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NASA Confirms Toxic Seas In Earth's History

"The sulfide would have come from bacteria that reduces sulfate carried into the oceans by the weathering of rocks"

1.6 billion-years-old rocks studied by team of Harvard University scientists, the Massachusetts Institute of Technology, Australian and British scientists analyzed pigments preserver in rocks found in Northern Australia, the McArthur Basin.

The team included among many others Jochen Brocks, ex Harvard and currently at the Australian National University; Gordon Love, Massachusetts Institute of Technology; Stephen Bowden, University of Aberdeen, Scotland; Graham Logan, Geoscience Australia; and Andrew Knoll, Harvard.

Dr. Carl Pilcher, NASA's senior scientist for astrobiology: "This work suggests Earth's oceans may have been hostile to animal and plant life until relatively recently," said Dr. Carl Pilcher, NASA's senior scientist for astrobiology.

"If so, this would have profound implications for the evolution of modern life."

Roger Summons, Massachusetts Institute of Technology professor of geobiology: "The discovery of the fossilized pigments of purple sulfur bacteria is totally new and unexpected. Because they need fairly high intensity sunlight, it means the pink bacteria, along with their essential source of sulfide, close to the surface, perhaps as close as 20 to 40 meters."

"The sulfide would have come from bacteria that reduces sulfate carried into the oceans by the weathering of rocks."

Jochen Brocks, member of the team that analyzed the rocks: "The McArthur Basin rocks were deposited over a very large area and over many millions of years, so it's likely they formed under water that was intermittently connected to or actually part of an ocean. In turn, this implies the ocean had an abundant and continuous supply of hydrogen sulfide and must have been quite toxic to any oxygen-breathing organisms."

"In fact, for seven-eighths of Earth's 4.5 billion-year history, there was probably little oxygen in the oceans and certainly not enough to support oxygen-breathing marine animals."