New research involving the simulation of 100,000 random worlds suggests that chance played a major role in allowing Earth to maintain a habitable environment for the three to four billion years needed for the evolution of complex life.
Earth hasn’t always been the most pleasant place to live. It’s history is riddled with ice-ages, periods of unpleasant volcanism and even the odd cataclysmic asteroid impact.
Cyclical mass extinctions and climate shifts have brought life on Earth to the brink numerous times. However, the extraordinary fact remains that our home planet has somehow managed to remain continuously habitable for the past three to four billion years – long enough for single-celled life forms to evolve into human beings.
In a new study, Professor Toby Tyrrell, a specialist on Earth system science at the University of Southampton, set out to shed light on how our planet has managed to remain habitable, and to what extent luck may have played a role in its continued success.
To this end Professor Tyrrell used the Iridis supercomputing facility located at the University of Southampton to model 100,000 randomly different worlds. He then simulated how their evolutionary paths, and therefore their temperatures, were affected by climate-altering events over the course of three billion years.
The evolution of each digital planet was simulated 100 times, and for each run different random events were inflicted upon the worlds.
It was discovered that out of the 100,000 planets, only one was able to maintain habitability for all 100 of its simulations. The remaining worlds that were able to maintain a temperature suitable for sustaining life for three billion years were only able to do so in some of their simulated histories, and thus had a probability of being habitable rather than a certainty of it.
Nine percent, or 8,710, of the digital planets were found to be habitable for three billion years in at least of their 100 simulated runs. Of these, roughly 8,000 worlds had a success rate of less than 50 in 100, and 4,500 of the planets were habitable less than 10 times out of their 100 simulations.
According to the author the results suggest that Earth’s habitability was not a simple inevitability, but rather that our planet, or rather every currently living species on it have been statistically lucky regarding the environmental calamities that life on our world has been forced to endure.
"We can now understand that Earth stayed suitable for life for so long due, at least in part, to luck," explains Professor Tyrrell. "For instance, if a slightly larger asteroid had hit Earth, or had done so at a different time, then Earth may have lost its habitability altogether. To put it another way, if an intelligent observer had been present on the early Earth as life first evolved, and was able to calculate the chances of the planet staying habitable for the next several billion years, the calculation may well have revealed very poor odds."
The paper has been published in the Nature journal Communications Earth & Environment, and Professor Tyrrell discuses his research in the video below.
Source: University of Southampton
