Alien life may have thrived in other parts of the solar system but scientists have not yet confirmed finding one. Now, a new study offers a possible answer why the discovery of aliens in extraterrestrial worlds remains elusive.
In the new study, researchers from the Australian National University suggest that aliens may have existed once in other planets but they probably died long before we came into being.
They did not also thrive long enough to evolve into complex multicellular forms. The researchers attribute the cause of this early extinction to rapid changes in the climates of young planets.
Study researcher Aditya Chopra said that early life is fragile and rarely evolves quickly enough to survive. Early planetary environments are likewise unstable.
To make a planet habitable, life forms have to regulate greenhouse gases to keep the surface temperatures stable.
The process, known as Gaian regulation, happened on Earth but Chopra and study co-author Charley Lineweaver said that what happened to our planet is likely a rare occurrence.
Planets Earth, Mars and Venus may all have been habitable about 4 billion years ago but Venus and Mars underwent extreme climate changes.
Venus became so hot lead could melt on its surface, where the temperature is now around 872 degrees Fahrenheit (467 degrees Celsius). Mars, on the other hand, has turned into an icebox with night temperatures dropping to about -100 degrees Fahrenheit (-73 degrees Celsius).
The researchers said that had there been early microbial life that thrived on the two planets, it would have failed to stabilize the fast-changing environment. The existence of life for a short period of time on other planets and its abrupt extinction is what the researchers called 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.
The researchers said that this theory can help shed light on why we have not yet found alien life despite the universe teeming 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.
