On September 14, sources confirmed that a research paper entitled phosphine gas in Venus clouds was published in nature astronomy. The paper shows that scientists have discovered phosphine in Venus cloud through telescope. Phosphine is a toxic gas related to life on earth, which is considered as a potential biological signal and can be used as evidence of life on other planets and celestial bodies. The mysterious and enduring proposition of extraterrestrial life is also the frontier of modern scientific research. “Are we the only one in the universe?” According to Li Di, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, the exploration of extraterrestrial civilization is one of the traditions of natural science research, with the purpose of “helping to understand human position in the universe”. The Maxwell Telescope (jcmt), located in Hawaii, USA, is the largest single submillimeter telescope in the world. In February 2015, the East Asian Observatory officially took over the scientific operation and management of jcmt. The great science center of the Chinese Academy of Sciences is one of the four core members of the East Asia observatory. “The discovery of phosphine in the atmosphere of Venus is a significant scientific achievement of overseas equipment managed and operated by CAS.” Li Di said. < / P > < p > a stone stirs up a thousand layer waves, which excites scientists and ordinary people. But David Clements, an astrophysicist at Imperial College London, is wary: “this finding is only indirect evidence that there is no real proof of life, but cordite is clearly floating in the air, which may indicate something.” What is phosphine? Why is its discovery associated with life? According to Wang zhuoxiao, a doctoral student in Astrophysics at the Institute of advanced research of Tsinghua University, phosphine is a small inorganic molecule with strong chemical activity, which will be oxidized quickly in the earth’s oxygen rich atmosphere. If the formation of phosphine is analogous to pushing a rock up a mountain, a very efficient and specific chemical reaction is required to push the stone to the top of the mountain. However, a slight disturbance will make the rock fall down the mountain immediately. So the formation of phosphine is very difficult, and it disappears too fast to be detected. < / P > < p > “therefore, once we observe phosphine, we can be sure that there must be an efficient and specific chemical reaction, which is continuously producing phosphine. However, we do not know exactly what kind of chemical reaction it is. We only know that it is the result of life activities Wang zhuoxiao said that there is no significant record of phosphine in the natural environment without life activities. < / P > < p > the researchers made a simple estimate of all possible nonliving processes and found that the estimates were not sufficient to explain the observations. This shows that there are at least two sources of phosphine, one is other unknown non life processes, these processes release a certain amount of phosphine, and the other is the process of life activities. < / P > < p > “astrobiologists tend to regard phosphine as a kind of life tracing signal, and think that only life activities can have this kind of efficient chemical reaction and continuously produce a large amount of phosphine.” “We don’t know whether phosphine can be produced by other unknown abiotic chemical reactions outside the earth,” Wang said So the researchers say phosphine may have come from unknown photochemical or geochemical processes on Venus, or from life activities similar to those on earth. < / P > < p > it is also worth mentioning that the atmosphere of Venus is mainly composed of inert carbon dioxide, sulfuric acid and other acidic gases. Compared with the earth, phosphine will exist for a relatively long time. So the significance of this discovery is not the exact evidence of life, but also the evidence of unknown chemical reactions active in the atmosphere of Venus. < p > < p > Venus is known as the “hell planet”. Its surface temperature is more than 400 degrees Celsius, and even some metals can be melted. The pressure is 40 times of the atmospheric pressure on the earth’s surface. Therefore, Wang zhuoxiao mentioned that there is almost no life on its surface. However, phosphine was found at a height of 40 to 60 km from the surface of Venus, which can be called “temperate zone”. The temperature here drops to 50 ℃ to 0 ℃, and the atmospheric pressure drops to about one atmosphere of the earth. Therefore, if there is life activity, the temperate zone will be a very suitable choice. “If there are microbes, they may be suspended in a temperate zone, moving up and down by condensation and gasification of gases, obtaining different temperatures and performing different metabolic reactions. Although Venus has no oxygen in its atmosphere, it’s not a problem for anaerobic bacteria at least Wang zhuoxiao said. < / P > < p > “the atmosphere of Venus is not particularly” extreme. ” Li Di stressed that the extreme definition is for human beings. In fact, there are many kinds of life on earth. For example, lichen can live for 10000 years, and it can survive in very low temperature, little oxygen and even in outer space. “Extremes are relative statements and need a frame of reference,” he said. The environment in the Mariana Trench is extreme, but there are also creatures that don’t have eyes and don’t need sunlight. Life can still exist in extreme environments such as high temperature, low temperature, aerobic and anaerobic conditions. We do not have a complete understanding of life forms. ” Therefore, it is better to explore what forms of existence can be defined as life activities than to emphasize the extremes of the environment. In Li Di’s opinion, the real value of this discovery needs further research. On the one hand, how to process and interpret the newly discovered data is worthy of further examination. Whether there are other life process related components in Venus atmosphere, Mars surface or deep space is worth further exploration; on the other hand, human beings still need to continue deep space exploration, because we still need to see the “living body” in the end. < / P > < p > how to find the life signal? According to Wang zhuoxiao, oxygen molecule is the best signal from the perspective of chemical activity. It can be estimated that if there is no continuous supply of plants, all oxygen on the earth will be solidified into rocks within a million years. So if you look at the signals of oxygen molecules on other planets, you can be sure that there are plant life similar to the earth. In addition, water is also a key tracer signal. It is said that “water is the source of life”. To be specific, almost all chemical reactions in life are carried out in solution. For example, the cellular environment in our body is a liquid environment in which molecules can fully contact and react. If there’s an underground hot spring, it’s a good signal. For example, Cassini has seen hot springs from Enceladus. Life on earth is summarized as “carbon based life”. Organic molecules composed of carbon atoms constitute the basic unit of life. Therefore, organic molecules are also a good tracer signal. Similarly, Cassini detector has identified a large number of organic molecules in the hot spring ejected from Enceladus. Cui Jun, a professor at the school of Atmospheric Sciences at Sun Yat sen University, said that since there are generally carbon based life on earth, the scientific and rigorous method in the exploration of extraterrestrial life is to analyze the ratio of carbon isotopes, that is, the ratio of carbon 12 to carbon 13. This is because the carbon isotope ratio of abiogenic and biogenic is very different, and it can be used to judge whether there is life activity. < / P > < p > “phosphine is much more chemically active than methane. Even if phosphine can be confirmed on Venus, it is only indirect evidence of the existence of life, and it may be produced by an abiotic process. We can’t judge whether it is produced by an abiotic process. Only by sending a probe to Venus and detecting microbes in the place where phosphine exists in the atmosphere, can we say that there is life on Venus Wang zhuoxiao said that even if you see traces of liquid water, underground lakes and methane on Mars, they can only be indirect evidence. Only when curiosity or other Mars rovers sample direct evidence of life, can we confirm the existence of life on Mars. For Venus, there is no clear scientific mission to orbit or land, but the discovery of phosphine will undoubtedly promote the development of Venus exploration mission. In the future, we should see the detector working in the atmosphere of Venus, and then we can determine whether there is life on Venus. Global Tech