Scientists found that the meteors pummeling our planet in its first two eons carried an unexpected gift: phosphorus, a key ingredient in the formation of all known life.

In an examination of samples from Australia, Zimbabwe, West Virginia, Wyoming, and Florida, scientists from the University of Florida and the University of Washington found phosphite only in the oldest samples, in materials from the early Archean period – about 3.5 billion years ago – in Australia.

The new research, published in the current Proceedings of the National Academy of Sciences, brings a potential close to a chapter in the mystery of life on Earth: how Earth's earliest life forms, which evolved from RNA alone before the modern DNA-RNA protein developed, synthesized phosphorous.

In its modern form, phosphorous is insoluble and unreactive – a poor building material. But the latest research suggests that the phosphorous that arrived on ancient Earth via space rocks was a reactive form.

This space version, an iron–nickel phosphide mineral called schreibersite, is soluble and would have become reactive when dissolved in water. It also would have seeped through Earth's nascent oceans, becoming abundant enough to give Earth a decent go at producing life. Scientists have so far not found any homegrown sources that would have been plentiful enough to do so.

“The importance of this finding is that it provides the missing ingredient in the origin-of-life recipe: a form of phosphorus that can be readily incorporated into essential biological molecules like nucleic acids and cell-membrane lipids,” said Roger Buick, a UW professor of Earth and space sciences, in a press release.

The new finding is also bad news for those hoping to witness a replay of the beginnings of life on Earth.  Because the conditions in which life developed here billions of years ago no longer exist, the chances that new life forms will again spring from inorganic compounds is nil, at least outside of a laboratory. 

“Phosphorus chemistry on the early Earth was substantially different billions of years ago than it is today,” said Matthew Pasek, the lead author on the article and an assistant professor of geology at the University of South Florida, in a press release.

Quelle: USF