Enceladus（Mimas, Mimas, Greek: joint venture, rarely spelled as joint venture)SaturnA satellite of,William Herschel Enceladus was discovered in 1789, citing one of the Greek mythsTitan GiantName.At that time, William Herschel's sonJohn Herschel In his 1847 book The Results of Astronomical Observations at the Cape of Good HopeTitans The name of the giant names the seven knownSaturn satellite, including Enceladus, for the reason thatSaturnus（Roman mythIngod of agriculture, equivalent toCronus）He is the leader of the Titans.
On September 17, 1789, astronomer William Herschel discovered Enceladus.He recorded this discovery like this: "On September 17, 1789, my forty foot telescope was in excellent condition, and I found the seventh satellite, which was located at the westernmost side of the orbit at that time."
Naming basisRiedelandScottThe Greek English dictionary of Mimas, the adjective case of Iapetus
Enceladus looks like an egg in the picture taken by Cassini
Is Mimantean (its case is Mimantis in Latin, and is μ ῑ μ ≤ ντο in Greek).In practice, English adjective case such as Mimansian or Mimian is very common, and the phrase "of Mimas" is more frequently used.
name
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Mimas is named after a Titan in Greek mythology.At that time, John Herschel, the son of William Herschel, named seven known Saturnian moons, including Titan, after Titan giants in his 1847 book The Results of Astronomical Observations in the Cape of Good Hope. The reason was that Saturnus (the god of agriculture in Roman mythology, equivalent to Cronus in Greek mythology) was the leader of the Titans.According to Riedel and Scott's Greek English dictionary, the adjective case of Mimantean is Mimantean (its possessive case is Mimantis in Latin, and μ ῑ μ ≤ ντ ο in Greek).In practice, English adjective case such as Mimansian or Mimian is very common, and the phrase "of Mimas" is more frequently used.
physical characteristics
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The density of Mimas is low (1.17), which indicates that it may be composed ofIce bodyAnd a small amount of rock.becauseTidal effectThe moon is not a standard sphere;histhe major axisAboutStub shaft10% long.fromCassiniAccording to the pictures sent back by the spacecraft, Titan is more like an egg.
Mimas surface map
The most prominent feature of Iapetus is a giant moon with a diameter of 130 kilometersImpact crater——In memory of the discoverer William Herschel (1738-1822) of Mimas, it was named Herschel Crater.The diameter of Herschel crater is close to one third of the diameter of the satellitePit marginUp to 5km, some pits are 10km deep, and the central peak is 6km higher than the pit bottom.If there were an impact crater of the same proportion on the earth, its diameter would reach 4000 kilometers, which is more than the width of Canada.The impact event that formed this impact crater almost smashed Mimas: the fracture topography can still be clearly seen on the opposite side of the impact crater, which may be caused by the shock wave across the star after the impact.Due to the existence of this large impact crater on the surface of the star, Iapetus and《Star Wars》InDeath StarAmazing similarity.
In addition, there are many smaller impact craters on the surface of Mimas, but none of them can matchHerschel craterMatch.Although Mimas has been heavily bombarded, the process of crater formation is different.Most of its surface is covered with impact craters with a diameter of more than 40 kilometersAntarctic regionHowever, there are few impact craters with a diameter of more than 20 km.This indicates that some geological activity has removed the larger impact craters in these regions, or something or mechanism has prevented the bombardment of the larger stars on the Antarctic region.
Scientists on Enceladus have identified two major geological structures: impact craters andcanyon。
Saturn Ring
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Enceladus behind the F ring
From the actual effect, Saturn's two widest rings have been cleaned up together——A-ringandB ringBetweenCassini circular seamThe role of the substance in.The particle track at the inner edge of Cassini circumferential crack is 2:1 of that of IapetusresonanceThat is, these particles have gone around for two weeks, and Mimas has just gone around for one week.During this period, Mimas constantly exerted tension on the particles in Cassini's annular gap from the same direction, forcing these particles to enter the new orbit in the outer layer of the annular gap.Enceladus also maintains a resonance relationship with other structures, such asC-ringKeep 3:1 with the boundary of ring BTrack resonanceRelationship, andPandoraThe 3:2 orbital resonance relationship is maintained.Recently, it was found that Mimas also interacted withG ringIt maintains a 7:6 co rotating centrifugal resonance relationship, which is located 15000 kilometers inside the orbit of Enceladus.
probe
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Enceladus
CassiniMimas has been photographed from the middle distance for many times. The most recent one was on August 1, 2005, with a distance of 63000 km.Cassini's follow-up mission included several non directional approaches to Mimas.The two times with good observation conditions were on October 24, 2008 and October 14, 2009 respectively.And the closest oneobservationIt will take place on February 13, 2010, only 9500 kilometers away.
mass culture
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In some ways, Iapetus and《Star Wars IV: New Hope》The Death Star in is very similar, and the latter is hundreds of kilometers in diameter in the play.This is just a pure coincidence, because in the first picture of Iapetusclose-up shotThe film was released three years before the pictures were sent back to Earth.In the novel《Red Dwarf 》In, Mimas is where David Leicester lived before he was awarded the "Red Dwarf Star".Enceladus is the location of the federal emergency rescue station in Star Trek.
Cassini
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Scientists said that due to the influence of light, gravity and other factors,CassiniDetector No[1]The photos of Saturn's latest moon Mimas sent back show that Mimas has some blue stripes on its appearance, giving a cold feeling, especially when observing from the north of Saturn.These colors are formed by the reflection of the halo around Mimas. When the dark night of Mimas comes, these gorgeous colors will disappear[2]。
Photos of Mimas blue from Cassini
Previously, pictures of Mimas sent back by Cassini were taken from Saturn's southern hemisphere[3]The color of the picture is warm brown and gold, but the picture taken from the north of Saturn is completely different. The dark blue color lets us see the other side of Titan, and also lets us have a new understanding and understanding of its atmospheric composition.Scientists say that the reason for this phenomenon is that the blue light used in the last photo was blocked by the atmosphere of Enceladus.
This blue photo of Mimas shows an area about 398 kilometers (247 miles) from the field.The blue and heaviest part on the right side of the picture is caused by overexposure.In the photo, we can also see that there are some dark areas between the circles of blue light. These areas are the B halo of Enceladus, that isAir densityThe area covered by the largest halo.
In the solar system, Saturn is the second largest planet after Jupiter. Its volume is more than 100 times that of the Earthgravitational fieldIt can reach 13 million kilometers away, while the gravity range of the earth is only 930000 kilometers.Because of this, the earth has only one satellite - the moon, while Saturn has many large and small satellites around it, forming a quite large Saturn system;Its number of satellites is also second only to Jupiter in the solar system.IapetusEnceladusIn 1789, the famous British astronomer F. W·herschel It is found that the diameters are about 390 km[7]And 500 km.
As a spacecraft specializing in Saturn, Cassini began to orbit Saturn on July 1, 2004. It has been discovering Saturn's new moon and revealing“Iapetus”His life experience and solution“Iapetus”“Yin and Yang faces”Mystery and explorationSaturn's ringsThe structure and shooting of Saturn's new radiation belt have made gratifying achievements and great contributions.[4]
Shocking collision
Herschel crater
There is a huge and ancient impact crater on Enceladus, which indicates that the celestial body had a shocking collision before, and this huge depression is calledHerschel craterIt is 80 miles in diameter, while Mimas spans only 247 miles.[4]
Herschel crater is named after the astronomer William Herschel, the discoverer of Mimas.The crater is about 139 kilometers wide, accounting for about one-third of the diameter of Mimas. Large craters usually have a lone peak in its center, such as the Odyssey crater on Titan.The isolated peak in Herschel crater is about the same height as Mount Everest.In this image, the shooting angle is the hemisphere of Mimas with its back to Saturn.Above is the northern part of Mimas, which inclines about 21 ° to the left.This image is created byCassini probe Was taken on October 22, 2016.The image was taken about 185000 kilometers above Mimas, and the angle between the sun, Mimas and the detector was about 20 °.[5]
Latest research
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In February 2024, an international research team recently published a paper in the British journal Nature, saying that on the basis of the observation data of the US Cassini Saturn probe, they further analyzed the internal structure, rotation activities, orbital changes, etc. of Titan, and believed that there was aOceans.[8]
world record
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Mimas is the smallest circular satellite.(Guinness World Records)[6]
