The truth is out there. But it might be dead.
That's the conclusion Australian scientists have come to in a paper published in the journal Astrobiology. The cosmologists take on the prevailing hypothesis that life-harboring planets are rare because it is uncommon to have the ingredients for life, and for those ingredients to evolve in such a way that they create the perfect environment for complex life to emerge. The scientists propose an alternative hypothesis.
Perhaps, they say, life has emerged on other planets in our universe. But then that life was killed by climate change.
The scientists point out that for life to evolve and thrive, the biosphere must be perfectly calibrated to regulate greenhouse gases, and to reflect a certain amount of the sun's light back into space (a factor called "albedo"). The young planet's job, then, is to quickly adjust to maintain surface temperatures suitable for water, and in turn, for life.
If their theory is correct, then planets which might be habitable would not stay habitable for long; they need life to emerge and stabilize the planet's climate. A planet like ours, which evolved complex life capable of advanced technology, then might fall prey to that same technology, just as our home is just about reaching its expiration date, thanks to human-caused climate change.
The new theory, called the "Gaian Bottleneck," would suggest that a planet's likelihood of having life would have less to do with how close it is to its sun (though this is important, too), and more to do with that planet's ability to regulate temperature and gas flow.
But before you think the climate change "skeptics" have it right, and that climate change would happen without us anyway, note that the scientists do not claim that death by climate change is inevitable, but rather that in order to stave it off, the world's citizens must actively fight to counter it. It is a case for more caution about climate change, not less.
"Life on Earth probably played a leading role in stabilising the planet's climate," said co-author Associate Professor Charley Lineweaver from the ANU Planetary Science Institute. Hopefully, we won't play a leading role in destroying it.
The paper was published Jan. 20 in the journal Astrobiology. A complete copy of the paper has been made available by the researchers for free, here.
