Prometheus flows for 75 to 95 kilometers (47 to 59 miles).A major eruption in 1997 produced fresh lava flows more than 3500 kilometers (1350 miles) long and flooded the nearby Pillan crater.
New Horizons' five consecutive images show that the Tevashta crater of Io ejects objects 330 kilometers above the surface.
After analyzing the traveler's images, scientists believe that these fluids are mainly composed of various molten sulfur compounds.However, subsequent observations by the ground-based observatory and Galileo show that these fluids are composed of basalt, mafic and ultramafic.Such a hypothesis is based on the temperature measurement of Io's "hot spots" or the results of thermal radiation positions. These results suggest that the temperature should be at least 1300K, and there are more points up to 1600K. It is estimated that the original eruption temperature can reach 2000K. However, because the temperature was modeled too high using the wrong temperature model at the beginning, it has been confirmed that the temperature was overestimated later.
The discovery of the current beam in the Peilei volcano and the Rocky crater is a sign that Io has active geological activities.Usually, these streams are formed by sulfur and sulfur dioxide erupting from the volcano at a speed of 1 km (0.6 miles) per second. The substances found in the streams also include sodium, potassium and chlorine.These streams appear to be formed by one of the following two methods.The largest current beam of Io is when the molten magma ejects sulfur and sulfur dioxide from the crater or lava lake, and often pulls out silicate volcanic debris. These current beams will form red (short chain sulfur) and black (debris of silicate igneous rock) sediments on the surface.The largest stream beam observed on the Io surface is a red circular deposit with a diameter of 1000 km (620 miles), such as Peilei volcano, Tevashta crater and Dazhbog crater, which are all caused by various forms of stream beams.Another form of flow beam is caused when the lava flow vaporizes the sulfur dioxide frost at the bottom, sending sulfur into the air.In this form, streams often form bright, rounded sulfur dioxide deposits.The height of this type of beam is usually less than 100 km (62 miles), and the beam can last for a long time, such as Prometheus, Amirani, and spirit producing volcanoes.
mountain range
There are 100 to 150 peaks on the surface of Io, with an average height of 6 kilometers. The highest one is Bo ö saule Montes at the South Pole, up to 17.5 ± 1.5 kilometers.The mountains are usually huge, with an average length of 157 kilometers. The isolated structure seems to have no global tectonic model, just like the mountains on the earth.Io must have a crust made of silicate rocks to support these huge peaks. In contrast, the crust made of sulfur cannot be produced.
Although Io's extensive volcanism shows many characteristics, almost all mountains have structures derived from crustal movement.Most of the peaks in Io are not caused by volcanoes, but by the compression stress on the lithosphere, which is raised by the frequent uplift and reverse fault of Io crust.The compressive stress leading to the formation of the mountain peak is the result of the continuous burial of materials from volcanic deposits.The global distribution of mountains seems to be commensurate with the volcanic structure;There are only a few volcanoes in the peak distribution area, and vice versa.This suggests where the lithospheric structure of large-scale regions is controlled by compression (supporting the formation of mountains) and expansion (supporting the formation of volcanoes).Regional, however, mountains and craters are often close together, which means that when the mountains were formed and reached the surface, faults were formed, causing magma erosion.
The peaks on Io (usually the rising structure of the surrounding plains) have various shapes.The plateau is the most common, and its structure is similar to the large, flat topped mountains and solid surfaces.Other mountains seem to be the crust that has been lifted, with gentle slopes, and are formed from the old surface;The steep slope of the surface material is the result of the uplift of the underlying material under the compressive stress.Both types of mountains often have steep slopes forming one or more edges.On Io, only a few mountains appear to be volcanoes at the source. These mountains are similar to shield volcanoes, and the slope is gentle (6 – 7 °). There is a small caldera in the center and along the nearby shallow inclined edge.These volcanoes are generally smaller than the average size of Io's Mountains, averaging only 1 to 2 kilometers (0.6 to 1.2 miles) high and 40 to 60 kilometers (25 to 37 miles) wide.There are also several shield volcanoes with more gentle slopes. Because lava flows radially from the center, it can be inferred from the typology that they are the volcanoes on Io, like the LaVolcano structure.
Almost all mountains seem to be in the stage of degradation. Large landslide deposits are a common phenomenon of the mountain foundation on Io, so collapse is suggested to be the main form of degradation.The common feature of the Fangshan Mountain and the Plateau in Ai'ao is the scalloplike edge, which is the result of the infiltration of sulfur dioxide from the crust of Ai'ao, resulting in the weakening of the mountain edge area.
The aurora glows in the upper atmosphere of Io. Different colors come from different components in the atmosphere (green comes from sodium atoms, red comes from oxygen atoms, and blue comes from volcanic gases, such as sulfur dioxide).The image was taken in Aoshi.
atmosphere
Io's atmosphere is extremely thin, only one billionth of the earth's atmospheric pressure. Its main component is sulfur dioxide, and there is also a little sodium chloride, sulfur monoxide and oxygen.The thin Io atmosphere means that the detectors that land in Io in any way in the future do not need to install heat shields to protect the instruments, but need anti propulsion rockets for soft landing.The thin atmosphere also makes the landing equipment strong enough to resist Jupiter's strong radiation, which also makes the thin atmosphere thick.
The same radiation (in the form of plasma) also strips the atmosphere, so the atmosphere must be replenished frequently.The most striking source of sulfur dioxide is volcanism, but the continuous exposure of the atmosphere to sunlight will also sublimate frozen sulfur dioxide.The atmosphere is mainly confined to the equator, because it is the warmest place, and most of the active volcanoes that can form current beams are also on the equator.Other changes will also exist, with the highest density near the crater (especially the crater with current beam), as well as Ao's anti wood point (the point on Ao that is farthest from Jupiter, where the amount of sulfur dioxide frost is the most abundant).
High resolution images taken by satellites show that astronomers can observe auroras similar to glow during eclipses.This phenomenon comes from the effect of radiation and atmosphere, like the aurora of the earth.Auroras usually appear near the magnetic poles of planets, but the brightest auroras of Io are located in the equatorial region.Io itself has no magnetic field, so electrons along Jupiter's magnetic field approach Io and directly hit the satellite's atmosphere.The more electrons hit the atmosphere, the brighter the aurora will be. The magnetic line of force is tangent to the satellite (that is, close to the equator), so the gas column passing there will be the longest.The observed "wobble" of the combination of the aurora and the tangent point on Io indicates the change direction of Jupiter's inclined magnetic dipole field.
Observation history
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Galileo, discoverer of the Io satellite
Io's first observation report wasGalileoIt was proposed on January 7, 1610.The discovery of Io and other Galilean satellites of Jupiter was published in Galileo's March 1610Star boundary report。[7]Simon Marius, 1614Marius JupiterChina claimed that he discovered Io and other moons of Jupiter in 1609, a week earlier than Galileo.Galileo questioned this statement and refuted Marius' plagiarism and plagiarism of his achievements.Galileo published his discovery before Marius, and he believes Marius also knows about it.
Io
In the next two and a half centuries, Io has not yet been resolved, and it is still only a light spot with brightness of 5 in astronomers' telescopes.In the 17th century, Io and other Galileo satellites served a variety of purposes, such as assisting the crew to measure longitude and verify Kepler'sThird law of planetary motion, and measuring the time that light travels between Jupiter and Earth.[7]withCassiniEt alephemerisBased on,LaplaceCreated a mathematical theory to explain IoEuropa, andGeinimideOrbital resonance of.[7]This resonance will have a profound impact on the geology of these three satellites.
The improvement of telescope technology enabled astronomers at the end of the 19th century and the beginning of the 20th century to analyze (be able to see) the surface characteristics of large areas on Io.In the 1890s,BarnardFirst, we observed the photometric changes between Io's equator and polar regions, and correctly measured that the photometric changes in these two regions were due to the differences in color and albedo, not because Io was oval, as inWilliam Pickering And what his companion advocated, not what Barnard originally advocated, were two different celestial bodies.[8]Later telescope observations confirmed that Io was clearly reddish brown in the polar region and yellowish white in the equatorial zone.
Telescopic observations in the mid twentieth century began to notice the nature of the Io anomaly.Spectroscopic observation suggested that there was no water ice on the surface of Io (rich materials were found on other Galileo satellites);The same observation also shows that the main components are sodium salt andsulfur。[9]Radio telescope observations revealed that Io had some influence on Jupiter's magnetosphere, such as those observedTen meterThe wavelength burst is related to Io's orbital period.[10]
Pioneer
The first spacecraft passing near Io wasPioneer 10 andPioneer 11 The twin spacecraft were launched on December 3, 1973 and December 2, 1974 respectively[11]The radio tracking provides the estimation of the improvement of Io quality and the best value of Io size.It is believed that Io has the highest density among the four Galileo satellites, and is mainly composed of silicate rocks, rather than water ice.Pioneer also revealed that Io has a thin atmosphere, and there is a strong radiation belt near the orbit.The only good picture obtained by Pioneer 11's camera shows Io's Arctic region.Pioneer 10 originally planned to take photos when it approached Io at a close range, but this observation failed due to the high radiation environment.[11]
Voyager
Mosaic map of Io South Pole taken by Voyager 1
When another pair of spacecraftVoyager 1andVoyager 2In 1979, they passed through Io, and their more advanced image system can obtain better images.Voyager 1 flew over the satellite from 20600 kilometers on March 5, 1979,[12]It was sent back to the near image, which was strange and colorful but had no impact crater.[13]The highest resolution image shows a relatively young surface dotted with grotesque pits, mountains higher than Everest, and features similar to lava flows.
After a brief encounter, the Traveler EngineerLinda Mona BiduoNotice that in one image there is a stream beam radiating from the surface.analysisVoyager 1After taking other images, a total of 9 photos with this stream beam were found, which confirmed that Io has active volcanic activity.stayVoyager 1Not long before I met Io,Stan Peale、Patrick Cassen、And RT. Reynolds once published a paper, and the author calculated thatEuropaandGeinimideThe orbit resonance of Io will be huge, and there will be tidal heating in Io (seeTidal heatChapter of).Data from this flyby shows that Io's surface is controlled by sulfur and sulfur dioxide frost.These ingredients also control the thinatmosphereAnd around the Io trackPlasma ring(It was also discovered by travelers.).[14]
Voyager 2 swept by at a distance of 1.13 million kilometers (702150 miles) on July 9, 1979. Although it was not as close as Voyager 1, comparing the images of the two spacecraft showed that some areas of the surface had changed in the past five months.On the other hand, Voyager 2 observed Io's crescent shape when leaving Jupiter's system, and showed that 8 of the 9 streams observed in March were still active, onlyPeilei VolcanoIt has been extinguished.[15]
Galileo
GalileoAfter a 6-year voyage from Earth, the spacecraft arrived at Jupiter in 1995 and continued its follow-up observation following the discovery of the Voyager spacecraft and the observation of the ground-based observatory for many years.Io's position is within the strongest radiation belt of Jupiter, which hinders the observation of short distance and long time flying. But Galileo's main task is to study Galileo satellites. In the first two years of the mission, the orbit will enter and closely pass these satellites.Although no image was obtained during the flyby on December 7, 1995, there were still significant results, such as the discovery of a huge iron core similar to a rocky planet inside the solar system.[16]
The encounter between Galileo and Io
date
Distance (km)
December 7, 1995
eight hundred and ninety-seven
November 4, 1996
244,000
March 29, 1998
252,000
June 30, 1999
127,000
October 11, 1999
six hundred and eleven
November 26, 1999
three hundred and one
February 22, 2000
one hundred and ninety-eight
August 6, 2001
one hundred and ninety-four
October 16, 2001
one hundred and eighty-four
January 17, 2002
one hundred and two
November 7, 2002
45,800
stayGalileoDespite the lack of close-up shots and mechanical problems, a lot of information was sent back and some important discoveries were made during the main mission of.Galileo observed the main eruption of Pillan volcano, and confirmed that the volcanic eruption was caused by silicate rocksPlasmaAnd magnesium richMaficandUltramaficComposed of sulfur and sulfur dioxide, similar to water andcarbon dioxideRole played.During the main period of the mission, almost every orbit obtained Io remote images, revealing a large amount of volcanic activity (the rock plasma from both the surface and the volcanic flow beam emits radiant heat when cooling), numerous mountains and extensive morphological changes, as well as between the ages of travelers and Galileo, and during Galileo's different orbits,A change that occurs on a surface.
Galileo's mission was extended twice in 1997 and 2000. During these extended missions, the spacecraft flew over Io three times from the end of 1999 to the beginning of 2000;From the end of 2001 to the beginning of 2002, it flew over again three times.The observation of these encounters revealed the geological process of Ao volcano and mountain, ruled out the appearance of magnetic field, and confirmed the degree of volcanic movement.[17]In December 2000,CassiniThe spacecraft is goingSaturnI had a brief encounter with the Jupiter systemGalileoJoint observation.This observationTevashta craterA new beam was found and the aurora of Io was observed.[18]
Follow up observation
Surface feature changes of Galileo and New Horizon after eight years
stayGalileoThen in September 2003, the hot dilemma appeared in Jupiter's atmosphere, and ground-based telescopes observed new volcanic activity in Io.In particular, from HawaiiKeck telescopeOfadaptive optics Acquired images, andHubble Space TelescopeAllows astronomers to monitor Io's volcanic activity.These images allow scientists to monitor Ao's volcanic activity without using spacecraft.
go toPlutoandKuiper beltSpacecraftNew Horizon NoOn February 28, 2007, he approached Jupiter and Io on the way.During its approach to Io, it obtained many Io remote observation data, includingTevashta craterIt is confirmed that the huge current beam is the largest since the first current beam of Peilei volcano was observed in Io in 1979.The new field of vision number is also capturedGirru PateraThere are also some volcanoes that have been observed in Galileo before the early eruption.[19]
At present, two plans to explore Jupiter's system are about to be implemented.Juno The spacecraft was launched in 2011. Although its imaging capability is limited, it can use the Near Infrared Spectrometer (JIRAM) to provide Io's volcanic activity.Europa Jupiter System Mission(EJSM) YesNASAThe plan to cooperate with ESA was approved in February 2009, but the scheduled launch date is 2020, and two spacecraft will be used to study Io: NASA'sJupiter Europa OrbiterAnd ESAJupiter's Ganymede orbiter。[20]Because the main task of these two spacecraft is to study Jupiter's ice satellite, the observation of Io is almost at a relatively long distance. Before entering the orbit around Europa, Jupiter's Europa orbiters will approach and fly over Io for four times between 2025 and 2026, but ESA's contribution will still face competition in funding from other ESA projects.In addition to the two plans approved by NASA, several plans related to Io have been proposed.A plan called Io Volcano Observer will be launched in 2015. It is set as a discovery level mission and will fly over Io for many times, but this plan is still in the stage of concept research.[21]
On December 30, 2023, Juno spacecraft is expected to fly close to Io, which will be the closest flyby of the spacecraft to this satellite in more than 20 years. At that time, it will be only 1500 kilometers from the surface of Io.[30]
Research findings
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Number of Jupiter's moons
JupiterThe number of satellites has reached 63, of which the largest four are IoEuropa、GanymedeandGanymedeThe most famous, as early as 1610,GalileoHe has observed these four satellites through his telescope and proved that not all celestial bodies orbit the earth, becoming“Heliocentric theoryOne of the best evidences of "(Earth movement theory)", so in astronomy, we call these four big moons of Jupiter "Galilean moons".
VoyagerspacecraftWhen it passed near Jupiter about 20 years ago, it was observed that there were very activevolcanoActivity. Scientists on the ground continuously monitored Io and found that it wassolar systemThe celestial body with the most frequent volcanic activity.However, the Galileo spacecraft, which had just retired a few years ago, found that the temperature of the volcanic hot spots on the surface of Io was up to about 1610 degrees Celsius. In contrast, the volcanoes on the earth (such as the Kilauea volcano in Hawaii) were only about 1000 degrees Celsius, which immediately made Io asolar systemA celestial body whose middle surface temperature is second only to the sun (the sun's surface temperature is about 5700 degrees).It is known that there are more than 100 volcanoes on the surface of Io, and it is confirmed that the frequency of volcanic activity of Io is more than 30 times that of the Earth.Astronomers believe that the reason why Io's volcano is so active is that it is the closest one to Jupiter among the four, and is seriously affected by Jupiter's strong tidal force and magnetic field.
University of WashingtonPlanetary scientists use computers to simulate the volcanic eruption on the surface of Io. The results show that the high temperature of the lava on the surface of Io makes thesodium、potassium、silicon、ironSome of them become monatomic gas, while others maintain molecular state, such asSilicon monoxide、silicon dioxide、Iron monoxideAnd become part of Io's atmosphere.Scientists once predicted in 2000 that these evaporated rock components may produce some rare gases after interacting with sulfur or chlorine in volcanic gas, such assodium chloride、potassium chloride, magnesium dichloride, ferric chloride, etc.
Astronomers actually found it on the surface of Io in 2003sodium chlorideGas composition, but due to insufficient sensitivity of the observation results, the presence of potassium chloride gas cannot be detected.Now, scientists use the observation data of Galileo satellite and the observation results of their ground-based telescopes to analyze and find that sodium and potassium in the hot lava on the surface of Io are evaporating into gas and entering the atmosphere.In addition, they also found that silicon monoxide is the main component of silicon gas in lava;Since astronomers have observed the existence of silicon monoxide in space, especially the surface temperature ofStellar atmosphereTherefore, the discovery of silicon monoxide on the surface of Io is particularly remarkable. They also hope to directly detect silicon monoxide in the gas emitted by volcanoes.Relevant research results were published in Icarus (the main journal of planetary science) in May 2004.
Is the hottest satellite in the solar system
Photo mosaic of Io
In 2004, astronomers found that the hottest star in the solar system (except the sun) is not Mercury and Venus, which are always believed to be the closest planets to the sun, but Jupiter's moon Io（JupiterOne of the four brightest satellites. 400 years agoGalileoFirst found).
Of course, the reason why Io has such a high temperature is not the result of solar radiation, but the result of violent volcanic activity in its interior.In the inner solar system, no other planet or satellite can match Io in the number of volcanoes.
Astronomers first discovered strong volcanic activity on Io more than 20 years ago, when the Voyager spacecraft of the United States took a series of pictures of Io.Since then, the Galileo probe, which has worked near Jupiter for about 8 years, has also taken close photos of this hot satellite.Based on these photos, scientists determined that there was very intense volcanic activity on Io, and its surface temperature could reach 1610 degrees Celsius.
come fromWashington University in St. LouisThe computer simulation experiment of Io's volcanic eruption carried out by researchers ofsodium、potassium、silicon、ironAnd its compounds are melted and evaporated into the atmosphere.The gasification of these substances reacts with volcanic rock gases (containing sulfides and chlorides) to form Io's unique atmospheric components: sodium and potassium chlorides, and magnesium and iron dichlorides.
Gaseoussodium chlorideIt has been found on Io. In terms of conditions, it is necessary to find the gaseous statepotassium chlorideThe sensitivity of our detector needs to be improved.
Although scientists have obtained a lot of data about Io, these data are far from enough for scientists to uncover the mystery of Io: how can this satellite, which is only the size of the moon, maintain such a high magma temperature?Why can't such hot magma melt the surrounding rocks?How thick and firm is its lithosphere (including the crust and upper mantle)?If it had mountains on it, would it be higher than Mount Everest?Of course, it still needs continuous efforts of astronomers to solve this series of doubts.[22]
Frequent volcanic eruptions
Jupiter and Io
Scientists have found that the most active volcano in the solar system is about to erupt, and Ganymede, which has frequent volcanic eruptions, will probably go dormant one day in the future.
Before that, Io, the nearest big moon to Jupiter, has experienced many volcanic eruptions. Its surface is covered with volcanic ash, and there are dozens of active volcanoes on its surface.Io is about the size of the moon.Scientists said that the frequent volcanic activity on Io's surface was due to the combined influence of the gravity of Jupiter and its other three satellites.Because the gravity of Jupiter and its satellites triggered the gravitational changes in different regions of Io's surface, resulting in the stretching and crustal changes in different regions.
This gravitational pull causes Io's surface to move up and down every 10 meters, thus triggering intense crustal activity.After a long time of observation and research, the Paris Observatory of France has confirmed the reason for the frequent activity of this volcano.
Huge heat release observed in the near-infrared band
Scientists said that the most shocking thing is that if this movement is too intense, it will make nearby satellites enter a circular orbit instead of the previous elliptical orbit, then the laws of the solar system will change significantly.In fact, scientists have found this subtle change based on the observation data of Io since 1891.Professor Schubert of the University of California believes that once Io is dormant, the orbit of Jupiter will also change, which will change the orbit of the satellite.The scientists published the relevant research data in the journal Nature.[23]
In March 2014, scientists found that Io ejected nearly 300km high jets[24]。
On August 7, 2014, NASA reported on its website that three large-scale volcanic eruptions occurred on Io, one of Jupiter's four Galileo satellites, in two weeks in August 2013.[25]
Io
May 16, 2016Natural GeoscienceOn the online version, McKinnon and Michael T. Bland, scientists from the Astronomical Science Center of the U.S. Geological Survey, published an article on the computer model, which can build a digital simulated mountain.McKinnon said that planetary researchers believe that the mountains on Io may have been formed by its continuous volcanic eruption, which caused magma to spread all over the planet. The magma spewing to the surface of Io has a downward flow trend.As Io is a sphere, it is subjected to pressure during its downward flow, thus increasing its longitudinal depth.[26]
McKinnon said that this might explain why there is often a recent eruption of magma near high mountains.The pressure intensity in the deep crust is very strong. When the crack extends to the surface, the pressure is released, and the pressure environment of the whole fault changes accordingly, providing a channel for magma eruption.It can also explain an unimpressive feature of Io: the anti correlation between mountains and volcanoes.It is not only because the gradually heavier magma increases the pressure in the deep crust, but also because the temperature is gradually rising.The high temperature makes the rock expand gradually, but due to the lack of space, it is again in a compressed environment.As long as the volcano continues to erupt, it will take away heat, making the thermal stress lower and reducing the possibility of forming mountains.But once the eruption is over, the crust will become hot again, the thermal stress will increase, and the possibility of forming mountains will increase.[26]
In May 2023, NASA released a tweet to share the most recent photos of Io taken by JunoNew photo.[27]
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NASA plans to launch the Io Volcano Observatory (IVO) to Io in 2026 and arrive at Io in 2031.It will collect more data so that scientists can better understand Io's tidal heating and volcanic activity.[1]
On October 16, 2023, NASA's Juno spacecraft took the best pictures of Jupiter's moon Io in decades when it passed 11645 kilometers above it.[28]
On December 27, 2023 local time, NASA reported that the Jupiter probe Juno will fly close by Jupiter's moon Io on December 30, when it will be able to carry out high-definition observation of the planet known for its violent volcanic activities.[29]
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Io's interior isArthur Clark's novel《2010 Space Odyssey》(2010: Odyssey Two, 1984) mentioned that the discovery spacecraft observed Io and its hull wassulfurIs overwritten.
In TV series《Babylon V》In Babylon 5, Io is one of its colonies.
In ComicsMobile Warrior Pirate Steel BulletIn, the news that Io (called Io in the works) is the base of the Jupiter Empire was leaked to the Crusader Pioneers, so the Crusader Pioneers decided to attack Io.
