Astronomers have solved the mystery of where phosphorus, so key for life on Earth, actually first came from.
The element is found in everything from humans to the tiniest life forms, and is essential to create living things as we know them.
But the question of how it actually got to the early Earth has remained a mystery. The journey that helped to create all life has remained unmapped.
But astronomers have now tracked its journey through space, watching as it moves through star-forming regions to comets on the kind of journey that could have brought it to our planet. They have also shown how crucial its role in starting life on Earth might have been.
The newly published research shows how the molecules that contain phosphorus are formed, and how they might have been central to the beginning of life on Earth.
"Life appeared on Earth about 4 billion years ago, but we still do not know the processes that made it possible," says Víctor Rivilla, the lead author of a new study published in the journal Monthly Notices of the Royal Astronomical Society.
To track the journey of phosphorus, they looked into a region of space where stars are forming, known as AFGL 5142. By looking there, they could see where phosphorus-bearing molecules are born, in a vast process that comes alongside the formation of new stars and planetary systems.
Those observations allowed scientists to see that the molecules are born as the stars themselves are formed. As gas flows out of the newly formed stars, it opens up gaps between the interstellar clouds – and the molecules are formed on those vast gaps, as the shocks and radiation spill out of the baby star.
Astronomers then moved to look at how those molecules could have made their way across the universe, tracking their potential trail as they went. They looked at the comet 67P/Churyumov-Gerasimenko, which was examined by the Rosetta spacecraft, which carried an important sensor known as Rosina.
The scientists found that phosphorus-bearing compounds could get stuck in comets which would then transport them elsewhere in the universe.
"Phosphorus is essential for life as we know it," said Kathrin Altwegg, the Principal Investigator for Rosina and an author on the new study. "As comets most probably delivered large amounts of organic compounds to the Earth, the phosphorus monoxide found in comet 67P may strengthen the link between comets and life on Earth."