Our world is composed of many different things, of many different origins.

When the Earth formed, it had a nice mix of ingredients, but in the hot, mineral-forming mix, the heavy elements inconveniently sank downward, and in many cases, stayed permanently out of reach. On the list of sunk-toward-the-core elements is phosphorus, one of the most necessary elements for life. From the ATP the powers cells to the DNA that records who we are, phosphorus is a key ingredient in biological reactions.

So if the phosphorus the Earth formed with got locked away in our world, where did the phosphorus for life come from? It was originally thought that asteroid impacts and comets could be to blame, but new research points to a less flashy origin.

On any given day, we probably don’t notice dust or how it interacts with and builds up in the environment around us. Throw a rock through a window, and someone will notice. Smash a snowball into a wall, and someone is going to go see what just happened. But dust? Not so much. And this is because humans are bad at noticing gradual change, both in our homes and in our world.

New research published in JGR: Space Physics and led by John Plane finds that the constant bombardment of phosphorus-rich dust onto the Earth is likely the primary source of biologically used phosphorus. As grains burn up in the atmosphere, often seen as shooting stars, phosphorus from the grains and oxygen from the atmosphere form phosphorus monoxide. As this molecule travels through the atmosphere, it will undergo various reactions, becoming H3PO3 and H3PO4, as it settles as meteoric smoke particles through the atmosphere. If you were to try and measure the amount of material that lands on any one place on our planet each year, it would be a struggle; just a 100,000th of a gram hits each square meter each year, but our world is big, and that small amount adds up to about 1,000 kilograms of phosphorus incoming every year. It’s still not a lot, but given the fullness of time, it has been enough.

We aren’t just made of stardust that formed our world; we are also made of the constant influx of dust and the stuff of shooting stars.

More Information

Cosmic Dust May Be Key Source of Phosphorus for Life on Earth (Eos)

“Phosphorus Chemistry in the Earth’s Upper Atmosphere,” John M. C. Plane, Wuhu Feng, and Kevin M. Douglas, 2021 September 20, JGR Space Physics