“The universe is probably full of potentially habitable planets, so many scientists believe there must be aliens, many of them,” says Aditya Chopra of the Australian National University. “Early life is fragile, so we believe it rarely develops fast enough to survive. Most early planetary environments are unstable. To create a habitable planet, lifeforms need to regulate greenhouse gases, water and carbon dioxide to keep the surface temperature at a level. The mystery of why we have not received any signals from aliens so far may be less related to the origin of life or intelligence, and more - to the rarity of biological regulation of feedback loops on the planet's surface.
Life on other planets can be short and die out very quickly, astrobiologists at the Australian National University say. In a study aimed at understanding how life could have evolved, scientists realized that new life is likely to die out due to the increasing warming or cooling of its forming planet.
In 1950, over lunch, Enrico Fermi made a seemingly innocuous remark that worries every scientist searching for extraterrestrial life today. Fermi then discussed the possibility that the galaxy is inhabited by many complex societies. It would be logical to assume that we should have a large space company. But if there were many alien civilizations, they should have already settled in the galaxy.
Fermi realized that any civilization with a modest arsenal of rocket technology and immodest imperial manners could quickly colonize the entire galaxy. In just ten million years, each star system will be brought under the wing of an empire. Ten million years may seem long, but it is an instant compared to the age of a galaxy that is ten thousand million years old. Colonization of the Milky Way must pass quickly.
So Fermi immediately realized that the aliens had had enough time to flood the galaxy. But looking around, he did not see any clear evidence of this state of affairs. And so he asked more than an obvious question: "Where is everyone?"
A possible solution to the Fermi paradox, the ANU researchers say, could be a near-universal early extinction, which they called the "Geya bottleneck." “The Geye bottleneck model implies, for example, that the vast majority of the fossils in the universe will be represented by extinct microbial life, rather than multicellular species such as dinosaurs or humanoids, which take billions of years to develop,” says co-author Charlie Lineweaver.
Four billion years ago, Earth, Venus and Mars could have been completely inhabited. But billions of years after its formation, Venus turned into a greenhouse, and Mars into a freezer. Four and a half billion years ago, Mars could have had enough water to cover its entire surface in a layer 140 meters deep, but it is more likely that water filled a giant ocean that occupies half of the planet's northern hemisphere, up to 1600 meters deep in some places.
Venus and Mars may have had early microbial life that couldn't withstand changing environmental conditions, Lineweaver says. After all, life on Earth could play a leading role in stabilizing the planet's climate. Another fact in favor of the fact that we should look for fossil microbes, and not living extraterrestrial intelligence.
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ILYA KHEL