ET phoned home in the movie but the search for extraterrestrial life forms on other planets in our own solar system and beyond hasn’t been getting any calls back. A controversial new paper by a group of Australian astronomers suggests the reason is that, while aliens may have once existed, they’re all dead now. And the reason for their demise is climate change on their home planets. Uh-oh.
In their report in the current edition of the journal Astrobiology, scientists at the Australian National University attempt to solve Fermi’s Paradox (With so many stars making the probability high, why haven’t we encountered alien life?) from a different angle. They propose that reason why we haven’t had contact is because other planetary environments are too hostile for life to exist (like Venus) or that some form of life may have begun but was unable to stabilize or survive rapid changes in fragile planetary environments.
Using our own solar system as an example, it points out that Earth, Venus and Mars may have all been habitable four billion years ago but Venus became too hot and Mars too cold (The Goldilocks paradox?). This same situation is or has been occurring throughout the universe, says report author Dr. Aditya Chopra.
Early life is fragile, so we believe it rarely evolves quickly enough to survive. Most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable.
This interaction between organic life and inorganic matter on a planet as a means of (or reason for) survival is called the “Gaia Hypothesis,” another controversial theory proposed by chemist James Lovelock and microbiologist Lynn Margulis in the 1970s. The Gaia hypothesis is that Earth is a self-regulating system (called Gaia) of interactions between life forms, the atmosphere, water and land. (Does that sound familiar?)
The report proposes that having the right combination of Gaia so that life can begin and pass from microbial to multi-cellular is so rare that it should be called the Gaian Bottleneck.
So what these researchers are saying is not so much that higher forms of extraterrestrial life, possibly resembling Earth's humans or animals, have been completely killed off on other planets but that microbial life forms, like grains of sand, never survived passage from one side of the environmental hourglass to the other where they would have room to grow, evolve, return our calls or even visit us.
Controversial? Yes. Relevant to discussions about climate change? Definitely. A depressing prediction that we’ll never find alien life? Possibly.
Are we really alone? What do you think?