Why is Mars like a "pocket earth"?

In many science fiction novels, we all want to live like this in the future-due to environmental deterioration, earthquake and tsunami, comet impact and other reasons, human beings can not survive on the earth and begin to immigrate to Mars. There are many planets in the solar system. In the fantasy of opening up a second home, why do humans always have a soft spot for Mars? Is Mars really a "pocket earth"?

The time required for a planet to orbit once is called its period of revolution. The farther the planet is from the sun, the longer the period of revolution is. Period of revolution is a year on Earth. Similarly, we also call the time for Mars to go around the sun "the year of Mars".

It takes about 365.24 days for the earth to make one revolution around the sun. The distance from Mars to the sun is about 1.5 times that from the sun to the earth. One revolution around the sun is a "Mars year", which is equal to 1.88 years on the earth, that is, 687 days on the earth, which is equivalent to 668.6 "Mars days". Therefore, there will be 668 or 669 sunrises and sunsets on Mars last year.

Mars is 6770 kilometers in diameter, which is about 53% of the earth's diameter, and its surface area is almost as large as 15 China. If the earth is hollow, it will be filled with seven balls the size of Mars.

The gravity of the earth makes every object on the ground suffer a certain gravity, that is, we are used to saying that it has a certain weight If the same object is placed on the surface of Mars, the gravity of Mars will also make it have a certain weight. The mass of the earth is 9. 3 1 times that of Mars, so the gravity field intensity of the earth is 9.3 1 times that of Mars. However, the weight difference of the same object placed on the surfaces of these two planets is not 9.3 1 times. The reason is that the radius of Mars is smaller than that of radius of the earth, the distance from the substance on the surface of Mars to the center of Mars is smaller than that from the surface of the Earth to the center of the Earth, and gravity is inversely proportional to the square of the distance. Considering these factors comprehensively, it can be calculated that the gravity on the earth's surface is about 2.6 times that of Mars.

Therefore, a person who weighs 70 kilograms on the earth receives the same gravity on Mars as a person who weighs 26.9 kilograms on the earth. Of course, this person's mass has not actually changed, but only attracts this mass and makes people have the gravity of the planet surface. Although this kind of gravity is smaller than that on the earth, it is not much smaller than that on the moon, and the trained colonists are relatively easy to adapt.

The rotation axis of the earth is not completely perpendicular to the orbital plane of the earth, but is inclined by about 23.5, and the included angle with the orbital plane is 66.5, which leads to the change throughout the year. The rotation axis of Mars is also tilted, and the tilt angle is very close to the earth axis, which is 25. 17? . This means that the seasonal changes on Mars should be the same as those on Earth. However, the length of a year on Mars is twice as long as that on Earth. At the same time, Mars is farther away from the sun than the Earth, so every season on Mars is colder than the same season on Earth. For example, summer on Mars will never be as hot as summer on Earth.

Some astronomers have long noticed that there are some white spots near the edge of the circular surface of Mars. 178 1 year, the British astronomer Herschel knew the positions of the two poles of Mars after determining the inclination of the rotation axis of Mars. It suddenly dawned on him that one of those white spots was at the North Pole of Mars and the other was at the South Pole. People suddenly thought: they should be ice! There should be water if there is ice, which seems to be quite consistent with the earth.

In addition, the albedo of Mars makes people think that it may have an atmosphere like Earth. The albedo of a celestial body refers to the proportion of the light it reflects outward in all the light that shines on it. The moon and mercury have no atmosphere, and their bare rocks reflect only 7% and 6% of the total incident sunlight, that is, their albedo is 0.07 and 0.06 respectively. Venus's atmosphere is full of dense clouds that never dissipate, so its albedo is as high as 0.76, which means it reflects three-quarters of the sunlight. There are not as many clouds in the earth's atmosphere as Venus, so the albedo of 0.39 is only about half that of Venus. The albedo of Mars is 0. 15, which is less than half that of the earth, but more than twice that of the moon. It can be seen that Mars neither lacks the atmosphere like the moon nor has a fairly thick atmosphere like the Earth. It has an atmosphere, but it is thinner than the earth's atmosphere and partly cloudy.

With more and more understanding of Mars, people think it is like a small earth. In many ways, no other planet is similar to the earth like Mars. The more similar Mars is to the Earth, the more astronomers care about it, and the greater the public interest in it.

In fact, there is still a big difference between Mars and the Earth. The most prominent thing is that there are many species and vitality on the earth, and human civilization has emerged; Whether there is life on Mars is uncertain. But in any case, Mars is the planet most similar to the Earth. Scientists even imagine that one day in the future, Mars can be transformed into another home for human beings.