The 50-Year Debate on Martian Life

In 1976, NASA's Viking probes landed on Mars and detected carbon-based metabolic signals through soil sample analysis. This was a very intriguing result suggesting the possibility of microbial activity in Martian soil, but it also sparked considerable controversy.

The probes confirmed that the signal disappeared in a re-experiment involving heating the soil, and no clear evidence of life activity, such as microbial reproduction, was found. Due to these ambiguous results, the debate over whether the signals discovered by the Viking probes were truly caused by living organisms or by other non-biological chemical reactions remains unresolved even 50 years later.

This event marked a significant turning point in the history of Mars life exploration and stimulated both scientific inquiry and popular imagination regarding the existence of extraterrestrial life.

Professor Ji Ung-bae explained the situation at the time, saying, "There was a probe called Viking. It landed on Mars, and at that time, it discovered very tantalizing and even now controversial, very interesting data."

In the late 19th century, Italian astronomer Giovanni Schiaparelli recorded dark features observed on the surface of Mars as 'canali' in Italian. He presumed these to be naturally formed riverbeds or valleys. However, during the translation of this record through French to English, it was mistranslated as 'canal,' leading to a significant misunderstanding.

American astronomer Percival Lowell, based on this mistranslated information, became convinced that artificial canals existed on Mars. He imagined that an advanced civilization, striving to survive in Mars' extreme environment, had constructed a vast network of canals to transport water. He spent a considerable amount of his own money building an observatory and dedicating himself to Martian exploration.

Professor Ji Ung-bae explained the background of the translation error: "Schiaparelli himself originally called those dark features seen on Mars 'canali' in Italian, thinking they might be natural riverbeds formed by flowing water. But it was mistranslated into French, and then again into English as 'canal,' meaning an artificial waterway."

Percival Lowell's theory of Martian canals relied heavily on his personal imagination rather than scientific evidence. Lowell drew maps of the Martian surface as he saw it through his telescope, and these maps detailed a complex network of canals. However, other astronomers of the era, no matter how powerful their telescopes, could not find the canals Lowell claimed to exist.

Professor Ji Ung-bae pointed out, "Other astronomers, looking through the same telescopes, couldn't see the complex canals Lowell claimed. He seemed to have seen them with his mind's eye." Lowell's claims were, in essence, a result of the limitations of telescopes combined with the observer's subjectivity. Although proven a scientific error, Lowell's Martian canal theory greatly influenced science fiction works like Wells's 'War of the Worlds,' playing a decisive role in cementing Martians as an iconic presence in popular culture.

Mars has very different physical conditions compared to Earth. Its diameter is only half that of Earth, resulting in weaker gravity and a much smaller surface area. Professor Ji Ung-bae explained, "Looking at its actual size, Mars' diameter is only half that of Earth. So, Mars has weaker gravity and a much smaller area than Earth."

This small size and weak gravity prevented Mars from retaining the water and atmosphere it is presumed to have once had for long periods. As solar winds and cosmic radiation gradually caused the atmosphere and water to escape into space, present-day Mars became a very dry and barren environment. This stands in stark contrast to Mars' past, where the possibility of abundant water and a thick atmosphere has been suggested.

The Viking probes designed a sophisticated experiment to confirm microbial metabolic activity in Martian soil. The core of this experiment involved using radioactive isotope carbon. After injecting this radioactive carbon into the Martian soil, the experiment measured whether microbes in the soil would consume it and release carbon dioxide during metabolism.

Professor Ji Ung-bae explained, "Even if microbes living in the Martian soil carry out metabolic life activities with that carbon, we need to distinguish whether it's truly created through life activity or if it's a component originally present in the Martian atmosphere. So, they intentionally injected radioactive isotope carbon." If microbes consume radioactive carbon and release radioactive carbon dioxide, it could be strong evidence of life activity.

However, as mentioned earlier, although this experiment detected a significant signal, additional verification, such as heating experiments, yielded ambiguous results, leaving the debate about the existence of life on Mars unresolved.

Currently, methods for detecting extraterrestrial life involve searching for specific molecules like methane, carbon dioxide, and ammonia in planetary atmospheres. This is because these molecules are closely associated with life activities on Earth. However, the discovery of such molecules does not necessarily confirm the presence of life.

Professor Ji Ung-bae stated, "Because there is no standard yet that says 'this cannot be explained without life'," pointing out the absence of scientific criteria to definitively prove something is caused by life. One of the most important tasks in the search for extraterrestrial life is to establish objective and universal criteria that can identify signals unique to life, which cannot be explained by non-biological phenomena.

There is an active debate about whether the origin and evolution of life proceed according to universal principles. On one hand, some argue that life phenomena, like physical laws, are governed by certain universal principles. This perspective suggests that given suitable environments anywhere in the universe, life could evolve into similar forms.

On the other hand, some argue that the mode of life's evolution can vary greatly depending on the given environment. While it took approximately 4 to 5 billion years for life to originate and evolve into complex organisms on Earth, the possibility is raised that on other planets, complex life could evolve in just 1 billion years, depending on environmental conditions. Professor Ji Ung-bae explained these two opposing viewpoints, stating, "The side that claims the birth and evolution of life are also governed by universal principles like physical laws, and the side that claims a wide variety of dramatic grammars are possible depending on the given environment, are in a fierce confrontation."

Carl Sagan is considered a pioneer who trailblazed the field of modern astrobiology. In his early career, he worked in biology laboratories, gaining a deep understanding of life phenomena. Based on this background, Sagan integrated astronomy, physics, and biology to systematize the possibility of extraterrestrial life and methods for its exploration.

Professor Ji Ung-bae emphasized, "Carl Sagan's academic achievement can be seen as essentially creating the completely new field we call astrobiology today." Sagan's efforts played a decisive role in elevating the study of extraterrestrial life from a realm of mere science fiction to a legitimate scientific discipline.

The history of life on Earth has been a series of contingent events. The most representative example is the impact of a massive asteroid in the Yucatán Peninsula of Mexico approximately 66 million years ago. This asteroid impact drastically altered Earth's climate and ecosystems, serving as a decisive factor in the extinction of the dinosaurs, who were then the dominant species.

Professor Ji Ung-bae emphasized the contingency of the asteroid impact, saying, "It's deduced that an asteroid hit the Yucatán Peninsula in the Gulf of Mexico, ending the age of dinosaurs. If Earth had rotated just a few more degrees at that time, the asteroid might have fallen on land instead of the Gulf of Mexico or at a different angle." If the asteroid had landed elsewhere or at a different angle, dinosaurs might have survived.

The extinction of the dinosaurs provided an opportunity for mammals to dominate the ecosystem. Mammals, which had lived in the shadows of dinosaurs with their small bodies, began to thrive by filling the void left by the dinosaurs' disappearance, eventually evolving into the ancestors of humanity. In this way, the history of life on Earth has been greatly influenced by unpredictable, contingent events.

In science fiction films, alien civilizations often invade Earth in spaceships or communicate directly, but in reality, this is almost impossible. The universe is too vast and distant, so even with highly advanced means of travel, flying to another star system through physical movement would consume an enormous amount of time and energy.

Professor Ji Ung-bae explained, "The universe is just too vast. So, no matter how much you develop means of transportation, traveling directly in a spaceship is almost impossible. Instead, it would be possible to accidentally catch radio waves coming from that star." Therefore, the first encounter with an alien civilization is more likely to occur through detecting their radio signals rather than a direct meeting.

If a civilization exists that has a much longer history of radio communication than Earth, the signals they send could travel through space and reach Earth, and humanity would first become aware of the existence of an alien civilization through these signals.

If the existence of an alien civilization is officially confirmed, it could lead to immense psychological changes in human society. We would be confronted with the fact that we are no longer the sole intelligent beings in the universe. This could significantly impact humanity's self-esteem. Professor Ji Ung-bae expressed the potential feelings of relative inferiority and fear of an unknown civilization, saying, "Oh, are we the most backward in the universe? Are we the weakest? Aren't we going to be eaten if we show off to them and act recklessly?"

Such fear could make humanity's attitude towards space development passive. There might be a tendency to not reveal our existence, fearing conflict with unknown alien civilizations, which could affect humanity's drive for space exploration. An encounter with an alien civilization would be a momentous event that fundamentally shakes humanity's worldview and values.

Distinguishing between artificial and natural signals from space is crucial in the search for alien civilizations, as natural phenomena can also produce strong radio signals. A characteristic of artificial signals is that they generally exhibit consistent patterns and repetition.

Professor Ji Ung-bae explained, "If a strong signal comes out repeatedly, like a pulse signal at very short intervals, then we can think it's a bit suspicious." While signals from natural phenomena tend to be random or irregular, signals sent by intelligent beings are likely to appear in mathematical rules or repetitive pulse forms. The fact that natural signals have physical limits in terms of specific output and duration is also an important distinguishing criterion.

Carl Sagan proposed using prime numbers as a method for communicating with alien civilizations. Prime numbers are natural numbers divisible only by 1 and themselves, a mathematical concept that can be universally understood by all civilizations. For this reason, prime numbers are considered the clearest means of conveying an intentional, intelligent message.

Professor Ji Ung-bae explained, "He suggested repeatedly sending prime numbers, which are divisible only by 1 and themselves. Numbers like 2, 3, 5, 7, sending signals like 'bang, bang, bang, bang' for these." If such a sequence of prime numbers is repeatedly observed from space, it is highly likely to be a message intentionally sent by an intelligent entity, rather than a mere natural phenomenon. This method is a highly creative and scientific approach to attempting basic communication between different civilizations in space.

In the past, research into extraterrestrial life, especially exoplanet exploration, was viewed with some skepticism in the scientific community. Some fellow scientists considered such research unrealistic and a waste of funding. Professor Ji Ung-bae noted the stark change between past and present: "Just over 10 years ago, if you were in the exoplanet research community, colleagues would have looked at you with pity, but now they are the most envious. This is because they are most likely to receive research funding."

Recently, exoplanet detection technology has advanced dramatically, leading to the discovery of numerous exoplanets, some of which are suggested to have Earth-like environments. These discoveries have elevated extraterrestrial life research from mere speculation to a legitimate scientific endeavor.

Now, extraterrestrial life research has established itself as a major field that integrates cutting-edge technologies and knowledge from various disciplines, including astronomy, physics, and biology. As a result, extraterrestrial life research can secure much more funding than before, and it has become an attractive field that draws the interest of many young scientists. These changes brighten the future of astrobiology even further.

Professor Ji Ung-bae expressed caution about "cosmic utopian" thinking, which seeks to solve current environmental problems or social challenges on Earth through space migration. Some hold an optimistic view that all problems experienced on Earth will be resolved by migrating to Mars or other planets.

However, Professor Ji Ung-bae stated, "I thought that the idea that all the problems we are experiencing on Earth will be solved if we go to Mars was a bit of cosmic utopian thinking," pointing out that such an idea is unrealistic. If humanity fails to solve the fundamental causes of environmental destruction on Earth, similar problems could recur even if we migrate to other planets.

He emphasized that the true solution lies not in finding a new home, but in preserving Earth's environment and exploring ways to live sustainably, offering a critical perspective on indiscriminate space migration theories.