June 5, 2013
Meteorite Impacts Brought Life-Producing Phosphorus To Early Earth
Lee Rannals for redOrbit.com - Your Universe Online
New research published in the Proceedings of the National Academy of Sciences has determined that meteorites that impacted Earth some 3.5 billion years ago could have helped kick start life on this planet.Scientists at the University of Washington and the University of South Florida have found that the heavy bombardment by meteorites early in our planet´s history provided the reactive phosphorus that was essential for the development of life on Earth.
“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.
The scientists say the meteorites delivered phosphorus in minerals that are no longer seen on the surface of the Earth, and that these minerals subsequently corroded in water to release phosphate, a salt of phosphoric acid.
“Meteorite phosphorus may have been a fuel that provided the energy and phosphorus necessary for the onset of life,” said Matthew Pasek, an assistant professor of geology at the University of South Florida and lead author of the paper.
“If this meteoritic phosphorus is added to simple organic compounds, it can generate phosphorus biomolecules identical to those seen in life today.”
He added that the reason we do not see new life forms on Earth today is because conditions under which life arose billions of years ago are no longer present.
“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 said.
Previous studies showed that the earliest biological forms might have evolved from RNA alone, before the modern DNA-RNA-protein life emerged. However, scientists didn't know how early these organisms were able to incorporate phosphorus from their environment.
Meteorites would have provided reactive phosphorus in the form of the schreibersite, a iron-nickel phosphide mineral that releases soluble and reactive phosphite when placed in water. Phosphite is the salt scientists believe could have been incorporated into prebiotic molecules.
While occurring naturally on Earth only rarely, schreibersite is a fairly common component in iron-nickel meteorites. The researchers concluded that although there could be some other sources of phosphite, no terrestrial sources could have produced the quantities needed to be dissolved in Earth´s oceans.
“This finding opens the way for a lot more prebiotic chemical experimentation and may even allow us to produce a catalytic replicating RNA molecule in a test-tube, mimicking what might have naturally happened during the origin of life,” Buick said.
Phosphorous was one of the chemicals that NASA's Curiosity rover discovered on Mars after its first drilling analysis back in March. The space agency said that its Martian rover discovered the presence of sulfur, nitrogen, hydrogen, oxygen, carbon and phosphorus.