Mars has two small satellites with an average diameter of more than 10 km, named after two sons of Ares-Phobos and Driss. The ancient Romans called Mars "the myth of Mars", a god of war with armor and blood. The symbol of Mars is ♂. The name of Mars and the symbol of Mars are still used in the world today.
1609, Italian scientist Galileo observed Mars with a telescope for the first time, creating a precedent for human beings to observe Mars with scientific instruments. 1666, g Cassini observed Mars through a telescope and determined its rotation period, and calculated that the daily length of Mars was 24 hours and 40 minutes. 1672, Huygens first discovered that there was a white spot at the south pole of Mars, which might be the polar cap, and first put forward the conjecture that there might be extraterrestrial life. 1777- 1783, the British astronomer W. Herschel studied Mars with his own telescope, mistakenly believing that the dark place on Mars is the ocean, the bright place is the land, and all the planets are inhabited by life. He also predicted that perhaps Martian residents also enjoy an environment similar to ours.
1877 After observing Mars, the director of Milan Observatory, Ya Parelli, announced that he had seen "Canary" on Mars. The original meaning is that the road is misinterpreted as a "canal". Later, it was inferred that if there were canals on Mars, Martians would dig and use them to prosper agriculture. At the end of 19, enthusiastic research on the Mars Canal began, and a large number of novels and movies about "Martians", "Martians attacking the Earth" and "Fighting Martians" came into being. 1905, the Earl Mars Observatory of the United States photographed 38 "canals" on Mars.
Known Mars
The eight planets in the solar system, in the order from near to far from the sun, are: Mercury, Venus, Earth and Mars, which are called terrestrial planets or inner planets because of their small size, high density and firm rock surface; Beyond Mars are four giant planets, Jupiter, Saturn, Uranus and Neptune, also known as woody planets.
The average equatorial radius of Mars is 3,393 kilometers, which is only 53% of that of the Earth. The mass of Mars is10.74% of the mass of the earth; Mars' orbit around the sun is elliptical, with a period of 687 days, that is, 1.88 earth year; Mars' rotation is similar to that of the earth, and its rotation direction is the same as that of the earth. The rotation period of Mars is 24.63 hours a day. The rotation axis of Mars is inclined with an inclination of 25. 19. Therefore, there are four seasons on Mars, but each season is about twice as long as the Earth's season.
The distance between Mars and the sun is farther than that of the earth, with an average distance of about 228 million kilometers (about 65.438+0.5 billion kilometers on the earth), and the annual average temperature on the surface of Mars is -57. C, the surface temperature varies from 20℃ to-139℃. Mars is colder than the earth, and the temperature difference between day and night is larger than the earth.
The gravity acceleration on the surface of Mars is 3.72m/s 2, and the escape velocity is 5.0m/s, while on the earth it is 9.75m/s 2 and 1 1.2m/s respectively. Therefore, Mars has a weak gravitational field, sparse atmosphere and easy escape. The average surface pressure is only 700 Pa, which is less than 1% of the earth's sea level pressure. The main component of the Martian atmosphere is carbon dioxide (95.3%), followed by N2 (2.7%). Due to the thin atmosphere and high wind speed on Mars, the wind rages on the surface of Mars, forming widely distributed active dunes and deserts. Typhoons and tornadoes often occur on Mars. When the wind speed reaches 50 ~ 100 m/s, 100 micron dust is blown into the atmosphere, forming a regional sandstorm. Every Mars year, there are about hundreds of regional sandstorms, and several regional sandstorms occasionally unite to roll a large amount of dust to an altitude of 30 kilometers and develop into a global sandstorm that can last for several weeks.
The terrain of Mars is obviously asymmetrical, and the terrain in the southern hemisphere is higher than that in the northern hemisphere. Two-thirds of the surface of Mars is ancient terrain with very dense impact craters. There are countless network valley systems in the southern hemisphere, which seem to be cut by running water. The longest and largest Mariner Canyon in the solar system is more than 3,000 kilometers long, 600 kilometers wide and about 8 kilometers deep. On earth, the Grand Canyon in Arizona is only 800 kilometers long, 30 kilometers wide and 1.8 kilometers deep. The most impressive feature of Mars is the huge shield volcano. For example, the Olympic volcano is a giant, with a diameter of 550 kilometers and a peak height of 27.4 kilometers, which is the highest peak in the solar system. The northern hemisphere of Mars seems to be a huge ocean basin, a "sea" where "rivers" converge. Mars is a cold and dry desert world.
Looking for signs of life
From 196 1 year, the United States and the former Soviet Union launched a fierce competition on Mars exploration.
In 2003, ESA began to launch the "Mars Express" to explore Mars. So far, 42 explorations have been made on Mars. This detection method realizes the flying, circling and soft landing of Mars, the patrol of the rover and the on-site analysis of samples, breaks through a series of key technologies, greatly improves the ability of human beings to explore the solar system and obtains a scientific understanding of Mars. The scientific problems of Mars exploration mainly focus on detecting the information of Mars life activities, detecting and studying the evolution of Mars, and comparing it with terrestrial planets, discussing the long-term transformation of Mars and the prospect of a large number of immigrants establishing human second habitat in the future, so as to serve the sustainable development of human society.
The primary task of Mars exploration is to detect the information of life activities on Mars. Through a large number of mars orbiter mission probes, especially the Viking 1 Viking 2 lander launched by the United States in 1975 and the Phoenix lander launched in 2007, a series of life activity information detection and life science experiments have been carried out on the surface of Mars, which proves that there are no signs of life activity on the surface of Mars today.
Just as people were desperate to explore life on Mars, trace amounts of water vapor and methane were found in the Martian atmosphere, which rekindled the hope of exploring life on Mars. All life activities will inevitably release methane, and methane in the atmosphere may prove that life activities on Mars are the lowest. Most of the natural gas reservoirs (mainly methane) widely distributed on the earth are also biogenic; However, some abiotic gas reservoirs have also been discovered in Daqing and other places. Therefore, the key issue is to scientifically judge whether methane in the atmosphere of Mars is biogenic or abiogenic. Because the content of methane in the Martian atmosphere is only 30ppt( 1ppt is a part of 1 trillion), the isotope mass spectrometer of the Mars exploration satellite does not have the technical ability to determine the carbon isotope of methane and other compounds, and the answer can only be given after the technical breakthrough.
1984, a Martian meteorite ALH8400 1 was found in Mount Allen, Antarctica. American scientists observed meteorite slices under an electron microscope and found that there were a large number of microbial "fossils"-bacteria in meteorites. The cross section of the micro-body is only about 1% of the hair size. According to the determination, the age of ALH 8400 1 is 3.6 billion years, which indicates that the lowest life-bacteria was bred on Mars 3.6 billion years ago. At that time, the biological level of the development of the earth was also the lowest microorganism-bacteria. This problem has caused a wider scientific debate: since the biological "fossils" of Mars can be brought to the earth now, the life materials of Mars can also be brought to the earth with meteorites in an older era, and perhaps the life of the earth is the offspring of the life of Mars. Of course, the opposite may be true. Life materials of the earth can also be brought to Mars with meteorites of the earth, but life on Mars is the offspring of life on the earth. Maybe both the earth and Mars once developed their own lives. Because of the harsh environment on Mars and the abortion of life, life on earth has evolved and multiplied. ALH8400 1 After careful study by scientists all over the world, a group of scientists cited a large number of facts to prove that these "fossils" are not fossils of life, but special structures formed by natural processes and are typical abiotic causes. Whether there is life on Mars remains a mystery.
Hope still exists.
Mars doesn't have any information about life activities now. Mars may have developed life in the past, and there is indeed an environment in the evolutionary history of Mars where the climate is suitable for the generation and survival of life. A large number of detection results show that there are a large number of ancient river systems and water traces on the surface of Mars. One of the necessary conditions for the emergence and evolution of life is the existence of water. There was a lot of water activity on Mars, which undoubtedly provided favorable evidence for the view that there was living matter on Mars. To confirm that life once existed on Mars, we must find the sedimentary rocks on the surface of Mars and find the biological fossils of Mars in the sedimentary rocks.
Does Mars now have the conditions and environment for the existence and reproduction of life?
According to the discovery and research of various life forms in extreme environments, such as submarine black chimney, polar ice sheet, salt lake silt and hot desert, it shows that the environment on the surface of Mars still has the conditions for life reproduction. Because the surface of Mars is dry and there is no water activity, a large number of facts prove that the water body of Mars is buried underground. It is possible to find the lower life forms of Mars by detecting the buried position of groundwater on Mars.
There is still a long way to go to explore life on Mars!