Astronomers called back and said, "No one knows!" It was repeated 50 times.
This happened before man explored the universe. Later, in July 1965, NASA successfully launched the space probe Mariner 4 for the first time, flew over Mars at close range, and sent back 22 black-and-white images to the Earth. These images show that this mysterious planet is full of terrible pits. Obviously, like the moon, it is a completely lifeless world. In the following years, Mariner 6 and Mariner 7 also flew over Mars, and Mariner 9 circled Mars. They sent back 7329 photos to the earth. 1976, "Viking 1" and "Viking 2" entered long-term orbits, during which more than 60,000 high-quality images were sent back, and some lander components were placed on the surface of Mars.
At the beginning of 1998, although everyone was keen on writing at that time, "Is there life on Mars?" It can only be "no one knows". However, scientists have more information and formed a series of opinions on this issue.
Although the appearance of Mars is scarred, many scientists now believe that there may be the lowest level of microbial organisms similar to bacteria or viruses under the surface of Mars. Although other scientists think that there is no life on Mars now, it does not rule out that there may have been an era of "biological prosperity" on Mars in very distant ancient times.
The scope of these debates is expanding, and one of the key factors is whether some possible microbial fossils have been found from Martian fragments or rocks that arrived on the earth as meteorites, and whether chemical evidence of life processes has been found. This evidence must be identified together with the positive test results of the life process-the Viking lander has already carried out such a test.
There are many puzzling factors in the story of exploring life on Mars. Among them, the unusual tubular structure in Martian meteorites is considered as evidence that life once existed on Mars, including the official conclusion released by NASA: 1976, Viking's exploration of Mars "has not found any convincing evidence to prove that there is life on the surface of Mars".
However, Gilbert Levin cannot accept this statement. He is one of the leading scientists involved in the Viking project. He conducted the "radioisotope tracking release" experiment, which showed an accurate positive reading. At that time, he wanted to publish the results truthfully, but his colleagues at NASA stopped him.
In 1996, Dr. Levin commented: "They put forward some explanations to illustrate my experimental results, but none of them are convincing. I believe that there is life on Mars today. "
It seems that Levin's colleagues prevented him from publishing his experimental results because his experiments were contrary to the negative results of other experiments designed by some older colleagues.
The fact that the mass spectrometer on Viking did not detect any organic molecules on Mars attracted special attention. However, Levin later proved that the working voltage of the mass spectrometer on this detector is seriously insufficient-in a specimen, its minimum sensitivity is 6.5438+million biological cells, while the sensitivity of other normal instruments can be reduced to 50 biological cells.
1In August 1996, NASA announced that they had found obvious traces of microbial fossils in the Martian meteorite numbered ALH8400. It was only at this time that Levin was encouraged and published his own experimental results. The evidence released by NASA strongly supports Levin's view that there has always been life on this red planet, despite the extremely harsh environment there: "Life is more tenacious than we thought. Microorganisms were found in the atomic fuel rods inside the atomic reactor. Microorganisms have also been found in the deep sea where there is no light at all. "
Colin Pillinger, a professor of planetary science at Auburn University in the UK, agrees. He said: "I fully believe that the environment on Mars was once conducive to the production of life." He also pointed out that some life forms can survive in the most unfavorable environment, "some can hibernate at a fairly low temperature below zero;" Experiments have proved that 150℃ also has life forms. Can you find something more tenacious than life? "
It's terribly cold on Mars-the average temperature everywhere is ~ 23℃, but in some areas it has dropped to-137℃. Gases that can support life on Mars are extremely scarce, such as nitrogen and oxygen. In addition, the air pressure on Mars is also very low. If a person stands at the "reference height of Mars" (the so-called "reference height of Mars" is the height unanimously determined by scientists, and its function is equivalent to the sea level on the earth), the atmospheric pressure he feels is equivalent to the pressure at an altitude of 30,000 meters on the earth. At these low pressures and temperatures, even if there is water on Mars, it will never be liquid water.
Scientists believe that life cannot germinate anywhere without liquid water. If this is correct, then the evidence of life on Mars in the past and now obviously must mean that Mars was once full of liquid water-we will see irrefutable evidence to prove this. There is no doubt that the liquid water on Mars later disappeared. However, this does not necessarily mean that any life can't survive on Mars. On the contrary, some recent scientific discoveries and experiments show that life can thrive in any environment, at least on earth.
During the period of 1996, some British scientists drilled more than 4,000 meters in the Pacific Ocean and found "a thriving underground world of microorganisms ... (These) bacteria show that life can exist in extreme environments, where the pressure is 400 times that of sea level and the temperature is as high as 170℃".
Scientists studying active volcanoes over 3,000 meters below the sea floor have also discovered some animals, which belong to the so-called gobies and live in territories full of various bacteria, while those bacteria thrive on the boiling, mineral-rich mantle plume rising from the sea floor. These animals are usually only a few millimeters long and look like worms, but here, their size is deformed and they develop into huge monsters. Their appearance is reminiscent of the mythical salamander, a big bug or reptile that is said to live in fire.
The bacteria on which gobies and gobies depend are almost as strange in appearance. They don't need sunlight to provide energy, because at this depth of the sea, no sunlight can penetrate. But they can use "the heat of boiling water from the bottom of the sea". They can digest "minerals in hot seawater" and do not need organic debris as nutrition. This kind of animals are classified as extremely deformed "autotrophs" by zoologists. They can extract carbon from carbon dioxide by feeding on basalt and using hydrogen as energy.
Scientists' reports claim that other autotrophs have been found at 3000 meters under the sea, where the only heat source is the heat of rocks ... These organisms can be found at the high temperature of 1 13℃ ... They can also be found in acid solution; These organisms can be found in the harmful environment of benzene and ethyl ketone, and in the deep sea of Mariana Trench 1 1000 meters.
It is conceivable that there may be such creatures on Mars, and they may be enclosed in permafrost with a thickness of 10 meter. It is believed that there are such permafrost beneath the surface of Mars, and they may have existed in the suspended atmosphere of Mars for a very long time.
On the earth, dormant microorganisms have been wrapped in amber for tens of millions of years and preserved. 1995, scientists in California successfully revived these microorganisms and put them in a sealed laboratory. Other microbial organisms with reproductive ability have been isolated from crystalline salt, and their age is over 200 million years.
In the laboratory, "bacterial spores are heated to boiling point and then frozen to -270℃, which is the temperature range of interstellar space." Once the temperature conditions improve, these bacterial spores will revive immediately. "
Similarly, some viruses can be activated in cells, even though they are inactive outside such biological tissues. In their dormant state, these terrible little creatures (whose bodies are shorter than the wavelength of visible light) can almost never die. After careful examination, scientists found that they were extremely complex, with a genome consisting of 1.5 × 104 nucleotides.
As NASA continues to explore Mars, scientists believe that there is a high possibility of cross-infection between Mars and the Earth. Indeed, this cross-infection may have occurred long before humans began the era of space flight. Meteorites on the surface of Mars fell to the earth. Similarly, some people think that rocks "splashed" from the earth due to the impact of asteroids sometimes reach Mars.
It is conceivable that life spores on the earth may be carried by the Martian meteorite itself-and vice versa, life spores may also be brought from the earth to Mars. Professor paul davis of the University of Adelaide pointed out:
For life on earth, Mars is not a particularly suitable place to live ... However, some bacterial species found on earth can still live on Mars ... If the desolate surface of life Mars was firmly rooted and developed on Mars in the distant past, then when its living conditions gradually deteriorate, life may gradually adapt to its even worse environment.
Is there life on Mars? Perhaps, until human footsteps set foot on Mars, it will never have a clear answer. ...