Long journey: from the moon to Mars

The following is the video and text arrangement reported by Mozi Salon's "Mars, China is Coming" activity (1 18 20201October).

2020 1 1 18 Mars

The following is the video and text arrangement reported by Mozi Salon's "Mars, China is Coming" activity (1 18 20201October).

2020 1 1 18 Mars | China came to Yongchun Zheng _ Tencent, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences.

Roaming livable zone-the earth and its neighbors

The earth is our only home and the only planet in the whole universe where life is confirmed. This blue planet, with blue sky, white clouds, green trees and red flowers, is full of vitality and carries all the joys, sorrows and hopes of mankind.

My science major is called "environmental protection", and the most important slogan of environmental protection is "only one earth". We only have one earth, so we should protect this planet. If one day the earth is really destroyed, is there anywhere else we can go? Let's take a look at our solar system first.

There are eight planets in the solar system, and our earth is the third planet where life was born. The earth is within a certain width, which is called the livable zone of the solar system, that is, not far from the sun. The temperature here just allows water to have three States-solid, liquid and gas. Only in this case can there be life.

Venus, the second planet, is called Venus in the west, that is, the god of beauty and the god of love. But in fact, this is a violent planet, a hellish planet. The temperature above it is 460 degrees Celsius, and the atmospheric pressure is 90 times that of the earth. Our spaceship can only live for about three minutes when it lands on Venus, and it will soon be gone. Moreover, Venus is covered with volcanic eruptions, lava flows and concentrated sulfuric acid rain-this is a planet that cannot be suitable for life. Not long ago, it was said that there might be life on Venus, but everyone should take a closer look at that paper, which said that there might be life at a height of 50 or 60 kilometers on Venus. Because only the temperature of 50 or 60 kilometers is suitable enough, it is possible to have life, which is basically impossible. As a result, it didn't take long for the article to admit that there may be a problem, not necessarily related to life signals, but may be a problem with data processing.

Then we will look out from the earth, first at the moon, then at Mars, and have a look along the way.

First, let's look at the earth where we live.

Comparison of the sizes of the Earth and Mars

This is the real size contrast between the earth and Mars. The diameter of Mars is half that of the earth, and the diameter of the moon is half that of Mars. Mars gravity is 1/3 of the earth's gravity, and the moon gravity is 1/6 of the earth's gravity. Therefore, you can hardly walk on Mars like you do on Earth. If it is lighter and less attractive, we may not be able to walk, and we may have to jump around. But compared with the sun, the size of the earth is only one tenth of its 1.3 million. In the overall mass of our solar system, the mass of the sun accounts for 99.86%, and other planets and asteroids are insignificant.

Pale Blue Dot

There is a small point in the white circle on this picture, which is our earth. This was once the most influential photo in space history, and it was called "dim blue dot". 1990, voyager left the earth 13 years. At that time, many people worried that it would lose contact with our earth one day, hoping that it could look back at the earth and take a picture of our earth and the solar system, and finally lost contact with us. As a result, only one big sun can be seen in that photo, but we believe there must be the earth around it, so we finally found it next to it. It turns out that it is so small that you can't even see the moon. This philosophical photo shows us arrogant human beings their true colors. It turns out that we are so small that we are a dusty planet suspended in the sun. Carl sagan wrote a book for this, called "Dim Blue Dot"; There is also a documentary of the same name, full of philosophical meaning.

The Moon Sea on the Moon

The moon is the natural satellite of the earth, the closest celestial body to the earth, and the outpost and transit station for human beings to leave the earth for deep space. There are some black places on the moon called "Moon Sea". For example, the "Jade Rabbit" that people often say is actually a rabbit-shaped moon sea. 1609, when Galileo observed the moon through a telescope, he thought that these black places were all oceans, so he called them "Moon Sea". In fact, last month, the sea was covered with black lava plains formed after magma cooled, and there was no water.

Chang 'e III achieved a soft landing on the lunar surface.

In 20 13, China's Chang' e III landed in the east of Hongwan on the moon and the northwest corner of Yuhai. In 20 19, "Chang' e IV" landed on the back of the moon, and the wheel marks carved by it were the first traces left on the back of the moon in human history. In 2020, Chang 'e V returned from the moon. After more than ten years' efforts, China's lunar exploration team, supported by our strong comprehensive national strength, has achieved the three-step mission of circling, descending and returning, and we have reason to be proud of it.

The Long Road of Exploration —— The course of human understanding of Mars

Next, let's take a look at our protagonist today, which is Mars.

In East Asia, such as China, Japan and South Korea, the five planets of gold, wood, water, fire and earth visible to the naked eye in the night sky, together with the sun and the moon, which are the brightest planets day and night, are collectively called "Seven Obsidian". One week is named after "Seven Obsidian", and Tuesday is called Fire Obsidian Day, which is still used in Japan. Sunday, sun day, is Sunday; Monday, Moon Day, is Monday.

Before the space age, we mainly used telescopes to observe Mars. Although the resolution of the telescope is not high, we have made many new discoveries and even made many small bridges in the middle. We thought there were humans, life, canals and agriculture on Mars, but later we realized that none of them actually existed. But we know Mars again and find that it may be suitable for life. We may emigrate to Mars.

It takes 365 days for the earth to go around the sun, and about 687 days for Mars. Four seasons can be formed on the earth because the rotation axis of the earth is tilted at 23.5 degrees, while the rotation axis of Mars is tilted at 25.2 degrees, which is very close, so there are four seasons on the earth and four seasons on Mars.

The map of Mars was drawn on 1877.

1877 There was an opportunity called "Mars Rush", that is, the sun, the earth and Mars were in a straight line. At that time, it was particularly clear to observe Mars from the Earth. At that time, there were some obvious straight lines on the map of Mars, which caused a sensation all over the world.

At that time, people thought that these straight lines must have been formed by artificial excavation and called them "Mars Canal". There was a wealthy real estate businessman named Lowell. He didn't even have a house to build, and he devoted himself to astronomy. He invested himself to build a Lowell Observatory, bought the best astronomical telescope at that time, and hired astronomers to observe. He even wrote three books saying that Martians dug two canals in two years. Because when he looked at it two years ago, these two canals did not exist. Two years later, he found that there were two more, saying that Martians must have encountered some inevitable huge drought, and they dug two canals urgently to drain the melting snow in the Arctic and Antarctic to irrigate agriculture in the equatorial region. If they can't survive the drought, they will send soldiers to attack the earth. It was later discovered that the contents of these books were all wrong.

Qian Fan is competing with each other-the journey of exploring Mars.

Next, let's take a look at the journeys of countries around the world to explore Mars.

Earth orbit and Mars orbit

Starting from the earth to Mars is just like we are on the playground, starting from the third runway to chase the people on the fourth runway, so when he has an angle with you, he must be chasing the shortest distance. So from the earth to Mars, there is only one chance every 26 months. When the spacecraft set off from the earth, Mars was 44 degrees ahead of the earth. At this time, it will be launched from the earth, and there are still seven months before the spacecraft reaches Mars. By this time, Mars has been left behind by the earth, because Mars is slower than the earth. The green orbit in the middle of the picture above is the orbit of the spacecraft from Earth to Mars. This orbit was discovered by German physicist Herman more than 100 years ago, and it is called Herman transfer orbit.

1964, the photo of the surface of Mars taken by Mariner IV.

From 1960, human beings began to explore Mars, but they all ended in failure at the beginning. It was not until 1964 that Mariner IV successfully flew over Mars and sent back a blurred picture of the surface of Mars. 1976, Viking I and Viking II landed on Mars for the first time, bringing clearer photos.

1976, the photo of the surface of Mars taken by Viking-1.

We have conducted more than 40 mission to mars missions, and these missions are always divided into three categories: orbiters, landers and rovers. The three types of probes landed on Mars from above, and then patrolled Mars, which made our understanding of Mars more and more profound. So far, four rovers have landed on Mars. At present, there is another rover working on Mars. The name of this rover is Curiosity.

Various types of Mars probes

The fog is disappearing-lift the veil of Mars

Terrain comparison between the Earth and Mars

Nowadays, with the completion of exploration missions again and again, human beings have more scientific understanding of Mars and slowly unveiled the mysterious veil of Mars.

Like the earth, there are continents and oceans on the surface of Mars, but there is no water in the oceans of Mars now. But in the past, when the environment was right, there was water in the ocean on Mars. The highest mountain on Mars is Mount Olympus, with a height of 22,000 kilometers, which is equivalent to three times that of Mount Everest.

Comparison between Mount Olympus (Mars) and Mount Everest (Earth)

Mars used to be warm and humid in history. This photo taken by Curiosity used to be a lake. The lake has dried up, leaving sediment at the bottom. You can see that there is a trace washed by the river on the shore of the lake.

Lake Mars photographed by Curiosity (the arrow is the trace of river erosion)

Dew on Phoenix's landing leg

Even now, there is water on Mars. Dewdrops condensed on the landing leg of Phoenix probe indicate that there is water in the atmosphere of Mars. There is still methane in the atmosphere of Mars, but it is still unknown whether this methane is formed by living things.

Ask what the sky is full of —— China's exploration of Mars.

"There are many corners, but who knows the number? What is the sky? Twelve points? " 2300 years ago, the famous patriotic poet Qu Yuan put forward 177 questions about the earth, the universe and human society in Tian Wen's 388 poems, which represented the tireless exploration and pursuit of the unknown world by ancient Chinese people. After 2300 years, in 2020, China's planetary exploration program was named "Tian Wen" series. Tian Wen plans to explore not only Mars, but also planets and asteroids in the entire solar system.

On July 23, 2020, 12: 4 1, Long March 5 was launched from Hainan Wenchang Space Launch Center with a blue flame, and Tian Wen-1 was sent to Mars. "Tian Wen 1" will fly over 400 million kilometers and will arrive at Mars in February 20021and be captured by its gravity.

"Tianwen-1" consists of several parts, including an orbiter that can carry out remote sensing detection and communication relay at the same time, a lander that can plan to achieve a soft landing in May 20021year and a rover placed in it. It takes only seven minutes from the lander entering the Martian atmosphere to landing, but it takes ten to twenty minutes for the signal from Mars to return to Earth, depending on the distance from Mars to the Earth. Therefore, this process can't be intervened by people on earth in real time, but only by the spacecraft's self-operation. It is precisely because of this extremely arduous challenge that only the United States has successfully achieved a soft landing on Mars, and the landers of other countries have crashed during the landing. If the "Tian Wen-1" mission is successful, China will become the second country in the world to successfully land on Mars.

The rover and lander of Tian Wen I.

Now Mars is still a desert planet. In the next 20 years, humans will land on Mars for the first time. In the next 50 years, we may have a small town on Mars. In the next 100 years, we may have a city with a population of one million on Mars. In the next 1000 years, we may transform Mars into a planet like Earth. These things that used to sound like science fiction are getting closer to reality now. By then, the earth, the cradle of mankind, will also become the hometown of mankind, and the moon, the satellite of the earth, will become a natural space station that will never fall. Mars, the most earth-like planet, will become an important branch of solar system civilization.

Yongchun Zheng: Researcher of National Astronomical Observatory, Chinese Academy of Sciences, planetary science expert, popular science writer, and national chief science communication expert in the field of moon and deep space exploration of China Association for Science and Technology. He was awarded the "Top Ten Science Communication Figures in China" and the Science Communication Award of China Science and Technology Publishing House Association. In 20 16, he won the "carl sagan Prize" of the American Astronomical Society and became the first China scientist to win the prize.

Speaker | Li Xiangyang

Text finishing | Liu Chaoliang, Wang Jia

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