NASA exobiology researchers confirmed Earth's oceans were once rich in sulfides that would prevent advanced life forms, such as fish and mammals, from thriving. The research was funded in part by NASA's exobiology program.
A team of scientists from the Massachusetts Institute of Technology and Harvard University, working with colleagues from Australia and the United Kingdom, analyzed the fossilized remains of photosynthetic pigments preserved in 1.6 billion-year-old rocks from the McArthur Basin in Northern Australia.
They found evidence of photosynthetic bacteria that require sulfides and sunlight to live. Known as purple and green sulfur bacteria because of their respective pigment colorations, these single-celled microbes can only live in environments where they simultaneously have access to sulfides and sunlight.
The researchers also found very low amounts of the fossilized remains of algae and oxygen-producing cyanobacteria. The relative scarcity of these organisms is due to poisoning by large amounts of sulfide.
"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."
Interesting. Read more here.
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