“The mystery of why we haven’t found signs of aliens yet may have less to do with the likelihood of life or intelligence emerging, but rather with the rare rapid emergence of biological regulation of feedback loops on planetary surfaces,” says Aditya Chopra of Australian National University. "The first life is fragile, so we think it rarely develops fast enough to survive."
How did life come about?
In short, life on other planets is likely to be very short-lived and disappear very quickly, according to astrobiologists at the Australian National University. In a study aimed at understanding how life can evolve, scientists realized that new life usually dies out due to the increasing warming or cooling of its own planet. The group of scientists found the answer in the so-called "theory of Gaia" by James Lovelock.
In the 1970s, chemist Lovelock and biologist Lynn Margulis developed the idea that our Earth could be like a living organism, a self-regulating entity that uses feedback loops to maintain conditions suitable for life. They christened the potentially living planet Gaia - after the Greek goddess of the Earth.
The search for “other lands” is in many ways a search for “other gays,” and NASA's plans to discover other planets similar to Earth are highly dependent on Lovelock's understanding of the relationship between life and the universe in the context of Gaia's theory.
Life took over the Earth with an almost irrepressible haste. When the Earth was young, debris left over from the formation of the solar system fell on it, creating an extreme environment in which life might not last long. This continued for 600 million years after the formation of the solar system. However, we have evidence that once the bombing was over, life began.
According to John Gribbin, author of the book 'Alone in the Universe', the Earth's orbit is located in an extremely favorable place in the solar system from the point of view of the prospects for the development of intelligence. But the situation is not as obvious as it seems at first glance. The presence of life on Earth plays a role in regulating our planet through the greenhouse effect. Gases such as carbon dioxide heat the Earth's surface, trapping heat that might otherwise escape into space.
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Today, this natural greenhouse effect makes the Earth 33 degrees warmer than the surface of the airless Moon, although the Earth and the Moon are almost the same distance from the Sun. When the Earth first formed, Gribbin writes, the atmosphere was rich in these greenhouse gases and kept the planet from freezing, even though the sun was colder. As the sun warmed up and life appeared on Earth, living things pulled carbon dioxide from the air and deposited it in the form of carbonate rocks, reducing the strength of the greenhouse effect. Life changes the amount of carbon dioxide in the air through feedback processes that keep the planet warm when the sun cools and prevents it from overheating when it warms up.
This is the foundation of James Lovelock's theory of Gaia, which gives us space to search for life beyond the solar system. Lovelock's main question was: What makes the Earth special? “The air we breathe can only be an artifact that is maintained in a stable state by biological processes far from chemical equilibrium. Living things must regulate the composition of the atmosphere not only today, but throughout the entire history of life on Earth - literally over billions of years.
But then a riddle arises: why the greenhouse effect did not go all out when the sun warmed up, why did not the same thing happened that happened to Venus? The answer, according to Lovelock, is that life regulates the composition of the atmosphere, gradually removing carbon dioxide as the sun heats up, keeping the temperature on Earth comfortable for life.
Scientists at the Australian National University believe that the reason we have not found signs of advanced technological life may be because all aliens are extinct. “Extinction is a cosmic order for most of life that has ever appeared,” the study authors write.
About four billion years ago, Earth, Venus and Mars could have been inhabited. However, a billion years after its formation, Venus turned into a greenhouse, and Mars froze in ice.
Early microbial life on Venus and Mars, if any, could not stabilize the rapidly changing environment, says co-author Charlie Lineweaver of the ANU Institute of Planetary Science. "Life on Earth has probably played a leading role in stabilizing the planet's climate."
Wet, solid planets with the ingredients and energy sources for life seem to be ubiquitous, however, as noted by physicist Enrico Fermi in 1950, no signs of extraterrestrial life were found.
The likely solution to the Fermi paradox, scientists say, will be a near-universal early extinction, which they dubbed "Gaia's bottleneck" (as they call any bottleneck). "One curious prediction of Gaia's bottleneck is that the vast majority of the fossils in the universe will be made of extinct microbial life, rather than multicellular species like dinosaurs or humanoids, which take billions of years to develop," says Linweaver.
"Could the planet, in a sense, be alive?" Asks NASA astrobiologist David Grinspoon. This is not the first time he has put forward such a concept. In his 2003 book Lonely Planets, Grinspoon presented the "living world" hypothesis, a slight variation on the well-known Gaia hypothesis.
Since then, this idea has been quite vividly discussed, but it was considered more philosophical than scientific. Nevertheless, many researchers agree that this concept has helped the science of the Earth system move forward, allowed us to understand that many of the Earth's cycles are water, nitrogen and carbon cycles; plate tectonics; climate - deeply interconnected and modulate, or modulate life on Earth.
“Gaia might just be a good metaphor,” says Grinspoon. "But I'm wondering if life can be considered something that not just happened on our planet, but what is happening to our planet."
“It's not easy to separate the living and non-living parts of the Earth,” he adds. “Life has made the Earth what it is, to a great extent. This is the general meaning of the Gaia hypothesis, and the Living Worlds hypothesis simply transfers this idea to other planets."
“The idea of the origin of life, separated from the birth of the living world, has interesting implications for life elsewhere,” Grinspoon writes. "If Gaia's self-regulation is responsible for the Earth's longevity, then we need to find other places where this global organism developed, and not just places where life could once have arisen."
In other words, our search for life must target locations with active geological and meteorological cycles, potentially signaling a living biosphere.
So far, we have found nearly 2000 planets orbiting distant stars, and we continue to find new ones. While these worlds may be too distant for us to find any direct evidence for life in the near future, scientists are becoming increasingly proficient in determining the composition of their atmospheres. Perhaps one day this skill will allow us to distinguish between a "failed biosphere" and potentially living worlds.
Ilya Khel