Even though Matthew Pasek is an assistant professor of geology at the University of South Florida, he thinks he's figured out an interesting equation:
Phosphorus from a meteorite that crashed to Earth 3.5 billion years ago + water = the earliest life on the planet.
The findings were recently published in the June edition of the Proceedings of the National Academies of Sciences.
Pasek and researchers from the University of Washington and the Edinburgh Centre for Carbon Innovation looked at Earth core samples of limestone from around the world -- Australia, Zimbabwe, West Virginia, Wyoming, and Avon Park, Fla.
They found that only the Australian sample of limestone, which dated back to the early Archean eon (around 3.5 billion years ago), had the presence of "reactive phosphorus." During that time, Earth was hammered by meteorites -- Pasek estimates as many as one meteorite striking somewhere on the planet each second.
As this "reactive phosphorus" can't be found in any minerals on the surface of the earth, only in the limestone about a thousand feet below ground level, Pasek and his colleagues concluded that meteorites brought the phosphorus-containing minerals to Earth.
Pasek explained why that phosphorus was so important in an interview with WUSF's University Beat.
"When you take that meteorite mineral and dump it in water, you can actually form new compounds with it, and some of these (compounds) can actually get incorporated into biological molecules pretty easily," he said.
These include molecules like "glycerol phosphate," which makes up cell membranes -- "sort of the boundary layer between cells and everything else," says Pasek, "and the glycerol phosphate is an important part of that."
And also important for researchers is the fact that conditions on Earth 3.5 billion years ago seemed for more conducive for a life-creating reaction between phosphate and the planet's environment -- something we don't see today when similar ingredients interact.
"We have this idea that there's some changes on the 'early Earth' from where we look at now that the Earth has been modified itself by the action of life," Pasek says. "So if we can actually see what the primordial geology and geochemistry was of the Earth, we might be able to get a better idea of what might have kicked life into gear. And so this phosphorus signature is one of those good signs that something was different on the 'early Earth' versus today."
To hear more from Pasek, including his thoughts on what it's like to hold a 3.5 billion year old chunk of rock that may contain the secrets of life's origins, click on the audio link above.
