Scientists Confirm Toxic Seas During Earth's Evolution

Oct 07, 2005

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.

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."

"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," said Roger Summons, Massachusetts Institute of Technology professor of geobiology. "The sulfide would have come from bacteria that reduces sulfate carried into the oceans by the weathering of 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," said team member Jochen Brocks. "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."

This research continued the efforts of NASA and partner institutions to understand the early history of the Earth. Research results were published in the Oct. 6, 2005, edition of Nature magazine.

The research was conducted by a team working in Summons' laboratory. Team members include Jochen Brocks, formerly of Harvard and now at Australian National University; Gordon Love, Massachusetts Institute of Technology; Stephen Bowden, University of Aberdeen, Scotland; Graham Logan, Geoscience Australia; and Andrew Knoll, Harvard.

Source: NASA

Explore further: Mapping the world's linguistic diversity—scientists discover links between your genes and the language you speak

Related Stories

Antarctic life – highly diverse, unusually structured

Jun 25, 2015

The variety of plant and animal life in the Antarctic is much greater than previously thought, reveals an assessment of Antarctic biodiversity published by a team of scientists in the journal Nature this w ...

Intelligent life in the universe? Phone home, dammit!

Jun 15, 2015

We've been conditioned by television and movies to accept the likelihood of intelligent life elsewhere in the Universe. "Of course there's intelligent life out there; I saw it last week on Star Trek." We've ...

Hardy bacteria thrive under hot desert rocks

Jun 01, 2015

Beneath the rocks scarring California's Mojave Desert are colonies of cyanobacteria, tiny creatures thought to be some of the first on Earth to convert light from the Sun into energy in the process known ...

Recommended for you

Lady, you're on the money

22 hours ago

So far, women whose portraits appear on U.S. money have been a party of three. Excluding commemorative currency, only Sacagawea, Susan B. Anthony and Helen Keller appear on coins in general circulation, according ...

Old World monkey had tiny, complex brain

Jul 03, 2015

The brain hidden inside the oldest known Old World monkey skull has been visualized for the first time. The creature's tiny but remarkably wrinkled brain supports the idea that brain complexity can evolve ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.