Privileged Planet: phosphorus from cosmic dust (Introduction)

by David Turell @, Thursday, November 25, 2021, 15:58 (9 days ago) @ David Turell

Phosphorus is a vital part of living biochemistry and especially in genome DNA and RNA:

"Without phosphorus, there’s no life. It’s a necessary part of DNA, RNA, and other biological molecules like ATP, which helps cells transport energy. But any phosphorus that was present when Earth formed would’ve been sequestered in the center of the molten planet.

"When Earth formed, phosphorus was part of the materials that coalesced into the planet. But one of Phosphorus’ properties means that much of the initial element is gathered in the Earth’s core, rather than the Earth’s crust. Phosphorus is a siderophile element, meaning it likes to dissolve in iron. Since so much of Earth’s iron sank to form the planet’s core, it took much of the phosphorus with it.

"Because of that, no phosphorus was available for life when Earth formed, and it had to come from somewhere else. It also had to arrive on Earth over a long period of time. Previously, scientists hypothesized that meteorites and comets might be the source. But a new study suggests that phosphorus might come from cosmic dust.


"Each year, thousands of tons of cosmic dust reach the Earth’s surface. Most cosmic dust is tiny particles only a few hundred micrometres in size. A lot of it is silicate minerals, the most common type of minerals on Earth, including quartz, olivine, and feldspar. Some cosmic dust includes carbonaceous material, sulphides, metals, and other minerals and compounds, including phosphorus. Almost any object in space—but especially asteroids and comets— can produce it through processes like volcanism and outgassing, or by impacts.

"Before phosphorus is useful to living things, it must be in the form of phosphates or metal phosphites. In the paper, the authors show that cosmic dust can go through a series of chemical reactions as it travels through the atmosphere, eventually stabilizing and settling to the Earth’s surface.


"Not all of the phosphorus that enters Earth’s atmosphere becomes biologically useful phosphorus. The researchers estimate that about 11% forms metal phosphites which become meteoric smoke and eventually settle to the Earth’s surface.


"If they’re correct, their results have important implications in our understanding of the history of life on Earth. Firstly, initial phosphorus was sequestered in the Earth’s core, unavailable for life. Their model shows how cosmic dust could be a continuous source of biologically-available phosphorus."

Comment: we are here, so the phosphorous must be provided. All part of fine-tuning.

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