92: Life's Fifth Element Came From Meteors

By Anne Sasso|Monday, January 03, 2005

Scientists argue that life’s building blocks—carbon, oxygen, hydrogen, and nitrogen—were abundant in early Earth. But where did the fifth critical element—phosphorus—come from?

In August researchers at the University of Arizona found an answer:  Schreibersite, an iron-nickel phosphide that occurs in iron meteorites, could have provided all the phosphorus needed. “We’re suggesting that iron meteorites played a role in the origin of life,” says Matthew Pasek, a doctoral student at the university’s Lunar and Planetary Laboratory.

Dante Lauretta, an assistant professor and Pasek’s thesis supervisor, sees a two-parent meteorite scenario. “You’ve got the carbonaceous meteorites bringing in your amino acids, sugars, and nucleobases,” he says. But they lack phosphorus. “Iron meteorites would bring that in very nicely,” he theorizes. “The reason that life originated on Earth is because this is the place where you have liquid water. Where all these components could then meet and mix and react with each other.”

Researchers found the link by submerging phosphorus-bearing meteorites in pure water. “All the phosphates were pretty boring, but then we hit this phosphide—schreibersite—and it was the most beautiful NMR [nuclear magnetic resonance] spectrum that Matt had ever produced,” Lauretta says. “It meant that there were a lot of different and complicated compounds in there. And then we said, ‘This is important!’ ”

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