A recent study has found that as many as 100 million planets in our galaxy have the potential to harbour complex life.
The report, compiled by a group of international astronomers and astrobiologists from universities in Texas, Cornell, Puerto Rico and Berlin's Technical University, studied the 1,700 planets so far discovered in our Milky Way galaxy.
Of those 1,700, it found only 11 that were more habitable than Jupiter’s Europa moon, a planet which astronomers believe contains vast oceans beneath its icy shell.
However, using a newly-devised Biological Complexity Index (BCI), which appraises planets’ capacity to maintain life by taking criteria such as the planet’s temperature, age and geophysical profile into account, the experts speculate that there may be as many as 100 million planets that could potentially support the evolution of complex life.
Indeed, of the top 10 planets profiled, Earth was actually ranked second to a planet with a similar composition called Gliese 581c which is located over 20 light years away. The presence of Mars at number seven on the list serves to emphasise the researchers’ point that while these planets could conceivably play host to complex life, there’s no guarantee that all the contributing conditions actually exist.
According to the research, which appeared in the Challenges in Astrobiology journal, it was “the first quantitative assessment of the plausibility of complex life throughout the universe based on empirical data”, providing another promising if not slightly speculative step in the quest for intelligent life elsewhere in our universe of roughly 500 billion planets.
Given the enormous imponderables of such a sprawling study area, there’s been much conjecture over the number of planets that could be as hospitable to life as Earth.
The National Academy of Sciences in the US published a report last year which stated that at least two billion planets in our galaxy alone that have liquid water on their surfaces and that orbit in the habitable or so-called ‘Goldilocks’ zone around a star.
The researchers clarified in an auxiliary statement that “complex life” does not necessarily mean intelligent life, it merely refers to organisms larger and more complex than microbes, but emphasised that this does not rule out the potential for development of animal life on planets where optimal conditions exist.