Scientists have suggested that a key building block of life, phosphate, may have been delivered to Earth in its first billion years by meteorites or comets.
The study was led by the University of Hawaii at Manoa and published in Nature Communications. In it, they used an ultra-high vacuum chamber, the W. M. Keck Research Laboratory in Astrochemistry, to cool simulated interstellar grains down to -270°C (-450°F).
These grains were coated in carbon dioxide and water, something commonly found in molecular clouds that give birth to stars, and also phosphine. The latter is poisonous to us on Earth. But if it reacts to form other chemicals, then it can be pretty useful.
In the vacuum chamber, the researchers exposed their interstellar dust to ionization radiation, simulating cosmic rays in space. This produced things like phosphoric acid, which, hey, is actually pretty useful for getting life going.
"On Earth, phosphine is lethal to living beings," lead author Andrew Turner said in a statement. "But in the interstellar medium, an exotic phosphine chemistry can promote rare chemical reaction pathways to initiate the formation of biorelevant molecules such as oxoacids of phosphorus, which eventually might spark the molecular evolution of life as we know it."
The idea that the building blocks of life could have been delivered to Earth isn’t entirely new. We’ve found other evidence of useful molecules or chemicals forming in interstellar space, while comets have been proposed as a method to bring them here.
"The phosphorus oxoacids detected in our experiments… might have also been formed within the ices of comets such as 67P/Churyumov-Gerasimenko, which contains a phosphorus source believed to derive from phosphine," co-author Professor Ralf Kaiser said in the statement.
What’s more, as comets contain material that dates back to early in our Solar System, it could be that they picked up phosphine from the interstellar medium, noted co-author Cornelia Meinert of the University of Nice in France. Once they arrived here, this phosphorous could have helped life thrive.
Understanding when and how life arose on Earth is an ongoing question. Finding that out would not only tell us about our own beginnings but the chances of life starting elsewhere in the universe too. The arrival of phosphorous is another important piece in that puzzle.