Study: Meteorites Gave Earth Life
By Rossella Lorenzi
Iron meteorites may have been responsible for the evolution of life on Earth, according to NASA funded research.
In a study to be published shortly in the journal Astrobiology, University of Arizona's Dante Lauretta, assistant professor of planetary sciences, and doctoral candidate Matthew Pasek, suggest that iron meteorites brought enough phosphorus to Earth to give rise to biomolecules which eventually assembled into living, replicating organisms.
Phosphorus plays a key role for life on Earth. It forms bonds with sugar to provide structure to DNA and RNA, and is vital to metabolism because it is linked with life's fundamental fuel, adenosine triphosphate (ATP), the energy that powers growth and movement.
Moreover, it provides support for life as part of the phospholipids that make up cell walls and the bones of vertebrates.
"Despite its importance, studies of the early evolution of life on the Earth have been plagued by a lack of phosphorus in the terrestrial environment.
"Much of the phosphate on Earth is bound in insoluble phosphorus salts and mineral, like apatite. As such, the amount of phosphorus available for the evolution of life using terrestrial minerals is minimal," Pasek told Discovery News.
Meteorites have several different minerals that contain phosphorus. The most important one is iron-nickel phosphide, known as schreibersite.
Extremely rare on Earth, this metallic compound is ubiquitous in meteorites, especially iron meteorites.
In a lab experiment, the researchers mixed schreibersite with room-temperature, fresh, de-ionized water and analyzed the liquid mixture using nuclear magnetic resonance.
"We saw a whole slew of different phosphorus compounds being formed. One of the most interesting ones was P2O7 (two phosphorus atoms with seven oxygen atoms), one of the more biochemically useful forms of phosphate, similar to what is found in ATP," Pasek said.
Previous experiments have formed P2O7, or pyrophosphate, but only at high temperatures or under extreme conditions, never by simply dissolving a mineral in room-temperature water.
"This allows us to somewhat constrain where the origins of life may have occurred. If you are going to have phosphate-based life, it likely would have had to occur near a fresh water region where a meteorite had recently fallen. We can go so far, maybe, as to say it was an iron meteorite," Pasek said.
Studies on the geochemical environment of the genesis of life presented last week at the 32nd World Geological Conference in Florence, Italy, support the U.S. research.
"Indeed, meteorites may have been the potential source of organic compounds on the early Earth," Vinod Tewari of the Wadia Institute of Himalayan Geology, India, said.
Phosphorus' link with ATP is especially important, according to Erik Galimov, of the Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow.
"There are quite evident prerequisites of life: presence of water, availability of primary organic compounds, source of energy, and favorable range of temperature.
"However, there should be some additional key factor providing chemical evolution toward the genesis of life. ATP is a key compound," Galimov said.
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