Panspermia: Life from one world to the next

Panspermia claims that planets were seeded with life brought in by inter-stellar forces and bodies.

The question of how life began has invited numerous hypotheses. One that has prevailed since ancient Greece is panspermia. It was first posited by the Greek philosopher Anaxagoras (500-428 BC), who coined the term and first articulated life’s potential to travel as ‘seeds’ between planets.

While this concept found echoes in the thoughts of other philosophers of his time, such as Anaximander and Thales, it remained in the realm of the speculative for many centuries until scientific advances in various fields brought it into focus.

Some of the more important studies demonstrated that microorganisms could endure the extreme conditions that come with being ejected from a planet, navigating the rigours of interplanetary travel, and withstanding the impact of reaching a new world.

Nineteenth-century researchers, including Swedish scientist Svante Arrhenius, also contributed to this discourse by suggesting mechanisms – like radiation pressure from the Sun – that microorganisms could be propelled by through space.

In its modern version, the idea of panspermia advances three stages: escape from a planet, transit through interplanetary space, and landing on another planet.

But because panspermia simply attributes the origin of life on one planet to a different planet, it doesn’t actually explain how life came to be. It is in fact a fringe theory in the scientific community because scientists agree that it is hard – if not impossible – to prove.

It has also become the seed of many controversies, including one suggesting the interstellar object ʻOumuamua was an alien object engaged in panspermia.