Tuesday, July 16, 2013
Solving a mystery than 3,500 million years
Scientists cannot know for sure if there is life in space outside the Earth, but new research by a team of scientists led by an astrobiologist at the University of South Florida (USF) shows that one of the key elements that produced life on Earth was brought to Earth by meteorites.
In an article published in the Proceedings of the National Academies of Sciences,
Matthew Pasek, Assistant Professor of Geology at USF and researchers from the University of Washington and the Center for Innovation in Carbon Edinburg, revealed new findings that explain how he came to Earth reactive phosphorus was an essential component of the first forms of life.
The scientists found that over the eons Hadean and Archean -the first of the four major eons of the early history of the Earth intense meteorite bombardment reactive phosphorus provided that when released in water can be incorporated into prebiotic molecules. Scientists documented phosphorus in Archaic limestone, showing that it was abundant about 3,500 million years.
The scientists concluded that meteorites delivered phosphorus minerals not observed on the surface of the Earth, and these minerals were degraded in water to release phosphorus in a single view on the early Earth.
The discovery answers one of the key questions for scientists trying to understand the processes that gave rise to the first life forms: Why do not we see new forms of life today?
"The match could have been a meteorite fuel provided the energy and phosphorus necessary for the beginning of life," said Pasek, who studies the chemical composition of space and how it may have contributed to the origin of life. "If this match is added meteoritic simple organic compounds, biomolecules phosphorus can generate identical to those we see today in life."
Pasek said the research provides a plausible answer: The conditions under which life arose on Earth for billions of years are no longer present today.
"This research shows that this is indeed the case: The chemistry of phosphorus on the early Earth was considerably different for billions of years than it is today," he added.
The research team reached its conclusion after examining samples from the Earth's core from Australia, Zimbabwe, West Virginia, Wyoming and in Avon Park, Florida.
Previous research demonstrated that before the appearance of modern protein DNA and RNA that we know today, the first biological forms evolved RNA alone. What had baffled scientists, however, was to understand how these early life forms based on synthesized RNA phosphorus in the environment, which in its current form is relatively insoluble and non-reactive.
Meteorites have delivered reactive phosphorus ore as fosfuto schriebersite consisting of iron and nickel, which released soluble phosphite reagent water. The phosphite is the salt that scientists believe could be incorporated in prebiotic molecules.
Of all the samples analyzed, only the oldest, carbonate samples Archaic Coonterunah of Australia, showed the presence of phosphite. Natural sources include rays phosphite, geothermal fluids, and possibly microbial activity under extremely anaerobic condition, but has not been identified other terrestrial sources of phosphite and none could have produced the amounts of phosphite needed to be dissolved in the oceans early Earth that gave rise to life, the researchers concluded.
Scientists said phosphite meteorite would have been quite sufficient to adjust the chemistry of the oceans, with its chemical signature being caught later in which was preserved marine carbonate.
It remains possible, the researchers noted that phosphite other natural sources can be identified, perhaps in hydrothermal systems. Although this may lead to reduced overall meteoric mass needed to provide sufficient phosphite, the researchers said more work is needed to determine the exact contribution of separate sources so they are sure it was an essential ingredient for primitive life.
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