Now the team claims that findings from space probes sent to investigate passing comets reveal how the first organisms could have formed.
The 2005 Deep Impact mission to Comet Tempel 1 discovered a mixture of organic and clay particles inside the comet.
One theory for the origins of life proposes that clay particles acted as a catalyst, converting simple organic molecules into more complex structures.
The 2004 Stardust Mission to Comet Wild 2 found a range of complex hydrocarbon molecules - potential building blocks for life.
The Cardiff team suggests 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.