 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
NASA Scientists Confirm Toxic Seas During Earth's Evolution
Washington DC (SPX) 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. 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." "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. Community Email This Article Comment On This Article Related Links Results of Research funded by the NASA Exobiology Program Astrobiology at NASA SpaceDaily Search SpaceDaily Subscribe To SpaceDaily Express Explore The Early Earth at TerraDaily.com
Calculations Favor Reducing Atmopshere For Early Earth
St Louis MO (SPX) Sep 08, 2005Using primitive meteorites called chondrites as their models, earth and planetary scientists at Washington University in St. Louis have performed outgassing calculations and shown that the early Earth's atmosphere was a reducing one, chock full of methane, ammonia, hydrogen and water vapor. |
|
|
| The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement |
