Recent probes inside comets show it is overwhelmingly likely that life began in space, according to a new paper by Cardiff University Centre for Astrobiology scientists.

They suggest that radioactive elements can keep water in liquid form in comet interiors for millions of years, making them potentially ideal “incubators” for early life. They also point out that the billions of comets in our solar system and across the galaxy contain far more clay than the early Earth did.

The researchers calculate the odds of life starting on Earth rather than inside a comet at one in one trillion trillion (10 to the power of 24).