Planet Earth has managed to remain habitable for so long because of one simple reason: good luck.
Researchers at the University of Sourthhampton carried out mass simulations of climate evolution of 100,000 randomly generated planets.
Each planet was simulated 100 times with random climate-altering events occurring each time in order to see if habitable life could be sustained for three billion years like on Earth.
Of these planets, 9 per cent (8,700) were successful at least once but, of those, nearly all (about 8,000) were successful fewer than 50 times out of 100 and most (about 4,500) were successful fewer than 10 times out of 100.
Professor Toby Tyrrell, a specialist in Earth system science, said the results of the study, published in the Nature journal Communications Earth and Environment, suggested chance is a major factor in determining whether planets, such as Earth, can continue to nurture life over billions of years.
“A continuously stable and habitable climate on Earth is quite puzzling. Our neighbours, Mars and Venus, do not have habitable temperatures, even though Mars once did”, Professor Tyrrell said.
“Earth not only has a habitable temperature today, but has kept this at all times across three to four billion years – an extraordinary span of geological time.
We can now understand that Earth stayed suitable for life for so long due, at least in part, to luck”, he continued.
A number of other grand-scale events could have taken place to change the Earth’s habitability, such as if a slightly larger asteroid had hit Earth, or had done so at a different time.
“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,” Professor Tyrrell added.
These poor odds mean that the chances of finding inhabitable “twin Earths” elsewhere in the universe are also very slim – something astronomers have been particularly focused on as interstellar missions increase.
Additional reporting by agencies