TitanTitan）Is a satellite orbiting Saturn, isSaturnThe largest satellite in the solar system.Dutch physicists, astronomers and mathematiciansChristian HuygensIt was discovered on March 25, 1655, the first satellite in the solar system after the Galilean satellite of Jupiter.
As the only satellite in the solar system with a thick atmosphere, it is highly suspected of the existence of life. Scientists also speculate that methane in the atmosphere may be the basis of life.Titan can be regarded as a time machine, which can help us understand the initial situation of the earth and reveal the mystery of how life on the earth was born.
Titan's surface gravity is extremely low, which is similar to that of the moon, but has a strongatmosphereOf its surfaceAtmospheric pressureAbout 1.5 times that of the earth, this strange phenomenon has a great impact on the researchplanetAtmospheric science is a good subject.At the same time, the dense atmosphere and relatively low surface gravity make landing and takeoff easier.
Name Origin
Announce
edit
titan
Huygens simply called this satellite he found "Saturn Luna" ("Saturn's satellite").After that,Giovanni Domenico Cassini In order to express the respect for the kingLouis XIVThe four satellites that will be discoveredEnceladus-Thetis,Enceladus-Dione,Rhea-Rhea and Iapetus are named Lodicea Sidera (Louis).Astronomers are accustomed to numbering the five satellites with numbers.Other satellites are calledHuygens satelliteOr the sixth moon of Saturn (from the distance known at that time, Mimas and Enceladus were discovered in 1789).
titan
Titan, the English name of Titan, and the names of seven other Saturn moons known at that time came from Sir John Herschel (John Herschel was the son of Sir William Herschel, who himself discovered Titan and Enceladus).John HerschelIn the book "Results of Astronomical Observations in the Cape of Good Hope" published in 1847, the new satellite was named "Titan". Titan isCronos(HisRoman mythSatune) and his brothers and sisters.
physical characteristics
Announce
edit
Titan satellite map
Titan is the largest satellite of Saturn and the second largest satellite of the solar system, which is more than the planetMercuryIts size is only larger than that of Jupiter's largest satellite in the solar systemGanymedeSmall.But recent observations also show that the dense atmosphere may make people overestimate the diameter of Titan. Like many other satellites, TitanAsteroid 134340(OriginalPluto）The mass and volume should be large.Titan has an average radius of 2575km, a mass of 1.345 × 10 ² ³ kg, and an average density of 1.880 × 10 ³ kg/m3.Titan's orbit around Saturn has a half length of 1221850 kilometers, an eccentricity of 0.0292, an intersection angle of 0.33 ° between the orbital plane and the equatorial plane of Saturn, and a revolution period of 15 days, 22:41:24 seconds.Titan's rotation period is the same as the revolution period, which is similar to the moon.Titan has a dense atmosphere, which is mainly composed of nitrogen. The surface atmospheric pressure is 1.5 × 10 Pascal, and the surface temperature is - 179.15 ℃.
Titan mass vsGanymede，Ganymede，Triton , asteroid 134340（Pluto）Generally similar.One half of Titan is water ice and the other half is solid material.There is a solid core 3400 meters below several different crystalline ice layers.The core should still be hot inside.Although Rhea and other Saturn moons are similar, the core density of Titan is higher, because its huge size causes gravity to compress its interior.
Atmospheric conditions
Announce
edit
titan
Atmospheric conditions Titan is known to have a real atmosphere, and other satellites only have trace gases at most.The existence of the atmosphere was firstGerard Kuiper(Gerard P. Kuiper) UseSpectral telescopeYes, he found Titan's atmospheremethaneThe local pressure reaches 100 mbar.Later, the observation of the traveler's spaceship also confirmed that Titan has an atmosphere. In fact, the atmospheric pressure of Titan is a little higher than that of the Earth, and the pressure on the planet's surface is 1.5 times that of the Earth.Dense clouds on Titan's surface[1]It covers its surface landform.It is generally believed that Titan's surface is solid or liquid ethane.From the earthradarThe survey found that there was no large-scaleethaneThe ocean, however, may still have small ethane lakes.Later, scientistsCassiniThe photos sent back by the spacecraft were studied, and it was believed that Titan might not have a liquid methane ocean at all.Researchers once observed Titan through ground-based telescopes. They thought at that time that there were all kinds of signs indicating that there might be liquid oceans on this Saturn satellite.However, scientists still have doubts about the conclusion, because previous observations have shown that Titan does indeed have flashing liquid reflections on its surface, especially the results observed through a large radio telescope a few years ago have proved that there is probably a liquid ocean.
98.44% of Titan's atmosphere isnitrogen, the only nitrogen rich star in the solar system other than the Earth, where there are a large number of different kinds of hydrocarbon residues (includingmethane、ethane、Butanediyne、Propargyl、Propargyronitrile、acetylene、propane, andcarbon dioxide, cyanogenHydrogen cyanideandhelium）。These hydrocarbons are believed to come from methane in Titan's upper atmosphere.When methane reacts with solar radiation, it will produce thick orange smoke clouds.The organic sediment on the surface of Titan that seems to be coated with a layer of tar is called tholin.Titan has no magnetic field protection, so when it sometimes runs outside Saturn's magnetosphere, it is directly exposed tosolar windBelow.This causes the atmosphere to ionize and release some molecules in the upper atmosphere.
Near the surface, the temperature of Titan is about 94K (- 179.15 ℃).Water ice sublimates at this temperature, so there will be a small amount of water vapor in the atmosphere. Titan's surface has different clouds besides the global fog.Clouds may consist of methane, ethane, or simple organic matter.Other rare complex chemicals are responsible for Titan's orange appearance in space.
November 2004CassiniFly over Titan's bright, cloudy South Pole, but do not find the expected methane.This puzzled scientists. The research on cloud composition is still in progress, and people's past knowledge about Titan's atmosphere may need to be rewritten.
In 2004, Cassini observed the atmosphere and found that Titan's atmosphere was "super rotating". Like Venus, its atmosphere rotates much faster than the surface.
According to the American Science Daily, SpainUniversity of GranadaandUniversity of ValenciaThe physicists ofTitan's atmosphereThere are natural electrical activities such as lightning storms in the.Scientific groups believe that organic molecules and early life forms may be formed in the upper atmosphere of planets or satellites with lightning storms.
Since Spanish astronomer Josie Comas Sula discovered that Titan has an atmosphere in 1908, no atmosphere has been found on other satellites.He explained, "On Titan, there are atmospheric clouds with transfer motion, so static electric fields and storm conditions can be formed.According to the theory of Russian biochemist Alexander Opagin and the experiment of Stanley Miller, Titan's atmosphere with lightning storm activity may form organic matter and early life forms. Under this condition, organic compounds can be synthesized from inorganic mixtures by releasing electricity.
Surface characteristics
Announce
edit
Cassini photographs of Titan
Until 2004, the understanding of Titan's surface map was still very poor.In any case, human usehubble space telescope Infrared and Cassini-Huygens"Shoot" to a high brightness, withAustraliaPicture of the size area.The unofficial name of this area is' Xanadu Region ';Nobody knows what it is like there.alliedHubble Space Telescope, Keck Telescope andVery large telescopeAnother dark area of similar size on Titan has also been observed, and people speculate that it may be a liquid methane or ethane ocean, but the data observed by Cassini may be other substances.Cassini also sent back a large number of high-resolution geomorphic images of Titan, including mysterious linear stripes, which some scientists believe may be caused by crustal movement.
An observation over Titan on November 26, 2004 found that there were only a few impact craters on the smooth surface of Titan, and the light dark contrast of these craters was strong under the effect of light.This is probably due to the frequent crustal reconstruction caused by Titan hydrocarbon rain or hydrocarbon snow falling into the crater or volcanic eruption activity.The spectrometer of the detector found that the wavelength of solar light emitted from bright and dark areas is the same, which means that they may be composed of the same substance (or at least covered with the same substance).As for what substance it is, people still don't know.Hydrocarbon lakes or seas that people hoped to find by observing objects or liquid reflected light with detectors have not been detected.This led scientists to suspect that Titan's surface may be completely icy or muddy.[2]
In order to better understand the surface topography, Cassini spacecraft usedRadar remote sensing mapping technology。The first picture returned shows that the surface is a complex, rugged and flat area.This landform seems to be caused byvolcanoCaused by.The volcano may erupt water andammonia。In addition, some striated landforms like those produced by wind erosion have also been found.There are also some impact craters that seem to have been filled, and the liquid in them may beLiquid hydrocarbon。What is or is not in the lake is still uncertain.In other areas, the signals returned may be solid or liquid, but other explanations still exist.Titan looks really smooth. There is no landform higher than 50 meters on its surface.
Astronomers believe that Titan is distributed with manyethaneThe cold degree of this satellite is more thanAntarctica。Scientists say that although Titan is colder, its wind, rain and tectonic process make it the most similar object to the Earth in the solar system.Although the average surface temperature of the satellite, which is as low as minus 292 degrees Fahrenheit and minus 180 degrees Celsius, will keep the water solid all the time, there are liquid methane and ethane on its surface, which can provide a habitat for life, but no oxygen is difficult to ignite.
Observation history
Announce
edit
In 1655,Dutch astronomerChristian HuygensHe aimed his new telescope at Saturn to study its rings, but to his surprise, there was a huge moon beside Saturn, Titan, Titan.
In 1907,Spanish astronomer Jose Comas Sola observed the shadow on the circular boundary of Titan from the telescope, pointing out that it is a symbol of the existence of atmosphere.[3]
On September 1, 1979,Pioneer 11 flew past Saturn 20800 kilometers from Saturn and took pictures of Saturn's giant moon Titan.It is preliminarily judged that the temperature on Titan is extremely low, and life is almost impossible to survive.
On November 12, 1980,Voyager 1 flew over Saturn from 124000 kilometers away. Nine months later, on August 25, 1981, Voyager 2 flew over 100800 kilometers away from Saturn.The detection results of these two detectors on Titan show that the main component of Titan's atmosphere is nitrogen, and the other components are argon (6%), methane (2-3%), and hydrogen (0.6%).The surface atmospheric pressure is 1.5 × 10 Ω· Pa, but the surface temperature of Titan is very low, - 179 ℃. At the tropopause, 45 kilometers above the surface, the temperature is lower, - 203 ℃, which is hard to expect to breed life.
On December 13, 2004,Cassini's Saturn probe flew over Titan for the second time.
On December 24, 2004,Cassini Saturn probe releases Huygens sub probe.
On January 14, 2005,HuygensThe sub detector landed on the surface of Titan and sent back more than 300 pictures of Titan to the ground observation station.
From October 2007 to July 2008,The Cassini Saturn probe will explore Titan 10 times while completing other exploration tasks.
Voyager
Voyager 1andVoyager 2Titan has been explored.Voyager 1 tried to get as close to Titan as possible;Unfortunately, there was no instrument on Voyager 1 that could penetrate the mists on Titan, because it was not known that there were clouds above.Many years later, after the complicated digital processing of the pictures taken by Voyager 1's orange filter, although the cause of bright and dark landforms in Xanadu and Sickle areas still could not be explained, since then, these areas have been observed by the Hubble Space Telescope with infrared.Voyager 2 has only roughly explored Titan, and the Voyager 2 team must "adjust the orbit to allow Voyager 2 to inspect Titan in detail" and "use another visitUranusandNeptuneTrack ".Since Voyager 1 could not observe its surface topography, Voyager 2 team chose the latter option.
Pioneer
On September 1, 1979“Pioneer 11 ”Fly over Saturn and investigate Titan.However, when Pioneer 11 visited Titan, it was caught in a strong solar wind, which seriously affected the information sent back.The ground control center only received five high-resolution photos taken by it at 350000 km.In the photo, Titan presents a beautiful orange, like a ripe orange.Voyager 1 flew to Titan on November 11, 1980.It is only 4000 kilometers away from the cloud top, and the exploration has been a complete success.It was this time that the diameter of Titan was measured to be 4828 kilometers, instead of 5550 kilometers previously thought.
Only Pioneer 11, Voyager 1 and 2 have flown to Saturn to explore Saturn.On September 1, 1979, Pioneer 11 became the first probe to visit Saturn after six and a half years of space travel.It flew over the top of Saturn's cloud 20200 kilometers away, made a 10 day exploration of Saturn, and sent back the first batch of pictures of Saturn.Pioneer 11 not only found two new rings of Saturn and Saturn's 11th satellite, but also confirmed that Saturn's magnetic field is 600 times stronger than the Earth's magnetic field.On September 2, it passed through the plane of Saturn's ring for the second time, and turned to Titan using Saturn's gravitational force, thus detecting the planet that may be pregnant with life.
On November 12, 1980, Voyager 1 flew over 12600 kilometers from Saturn and sent back more than 10000 color photos.This exploration not only confirmed the existence of Titan, Eleven and Twelve, but also found three new Saturn moons.When it flew less than 5000 kilometers away from Titan, it first detected and analyzed the atmosphere of the largest moon of Saturn, and found that there was neither enough water vapor in Titan's atmosphere nor enough liquid water on its surface.
On August 25, 1981, Voyager 2 flew 10100 kilometers from the top of Saturn's cloud and sent back more than 18000 pictures of Saturn.The survey found that the surface of Saturn is cold and windy, and there are strong and stable storms in the high latitudes of the Northern Hemisphere, even stronger than the storms on Jupiter.Saturn also has a large red spot, 8000 kilometers long and 6000 kilometers wide, which may be caused by disturbance and rotation when the updraft in Saturn's atmosphere falls back into the clouds.There are also flashes of lightning passing through Saturn's ring from time to time, whose power is tens of thousands or even hundreds of thousands of times more than the lightning on the earth.It confirms once again that Saturn has seven rings.Saturn's ring is composed of particles and gravel with a diameter of several centimeters to several meters. The particles in the inner ring are smaller, while the particles in the outer ring are larger. Due to the different particle densities, the rings show different colors.Each ring can be subdivided into thousands of small rings, large and small. Even the Cassini seam, which is considered to be empty, also has several small rings. In the high-resolution photos, it can be seen that there are five small rings intertwined with each other in the F ring.The overall shape of Saturn's ring is like a huge compact disc, stretching from the top of Saturn's cloud to 320000 kilometers away.
Voyager 2 discovered 13 new Saturnian moons, increasing the number of Saturnian moons to 23.It inspected 9 of them and found thatEnceladusThere is a large circular mountain on the surface, with a diameter of 400 kilometers. The bottom rises upward to form a dome, and there is also a huge crack, which encircles the satellite almost 3/4 of a week;IapetusOne hemisphere of is dark, the other is very bright;IapetusIts rotation period is only 9~10 hours, which is far from its revolution period of 550 days;The actual diameter of Titan is 4828 kilometers, instead of 5800 kilometers originally thoughtSolar system planetsThe second largest satellite in China, it has a dark and cold surface, a sea of liquid nitrogen, a dark red sky, and occasionally sprinkles a few nitrogen rain mixed with hydrocarbons. This is an ideal place for human beings to understand the origin of life and various chemical reactions.
Cassini Huygens
Landscape near the land where Huygens landed
In order to further explore Saturn and uncover the mystery of Titan's life, the United States and ESA jointly developed a valuableCassini Saturn probe。The probe was launched on October 15, 1997, starting a 7-year long journey.It is expected to fly into nearby space in 2004, carry out 4-year exploration around Saturn, and land on Saturn's largest satellite Titan for the first time for field investigation.Cassini is about 2.7 meters in diameter and weighs 6 tons in total. It is composed of an orbital probe and a lander.Its orbital detector is named Cassini, and has 12 typesDetecting instrument；The lander, named Huygens, is equipped with six scientific instruments.In order to speed up its flight to Saturn, Cassini flew over Venus in April 1998, gaining its first acceleration.Then it circled the sun and flew over Venus again in June 1999, gaining the second acceleration.In August of the same year, it flew near the earth, gaining the third acceleration.
After that,Cassini detectorIt will fly over Jupiter in December 2000 and get the last acceleration.It is scheduled to fly to its destination in July 2004 to meet Saturn and enter its orbit around Saturn.In November of the same year, the Huygens lander will leave the Cassini probe and fly to Titan, pass through its clouds and land on Titan, and then send the detected data back to Earth through the Cassini orbiter flying around the earth.The mission of Cassini after entering the orbit around Saturn is to fly 74 circles around Saturn, investigate the dynamics of Saturn's atmosphere and atmospheric circulation on the spot, and fly to many Saturnian satellites for many times, including 45 times flying around Titan. It is estimated that 500000 images of Saturn, Saturn's rings and the family of Titans can be sent back from close range by mapping the surface structure of Titan through its cloud layer with radar.Huygens will become the first probe to land on the satellite of a major planet.It will use its instruments to analyze Titan's atmospheric composition, measure wind speed and detect suspended particles in the atmosphere during the 2.5 hour landing process, and maintain its working state for 1 hour after landing to reveal whether there is water ice frozen ocean and whether there is life in some form on Titan.The data and images it collected were sent back to Earth through the Cassini probe.
Cassini HuygensArrived on July 1, 2004SaturnAnd began to use radar to measure the surface topography of Titan;Cassini probe On November 26, 2004, it leaped to the top of Titan and took many high-resolution images of Titan's surface, showing bright and dark patches that the human eye had never seen before.Cassini released Huygens on Christmas Day, December 25, 2004, and Huygens entered Titan's atmosphere on January 14, 2005 for detailed exploration.The Huygens probe can send relevant data back before Titan's atmosphere burns down.
The Huygens probe landed on Titan on January 14, 2005.
In December 2007, the Cassini orbiter saw it during its 38th flight near Titan“Ontario Satellite Lake”, but it could not be confirmed that it was liquid at that time.
With the breakthrough discovery of "Ontario Satellite Lake", experts believe that many "pits" similar to "Ontario Satellite Lake" in other regions of Titan may also be lakes.
In December 2009, NASA confirmed that there was liquid on the surface of Titan.
CassiniSpace probeCapture the sun's rays reflected by the lakes on Titan's surface.This discovery confirms the hypothesis that there is liquid on the surface of Titan.
Scientists believe that there should be many large lacustrine basins on some areas of Titan's surface, where there is liquid.Titan is the largest satellite of Saturn and has many similarities with the Earth, which has aroused great interest of scientists.In the past 20 years, scientists have established a complete theory of Titan.
They believe that Titan has liquid hydrocarbon (NGLs) oceans or lakes on its surface.Titan is also considered to be the only planetary body with liquid in the solar system except the Earth.Although the data sent back by Cassini cannot prove that there is a huge ocean on its surface, it clearly reveals that there are large lakes near the poles of Titan.
Since Cassini began orbiting Titan in 2004, scientists have been looking for the phenomenon of "specular reflection".However, Titan's northern hemisphere has been in the darkness of winter, and scientists believe that there are many more lakes in the northern hemisphere than in the southern hemisphere.
It was not until the autumn equinox in August 2009 that the sun began to shine directly on Titan's lakes in the northern hemisphere, which was also the beginning of spring in the northern hemisphere.
Due to the interference of the thick atmosphere above Titan, most of the sunlight reflected by the surface of Titan is blocked.The Cassini probe also accidentally took this rare picture.The photo was taken on July 8, 2009.[4]
The Huygens probe, which is jointly operated by NASA and the European Space Agency, drifts on Titan's biogas lake.According to a report released by the National Academy of Sciences on July 6, extraterrestrials may be much more strange than experts had predicted.Scientists need to consider expanding the list of features of extraterrestrial life, including so-called "weird" life forms that can thrive in places where life on Earth cannot survive.[5]
NASA announced on June 27, 2019 that if everything goes according to plan, Dragonfly will be launched in 2026, and land on Titan after eight years of navigation. After that, the probe will cruise the 5150km wide satellite for at least 2.5 years, during which it will make 24 flights with a total range of about 180km.The goal of this mission is to record the chemical composition of Titan in detail.Some scientists believe that the hydrocarbon ocean on Titan may be pregnant with its unique and strange life forms.In addition, since the environment of Titan is very similar to that of the early Earth, the observation results of this mission may also help to understand the chemical process of the emergence of life on the Earth.[6]
scientific research
Announce
edit
Or there is life
Artistic concept map of hydrocarbon "iceberg" on Titan
Titan is rich in organic compounds, nitrogen and other elements, which is similar to the environment of early life on Earth.Cyanide and hydrocarbon on Titan can generate nitriles under certain conditions, which can be hydrolyzed by water ice on the planet to generate carboxylic acids and amines, which can also generate amino acids of great significance.However, there are also important factors restricting the existence of life on Titan.First, the temperature is too low; second, liquid water has not been found; third, Titan has nomagnetic fieldProtection, so when it sometimes runs outside Saturn's magnetosphere, it is directly exposed to the solar wind, and radiation may make life impossible.
Scientists say the huge hydrocarbon "iceberg" lake on Saturn's moon Titan can form strange life forms.NASA researchers said that this latest theory may also explain the strange readings from the huge lakes and oceans on the satellite[7]。
The discovery of a huge lake of liquid methane
The new lake on the surface of Titan covers an area of 13000 square miles (34000 square kilometers). It is located in the south pole of Titan and has some lake characteristics.Since the Cassini probe arrived at the Saturn system in 2004, scientists have been committed to studying the characteristics of methane lakes near Titan's poles, which confirmed that methane rain also exists in large, cold satellites.
Effect Picture of Titan's Surface Lake
Scientists point out that this new lake is only shallowswampBut observational data show that when the storm comes, the lake will form liquid methane deep enough to flow forward.Not long ago, Elizabeth Tuttle, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, said, "The thunderstorm model on the surface of Titan shows that a storm can form methane rain tens of centimeters deep." Tony DelGenio, a member of the research team of NASA Goddard Space Research Association, said,This study is the most direct evidence that Titan has liquid methane on its surface.
Tuttle said: "People saw that this kind of cloud layer over Titan is very similar to the cloud layer of the earth, and people found signs of liquid torrents on the surface of this area." Deljanio added that scientists of the Cassini probe had not noticed the formation of this new lake before, because scientists were aware that heavy rain might occur in this area,They put more effort into observing the characteristics of heavy rain, ignoring the signs of new lakes forming on the surface of Titan.
Scientists found a newly formed methane liquid lake on Titan
Scientists are very excited about this research discovery, which reveals the change of Titan's climate characteristics. When Cassini probe arrived at the Saturn system in 2004, when Titan was in summer in the southern hemisphere and winter in the northern hemisphere, storm clouds mainly gathered in Titan's Antarctic region.The season is approaching the vernal equinox, and there is no longer any southern hemisphere storm.Deljanio said: "Storms are mainly concentrated in mid latitudes, occasionally in low latitudes." In 2008, the Cassini probe has completed its 4-year survey mission, and plans to extend the survey time to 2010.The detector is now operating normally, and the task operator hopes to further extend its working life in the future.
Tuttle isJohns Hopkins UniversityRalph Lorenz, a colleague of the laboratory, was not directly involved in this research. He pointed out that such research would help people to idealize the characteristics of the Earth's climate change.He wrote in an email: "Titan's atmosphere has a large amount of methane wet gas, so after a long drought there will be strong storm weather."[8]
On October 31, 2014, NASA's Cassini spacecraft found methane clouds in the upper atmosphere of Saturn's largest moon Titan.
Carrie Anderson, a scientist of the Cassini Project of Goddard Space Flight Center and the first author of a research paper on this discovery, said: "It is totally unexpected that methane clouds can form at such a high altitude in Titan's atmosphere. No one thought this was possible before."[9]
Ice sealed underground or ocean
On July 2, 2012, it was reported on the website of NASA that the latest data from the Cassini probe showed that Saturn's largest moon Titan may have a liquid water layer under its icy ground.A paper on this discovery has been published in the latest issue of Science.
First author of the paper, member of Cassini project team,The First University of Rome, ItalyLuciano Iess said: "Cassini has detected a large range of tidal fluctuations on Titan, which almost certainly leads to the conclusion that there is a hidden ocean under its surface." He said: "The search for water is an important target of the solar system exploration, and now we have locked in a new celestial target that may be rich in water."
What led scientists to make this discovery was tidal deformation.Saturn's huge gravity will make Titan constantly pull up or squeeze out of shape.If Titan is completely composed of solid rocks, the gravity from Saturn will cause its surface to rise, forming the so-called "solid tide", which should be about 3 feet (about 1 meter) high.However, the measured data of Cassini shows that the uplift is as high as 30 feet (about 10 meters).This data suggests that Titan is not entirely composed of solid rock material.
At first, scientists were not sure whether Cassini could detect the tidal bulge caused by Saturn's gravity.However, the Cassini probe actually did it. It flew over Titan at close range for six times from February 27, 2006 to February 18, 2011, during which time it accurately measured the gravity field of Titan.These gravity field data, together with the help of NASA Deep Space Network (DSN), finally accurately gave the magnitude of Titan's surface tidal uplift.
Sami Asmar fromNASA Jet Propulsion Laboratory(JPL), who is also a member of the Cassini project team, said: "We have carried out ultra-high precision measurements. Fortunately, the Cassini probe and the Deep Space Network antenna have maintained a very stable connection. Titan's tidal bulge formed under the tidal force of Saturn is not significant compared with the tidal bulge formed on other giant planets, such as some satellites of Jupiter.However, in the absence of field drilling conditions, gravity field data is the best way for us to know the internal structure of Titan. "
The ocean layer beneath Titan need not be very thick and deep to form the tidal uplift effect of measured values.A liquid water layer located between its hard deformable shell and the inner rock mantle layer can make Titan appear as the bulge or compression phenomenon reflected by the observation when orbiting around Saturn.Since Titan's surface is mainly composed of water iceOuter solar systemSatellites are very common, and scientists believe that Titan's main component of the ocean should also be liquid water.
On Earth, gravity from the moon and the sun will cause tides on the surface ocean.In the open sea, this uplift can reach 2 feet (about 60 cm).Gravity from the moon and the sun will also cause the formation of earth tides in the crust, with an amplitude of about 20 inches (50 cm).
Scientists speculate on the possible internal structure of Titan
The existence of a liquid ocean beneath Titan's surface does not in itself constitute a conclusion that life may exist here.Scientists tend to think that life is more likely to occur only when there is direct contact between liquid water and rock.But we can't confirm whether the bottom of this ocean is made of rocks.
This detection result is of great significance for uncovering the mystery of the continuous methane supply on Titan.Titan's atmosphere is very rich in methane, but researchers believe that methane in the atmosphere should be unstable. If Titan's atmosphere can maintain a rich methane content for a long time, then there must be a source that can continuously supply methane.
Jonathan Lunine isCornell University He said: "It is very important to find that Titan has a liquid water layer underground, because we hope to understand how methane is stored inside Titan and how the stored methane is released."He said: "This is very important, because all the unusual things of Titan are related to the rich methane content, but the methane gas in its atmosphere should have been destroyed in a geological sense in a short time."
Imagine an underground ocean composed of liquid water, which is full of ammonia. The ammonia water rises to the surface layer along the cracks and pores, releasing methane gas in the ice.At the same time, such an underground ocean can also serve as a methane storage pool.[10]
Discovery of huge high-temperature dome structure
Cracking dome structure
On October 22, 2012, according to the latest image sent by NASA's Cassini probe, scientists identified some huge high-temperature dome structures on Saturn's largest moon Titan.This is very similar to what you see when baking bread. When baking, the skin of the bread will bulge and crack.Now scientists believe that a similar situation is taking place on Saturn's largest moon.
Previously, scientists had observed similar terrain on the surface of Venus. On the top of a volcano named Kunapipi on the surface of Venus, the detector photographed a dome shaped bulge about 20 miles (30 kilometers) in diameter.Researchers also believe that a 70 km long narrow rift observed on the surface of Titan is also caused by the surface cracking caused by the upwelling of the lower material, which may be magma.
Rosaly Lopes, radar equipment scientist of Nasa's Jet Propulsion Laboratory (JPL) Cassini project team, said: "This dome structure has never been observed on Titan before, which shows that even after eight years of exploration, this planet continues to surprise us."
This unique tectonic terrain may be similar to the rock cap on the earth, which is formed by the condensation of ascending and invading lava.UtahHenry HillIs a typical representative of this landform.This image showing the dome structure was taken by the Cassini spacecraft using radar equipment on May 22, 2012.
Another Cassini team led by Ellen Stofan carefully examined the radar images of Titan's southern hemisphere and found traces of ancient coastline here.Titan is the only planet other than Earth confirmed to have stable liquids on its surface, although these liquids are not water, buthydrocarbon。
The existence of vast oceans is only observed in the northern hemisphere of Titan.However, the analysis of the data collected by the Cassini probe between 2008 and 2011 shows that there was once a vast shallow sea area near the south pole of Titan.
Dr. Stoffin and her colleagues identified two dry or largely dry oceans in Titan's southern hemisphere.The area of one such dried up ocean may once have reached 475x280 kilometers, and the depth may reach hundreds of feet.Ontario Lacus, the largest lake in the southern hemisphere of Titan, is located within a dry ocean, which seems to be the only part of the once vast ocean.
Another research team led by Dr. Oded Aharonson of Caltech, a member of the Cassini radar team, believes that Titan is experiencing long-term changes similar to the Milankovitch cycle of the Earth, which is the result of long-term regular changes in orbital operation.This long-term climate change will cause the liquid on Titan's surface to migrate back and forth between its northern and southern hemispheres.According to this model, Titan's southern hemisphere should have had a vast ocean about 50000 years ago.
Dr Stofen said: "The ocean on Titan's surface is just breedingPrebiotic chemistryWe also know that it is migrating between the northern and southern hemispheres in a cycle of about 100000 years. "He said: "I would like to take a closer look at the oceans in Titan's northern hemisphere and the dried up marine relics in the southern hemisphere to understand how far these pre life chemical evolution has gone."
Cassini team has basically confirmed the stability of Titan's northern hemisphere ocean system.They have been continuously monitoring the oceans of Titan throughout the past season (i.e., about six years on Earth).In this released image, taken on May 22, 2012, scientists found that the shoreline of lakes in the northern hemisphere has not changed, which indicates that lakes in the northern hemisphere are not seasonal events.In contrast, after a storm in 2010, Titan's equator appeared significantly darkened regions.[11]
Titan is the largest moon in the solar system and has been named Titan.In Greek mythology, the Titans were a giant family.Titan is the planet that scientists believe is the most likely to have life in the solar system except the Earth.It is the only satellite in the solar system with a thick atmosphere.Unlike the Earth, the Earth's atmosphere is mainly composed of nitrogen and oxygen, while Titan's atmosphere is mainly methane.In addition, the dense atmosphere reflects most of the light, causing the anti greenhouse effect, making the surface of Titan very cold. The temperature is only minus 180 degrees Celsius, so there is no liquid water.But in 2005, two research groups of scientists proposed that,Alien microorganismMaybe it lives in the liquid hydrocarbon of Titan Lake.Scientists said that acetylene formed in Titan's atmosphere and fell to the surface of Titan.Alien microbes eat acetylene and combine it with hydrogen to obtain energy.
Since then, dozens of lakes have been found on Titan's surface, which scientists believe are full of liquid ethane and methane mixture.However, no one knows the specific content of acetylene in Titan Lake because no probe spacecraft directly sampled the lake.In 1989, a scientist estimated that the content of acetylene in the hydrocarbon liquid in Titan Lake was only a few ten thousandths.
A team of scientists led by Daniel Cordier of the National Institute of Higher Chemistry in Rennes, France, made a new calculation of the acetylene content in Titan Lake.According to the latest data obtained from the Cassini Huygens mission to explore the Saturn system, they made the latest estimate that Titan Lake contains more acetylene.If there are extraterrestrials on Titan, the acetylene in the lake is enough to provide food for any hungry extraterrestrials.In 2005, Cassini's Huygens probe landed on Titan, which is full of liquid methane.Huygens was working on Titan for 24 hours, focusing on detecting possible signs of life on Titan.[12]
Related information
Announce
edit
That is, the ancient earth
In people's impression, Mars has always been an ideal place for extraterrestrial life and human migration.However, as the appearance of Titan was gradually revealed, this view gradually faded.Human studies have found that Titan was the Earth 4.5 billion years ago.Titan has two characteristics preferred by life, namely boiling organic compounds and dense protective atmosphere.Titan is the only satellite in the solar system that has a qualified atmosphere, and it is also one of the only four rocky planets in the solar system that have a dense atmosphere. The others are Earth, Mars and Venus.In some ways, Titan's atmosphere is the most Earth like.Its atmosphere is mainly composed of nitrogen, and its pressure is slightly higher than that of the earth.It even has clouds on it, but these clouds are composed of methane and other hydrocarbons, not water.Many astrobiologists are eager to study Titan's atmosphere as the prototype of the Earth's atmosphere, hoping to find out how complex organic molecules were produced before the emergence of life on Earth.
Orange Sky
Observing from the earth, Titan is surrounded by a thick atmosphere, which makes people unable to see its true appearance.According to spectral analysis, there are intense chemical reactions in the atmosphere.On January 14, when the Huygens probe successfully landed on the surface of Titan, the earth people really witnessed part of the "appearance" of Titan with the help of Huygens' eyes.In its only 30 minute "life span", the lander took a large number of pictures. One of the pictures of Titan's surface shocked the world - the vast plain is scattered with large and small stones and ice like objects, and the orange sky is fascinating.This is the first time that human beings have landed on this mysterious land. Will life be born here?Scientists are full of expectations.
There are "lakes"
On June 29, 2005, a picture taken by the Cassini spacecraft orbiting Saturn shocked the world again.The photo shows that Titan has a landform similar to a lake in its Antarctic zone.After observation, the landform is about 234 kilometers long and 73 kilometers wide. It looks like a dark spot with smooth and winding borders, surrounded by light colored clouds of Titan.Scientists from NASA's Jet Propulsion Laboratory believe that this may be one of the methane lakes on Titan's surface, and methane is one of the organic substances necessary for terrestrial life.In the future, Cassini will fly over Titan 39 times. If this "dark spot" is photographed reflecting like a mirror, it can prove that it is a real liquid lake. If it is confirmed, then we have reason to believe that new life will be born here.
Give birth to life
Does "extraterrestrial life" exist?Every time our earth probe "visits" other planets, it is with this question to inquire.In the known solar system, Mars and Titan are the planets with the most living conditions. Although there are some imaginations, from the results of Cassini's exploration, Titan is very similar to the Earth 4.5 billion years ago.According to analysis, from the activity of Titan, if there is no accident, a new terrestrial life will appear on Titan in 1.5 to 2 billion years, and human beings will no longer be lonely in the solar system.
Safer than Mars
The earth is not our eternal home, and the sun, the source of our life, only has 5 billion years of life left.In more than 5 billion years, the sun will leaveMain sequence starAt that time, great changes will take place in the sun. The sun will slowly expand, and all the inner planets will be mercilessly swallowed by the sun, let alone the earth. What is our fate?Fortunately, at the beginning of the 21st century, we learned at least a general overview of Titan on the surface, which made us believe that Titan is an ideal place for our migration, much better than Mars.First, Titan has a thick atmosphere, which is the most powerful barrier against any invasion of the universe.Second, Titan is far away from the sun. Even after the sun expands, it will not have an impact.In addition, Titan, which was originally cold, will be "warmed" by the temperature of the expanding sun to a level acceptable to human beings. In addition, at that time, the atmospheric pressure on Titan was basically suitable for the survival of terrestrial life, and this place will become another home for human beings.These are difficult to achieve on Mars.
Lakes and seasons
The latest observation shows that the largest lake on the surface of Titan is as smooth as a mirror. The liquid of the lake is methane and ethane as dense as honey. The drop of the lake surface is not more than 3 mm.
U.S.AStanford UniversityHoward Zebker, one of the members of the research team, said: "Unless you pour concrete into the lake, you can achieve real smoothness. This type of lake does not exist on the earth." Astronomers once doubted whether Titan, Saturn's largest satellite, is dry or wet,But a large amount of evidence shows that there are liquid lakes on the satellite.
The radar device of the Cassini probe arrived at the region of Saturn in 2004, and dark patches were found in the polar region of Saturn. The dark areas detected by the radar device suggest that the region is very smooth, suggesting that the surface of the liquid lake is very smooth and difficult to reflect the detection signal.
Spectral data show that the lakes clearly visible on the surface of Titan are full of methane and ethane, which can exist in liquid form on the icy surface of Titan.From a morphological point of view, they look like lakes.However, previous radar observation data show that the formation of this clear lake has a certain angle, and it is impossible to reflect bright radar flicker light from the lake surface, which indicates that the lake may be a dry riverbed or a bottom of mud dust filled with soot.
Researchers say Cassini's radar device is sensitive to Titan's largest lake“Ontario(Ontario Lacus) "observed that the lake spans 235 kilometers in the Antarctic, and its radar reflected signal is very strong.Person in charge of the studyStanford UniversityLauren Wye said, "It's like you hold a flashlight and shine directly into the mirror. Its direct reflected light will strongly stimulate your eyes."
The radar echo data of Cassini detector shows that the fluctuation of the surface of a lake with an area of thousands of square meters does not exceed 3mm, which is 10 times flatter than the previously observed data.Wye told the New Scientist Magazine: "It is really hard to imagine that even a solid surface, its surface smoothness is only within the millimeter range, let alone the surface of a liquid lake."
titan
Previous observation data show that the lake is in a liquid state, not a dry quagmire."If you walk beside a lake and see a dried lake, the muddy water there has dried and evaporated, and it may look very flat, but the dried mud will appear deep cracks. We can calculate that Lake Ontario on the surface of Titan may be a smooth lake that we have never seen before," Zeppel said
The evidence of liquid on the surface of Titan strengthens the similarity between Titan and the Earth. Titan is the only star with active climate cycle in the solar system. The lake on its surface evaporates liquid to form a cloud layer, and then rain returns to the surface to form rivers and channels.This makes Titan one of the best candidates for supporting the existence of life in the solar system.
If Titan has a liquid lake, there must be wind flow on its surface.Early computer simulations predicted that the waves in Titan's lakes were seven times higher than those in Earth's lakes.Zeberkel said: "This latest study runs counter to previous speculation. This is a special lake, and its surface is probably rough, but we have not observed the signs of undulating waves.Although we do not know the physical properties of methane and ethane at low temperature, we speculate that the liquid in the lake is very dense, with a certain viscosity, just like honey. "
The researchers pointed out that Titan's polar regions have alternate seasons, which can moderate and regulate the harsh climate.But its seasonal change is very slow. One year of Titan is equivalent to 30 years of Earth.
U.S.Aarizona state university Jonathan Lunine said: "This is the stage when Titan's polar region is in a static and dormant state within a year. In general, the evidence that Titan's surface lakes are full of liquid is conclusive. We believe that Ontario is full of liquid."
Zebulber said that we must further analyze the middle of the lake through some indirect measurement methods and models in the next step.
river course
The Cassini Saturn probe jointly developed by the United States, Europe and Italy found a strange trace on Saturn's largest moon Titan, which is similar to Egypt'sthe NileThe length from its "source" to the "large ocean" on Titan has reached nearly 400 kilometers, about 250 miles, which is the longest "alien river" discovered so far. The high-resolution radar imaging system on the Cassini probe revealed the existence of "dark river" on Titan for scientists, and it has a serpentine smooth nature,It indicates that there may be some liquid in it.
Previous observations and studies on Titan have shown that Titan is the only celestial body in the solar system that has a vast "ocean landform" except the Earth, and has a surface liquid circulation mechanism. However, Titan's atmospheric environment is really very cold, which means that even if there is water, it cannot flow freely.Scientists believe that Titan's liquid is composed of liquid methane, ethane and other hydrocarbons.Interestingly, the Titan river system shown by the Cassini probe is not a complete and unobstructed channel, but there are some fault lines, which indicates that there are fractures in Titan bedrock.[11]
river valley
The left picture shows the river valley, and the right picture shows the satellite image
Titan is the only planet that has stable liquid substances on its surface, but these liquid substances are not water, but hydrocarbons such as ethane or methane.
According to the Daily Mail website,NASAWith the help of the Saturn probe Cassini, scientists from NASA found a 400km long streamer on the surface of TitanLiquid hydrocarbon(hydrocarbon) valley whose shape is very similar to the Nile River on earth.
According to a radar photo taken by the Cassini space probe on September 26, 2012, the river valley flows through the north pole of Titan and finally flows into the Ligeia Mare located in the region, with a length of about 400 kilometers, which is the first time that humans have found such a huge "water system" outside the earth.In addition, because the whole river is dark, scientists infer that liquid hydrocarbons may be flowing in the valley.
titan
"Titan is the only star that has stable liquid matter on its surface other than Earth," NASA saidJet Propulsion LaboratorySteve Wale, the director of the radar project team, said: "This picture shows that Titan has a liquid cycle: 'rainwater' falls on its surface and flows into lakes and oceans with rivers, where 'rainwater' will be evaporated, and then start a new cycle again." On Earth, liquid refers to water, while on Titan, liquid refers to methane,But both of them affect almost all weather phenomena on the surface of stars. "
The Cassini probe is part of the Cassini Huygens mission, which includes NASA, the European Space Agency andItalian Space AgencyThe main purpose of the project is to carry out space exploration of the Saturn system.The Cassini probe was launched in 1997 and arrived at its destination in 2004. It began to orbit Saturn and made an in-depth investigation of Saturn's surface, atmosphere, halo, satellite and magnetic field.In 2005, Cassini began to detect the surface and atmospheric conditions of Titan, and sent the collected data back to Earth.
Titan is the largest satellite of Saturn, about 80% heavier than the moon, and is the only satellite known to mankind with a thicker atmosphere.[13]
Dormant ice volcano
titan[14]
On January 26, 2015, it was reported that American astronomers had found a 1000 meter high dormant ice volcano on Titan, surrounded by huge sand dunes, and a 1200 meter deep crater beside it.This iceberg is the largest ice volcano discovered by scientists on the satellite so far, and was named "Sotra" by astronomers.
It is reported that the volcanic eruption will be formed when the lava inside the earth erupts through the earth's crust.There is a thick layer of ice below the surface of Titan. The extreme temperature of the solar system creates a hard ice layer on Titan. If high heat continues to appear inside Titan, the ice layer will become melting ice with low density, and then it will erupt to form ice volcanoes.
According to scientists, "Sotra" is similar to the eruptions released by ice volcanoes on other satellites, that is, it will emit a lot of hot melting ice and gas.The methane gas in Titan's atmosphere will be decomposed by sunlight 1 billion miles away. If there are no resources to replenish methane gas in time, all methane gas will disappear in millions of years.But similar "Sotra" ice volcanoes can provide similar resources. When they erupt, they will release methane, ethane and other gases.Scientists speculate that Titan will have ice volcanoes like "Sotra" erupting every 1000 years, which will supply methane gas to Titan's atmosphere in time.Kirk said the discovery could well explain why the atmosphere of outer planets is rich in methane gas.[14]
Methane life
titan
According to the news released by NASA, an underwater ocean has been found on Enceladus, with total water storage even more than that of the Earth. We have reason to believe that there are more exotic satellites in Saturn's huge satellite group.Titan is a controversial satellite. Previously, scientists found traces of wind on Titan, which suggests that there may be waves on the surface of the liquid paraffin ocean on Titan. Compared with Enceladus, Titan is simply one of the bad stars in the solar system. Although there is no liquid water on Titan,But scientists still want to know whether there is life in its alkane ocean.
Scientists found that Titan's atmospheric pressure is 1.5 times that of the Earth, but its gravitational environment is relatively weak. It is a miracle that Titan can maintain a strong atmosphere with such low gravity.According to the data of Cassini Saturn probe, Titan's atmosphere is suffocating, with 95% nitrogen and 5% methane, so Titan's atmosphere is not breathable.If you are lucky enough to reach the surface of Titan, you may not need to wear a pressurized space suit. Since the atmospheric pressure is 1.5 times closer to the pressure of the earth, you just need to use a breathing mask and a cold proof space suit.
Seen from the surface of Titan, the sky is almost full of Saturn's shadow. About one-third to half of the sky is filled with Saturn's shadow, which is very sci-fi.Titan's gravity is about 14% of the Earth's, just a little weaker than the moon's gravitational field. The average surface temperature can reach minus 290 degrees Fahrenheit, about minus 179 degrees Celsius.Titan is also aTidal locking One side of the moon is always facing Saturn, which is the same as our moon, with only one side facing the Earth.
Titan is one of the few objects in the solar system that has liquid substances on its surface. Scientists believe that life may exist in the ocean of liquid hydrocarbons. Researchers from Cornell University even simulated a kind of life that can survive in Titan's ocean. They use methane as their energy source.However, whether there is extraterrestrial life on Titan still needs field investigation. If one day the probe can reach below the alkane ocean of Titan, it may be able to confirm whether there is life here.[15]
There are signs of life
Announce
edit
According to the US Space Network, in the past 30 years, scientists have known that a complex carbon compound called thorins exists in the atmosphere of comets and other planets in the solar system. Theoretically, Thorins can carry out a chemical reaction with water called hydrolysis, thus creating a complex molecular structure similar to the early stage of the Earth.
On Earth, complex organic molecules are considered to be the early stage of the emergence of life forms, such as the mixture before the origin of life.Titan is Saturn's largest moon, which is mainly composed of ice.Many ice may melt during meteorite collision or underground activities, forming "ice volcanoes" that eject "magma" containing mixed ammonia and water.
Did Sorens, formed in Titan's atmosphere, generate potential prebiotic organic molecules before water freezes through meteorite collision or ice volcano temporary reaction with liquid water?No scientist can explain it accurately.
Katherine Nish, a graduate student of the Department of Planetary Science at the University of Arizona in the United States, carried out a multi day research in the laboratory. She formed a substance similar to Solings through hydrolysis at near freezing temperature.She published this research report in《Astrobiology》Magazine.The liquid water exposed to Titan is believed to last for hundreds to thousands of years, and the reaction of melting solid ice into liquid water like this often occurs.It is likely that such reactions also occurred on early Earth.
In the laboratory, Nish mixed 5% methane and 95% nitrogen to form an organic mixture similar to Solings under low-temperature discharge. She dissolved the Solings sample in water, and then placed it in a 40 ℃ water environment to avoid freezing, and then measured its hydrolysis mixing ratio.The results showed that 10% Solings formed an organic mixture, which reacted with oxygen in water to form complex organic molecules.
When Nish's research report was published in a scientific journal, her theory was also criticized.James Ferris, a researcher and professor of Riselle Institute of Technology, has been engaged in the research on the chemical properties of Titan's atmosphere for many years.
Ferris used ultraviolet light to mix gases in Titan's atmosphere to carry out an experiment. He said, "The material structure formed by discharge is different from that of ultraviolet light decomposition, so its hydrolysis time is completely different. Many hydrocarbon compounds formed by photochemical processes do not react with water."
Nish responded by pointing out that the release of electrons or plasmas means simulating the interaction of charged particles.She agreed with Ferris that the ultraviolet ray radiation forms Solings more like the mist in Titan's atmosphere.But she believes that most of the compounds formed in this way do not react with water.
She admitted that her research work was not ideal to present the chemical characteristics of Titan's atmosphere. She said, "Solings formed at low pressure is more like Titan's mist than at high pressure. You can use ultraviolet light to make Solings at low pressure, but you cannot use plasma emission to make Solings at low pressure.A large number of Solings needed for our experiment must be produced by discharge technology, and only a small part can be generated by ultraviolet light photolysis. "
Nish's research does not fully demonstrate the chemical properties of Titan, which shows that similar chemical reactions can generate significant amounts of organic mixtures in liquid water environment.On the surface of Titan, molecules before the origin of life may exist in the melting water of collision craters and ice volcanoes. Such a process is likely to occur in the early life gestation stage of the Earth, when there was no significant amount of oxygen in the atmosphere of the early Earth.
Existence of life
Announce
edit
Saturn's big moon Titan has a magical surface environment in the solar system. A world full of liquid methane and hydrocarbons may have interesting life.U.S.ACornell Universitycelestial bodiesBiologyScientists and chemists believe that Titan is the twin brother of the Earth in many aspects. Titan is the largest satellite in the solar system, larger than Mercury. The atmospheric pressure on the surface is higher than that of the Earth, and there is also atmosphere.More importantly, Titan is the only planet in the solar system that has liquid substances on its surface except the Earth. The Cassini probe found lakes and rivers on Titan, and even in the polar region of Titan, scientists also found the largest lake.
Titan has complex organic molecules in its atmosphere, which scientists believe is the cornerstone of life, so they suspect that Titan may have strange creatures in its liquid methane world, such as being able to survive at minus 180 degrees Celsius and using liquid alkanes as energy sources.This conjecture is based on the investigation of Titan by Cassini detector. It is found that strange creatures may appear in the environment of liquid methane. The research team of Cornell University found that the formation of phospholipid molecules is an important step in the emergence of life on the earth, and Titan's environment helps the emergence of phospholipid molecules.
If there is life on Titan, it is almost certain that it is an individual cell with a cell membrane. Cassini spacecraft data found that there are very complex chemical reactions in Titan's atmosphere. Acrylonitrile may be the basic material in Titan's life cell membrane. At present, the laboratory can simulate the production of such substances in Titan's environment.Therefore, acrylonitrile membrane may be the cell membrane structure of Titan life, and the results of computational chemistry simulation show that it can adapt to the environment on Titan.In order to further prove whether there is life on Titan, we should send a probe to Titan's methane ocean, perhaps this is the most direct way to prove.[16]
No. 1 habitable planet
Announce
edit
Planetary livability index considers a group of completely different factors, such as whether the planet surface is rocky or frozen, whether the planet has an atmosphere, whether there is a magnetic field, etc.
Two index systems, namely, the habitability index of travel stars and the Earth similarity index, are designed to rank the possibility of planets that may have extraterrestrial life.The two types of index systems are respectively planet livability index and earth similarity index.According to the evaluation results of scientists, Saturn's largest satellite Titan and exoplanet Gliese 581g rank in two major indicators respectivelyLivable Planet RankingThe first is considered the most livable alien world.ExoplanetGliese 581gLocated in Libra, it is about 20.5 light years away from the Earth.The scientists' research results were published in《Astrobiology》Magazine.[17]
world record
Announce
edit
Titan is Saturn's largest moon.(Guinness World Records)[18]
The longest river channel on Titan 6 is the "visible river" deep valley, which is 412 kilometers long, setting a Guinness World record for the longest river system on other celestial bodiesRecords.[19]
