In the few lessons that mention the Future Human Project, Hua Feng heard about immigration—people have the impression that Mars has always been an ideal place for extraterrestrial life and human migration. However, as Titan's face is gradually revealed, this view fades.

Human research has found that Titan is the Earth 4.5 billion years ago. Titans have two characteristics that life prefers, and that is boiling organic compounds and a dense, protective atmosphere.

Titan is the only moon in the solar system with a qualified atmosphere, and one of the only four rocky planets in the solar system with a dense atmosphere, the others being Earth, Mars and Venus.

In some ways, Titan's atmosphere is most Earth-like. Its atmosphere is mainly composed of nitrogen, and the air pressure is slightly higher than that of the Earth. It even has clouds on it, except that these clouds are made up of methane and other hydrocarbons, not water. Many space biologists are eager to study Titan's atmosphere as a prototype of the Earth's atmosphere, hoping to discover how complex organic molecules were created before the emergence of life on Earth.

Viewed from Earth, Titan is enveloped in a dense atmosphere that prevents people from glimpsing its true face. According to spectroscopic analysis, there are intense chemical reactions in the atmosphere. On January 14, when the "Huygens" probe successfully landed on the surface of Titan, the earthlings really witnessed part of the "appearance" of Titan with the help of "Huygens's" eyes.

The lander took a large number of images in its only 30 minutes of "life", including one image of Titan's surface that shocked the world——— vast plains, scattered with large and small stones and ice-like objects, and the orange sky was fascinating. This is the first time humans have landed on this mysterious land, and will it give birth to life?

On June 29, 2005, the Cassini spacecraft orbiting Saturn once again shocked the world with a photograph taken by the spacecraft. Photographs show a lake-like feature in the Antarctic region of Titan. Observed at about 234 kilometres long and nearly 73 kilometres wide, the landscape appears to be a dark patch with a smooth, winding border, surrounded by light-coloured Titan clouds. Scientists at NASA's Jet Propulsion Laboratory believe it could be one of Titan's surface methane lakes, one of the organic compounds necessary for Earth-like life.

Cassini will fly over Titan 39 times in the future, and if any of the "dark spots" are photographed reflecting like mirrors, it will prove that it is a real liquid lake, and if it is confirmed, then we have reason to believe that new life will be born here.

Does "extraterrestrial life" exist? Every time our Earth probes "visit" an alien planet, they do so with this question. In the known solar system, Mars and Titan are the planets with the most living conditions, although there is some imagination in this, but from the results of the "Cassini" exploration, the shape of Titan is very similar to the Earth 4.5 billion years ago. According to the analysis, judging from the activities of Titan, if there is no accident, then a new earth-like life will appear on Titan in 15~2 billion years, and human beings will no longer be lonely in the solar system.

The earth is not our eternal home, and our source of life——— the sun, has only 5 billion years of life left. In more than 5 billion years, when the Sun will break away from the main-sequence star, the Sun will change a lot, the Sun will slowly expand, and all the inner planets will be mercilessly swallowed up by the Sun, not to mention the Earth, and what will be the fate of us human beings? Fortunately, at the beginning of the 21st century, we have at least superficially learned about Titan, and these profiles lead us to believe that it is an ideal place for us to settle, much stronger than Mars.

First of all, 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, and even after the Sun expands, it has no effect. In addition, the originally cold Titan will be "warmed" by the body temperature of the expanding sun to the point that it is acceptable to humans, and the atmospheric pressure on Titan at that time is basically suitable for the survival of earth-like life, and it will become another home for humans. None of this is very difficult to do on Mars.

The latest observations show that Titan's largest lake is as smooth as a mirror, and that the lake liquid is methane and ethane as dense as honey, with a drop of no more than 3 millimeters on the surface of the lake.

Howard Zeebecker of Stanford University, USA

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One of the research team members, he said: "Smoothing in the true sense of the word can only be achieved unless you pour concrete into the lake, which does not exist on Earth." Astronomers have wondered whether Titan, Saturn's largest moon, is dry or wet, but there is plenty of evidence for the presence of liquid lakes on the moon.

The Cassini probe's radar device arrived in the Saturn region in 2004 and found dark patches in Saturn's polar regions, and the dark areas detected by the radar devices 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 shows that lakes clearly visible on Titan's surface are filled with methane and ethane, which can exist in liquid form on Titan's icy surface. Morphologically, Zeebecker said, they look like lakes. However, previous radar observations have shown that the clear lake was formed at an angle, and it is not possible to reflect bright radar flashes from the surface of the lake, suggesting that the lake may be a dry riverbed or a soot-filled muddy bottom.

The researchers said the Cassini probe's radar device had a significant impact on the largest lake on Titan's surface, Lake Ontario (O. Ontario).

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io Lacus)" made observations, the lake has a span diameter of 235 kilometers in Antarctica, and its radar reflection signal is very strong. The study's leader, Lau Wye of Stanford University

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"It's like if you have a flashlight and you shine it directly at a mirror, and the light reflected directly irritates your eyes," Wye says. ”

The Cassini detector's radar echo data showed that the surface of the lake was several thousand square meters long, with a surface undulation of no more than 3 millimeters, which was 10 times flatter than previously observed. "It's hard to imagine that even a solid surface can be smooth in the millimeter range, let alone a liquid lake," Wye told New Scientist Magazine. ”

Previous observations have shown that the lake is in a liquid state, not a dry quagmire. "If you walk by a lake and see a dry lake, the muddy water there has dried up and evaporated, and it may look very flat, but the dry mud will have deep cracks," Zeebecker said. We can extrapolate that Lake Ontario on Titan's surface may be a smooth lake that we have never seen before. ”

The similarity between Titan and Earth is enhanced by evidence of fluid on the surface of Titan, the only star in the solar system with an active climate cycle, where 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 speculation, this latest study is a special kind of lake, most likely with a rough surface, but we don't see any 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 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.

Titan is the only star found to have stable liquid matter on its surface, but instead of water, these liquids are hydrocarbons such as ethane or methane.

According to a report on the website of the British "Daily Mail", scientists at NASA used the Saturn probe Cassini to discover a river valley about 400 kilometers long flowing with liquid hydrocarbons (hydrocarbons) on the surface of Titan, which is similar in shape to the Nile River on Earth.