Meteorites carried life-producing phosphorus to Earth

The scientists found that during the Hadean and Archean eons – the first of the four principal eons of Earth’s earliest history – the heavy bombardment of meteorites

provided reactive phosphorus that when released in water could be incorporated into prebiotic molecules.

The scientists documented the phosphorus in early Archean limestone,showing it was abundant some 3.5 billion years ago.

They concluded that the meteorites delivered phosphorus in minerals that are not seen on the surface of Earth,and these minerals corroded in water to release phosphorus in a form seen only on the early Earth.

The discovery answers one of the key questions for scientist trying to unlock the processes that gave rise to early life forms: Why don’t we see new life forms today?

“Meteorite phosphorus may have been a fuel that provided the energy and phosphorus necessary for the onset of life,” said Matthew Pasek,USF Assistant Professor of Geology.

“If this meteoritic phosphorus is added to simple organic compounds,it can generate phosphorus biomolecules identical to those seen in life today,” Pasek said.

Pasek said the research provides a plausible answer: The conditions under which life arose on Earth billions of years ago are no longer present today.

“The present research shows that this is indeed the case: Phosphorus chemistry on the early Earth was substantially different billions of years ago than it is today,” he added.

The research team reached their conclusion after examining Earth core samples from Australia,Zimbabwe,West Virginia,Wyoming and in Avon Park,Florida.

Meteorites would have provided reactive phosphorus in the form of the iron-nickel phosphide mineral schreibersite,which in water released soluble and reactive phosphite. Phosphite is the salt scientists believe could have been incorporated into

prebiotic molecules.

Of all of the samples analysed,only the oldest,the Coonterunah carbonate samples from the early Archean of Australia,showed the presence of phosphite.

Other natural sources of phosphite include lightning strikes,geothermal fluids and possibly microbial activity under extremely anaerobic condition.

However,no other terrestrial sources of phosphite have been identified and none could have produced the quantities of phosphite needed to be dissolved in early Earth oceans that gave rise to life,the researchers concluded.