LIVERMORE -- Life started with a dirty snowball, tossed at Earth from space.
That is the conclusion reached by a group of international scientists, confirming a theory conceived by a Lawrence Livermore Laboratory researcher.
The team fired a speeding projectile into a special ice mixture, creating a hot and high-pressure environment -- akin to the comets that streak through the heavens, piercing our atmosphere.
And presto: Out of the explosion came life's raw materials, called amino acids. This final product -- a pound of "goo," said Livermore Lab climate scientist Nir Goldman -- is a modest ancestor to our now-gloriously lively Earth.
But it is not the only explanation for how our home took its first halting steps to becoming alive. Dozens of other teams are exploring alternate theories.
"But these studies prove that this is one avenue in which amino acids were produced, early on," said Goldman. "It is exciting to ponder the different avenues that could have been the origin of life."
Using computer simulations performed on lab supercomputers, Goldman proposed in 2010 and again in 2013 that an icy comet crashing into Earth billions of years ago could have produced amino acids.
It is known that comets bombarded Earth between 4.5 billion and 3.8 billion years ago.
It is likely that the comet that triggered life hit us at an oblique angle, rather than in a direct smash, he said.
Amid the ice, the comets bore carbon dioxide, methane, ammonia and other trace gases -- precursors of amino acids.
These simple molecules could have supplied the raw materials of life, Goldman believes. And the impact with early Earth would have yielded the energy to drive this prebiotic chemistry.
Goldman's idea was put to the test -- and proven -- by British collaborators, whose findings are published in the latest issue of the journal Nature Geoscience.
Scientists at Imperial College London and the University of Kent sent their comet-like projectile at a speed of 7 kilometers per second into a sizzling environment that was 3,000 degrees Celsius and at a pressure more than 300,000 times Earth's atmospheric pressure.
Several complex organic compounds, including amino acids, were formed in what Goldman calls "a tar-like goo."
"All the raw materials, and resulting pressure and high temperatures, can drive the chemistry," he said. Then those molecules were organized into life's essential structures and devised a means to survive and reproduce themselves.
A different theory proposes that life emerged from the deep sea environment miles below Earth's solid surface, where cells live in the narrowest of cracks and fissures. Yet another asserts that a lightning bolt ignited a chemical reaction of the ocean and a mixture of simple gases in the atmosphere.
"This is one possible avenue," Goldman said. "These results present a significant step forward in our understanding of the origin of the building blocks of life."
Contact Lisa M. Krieger at 650-492-4098.