How long will it take for humans to enter Mars?

Mars and Venus are the closest planets to the Earth. Scientists generally believe that Venus is the past of the Earth and Mars is the future of the Earth. More than a dozen explorations of Venus by American and Russian scientists show that the environment on Venus is extremely bad, and it is definitely not suitable for "fragile" humans to live in. What about Mars? If there is life on Mars, people on earth will probably be happy to regard Mars as their "second hometown" one day. After the success of the first "flying to the moon" in 1969, the desire to March into Mars rose in people's hearts. Scientists can't wait to make a Mars exploration plan. The urgent question before them is: Is there life on Mars? Life on Mars

Around 1975, NASA launched two Viking Mars probes. According to the data provided by the probes, scientists speculated on the evolution process of the Martian environment: three or four billion years ago, the surface of Mars was very warm, with rivers and lakes densely covered and flowing water. At that time, there should be a lot of life on Mars. Two billion years ago, Mars suddenly warmed up, the atmosphere gradually decreased, and a lot of water evaporated. After the rivers and lakes dried up, the bumpy rivers and ditches on the surface of Mars today were formed. Mars, like the earth, is a little tilted and rotates. It also has four seasons in a year, but the four seasons are longer than those on the earth, which is equivalent to 16 months on the earth. Mars also has two poles. The North Pole is 2 kilometers in diameter, the crust is 4-6 kilometers thick, the South Pole is 7 kilometers in diameter and the crust is 1-2 kilometers thick. At present, the air on Mars is 95% composed of carbon dioxide, with little oxygen and water vapor. A white ice cap consisting mainly of water and carbon dioxide covers the poles.

in order to study what kind of life on earth can survive in the Martian environment for how long, American scientists have designed a device to simulate the Martian environment-cryostat, which is filled with the combined gas similar to the conditions of Mars that scientists try to make.

The air on Mars is thin and lacks the ozone layer, so that ultraviolet rays can reach the surface directly. Scientists use heavy hydrogen lamps to irradiate 1 million times more ultraviolet rays than the actual Martian environment, and use accelerators to irradiate 1 million times more cosmic rays to reproduce the Martian environment. The researchers used this device to put some creatures into it for experiments. Because of its small size, large animals and plants can't "get addicted" to it, but microorganisms can "enjoy" it.

First, the cryostat was exposed to a large number of high-intensity ultraviolet rays and cosmic rays for 2 years at the same place on Mars, and it was found that the survival rate of Bacillus spores was 25%. The survival rate of a mold spore that often breeds on stale biscuits is also 25%; However, the spore survival rate of Clostridium sporogenes, an anaerobic bacterium that only reproduces under hypoxia, is 4%-7%.

The researchers covered Bacillus spores with dry ice (1-2 mm thick) similar to Mars, and exposed them to ultraviolet rays and cosmic rays equivalent to the same place on Mars for 2 years. As a result, the survival rate of spores covered with dry ice was over 9%.

From this, scientists believe that even in the current Mars environment, there is still the possibility of life.

In 1994, a report about life on Mars in Russian Journal was even more astonishing. It is reported that in 1979, when the personnel of the American Space Center were studying the photos of Mars taken by the American Viking probe, they actually found the image of the Sphinx. But at that time, this photo did not attract the attention of researchers. As a result, this photo was bought by a computer programmer in the former Federal Republic of Germany.

NASA experts found a photo of Mars taken at different times from a pile of discarded photos. Although the Sphinx image is not clear, it is still faintly visible.

They processed these two photos of Mars taken at different times and from different angles by computer, and found that the nostrils and necklaces originally thought to be caused by radio interference are real, and the teeth in the eyes and half-open mouth are also revealed on the computer screen.

According to their calculation, the size of the Sphinx on Mars is: 1.5 kilometers from the hair to the chin and 1.3 kilometers wide! Researchers believe that only a very advanced civilized society can make such a big statue.

Later, a group of buildings, roads and strange circular squares were found 7 kilometers away from the Sphinx. The buildings are all large in size, and the largest central pyramid is almost 1 times as large as the famous Egyptian Cheops Pyramid! It is still unknown what the circular square that goes straight for one kilometer means. It may be a spacecraft launch site, an accelerator test site or a downtown square or something.

at present, it is not clear what materials the sphinx and the pyramids are made of. But as a rule, due to the dust storm on Mars, the general road will definitely disappear without a trace in 5 to 1 years. However, from the photos, the roads are basically intact, and some roads deliberately bypass potholes when they are built. Does this mean that the history of the city is not very long?

In order to find sufficient evidence, scientists try to prove the existence of life on Mars from other aspects. In 1994, the research team of NASA, consisting of 11 planetary scientists, microbiologists, soil biochemists and engineers, went to Le Chujila Cave in Carlsbad Cave National Park, New Mexico, USA, and collected bacterial specimens from the dark cave. The known depth of Le Chujila Cave is more than 48 meters. In the harsh environment of darkness, researchers discovered the existence of bacteria and fungi. In addition, they also found some bat bones, as well as the remains of a toothless mammal 25, years ago and a ring-tailed cat 45, years ago.

Scientists have also explored a perennial frozen lake in Antarctica. The lake is 3 meters deep, the ice layer is 4.6 meters thick, and the annual temperature is below MINUS 2 degrees Celsius. It is such a cold zone that blue-green algae and diatoms still exist. In addition, scientists have repeatedly found primitive microorganisms on the deep seabed, volcanic hot fountains and deep in the earth's crust. They don't need sunlight and oxygen, but rely on the heat, water and rocks there to sustain their lives. Professor Carlsted of the University of Dreygenburg said that these primitive microorganisms are probably the same ancestors of modern organisms. Is there water under the surface rocks of Mars? Is there heat in the deep crust? He thinks that if there is, then it is very possible that there are life forms on Mars. The researchers' latest discovery comes from a Martian meteorite called "Alan Mountain 841".

On August 7th this year, scientists from NASA and three universities, including Montreal, Georgia and Stanford, held a two-hour press conference at the headquarters of the Illiteracy Bureau in Washington, announcing that they had found reasonable evidence of life on Mars in the past.

researchers believe that the meteorite was formed on Mars 4.5 billion years ago, splashed into space when Mars was hit by an asteroid and other celestial bodies 15 million years ago, and landed on the ice surface in Antarctica 13, years ago. It was discovered by scientists in 1984, and its hometown was just confirmed by researchers recently.

Richard Zare, a member of the research team and a chemist from Stanford University, discovered an organic molecule called polycyclic aromatic hydrocarbons by using a laser and a mass spectrometer. Polycyclic aromatic hydrocarbons are closely related to life: these polycyclic aromatic hydrocarbons were found deep in the cracks of meteorites, and their density was much higher than that of polycyclic aromatic hydrocarbons in Antarctic ice sheets. This shows that these polycyclic aromatic hydrocarbons came from Mars, not from outer space or the earth. In addition, because the carbonates related to these polycyclic aromatic hydrocarbons were formed 3.6 billion years ago, it shows that the organic molecules were not attached to meteorites during interstellar travel (15 million years), and the magnetite particles and sulfur iron particles contained in spherical carbonate related to polycyclic aromatic hydrocarbons are very similar to the magnetic particles acted by bacteria on the earth in chemical composition, structure and morphology; The latest research shows that when the meteorite was formed, the temperature on Mars was -8 degrees Celsius instead of 7 degrees Celsius, which is impossible for living things to exist. Positive trivalent iron ions that may undergo redox reactions have been found in meteorites, and all life phenomena on earth are basically related to redox reactions, which indicates that there may have been water or oxygen on Mars.

Many Mars research experts believe that there is a great possibility of life on Mars, no matter from the results of experiments and meteorite research, or from the data provided by the Viking Mars probe.

Different voices

Although scientists agree with the idea of life on Mars, the skeptics are still unmoved. They think, before manned spaceship landed on Mars and found the exact evidence of life, all speculations can't be counted as facts, and there are still many loopholes in these speculations.

Four scientists, including Jim papak of the Institute of the University of New Mexico in the United States, said that they found no important evidence of Martian life when studying Martian meteorites. These four scientists have been studying a Martian meteorite that weighs more than 4 pounds and looks like a potato since last year. There is a trace of pyrite in this meteorite, which contains two sulfur isotopes-sulfur 32 and sulfur 34. On earth, once there are bacterial activities or other signs of life in this ore, the ratio of sulfur 32 to sulfur 34 will change, while the ratio of two sulfur isotopes on Martian meteorites shows no change, so it can be considered that there is no life activity. Papak said: Although they and NASA scientists are not studying the same fragment of Martian meteorite, these fragments should have the same geological characteristics, but he also pointed out that their research can not prove that NASA's statement is wrong, because life activities on Mars may be different from those on Earth, which will not change the sulfur isotope ratio of pyrite.

arens, a planetary research scientist at the National Academy of Sciences, believes that the conclusion about the existence of life on Mars can only be regarded as a "hypothesis", because at least we haven't confirmed a sample from Mars. He stressed that it is not certain that the meteorite that NASA concluded that there was life on Mars came from Mars, so it is necessary to take samples directly from Mars. Benoit, an expert in cosmochemistry in Arkansas, USA, also thinks that the statement of NASA about the existence of life on Mars in ancient times is an inference, because the same polycyclic aromatic hydrocarbons can be found in different meteorites.

International geoscientists also expressed doubts about the American discovery. Experts believe that a meteorite that cannot be determined by NASA now must come from Mars; Second, even if it comes from Mars, any traces of organic life on the surface of meteorites will usually be burned when they pass through the atmosphere due to high temperature oxidation and other aspects. Even if traces of life exist in meteorites, it is also difficult to preserve them. Zhang Yun, a professor of biology in Peking University, thinks that it can't be said that there was no primitive life on Mars billions of years ago. The key to the problem lies in how to determine that the trace of life material on this meteorite was brought from Mars, rather than being polluted by life on the earth after the meteorite fell to the earth.

German scientists have also expressed similar views. Wolfgang Skillbrant, a researcher at the Max plank Institute of Astrology, also believes that there were many meteorites in the solar system 3 billion years ago, so it is hard to say that the piece studied by NASA came from Mars. He believes that the so-called thing that fell from a celestial body to the earth 13, years ago is the object being studied as Martian material at present. This stone is likely to come from the earth itself, because there are many similar stones on the earth.

March on Mars

It seems that the only way to prove whether there is life on Mars is to take samples directly from Mars for research. At present, countries such as the United States and Russia are making ambitious plans to March into Mars. It is reported that in the next two years, the earth will send four envoys to Mars.

The first emissary was the American spacecraft Mars Global Observer. It plans to leave the earth in November this year and reach the orbit around Mars after ten months' travel. It will draw the topographic map of Mars, analyze the atmospheric composition of Mars and record the weather changes on Mars.

The second emissary is the Russian Mars 96. It also plans to leave the earth in November this year and arrive at Mars about ten months later. After reaching Mars, Mars 96 broke away from Proton rocket and split into three parts. Some of them stayed in orbit to photograph the surface of Mars, and investigated the composition and temperature of the atmosphere of Mars. The other two parts landed on Mars. Based on the past experience of Russia and the United States, Russian scientists have successfully studied a landing device consisting of two research stations and two input devices for the first time. In the past, there were hundreds of kilograms of landing devices, but now the device is just a "small witch" in weight. It landed directly on Mars at a speed of 8 kilometers per hour. At the moment of contact with Mars, the gas buffer quickly inflated, and each landing device was split in two. Some of them rotate the whole set of scientific research instruments to investigate the surface and atmosphere of Mars. The bomb-type needle penetrator penetrates 6-9 meters underground of Mars, and the penetration depth depends on the hardness of the rock. Needles and instruments are more than one person's height, with sharp heads, which are made of super-hard materials and equipped with high sensitivity and precision instruments. The main task of the penetrometer is to determine the composition of soil, physical and mechanical properties and magnetism, as well as the earthquake situation on Mars and so on.

The third messenger is the American Mars Pathfinder, which is scheduled to set off in December this year and land in Ares Valley on the Mars Plain on July 4th next year. It will release a robot to collect samples on the surface of Mars, and the spacecraft will also use a Mars off-road vehicle to inspect a dry river ditch on the surface of Mars to collect primitive microorganisms or fossils of primitive microorganisms on Mars. It is reported that this rover, developed by the United States and Russia, weighs 137 kilograms, is equipped with six wheels, a satellite antenna and a large number of sensors. Mars Pathfinder will return to Earth in 25 with rich information about Mars.

The fourth emissary is the American Mars Global Observer 2, which will leave the Earth in 1998 and plan to land on the surface of the South Pole of Mars. It will dig a deep ditch with a manipulator to measure the hardness of Martian soil and find water.

in addition, Russia also decided to launch another Mars probe called Mars 98 in 1998, and Japan also decided to launch a Mars probe called Planet -B in the same year.

It is reported that if a manned spacecraft is used to explore Mars, the United States alone will need to spend 4 billion dollars in the next 3 years, so the Clinton administration decided to give up the promise made by former President Bush on manned flight and adopt a cheaper way to retrieve samples without manned probes.

However, scientists have not given up the research on manned flight, but are making plans for manned spacecraft to explore Mars. Human exploration of Mars is of great significance, because no matter whether the Martian environment is suitable for human habitation, it will provide extremely valuable experience for human deep exploration activities in the future. (Yangzi Evening News 96.1.25)