The question of life’s origin on Earth has long intrigued scientists, with a growing body of research now suggesting it may not have started here at all. Instead, life — or at least its building blocks — might have arrived via asteroids or comets, a theory known as panspermia.
This once-radical idea has gained traction thanks to recent space missions. Japan’s Hayabusa2 and NASA’s OSIRIS-REx have returned samples from asteroids Ryugu and Bennu, respectively. Analysis of these samples has revealed organic compounds, including amino acids and components of DNA and RNA, suggesting that asteroids may have carried the essential ingredients for life to Earth. However, no direct evidence of life has yet been found.
The theory dates back to the 1970s, when British astronomers Sir Fred Hoyle and Prof Chandra Wickramasinghe proposed that life — and even diseases — could have extraterrestrial origins. Though initially ridiculed, their ideas have since been revisited in light of new findings.
In 1996, the discovery of what were believed to be fossilised bacteria in a Martian meteorite led to a public announcement by then-President Bill Clinton, highlighting the potential for alien life. Though the findings were later refuted, the event brought panspermia into mainstream discussion.
Further support comes from the TRAPPIST-1 system, where planets orbit closely together, making the transfer of material — and possibly life — between them more feasible. Researchers estimate that material ejected from one habitable planet there could reach another in just 100 years.
Despite these promising signs, scientists caution that having the right ingredients doesn’t guarantee life will form. Bennu, for instance, had the necessary compounds but lacked the conditions to “bake the cake,” as NASA’s Dr Jason Dworkin put it.
Looking ahead, missions like NASA’s Perseverance rover on Mars and the Europa Clipper, set to explore Jupiter’s icy moon, may offer more clues. Scientists are also keen to retrieve samples from comets, which could hold even more primordial material.
While definitive proof remains elusive, the possibility that Earth was seeded with life from space is now a serious scientific consideration — one that could reshape our understanding of life’s place in the Universe.
