In the gorgeous and restrained spaceship rest cabin, Hua Feng spent the first three days thinking back to the previous lessons. The Aurora 3 ship they were flying on was one of the few long-range interstellar spacecraft in the Academy. The whole volume is the size of a dozen football fields, and the whole is an oval spherical in the shape of a disc.

Three days later, the Earth was no longer visible to the naked eye, and the Sun was literally a flaming oversized fireball.

Hua Feng vaguely remembers that the evidence of fluid on the surface of Titan remembers that the similarity between Titan and Earth is enhanced by the fact that Titan is the only star in the solar system with an active climate cycle, and the lakes on its surface evaporate to form clouds, and then rain returns to the surface, forming rivers and channels. This makes Titan one of the candidates for the best support for the existence of life in the solar system.

If there is a liquid lake in Titan, then there must be wind currents on its surface. Early computer simulations predicted that waves in Titan's lakes were seven times as tall as those in Earth's lakes. "Contrary to previous speculations, this latest study is a special kind of lake, most likely with a rough surface, but we have not observed signs of undulating waves," Zeebecker said. Although we do not know the physical properties of methane and ethane at low temperatures, we speculate that the liquid in the lake is very dense and has a certain viscosity, like honey. ”

The researchers point out that there are alternating seasons in the polar regions of Titan, which can moderate and regulate the harsh climate. But the seasons change very slowly, and one year of Titan is equivalent to 30 years on Earth.

Jonathan Lunin, Arizona State University, USA

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"This is the period when the polar region of Titan is dormant for a year, and in general, the evidence that the surface lakes of Titan are full of liquids is conclusive, and we believe that Lake Ontario is full of liquids," said e). ”

Zeebecker said that the next step is to drill down into the middle of the lake, using a number of indirect measurements and models.

The Cassini Saturn probe, jointly developed by the United States, Europe and Italy, found a strange trace on Saturn's largest moon Titan, resembling the Nile River in Egypt, with a length of nearly 400 kilometers from its "source" to the "large ocean" on Titan, about 250 miles, which is the longest "alien river" ever discovered, and the high-resolution radar imaging system on the Cassini probe revealed the "dark river" of Titan for scientists , and has a sinuous smooth nature, suggesting that some kind of liquid may be present in it.

Previous observations of Titan have shown that Titan is the only object in the solar system other than the Earth that has a vast "oceanic landform" and has a surface liquid circulation mechanism, but Titan's atmosphere is indeed very cold, which means that even if there is water, it cannot flow freely. Scientists believe that the liquid on Titan is made up of liquid methane, ethane and other hydrocarbons. Interestingly, the Titan river system shown by the Cassini probe is not a complete and unobstructed ditch, but a partial fault line, suggesting a fault in Titan's bedrock.

With the help of the Saturn probe Cassini, scientists from the U.S. National Aeronautics and Space Administration (NASA) have discovered a valley about 400 kilometers long flowing with liquid hydrocarbons (hydrocarbons) on the surface of Titan, similar to the Nile River on Earth, according to the website of the British Daily Mail.

According to a radar photo taken by the Cassini space probe on September 26, 2012, the valley flows through Titan's North Pole and finally flows into the Ligeia Ma Sea in the region

e), with a length of about 400 kilometers, this is the first time that such a large "water system" has been discovered outside the Earth. In addition, because the entire river is dark, scientists have theorized that liquid hydrocarbons may be flowing in the valley.

"Titan is the only star we've found other than Earth that has stable liquid matter on its surface," says Steve Wall, head of NASA's Jet Propulsion Laboratory's radar program. "On Earth, liquid refers to water, while in Titan, liquid is methane, but both have an effect on almost all weather phenomena on the surface of stars. ”

The Cassini probe is part of the Cassini-Huygens mission, a joint project between NASA, the European Space Agency and the Italian Space Agency to conduct space explorations of the Saturn system. Launched in 1997, the Cassini probe arrived in 2004 to begin its orbit around Saturn, where it conducted an in-depth study of the planet's surface, its atmosphere, its rings, its moons and its magnetic field. In 2005, Cassini began surveying Titan's surface and atmospheric conditions and sending the collected data back to Earth.

Titan is Saturn's largest moon, about 80% heavier than the Moon, and the only moon known to have a thicker atmosphere.

On January 26, 2015, according to media reports, American astronomers discovered a 1,000-meter-high dormant ice volcano on Titan, surrounded by huge sand dunes and a crater about 1,200 meters deep next to it. This ice volcano is the largest ice volcano ever discovered by scientists on a satellite and has been named "Sot" by astronomers

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It is said that volcanic eruptions occur when lava from the Earth's interior erupts through the Earth's crust. The extreme temperature of the solar system creates a hard layer of ice on Titan, and if there is a continuous high heat in Titan's interior, the ice will become a dense melt of ice, and then it will erupt to form an ice volcanic eruption.

The scientist introduced, "Sot

a" Similar to the eruptions released by ice volcanoes on other moons, they emit large amounts of red-hot melt ice and gas. Methane gas in Titan's atmosphere is broken down by sunlight from a billion miles away, and if there are no resources to replenish it in time, all methane gas will disappear in millions of years. But something like "Sot."

"Ice volcanoes, however, provide a similar resource, releasing gases such as methane and ethane when they erupt. Scientists speculate that every 1,000 years Titan will have something like "Sot."

a" like an ice volcano eruption, which will replenish Titan's atmosphere with methane gas in time. Cork said the discovery could explain why the atmosphere of the outer planet is rich in methane gas.

NASA has announced that the discovery of a subglacial ocean on Enceladus, with a total storage capacity of even more water than Earth, gives us reason to believe that there are even more exotic moons in Saturn's vast constellation. Titan is a controversial moon, after scientists found traces of wind on Titan, suggesting that there may be waves on the surface of the liquid alkane ocean on Titan, compared to Titan, which is one of the harshest planets in the solar system, although there is no liquid water on Titan, scientists still want to know if there is life in its alkane ocean.

Scientists have found that Titan's atmospheric pressure is 1.5 times that of Earth, but the gravitational environment is relatively weak, and it is indeed a miracle that such a low gravitational force can maintain a thick atmosphere. According to the Cassini Saturn probe, Titan's atmosphere is suffocating, with 95% nitrogen and 5% methane, so Titan's atmosphere is unbreathable. If you're lucky enough to reach Titan's surface, you probably don't need to wear a pressurized spacesuit, as 1.5 times the atmospheric pressure is closer to Earth's, you just need a breathing mask and a cold-proof spacesuit.

Looking at the sky on the surface of Titan, almost all eyes are full of Saturn's shadow, and about one-third to one-half of the sky is filled with Saturn's figure, which is very sci-fi. Titan's gravitational pull is about 14% of that of the Earth, only slightly weaker than the Moon's gravitational field, and the average surface temperature can reach minus 290 degrees Fahrenheit, or about minus 179 degrees Celsius. Titan is also a tidally locked moon with one side always facing Saturn, which, like our Moon, has only one side facing Earth.

Titan is one of the very few objects in the solar system that has liquid material on the surface, and scientists believe that there may be life in the oceans of liquid hydrocarbons, and researchers at Cornell University have even simulated a life that could survive in Titan's oceans, using methane as an energy source. However, the existence of extraterrestrial life on Titan still needs to be investigated, and if a probe can reach the bottom of Titan's alkane ocean one day, it may be able to confirm whether there is life here.

For the past 30 years, scientists have known a species called Tholi

S) is found in the atmospheres of comets and other planets in the solar system, and it is theorized that Solins could undergo a chemical reaction with water called hydrolysis to create complex molecular structures similar to those of the early stages of the Earth.

On Earth, complex organic molecules are thought to be in the early stages of the emergence of life forms, such as mixtures known as pre-origin life. Titan is Saturn's largest moon, and it is mostly made of icy material. Much of the ice can melt during meteorite collisions or underground activity, creating "ice volcanoes" that eject "magma" that includes a mixture of ammonia and water.

Did Solins, which formed in Titan's atmosphere, form a meteorite collision or a temporary reaction of an ice volcano with liquid water to generate potential pre-life organic molecules before the water freezes? No scientist can accurately explain.

Catherine Nish, a graduate student in the Department of Planetary Sciences at the University of Arizona in the United States, spent several days in the lab studying the formation of a Solins-like substance through hydrolysis at near-freezing temperatures. She published the study in the journal Astrobiology. Liquid water exposed to Titan is thought to persist for hundreds to thousands of years, and reactions like this one that melt into liquid water are a frequent occurrence. It is likely that similar reactions occurred on the early Earth as well.

In the lab, Niš measured the rate of hydrolytic mixing of 5% methane and 95% nitrogen in a low-temperature discharge to form an organic mixture similar to that of Solins, which she melted in water and placed in 40 degrees Celsius water to avoid freezing. The results showed that 10% of the sollins formed an organic mixture, which reacted with oxygen in the water to form complex organic molecules.

When Niš's research was published in a scientific journal, her theories were also criticized. James Ferris, a research professor at the Reisler Institute of Technology who has studied the chemistry of Titan's atmosphere for many years, pointed out that Niš's research was "flawed" because she used the electrical discharge method to form Solins, which is likely to be formed by ultraviolet light and charged radiation particles.

Ferris used ultraviolet light to mix gas from Titan-like atmospheres in an experiment, saying, "The structure of matter formed by the discharge is not the same as that of ultraviolet photolysis, so its hydrolysis time is completely different." Many photochemical processes form hydrocarbons that do not react with water. ”

Niš reacted to this, noting that the release of electrons or plasma meant simulating the interaction of charged particles. She agrees with Ferris's statement that the ultraviolet radiation that forms Solins is more like a mist in Titan's atmosphere. However, she believes that most of the compounds formed in this way do not react with water.