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Scientists solve 3.5 billion-year-old mystery of life and its link to meteorites

It seems life may have received a boost from asteroids smashing into the surface of Earth early in its life.

According to a newly published report produced by researchers at the University of South Florida (USF) and the University of Washington, life-producing phosphorus may have landed on Earth 3.5 billion years ago, providing a boost to early life forms.

USF professor Matthew Pasek, who led the study, says the phosphorus, when released in water, may have over time incorporated themselves into prebiotic molecules. The phosphorus, which has been found in asteroids, was likely carried to Earth via comets and meteorites, which released the element when impacted Earth.

By focusing on the Hadean and Archean eons of early Earth, the scientists were able to discern that meteorites delivered phosphorus in minerals currently not seen on the surface of Earth. By examining Earth core samples from Zimbabwe, Australia, Wyoming, West Virginia, Florida the team was able to determine the origin of the minerals. According to researchers, the minerals likely corroded in water, releasing large amounts of phosphorus in a form only found during Earth’s early formation. The phosphite would have likely resulted in an adjusting of the chemistry of Earth’s early oceans, with its chemical signature later becoming trapped in marine carbonate where it was preserved.

“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,” said Roger Buick, a co-author of the study.

There are few natural sources of phosphite that are Earth-based. Some of the examples include lightning strikes, geothermal fluids  and possibly microbial activity under extremely anaerobic condition. However, none of the Earth-based forms could have produced the quantities of phosphite needed to be dissolved in early Earth oceans that gave rise to life, according to researchers.

According to the report, the conditions that led to a boom of life on Earth no longer exist and the elements delivered by asteroids are few and far between. Previous research has already confirmed that before the emergence of DNA-RNA-protein life , the earliest forms  of life on Earth evolved by relying on RNA alone. While the evolution of early life is fairly well understood, it remained unclear how early RNA–based life forms synthesized environmental phosphorus, which in its current form is relatively insoluble and unreactive.

This is not the first study to propose how life may have evolve from elements delivered to Earth via asteroids and comets. A number of scientists have examined and noted the abundance of reactive phosphorus in the form of the mineral schreibersite, a iron–nickel phosphide.

The report is published in the latest edition of the Proceedings of the National Academy of Sciences.