As scientific mysteries go, this is the big one. How did life on Earth begin? Not how did life evolve, but how did it start in the first place? What was the initial spark that lit the fire of evolution?
Charles Darwin solved the mystery of life's wondrous diversity with his theory of natural selection. But even he was flummoxed by the ultimate mystery of mysteries: what led to the origin of life itself?
In trying to answer the problem, scientists have turned to the stars, or at least the "builders' rubble" of meteorites and comets left over from the formation of our solar system some five billion years ago. These space rocks, they believe, could help to explain why life began here on Earth.
In fact, a growing body of evidence is now pointing to deep space as the possible source of the raw materials that formed the building blocks of life. The latest study, which focused on a class of meteorites that fell on to the Antarctic ice sheet, also suggests that life's origins may have been extraterrestrial.
An analysis of the meteorites has revealed that these rocks can be induced, under high pressures and temperatures, to emit nitrogen-containing ammonia, a vital ingredient for the first self-replicating molecules that eventually led to DNA, the molecule at the heart of all life.
"These particular meteorites have been preserved in the ice and are found pristine – that is, they show less terrestrial contamination," said Professor Sandra Pizzarello of Arizona State University, who led the meteorite study published in the Proceedings of the National Academy of Sciences.
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