Scientists have spent countless years and millions of dollars searching for life on other planets – efforts that have been all but fruitless thus far, and possibly for a very good reason, according to new research appearing in this week’s edition of the journal Astrobiology.
Alien life, Dr. Aditya Chopra from the Australian National University Research School of Earth Sciences and his colleagues explain in their study, would likely become extinct shortly after first appearing due to runaway heating or cooling on their fledgling habitable planets.
“The universe is probably filled with habitable planets, so many scientists think it should be teeming with aliens,” Dr. Chopra said Thursday in a statement. However, he points out that life, in its earliest stages, “is fragile, so we believe it rarely evolves quickly enough to survive.”
The majority of early planets have unstable environments, the researchers said. In order for a planet to be considered truly habitable, living beings would have to be able to regulate water, carbon dioxide and other greenhouse gases to keep its surface temperatures stable.
Biological regulation of the environment may be key to survival
Earth was probably not the only habitable planet in the solar system four billion years ago, Dr. Chopra and his fellow researchers claim. Venus and Mars may have also been habitable during this time. However, that changed about one billion years after they first formed.
Ultimately, Venus became too hot and Mars too cold, and any microbial life that may have been on those planets failed to stabilize conditions and died out. Life on Earth persisted at least in part because it was able to help stabilize the planet’s climate, according study co-author and associate professor Charley Lineweaver from the ANU Planetary Science Institute.
“The mystery of why we haven’t yet found signs of aliens,” Dr. Chopra said, “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.”
Even though there seems to be no shortage of water-filled, rocky planets that possess all of the basic ingredients and energy sources needed to support living organisms, no signs of surviving extraterrestrial life have yet been discovered. The reason may lie in what the study authors have dubbed the “Gaian Bottleneck” – a nearly 100 percent early extinction rate.
“One intriguing prediction of the Gaian Bottleneck model is that the vast majority of fossils in the universe will be from extinct microbial life, not from multicellular species such as dinosaurs or humanoids that take billions of years to evolve,” said Lineweaver.
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Feature Image: CSIRO Parkes radio telescope is in the search for alien civilisations. (Credit: Wayne England)
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