Europa, [juəˈrəupə]，Europa), in 1610GalileoFound, yesJupiterIt is the sixth known satellite of Jupiter, the fourth largest satellite of Jupiter, and the second closest to Jupiter among the satellites discovered by Galileo.
Europa is a temperate world, its surface is covered with ice and its bottom is an ocean.Scientists believe that the Earth's oceans are pregnant with life, while Europa, which has a similar environment to the Earth, may also be pregnant with life.Therefore, Europa's subglacial ocean has become one of the targets for scientists to search for extraterrestrial life.[1]
Europa (pronounced "yoo Roh puh" in English), discovered by Galileo in 1610, is the sixth known satellite of Jupiter and the fourth largest satellite of Jupiter. It is the second closest to Jupiter among the satellites discovered by Galileo.Europa is slightly smaller than the Earth's satellite moon, with a diameter of 3100 kilometers. It is the sixth largest satellite and the fifteenth largest celestial body in the solar system.Observations from the Hubble Space Telescope revealed that Europa has a thin atmosphere containing oxygen (1e-11 bar).
Only seven of the approximately 165 satellites in the solar system are known（IoEuropaGanymede、Ganymede、Enceladus、titanandTriton ）It has an atmosphere.Unlike the oxygen in Earth's atmosphere, Europa's oxygen is not biologically formed.It is most likely due tosunlightThe charged particles in collide with Europa's icy surface to produce water vapor, which is then divided into hydrogen and oxygen.Hydrogen disengages, leaving oxygen behind.
Europa andIoComposition andterrestrial planetSimilar: mainly composed of silicate rocks.But unlike Io, Europa has an ice layer with a thickness of up to 100 kilometers on its outer layer. Due to its internal energy source, deep under the ice or a liquid water world, the surface of this celestial body is very "smooth" and there are fewer impact pits, which indicates that the geological structure of Europa is relatively active. The data sent back from Galileo shows that Europa has an internal layered structure,It may have a small metal core.
On December 11, 2013, NASA announced that clayey minerals were found on the surface of Europa, which may lead to new life.Europa's surface is covered with ice. The temperature of the ice layer is about minus 26 degrees. There is an ocean under the ice layer, 96 kilometers deeper than the deepest ocean on Earth.
On September 26, 2016, NASA expert Jeff Youde said that Europa's underground ocean is considered to be the most promising place for life in the solar system except the Earth.
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Europa
Europa was discovered by Galileo and Marius, Simon in 1610. Galileo also found that some Europa has weakmagnetic fieldEvidence (equivalent toGanymede1/4 of).
Europa: in Greek mythologyPhoenicia(Phoenicia) PrincessEuropaEuropa, the daughter of Agenor.OkamiZeus(Zeus) turns into a white bull and seizes itCrete(Crete) and gave birth to three sons with her:Minos（Minos）、Ladamantis(Rhadamanthys) andSarpedon（Sarpedon）。
Europa was a beautiful Phoenician princess in Greek mythology, and the other three Galileo satellites were also named by Marius as Greek mythological charactersIo(Io, Io)GanymedeGanymede and Callisto are famous for their beauty.But before the middle of the 20th century, for a long time, this set of names was not recognized by astronomers.In the early literature, Europa was called Europa by position number.It was discovered in 1892Europa, more inward than any previously known Jupiter moon.1979Voyager probeThree more inner satellites have been found, so far, Europa ranks sixth.Nevertheless, the serial name is still inherited, and sometimes it is used in Chinese because of problems such as pronunciation. It is also commonly used to refer to Europa with "Europa".
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form
Four Galilean satellites
Europa andIoComposition andterrestrial planetSimilar: mainly caused bysilicateRock composition.But unlike Io, Europa has a thin ice shell.Data sent back from Galileo indicate that Europa has an internal layered structure and may have a small metal core.But Europa's surface is not like that of the inner solar system. It is extremely smooth: only a few hundred meters high terrain can be seen.The protruding marks appear to be albedo characteristics or some small fluctuations.
appearance
Europa cross
The surface photos of Europa and theiceThe photos of are similar.This may be because there is a layer of liquid water under the ice on Europa's surface, perhaps 50 kilometers deep, which is kept liquid by the heat brought by the tidal force.If the hypothesis is true, this will be the only place in the solar system that has a large amount of liquid water besides the Earth.
Europa's most striking appearance is a string of cross stripes all over the world.The larger one spreads outward to the light material zone, with a length of nearly 20 kilometers.The recent theory of their origin is that they are composed of a series ofvolcanoTo produce a spout or fountain.
come fromGalileoThe pictures sent back by Europa twice seem to confirm the earlier theory:CraterVery few, only three circular mountains with a diameter of more than 5 kilometers are found.This shows that it has a young and active surface.However, Voyager has made a small number of surface high-resolution maps, and the precise surface age of Europa is an outstanding issue.[2]However, some activities are obviously taking place, and some areas look like the melting of ice in the polar oceans when spring comes.The exact nature of Europa's surface and interior is not clear, but there is one surface“ocean”Exact evidence of.
Europa is another distinctive moon in the solar system.Europa is the brightest satellite in the solar system. The reason why it looks so bright is that it has a thick ice shell on its surface, which is full of meteorite impact craters and crisscross stripes.Europa's interior is likely to be very active. Under the ice crust, there is probably the largest liquid water ocean in the solar system, which is likely to contain life.
atmosphere
In 1994,Hubble Space TelescopeGoddard High Interpretation Spectrometer observed that Europa's surface is wrapped with an extremely thin atmosphere composed mainly of oxygen (1 surface pressure is about 1 μ Pa).Of all the known satellites in the solar system, only seven have atmospheres (the other six areIo, Ganymede, Enceladus, Ganymede, Titan, and Triton) are different from Earth, and the oxygen in Europa's atmosphere is non biological.It is likely that the impact of charged particles and the irradiation of ultraviolet rays in the sun caused some water molecules in the ice layer on Europa to decompose into oxygen and hydrogen. Hydrogen escaped due to low atomic weight, while oxygen with relatively high atomic weight was retained.
track
The average distance between Europa and Jupiter is 670900 kilometers, and it only takes three and a half days for Europa to make a revolution.Its orbit is very close to a perfect circle,EccentricityOnly 0.009.Like other Galilean moons, Europa was alsoTidal locking Therefore, there is a hemisphere always facing Jupiter.The heat and energy generated by the gravitational traction of Jupiter and other satellites in different directions provide necessary conditions for the possible liquefaction of the ice layer into the ocean and driving the geological movement below the surface.
Geological structure
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Europa Core
Europa's main composition andterrestrial planetSimilarly, it is mainly composed of silicate rocks.Its surface is covered by water, and it is speculated to be hundreds of kilometers thick (the upper layer is a frozen ice shell, and the bottom of the ice shell is a liquid ocean). The magnetic field data collected by the Galileo spacecraft orbiting Jupiter for scientific research from 1995 to 2003 show that Europa can generate an induced magnetic field under the influence of Jupiter's magnetic field, which suggests that,It is likely that there is a conductive layer similar to the salt water ocean in the interior of its surface layer, and Europa may also have a metallic iron core.
Surface characteristics
Europa
Europa's surface is generally smooth, with few undulations of more than a few hundred meters. However, in some areas, a fall of nearly one kilometer can also be observed.Europa is the smoothest celestial body in the solar system.Its striking crisscross lines, the so-called reflection features, are caused by low and shallow terrain.Europa has one of the highest albedo due to the very few impact craters.This also implies that its surface is quite "young" and "active";Based on the estimation of the comet impact frequency that Europa may experience, its "surface" age is about 20 million to 180 million years.
Europa
The most prominent features of Europa's surface are the dark stripes that are all over the planet.Close observation shows that the plates on both sides of the stripe move towards each other.The transverse span of the larger stripes can reach 20km, and it can be observed that the dark part of these wide stripes has a fuzzy transition with the outer edge of the plate.Regular lines and wide stripes with light colored fine lines may be caused by the eruption of ice volcanoes or geysers caused by the cracking of the surface ice crust and the exposure of warmer underlying materials.This has a similar effect to the ridge on the earth.It is supposed that most of the cracks are caused by the strong tidal pressure exerted by Jupiter;Because Europa has beentideLocked, it always keeps one direction towards Jupiter, and the fixed pressure pattern should be able to form a specific and predictable exception pattern.On Europa's surface, however, only the newly appeared cracks can match the predicted pattern. Other cracks can extend in all directions, and the older the cracks are, the more so.A more logical explanation is that Europa's surface rotates slightly faster than its interior. The ocean beneath the ice separates its crust from the lower mantle, and the ice crust is torn by Jupiter's gravity.Comparing the pictures taken by Voyager and Galileo, it can be calculated that Europa's shell rotates one more week than its interior every 10000 years.
Another remarkable feature of Europa is the dark spots, big or small, round or elliptical, which are all over the four fieldslenticulae, meaning "freckle".Some of these dark spots are raised like a dome, some are sunken like a pit, some are flat like a mirror, and some have rough texture.Most of the protruding hills have flat tops, which shows that they were originally formed by pushing and lifting together with the surrounding plains.It is speculated that the formation of dark spots is caused by the "warm ice" with higher temperature in the lower layer rising up under the action of diapir and penetrating the "cold ice" in the surface layer, and its movement mechanism is similar to the magma chamber in the (earth) crust.The smooth dark spots are caused by the molten water seepage when the "warm ice" breaks through the watch shell. Those rough and jumbled spots (also called "chaos" areas, such as the Conemara chaos) are composed of a large number of small pieces of the watch shell inlaid in the dark dome, just like an iceberg (earth) floating in the polar ocean.
Subglacial ocean
A spectacular fountain as high as 200 kilometers can be seen on Europa
The average surface temperature of Europa in the equatorial region is 110K (- 163 ℃), and the two poles are lower, only 50K (- 223 ℃), so the water on the surface is permanently frozen.But the heat provided by tidal forces may keep the water below the surface ice layer liquid.This conjecture was initially triggered by a series of conjectures about tidal heat (the consequences of slightly eccentric orbit and orbital resonance between Europa and other Galileo satellites).
It is speculated that Europa's topographical features imply the existence of an subglacial ocean.Some scholars have explained the distinctive chaotic zone on Europa's surface as a result of the seepage of the lower seawater from the surface.However, this interpretation is controversial. Most geologists studying Europa prefer to support a theory called "thick ice" model. They believe that even if such an ocean exists, it is almost impossible to have a direct impact on the surface.There are also considerable differences in the estimation of the thickness of the ice crust, some think it is thousands of meters, others think it is tens of kilometers.
If you are in Jupiter's moon Europa, you can see the spectacular scenery up to 200 kilometersfountain。This may be the best evidence of a huge ocean hidden beneath Europa's frozen surface.American and German researchers reported in the journal Science on December 12, 2013 that they used the images taken by the Hubble Space Telescope in November and December 2012 and 1999 to determine that there was too much hydrogen and oxygen in two different regions of Europa's southern hemisphere, but only one explanation was that these hydrogen and oxygen were electrolyzed from the water ejected from Europa.
The artistic imagination of ice piercing robot and culvert swimming robot.
The geysers on Europa erupt intermittently for about 7 hours each time.Because this phenomenon appears at the farthest distance between Europa and Jupiter and disappears when it is closest to Jupiter, researchers speculate that Jupiter played an important role in the tidal gravity of Europa, which may lead to cracks in the ice layer on Europa's surface at the farthest point, and fountains jet out from these cracks. When it reaches the near point of Jupiter, these cracks will gradually close.The appearance of fountains indicates that some areas of Europa's frozen surface may be easily "broken" by the internal ocean, which is of great significance for exploring whether Europa is livable in the future.Because this intermittent fountain will spray Europa's surface and deep materials into the air, it will not be necessary to drill holes on the ice to study Europa's composition in the future.
The fountain on Europa may resemble Saturn's moonEnceladusThe fountain on Enceladus is caused by high-pressure water vapor escaping from a very narrow fissure.However, the gravity on Europa is 12 times greater than that on Enceladus, so Europa's fountain will not escape into space like most of Enceladus, but will fall back to the surface of Europa when it erupts to a height of 201 kilometers.
For a long time, many scientists believe that Europa is the most likely planet to have life in the solar system except the Earth. This is because there is a huge ocean hidden under the ice layer on the surface of Europa, and life may exist if there is liquid water.NASA also announced on December 11, 2013 that clay type minerals were found on the surface of Europa for the first time, which means that there may be organic matter vital to the formation of life on Europa.[3]
Impact crater
High resolution image of Europa taken by Voyager 2
The few large impact craters on Europa's surface are the best evidence to support the "thick ice" model.The largest impact crater is surrounded by several concentric circles, and the crater is fairly flat filled with fresh ice.On this basis, combined with the estimation of the heat energy generated by tidal forces, it is inferred that the thickness of the ice shell is between 10 and 30 kilometers, which means that the ocean under the ice may be as deep as 100 kilometers.
The Galileo orbiter also observed that Europa will generate an intensity ofPeriodic changeThe weak magnetic field of Ganymede (its intensity is close to that of Ganymede, about a quarter of that of Ganymede).It is speculated that the polar ions in the salt water sea under the ice are the cause of the magnetic field.There is also evidence from spectral analysis that the reddish substance in the cracks on Europa's surface may be the salt deposited after volatilization of sea water seeping from under the ice (such asmagnesium sulphate），hydrogen sulfideIt is also a reasonable explanation for this phenomenon.However, since the pure substances of these two substances are colorless or white, other substances are also used to explain the cause of light red, such as mixtures containing sulfur.
Europa's mass is so small that the gravity of Jupiter's other moons seriously affects it.Under the gravitational pull of Jupiter and other Jupiter moons, Europa appearstidal friction And make Europa warm, so that ice and liquid water erupt from Europa's surface, which is very spectacular.Just like the volcanoes on earth, but the ice volcanoes on Europa erupt ice and liquid water.
glacier
The first moon of Jupiter has volcanoes, while the second moon Europa has glaciers, which is the opposite of Io. This puzzled scientists.Europa is a quiet world.Its terrain is very flat, and the highest hill is only 50 meters.Its surface is covered with a layer of crystal clear ice.Scientists received the photos sent back by the space probe Voyager 2. Through research, it is speculated that Europa has a solid core with an ice shell, and there may be a layer of liquid water between the ice shell and the core.It is this structure that forms the flat terrain of Europa, and makes it withstand the impact of meteorites and asteroids without deformation.Astronomer Stevenson and others calculated the heat dissipation of Europa, and confirmed that there is a liquid water layer between the core and the ice shell.Through several different models of experiments, they concluded that Europa has an underground ocean under the ice layer 25 kilometers deep.
ocean
NASAGalileoThe latest image sent back by the Jupiter probe shows that there is a large amount of liquid water on Jupiter's moon Europa, the ice mantle on its surface is only 1~2 kilometers thick, and there is an internal volcanic heat source.This is so far aboutExtraterrestrial objectsThe most powerful evidence for the existence of liquid water also increases the possibility of people searching for extraterrestrial life.If Europa really exists as scientists imagineOrganic compound, then it is satisfiedlifeExisting conditions.
Galileo probe Photos taken while flying over Europa only 586 kilometers away show that there seem to be some icebergs floating on the ice covered sea.The largest of these icebergs is 13 kilometers wide, and it can be clearly seen that they were broken down from the belt with grooves.Scientists were surprised by the similarity between the features in the photos and those in the Arctic region of the Earth.Galileo's earlier images showed that Europa had surface motion, but the scale of motion characteristics was about 80 kilometers, which may be attributed to plate motion without liquid participation.The iceberg found this time is floating on the liquid, not on the ductile mantle.
From the shadow cast by the icebergs, it can be calculated that they are 100~200 meters higher than the surrounding ice sea.Assuming that, like the earth, the density of ice is about 10% lower than that of liquid water, then about 90% of the iceberg should be below the ice surface.This means that the thickness of the iceberg should be 1-2 kilometers.
Only two impact craters were found on the frozen sea surface in the photo, indicating that the formation age here may be less than 1 million years ago.This increases the possibility that this area is newly formed and liquid water still exists, and this phenomenon may also exist in other parts of Europa.Newly discovered evidence shows that Europa's entire surface is several orders of magnitude younger.It is estimated that a large range of images with resolution less than 1 km will be usedImpact crater(about 10 kilometers in diameter), but some of these "impact" craters show that they are actually formed by the surface reconstruction process caused by Europa's internal phenomenon.For example, a polygon depression that can be seen clearly on a 70 meter resolution nearsighted image is mistaken for an impact crater on a large scale image.
The high resolution also enables researchers to count a large number of small impact craters (0.1~1km in diameter), and these data make the size/density distribution of impact craters three orders of magnitude lower than the value estimated based on the surface life of 1 billion years.This means that some areas of the satellite are 1000 times younger than originally estimated.It is not easy to convert the number of impact craters into the data of Jupiter's surface age, because people do not know as much about the passing amount of meteors near Jupiter as they do near the Earth.
Underground salt lake
NASA found that there is a huge saline lake under the ice layer of Europa, Jupiter's moon, whose water volume is roughly equal to that of the famousThe Great LakesThe total amount of water.
This newly discovered lake is located about 3 kilometers below Europa's surface ice layer. It represents the latest potential breeding ground for life found by humans in the solar system, and is also considered to be one of the most suitable environments for life in the solar system besides the Earth.
The scientists used the images taken by Galileo probe to compare and analyze the images of the floating areas of icebergs and ice cover areas in high latitudes on the earth, and preliminarily confirmed that "mixed landforms" (the two once puzzling areas on the images taken by Galileo probe are roughly circular and seemingly rugged) are irregular aggregates formed by the collision of floating icebergs,But in order to further confirm this discovery, scientists need more detailed data, which requires close observation with the help of detectors with ice penetrating radar.NASA is considering launching such a spacecraft before 2022 to carry special equipment to Europa for investigation.
There may be more undiscovered lakes beneath Europa's ice.Considering that the overlying ice layer of these subglacial lakes may be thin in some areas, with a thickness of only tens of meters, this will provide great convenience for exploring the potential signs of life in these lakes in the future.This smaller ice thickness may mean that there may be more opportunities to land here in the future and obtain sediment samples from these subglacial lakes for research.
Smooth interpretation
Is Europa heated by tidal force "friction" like Io?To what extent?Is there something hidden under the iceVolcanismWhat about?According to relevant British media reportsNatural satelliteScientists also plan to launch probes to Europa for close observation and research.The reason why scientists are interested in Europa is that they think there is a lot of liquid water under the dense ice layer of Europa.The geological map of Ganymede drawn by American scientists will help scientists to understand more about the geological evolution history of the satellite and determine the basic direction for further research on it in the future.This geological map was drawn by scientists based on the data obtained by Galileo and Voyager 2 probes.
As we all know, between 1998 and 2003, Galileo and Voyager 2 carried out relatively close exploration and research on Jupiter and its satellites respectively. According to the data obtained, scientists concluded that the geological history of Europa's surface is relatively young but rich in changes, and there is little volcanic activity on Europa.Many of the giant rift valleys on it may be caused by Jupiter's strong gravity.According to the University of ArizonaplanetLauren Greeley, director of the Geology Teaching and Research Office, said that the biggest difficulty in drawing Europa's geological map is whether scientists trust the relevant exploration data sent back by the probe.
The resolution of Europa's surface photos taken by Voyager 2 probe is 2 kilometers per pixel.The resolution of the photos taken by Galileo during its flight around Jupiter and its satellites can reach 12.6-0.23 kilometers per pixel.When drawing this geological map of Ganymede, scientists combined the data provided by the two probes.Scientists who believe that there is life on Europa also hold the view that Europa has all the necessary conditions for the birth of life, that is, there is liquid water, rich energy (mainly the strong gravity of Jupiter) and organic compounds on it.If there is life on Europa, it will be similar to the organism living in the deep water of the earth.After 2015, scientists will launch a special probe to Jupiter and its satellites.Lawn Greeley and from the US BureauJet Propulsion LaboratoryRobert Papalardo will lead dozens of astronomical experts to study how to detect the Jupiter system, including the flight orbit of the probe, and what scientific research instruments and equipment will be carried.Scientists also hope to launch a robot equipped detector to Europa, so that they can go deep below the ice layer of Europa to study its groundwater.However, this idea is very difficult to implement, because Europa's surface may be covered with ice up to 20 kilometers thick.
According to British scientist John Zarnetsky, if you want to study Europa, you must first launch an orbital probe to find out what is underneath the ice, and then use other detectors to find out.
Liquid water found below Europa's surface
Scientists found that Europa's polar rotation axis was offset by nearly 90 degrees. Such extreme changes indicate that there is a liquid ocean under the surface of Jupiter's ice shell, which further indicates that Europa is likely to harbor extraterrestrial life.This study was conducted byCarnegieInstitute, Lunar and Planetary Research Association andUniversity of California, Santa CruzThe research report was published in the journal Nature.
One of the members of the joint research team is Isam Cynsuma of the Carnegie Institute's geomagnetic department. He used pictures taken by the Voyager, Galileo and New Horizon spacecraft to draw a large arc basin with a diameter of more than 500 kilometers on the surface of Europa.It is reported that Europa has a radius of 1500 kilometers, slightly smaller than the moon.
By comparing the topographic features of the basin fault formed by the pressure of Europa's polar rotation axis migration, researchers measured that the polar rotation axis was offset by more than 80 degrees, and the previous rotation axis was about 10 degrees away from the current equator.
The violent shift of Europa's polar rotation axis is likely due to thick ice beneath the polar surface.Matsuyama said, "The rotating body needs to seek stable balance based on the maximum change of the rotating axis. For Europa, the thickness of its shell is inconsistent, which will lead to a large degree of imbalance. Therefore, Europa must change the rotating axis to seek a new stable state during operation."
Such a change is called "true polar shift", which is not due to the visual drift of slab architecture.On Earth, Mars andSaturnOfEnceladusThere is also a real polar shift on the.Matsuyama said that Europa has also been included in our research, which shows that we need to do more research on repositioning the planet.
At the same time, this research suggests that there is liquid water inside Europa. Scientists have guessed that the planet has a vast underground ocean based on the photos taken by the spacecraft. These photos reveal that there is a broken ice surface below the surface of Europa.The tidal force formed by Europa's gravity can heat the underground ice crust ocean into hot water. Even if the underground ocean cuts off the source of solar energy, the heat and liquid water can also breed life.
Europa may have fish life
In November 2009,University of Arizona Scientists Richard Greenberg and others have found that Europa may have fish like life
Europa may have fish like life
Today, many scientists believe that Europa has no land on its surface, but there is an ocean covering the whole world under the thick ice layer, with a depth of about 160 kilometers.Greenberg's latest research shows that Europa's ocean is absorbing a lot of oxygen, which is much more than the previous simulation predicted.Scientists believe that the oxygen is enough to support the existence of various life forms. Theoretically, there should be at least 3 million tons of fish like organisms in Europa's ocean.Greenberg explained, "Although we can't say that there must be life there, we at least know that the physical environment there supports the existence of life."
Woods HaierDeep-sea ecologyTimothy Shank, a scientist, believes that Europa's seabed environment is very similar to the "hydrothermal outlet" at the bottom of the Earth's oceans.As we all know, EarthSubmarine hydrothermal fluidThere are many life forms at the exit.So Shank insisted, "If there is no life on Europa, that would be strange."
Discovery
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Flyover observation
Most of the knowledge about Europa came from flyby observations during the Voyager and Galileo missions.
Plan I
The ambitious Jupiter orbiter program was canceled in 2005, but various proposals for Europa's future exploration mission have been constantly put forward[4]。
NASA 2006（American AirlinesThe budget of the National Aeronautics and Space Administration (NASA) includes the establishment of a fund for the future circumnavigation Europa program at the oral request of the United States Congress.In the imagination, the tasks of the plan include: to confirm whether there is an ocean under Europa's surface ice crust by means of gravity and height measurements;High resolution photography was conducted on the surface in a wide range, and the chemical composition of surface materials was confirmed through spectral analysis;And the use of ice piercingradarPenetrating detection of ice layer, etc.The plan even considers that the spacecraft will carry a small landing device to directly analyze the chemical composition of Europa's surface, and collect seismic wave data to determine the thickness and activity of the ice layer.However, it is uncertain whether the plan is actually possible to start, and there is no such fund in NASA's 2007 budget.
Plan II
Another possible plan is to use an impactor similar to the Deep Impact (DI) program.Hit Europa's surface violently with the impactor to stir up debris smoke, and let a small spacecraft collect debris through the smoke.Since there is no need to launch a lander from Jupiter or Europa's circumnavigation orbit - and of course, the step of taking off from the satellite again is omitted - the fuel consumption will be greatly reduced, so this idea is regarded as one of the most economical solutions.
other
There are some bolder ideas, such as launching aLanderLook for possible signs of life frozen in the shallow layer of the ice crust, or go deep into the interior to explore the ocean under the ice.The proposal is to send a giant nuclear power detector called Melt Probe (ice piercing robot cryobot), use it to melt ice and drill into the ice ocean, and release an autonomous underwater walker (culvert swimming robot cryobot) after contacting the water.This device can transmit the collected information back to the earth.Ice piercing and culvert swimming robots must be strictly disinfected to avoid mistaking the organic matter that may be carried from the earth for local organisms and avoiding the pollution of the sea under the ice.This bill has not yet entered the stage of serious planning.
Cryobot has been tested in Antarctica.As the drill bit melts the ice through the heat generated, the detector will "sink deeper and deeper".Melting ice is a good concept in theory, but if the detector encounters something deep in the ice, such as a large stone, it will fall into it.If the ice cannot be melted, then the exploration mission will come to an end.Hong Kong Polytechnic UniversityAnd Hungary's Graz Wiltrom Foster Institute designed innovative methods that perfectly integrate drilling technology and melting methods.The prototype of their "thermal drill" system performed well in the experiment, and the experimental results were published in the journal Planetary and Space Science in July 2008[5]。
On September 27, 2016, NASA announced a major discovery. Scientists observed that Jupiter's fourth largest satellite, Europa Europa, had water vapor erupting, and there might be life if there was water.
The Hubble Space Telescope observed that a column of water vapor on Europa's surface ejected outward along the direction of 7 o'clock.This is a strong evidence that there is a liquid ocean under Europa's ice layer, which can create favorable conditions for breeding life.
The researchers calculated the possible hydrogen content in Europa's oceans when seawater interacts with rocks, a process known as serpentinization.In this process, water penetrates into the pores between mineral particles and reacts with rocks to form new minerals and release hydrogen.
Researchers believe that as time goes by, there will be some cracks in the Europa Sea floor, because the rock interior of the planet has remained cold for billions of years since its formation.New cracks expose fresh rock to seawater, and then more chemical reactions to generate hydrogen occur.[6]
In September 2023, the Webb Space Telescope detected carbon dioxide on Europa's surface, but analysis shows that these carbon dioxide may originate from Europa's underground ocean.[11]
The Mystery of Life
The possibility of human migration
Europa
At the end of 2009, Richard Greenberg, a scientist at the University of Arizona in the United States, published a paper pointing out that at least 3 million tons of fish like complex organisms should exist in Europa's ocean.This pushed forward the hypothesis of Europa life proposed by scientists 13 years ago.Europa was discovered by Galileo in 1610. The spacecraft's exploration of Europa shows that there may be oceans under the ice layer of its shell, and the presence of oceans means that there may be life in it.Scientists have been trying to solve the mystery of their lives,
Can humans live on Europa, Europa?Experts from NASA believe that this Jupiter has great "livable" potential and may be suitable for human habitation in the future.Next, scientists will launch probes to investigate Europa's subglacial ocean to determine its thickness and distribution. Some studies believe that Europa's ocean may be similar to the Earth's, but also has a certain salinity.NASA Jet Propulsion LaboratoryDr. Robert Paparado believes that sending a probe to land on the surface of Europa is a very farsighted planetary science goal, but also a difficult technical challenge.
An article from the journal Astrobiology described in detail the three main goals of Europa's exploration mission in the future: first, at least two different depths should be used to monitor Europa's seawater salinity, organic substances and other pollutants;Second, investigate Europa's ice crust, marine physical environment and magnetic properties of surface materials;Third, scientists hope the probe can send back pictures of Europa's surface features.Europa is called the "Europa" planet, and its surface has all kinds of strange terrain, which is like a fairyland. According to the observation data of Galileo, scientists still do not understand the intricate and intertwined "mysterious thin lines" on the surface of the celestial body, and sending a probe to Europa can solve many key problems.
In March 2013, scientists believed that there was sufficient evidence to show that there was a huge salt water ocean under Europa's frozen surface, and there was also chemical exchange between the ice sea and the surface, which made the chemical substances in the ocean more abundant.California Institute of TechnologyAstronomer Professor Mike Brown believes that energy can enter Europa's subglacial ocean from these chemical circulation channelslifeIs very important.
Is there an ocean on Europa
The spacecraft's exploration of Europa indicates that there may be oceans on it.Because of thisJupiter satelliteIn the exploration of Europa, scientists attach most importance to Europa.
As early as 1979,Voyager 1When exploring Jupiter with No. 2, it was found that Europa was like a large sphere mixed with ice and cream chocolate, with curved stripes on its surface.After analyzing Europa's photos and exploration data, scientists proposed that the satellite's surface is covered with 5000 meters of ice, and there may be an ocean as deep as 50 kilometers below the ice.
From the photos taken by Galileo in 1996 at 160000 kilometers away from Europa, the planet appears to be in the shape of an ice shell, with crisscross cracks on its surface, like floating ice at the poles of the earth, indicating that the ice layer was once subjected to tremendous force.After research, scientists believe that this force is caused by Europa, Jupiter and the other three starsGalileo satelliteThe tidal force formed by the gravity between them not only forms the surface characteristics of Europa, but also makes the water inside Europa exist as liquid.
At the end of 1996, when Galileo passed 688 kilometers away from Europa, photos showed that there was water flowing on the surface of Europa.Scientists said that this phenomenon showed that Europa's core was very hot, and a large amount of heat energy was emitted from volcanic craters or hot springs, leading to the melting of some of the surface ice.
In January 1997, Galileo used a magnetometer to detect Europa's magnetic field, which showed that Europa could only have an internal magnetic field to interpret the obtained results.The conductivity of this inner conductive layer must be as strong as that of saline seawater.From this, scientists again concluded that Europa may have oceans.At the same time, the new photos sent back show that the location of Europa's surface cracks has changed, indicating that it is probably caused by ocean flow under the surface.
"Ice cream" with internal heat and external cooling "sandwich" is the ocean
In February 1997, when Galileo flew 586 kilometers away from Europa, photos showed that the largest iceberg on Europa's surface was 13 kilometers wide and 100 to 200 meters high.American scientistsStevenThey believe that Jupiter's gravitational action on Europa's core keeps the water under its ice mantle in a liquid state and becomes an ocean thousands of meters deep.Photographs taken by Galileo in December 1998 showed an 800 meter long fissure south of Europa.
In January 2000, Galileo found that Europa's magnetic north pole moved frequently when it passed 351 kilometers away from Europa.Scientists believe that this is the result of the electromagnetic field caused by Europa's salty ocean flowing under the ice.
After studying the photos of Europa's surface cracks, the Greenberg research team announced in September 2002 that Europa's ice layer was thin, and the observed surface cracks could make gases, heat and organic substances contact the water that might exist below the surface.This shows that Europa's possible oceans are the same as those on Eartharctic oceanbe similar.Since the Arctic Ocean can contact air and heat through cracks in the ice, the oceans on Europa can also contact the outside world through cracks in the ice.
Scientists based onVoyager 2And Galileo, the first Ganymede global map in 2007Geological structure mapIt is revealed that the surface geological structure is relatively young and rich in changes.In 2008, scientists found that Europa's polar rotation axis shifted more than 80 degrees.Such extreme changes indicate that the thickness of Europa's surface ice crust is inconsistent, and there is a vast ocean beneath it.Scientists also used photos obtained by various spacecraft to draw images of a large arc-shaped basin with a diameter of more than 500 kilometers on Europa's surface.After comprehensive analysis and research, scientists believe that Europa has a metal core inside, a stone shell outside the core, a liquid water ocean outside the shell, and an ice layer on the ocean surface.
Whether there are three basic elements of life
Since water is an important condition for breeding life, scientists inferred that there might be life in Europa's ocean after they found it.
After Voyager found that Europa's surface was widely distributed with curved brown stripes in 1979, some scientists thought that this meant that there were organic molecules on the planet, because many organic polymers were brown.At the same time, for the possible oceans, the environment can maintain the survival of organisms, so it is estimated that low-level organisms such as bacteria may survive on Europa.
In August 1996, American scientists proposed that there may also be volcanoes on the bottom of Europa, and the heat provided by its eruption is enough to enable some microorganisms that do not need sunlight and air to survive. This argument is called the Europa life hypothesis.There are three basic elements of life: water, sufficient heat and organic compounds under Europa's ice layer, and its environment is likely to meet the standards of cosmobiology.Around some volcanic craters in the deep ocean of the earth, there are primitive microorganisms breeding in the extremely harsh natural environment without sunlight and oxygen, because these places all have the above three conditions.Scientists who put forward and agree with Europa's life hypothesis believe that its life form can only be low-grade marine organisms inferred from environmental conditions.
These scientists believe that life on Earth originated from volcanic vents in the ocean, and this principle also applies to Europa.They speculated that under the influence of Jupiter's gravity, there was volcanic activity inside Europa.When Europa flies from one side of Jupiter to the other, Jupiter will squeeze Europa, causing the latter's core to be in a molten state, thus causing volcanic activity.Although the volcano did not eject the surface, it heated the water under the ice layer, making it liquid and forming an ocean.Io is squeezed more because it is closer to Jupiter, so the volcano ejects from the surface, leaving sulfur and other chemicals behind.There are also many similar compounds at the hydrothermal vents on the earth's seafloor, which are related to early life on the earth.So scientists infer that EuropaSubmarine volcanoActivities will also erupt similar compounds and create a warm environment, thus breeding and surviving life.
Four Detection Schemes to Uncover the Mystery of Life
The specific goal of human beings in search of extraterrestrial life is Mars at the first place and Europa at the second place.How to use space technology to solve the mystery of Europa's life?Scientists have proposed four feasible schemes.
First, sample by missile bombardment
Humans will launch a spaceship from the earth to Europa. When it flies close to Europa, it will launch a missile at the right time to violently bombard the surface of the target, making ice fragments fly high into the air. Then the spaceship will pass through the blown ice clouds, stretch out the "gel" to collect some of the broken ice, and transport it back to the earth for scientists to study, so as to determine whether there is life information.
Second, near space exploration with spacecraft
NASA andESAThe probe, called Europa Jupiter Galaxy Mission, is under development. It is planned to launch in 2020 and reach the detection area in 2026. The expected working period is three years.The detector consists of two orbiters.The United States is responsible for the Europa orbiter with cameras, spectrometers and a powerful radar system.When it enters the orbit around Europa for detection, the radar system can penetrate Europa's ice layer, calculate the ice thickness, and other instruments will study the signs of marine life.It will help scientists narrow the area where life may exist and provide basis for future detection.ESA is responsible for orbiters with cameras, spectrometers, dust analyzers, mass spectrometers or magnetometers, which will mainly detect Jupiter's satellites at that time.
Third, spacecraft landing detection
Russia will participate in a space research program of ESA from 2015 to 2025, so as to land on Europa to study simple life forms.The spacecraft of this project was built by French astronomersPierreIt is named after Laplace.Russia will develop a landing probe to be carried on the spacecraft.At that time, the landing probe will land on a crack in the ice layer on Europa's surface, melt some ice, and begin to look for traces of life, and then send the detection results back to the ground through the Laplacian spacecraft.
The fourth is to use robots to drill into the ocean for exploration
The plan is to launch two landing robots to Europa. One can drill through the ice to open a passage to the ocean, and the other can enter the ocean along the passage for exploration.The scientific instruments carried by the underwater robot can carry out surrounding investigation and find out microorganisms, including life forms different from those on the earth.The detection results will be sent back to the earth in time.To ensure that the detection effect is not affected by any factors other than Europa, the two highly automated robots must be completely sterilized.
Europa will verify or revise the cosmobiological standards
The significance of detecting whether Europa is alive or not is that, in addition to clarifying the truth, it can also verify or modify the cosmic biological standards.If life is found on Europa, it proves that the standards of astrobiology are at least applicable to solar system objects.If the inferred conditions are true and no life is found, this standard needs to be revised.If the inference condition does not exist, it is another matter.No matter what kind of truth is obtained, it can deepen human understanding of Europa and even the celestial bodies in the solar system, and promote the development of space science.
Other doubts
Moving to Europa?
Extremely cold and a little crowded
stayEight planets in the solar systemJupiter is the largest.Europa is one of the four major moons of Jupiter, with a diameter of 2920 kilometers, which is only about a quarter of the diameter of the Earth. Its volume is slightly smaller than that of the Earth's moon.Scientists speculate that Europa'ssurface temperature In the equatorial region, the average temperature is about - 163 ℃, and the two poles are lower, only - 223 ℃, so the surface water is permanently frozen.However, the heat energy provided by the tidal force may keep the water under the ice layer liquid. In addition, the 60 hour day on Europa also makes the cracks in the surface ice layer likely to receive sufficient sunlight.Even so, if one day humans can conquer Europa, it will be difficult to move for a long time.
Mars and Europa, which one did the Earthlings arrive first?
In addition to Europa, Mars is considered to be another star that may have life forms, because scientists have found that there may still be liquid water deep underground on Mars.Compared with Europa, Mars is closer to the Earth. Therefore, scientists have been paying close attention to the exploration of the mystery of Martian life.Mars and Europa have been used as the final destinations for launching new remote control probes in future space missions.Mars and Europa, who will be the first to prove that they are brothers or strangers to the Earth?[7]
The discovery of clay minerals in Europa
NASA announced on the 11th that clay minerals were first found on the surface of Jupiter's moon Europa, which is most likely to have life. This means that Europa may have organic matter that is crucial to the formation of life.
NASA said in a statement on the same day that a clay type mineral called layered silicate was found on the surface of Europa. It is likely that this mineral was brought by a comet or asteroid hitting Europa, and comets or asteroids that bring clay type minerals usually also carry organic matter.[8]
Possible life
It is speculated that there may belifeExists, and its living environment may beDeep-sea hydrothermal ventOr AntarcticLake Vostok (Lake Vostok), whose life form may be similar to some on the earthExtremophilebe similar.Although there is no evidence yet, based on the possible presence of liquid water, several missions have been sent to EuropaSpace probeThe proposal has been put forward (see the exploration section for details),
On December 11, 2013, the National Aeronautics and Space Administration (NASA) announced that the probe had found clay like minerals on Europa, which was covered by ice and snow, after its impact with comets and asteroids.According to the near-infrared image of Europa taken by Galileo in 1998, NASA research team believes that Europa has a mineral similar to acyl chloride.Because the central core of an asteroid or comet contains organic matter that can form life, NASA researchers said that Europa's ice and snow surface is very likely to hide vast oceans, and it may be possible to breed life after a long time,
Discover the fountain
American and German researchers reported that on Europa, one of Jupiter's moons, a fountain with intermittent eruptions was found, which is the best evidence that there is a huge ocean hidden under the frozen surface of Europa.Once there is water, it means there may be life!Scientists have long believed that Europa may have life.
According to foreign media, new research shows that Europa, a moon of Jupiter, is rich in important minerals, as well as the spectacular water column erupted from the underground ocean, which may be another livable place in the solar system.
According to the Independent on the 12th, the Hubble Space Telescope confirmed two giant plumes of water, 200 kilometers high, intermittently erupting on Europa. Another study found earthy minerals scattered on the frozen surface of the planet.
According to an article published in the journal Science, through the analysis of the data from the Hubble Telescope, it is found that the water column usually erupts at some specific time when Europa orbits around Jupiter, which indicates that the reason for the eruption is that the huge periodic tidal force increases the pressure of the planet's underground ocean, making its liquid eject from the ice crevices on the surface,
The report points out that Europa is the most important of the 63 known moons of Jupiter.Astronomers believe that there are oceans under its ice surface because the heat of tidal force keeps it liquid.Some scientists believe that there may be life in this ocean, and minerals and tidal heat can provide energy for it.
Another study of the data collected by NASA's Galileo project shows that the important earthy minerals found on Europa's surface may have been generated by the collision of the planet with an asteroid or comet.
NASAJet Propulsion LaboratoryJim Shirley said: "We often find important substances that constitute life in comets or primitive asteroids - organic minerals found on the surface of Europa and the residues of collisions with such comets may open a new chapter for us to search for life on this planet."
It is reported that many scientists believe that Europa may be the most suitable planet for life in the solar system except Earth.[9]
A new planetary science paper published by Springer Nature's academic journal Nature Communications pointed out that, based on data from the Greenland ice sheet, researchers believe that there may be very shallow liquid water on Jupiter's moon Europa.[10]
Future exploration
The "Europa Express Sail" will be launched in 2023 at the earliest, carrying nine instruments to the Jupiter system, running around Europa for more than three years, collecting important information about the satellite's geology, composition and hidden internal ocean, and evaluating the habitability of the satellite.[1]
Related research
In September 2023, two scientific research teams in the United States wrote in the latest issue of Science respectively that the data provided by James Webb Space Telescope showed that the carbon dioxide detected on Europa came from the ocean under its cold shell, which made people expect more about the potential life in its ocean.[12]
In 2024, Springer Nature's professional academic journal Nature Astronomy published a planetary science research paper that suggested that Jupiter's icy moon Europa might have less oxygen than previously predicted by the model, and this discovery would affect the potential habitability of Europa's subglacial ocean.[13]
