Scientists have long thought that alien life is likely to exist, or existed, and now a new study may have come up with the reason why we haven’t found it.
Researchers from the Australian National University suggest that there may have been alien life on extraterrestrial worlds, but that it may have died long before humans came to be.
Early life killed off by rapid environmental changes
In a new paper the scientists say that alien life did not survive for long enough to evolve into complex multicellular forms. They claim that the early forms of alien life died off due to the unstable nature of the climates of young planets.
Researcher Aditya Chopra said that the fragility of early life forms means that most often it cannot evolve quickly enough to survive. The problem is compounded by the fact that the environment on early planets changes rapidly.
In order for a planet to remain habitable, the life forms found on it must regulate greenhouse gases to maintain stable temperatures on the surface in a process known as Gaian regulation. It happened on Earth but Chopra and fellow researcher Charley Lineweaver say that it is likely a rare occurrence.
Lack of alien life explained by “Gaian Bottleneck Hypothesis”
It is thought that Earth, Mars and Venus could have all supported life around 4 billion years ago, before the latter pair suffered extreme changes in climate. Venus heated up dramatically, and surface temperatures are now around 467 degrees Celsius, while Mars has cooled significantly to the point where the mercury dips to -73 degrees Celsius at night.
According to the study, early microbial life did exist on the two planets but it couldn’t stabilize due to the rapidly changing environment. They have called the existence of life and its rapid extinction the “Gaian Bottleneck Hypothesis.”
“In the Gaian bottleneck model, the maintenance of planetary habitability is a property more associated with an unusually rapid evolution of biological regulation of surface volatiles than with the luminosity and distance to the host star,” the researchers wrote in their study published in the journal Astrobiology.
They claim that the theory helps to explain why alien life has not been found in a universe replete with habitable planets.
“The mystery of why we haven’t yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces,” Lineweaver said.