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A Warm Breath Of Carbon Dioxide
for Astrobiology Magazine Moffett Field (SPX) Sep 05, 2008 Early in Earth's history, our solar system was a much different place. When the sun was very young, it was faint and provided little heat for the Earth. However, even in its chilly beginnings, the surface of the Earth was ice-free. For years, scientists have proposed theories for this "faint young sun problem". Most of these theories are based on the idea that the early Earth must have had extremely high amounts greenhouse gases like CO2 in the aosphere in order to warm the planet. According to a team of German scientists, geological evidence of aospheric CO2 seems to indicate that levels were "far too low to keep the surface from freezing." However, their new study may provide a new answer to the problem. The study, under lead author Philip von Paris of the Institut fuir Planetenforschung (Institute for Planetary Research) at the Deutsches Zentrum fuir Luft- und Raumfahrt (German Centre for Air and Space Travel) in Berlin, was recently published in the journal Planetary and Space Science.
Shedding Light on a Classic Problem This means that the average temperature of the early Earth, 3.7 billion years ago, must have been above freezing. Scientists aren't sure how warm the Earth was, but it's generally accepted that the planet has been ice-free for most of its history. However, by looking at sun-like stars of different ages around the universe, astronomers believe that the sun's luminosity 3.7 billion years ago was significantly less than today. If the early Earth's aosphere was the same as it is now, there wouldn't have been enough sunlight to warm the planet. Temperatures would have been well below freezing up until 2 billion years ago. Most proposed answers to the "faint young sun problem" involve some degree of greenhouse warming on the early Earth in order to keep it from freezing over. In fact, many scientists believe that warming of the Earth occurred at much higher levels than those seen today due to the presence of gases like carbon dioxide (CO2), methane, ethane or ammonia. However, there are many uncertainties concerning whether or not each of these gases could have been present on the early Earth.
A Cool Drink of Water The study also included important parameters concerning the surface albedo (how much light is reflected away by the planet's surface) and the humidity of the aosphere. The new model was used to examine interesting points in the history of Earth, such as the end of a period of frequent asteroid impacts known as the Late Heavy Bombardment (3.8 billion years ago), the first evidence of oxygen production by cyanobacteria (2.9 billion years ago) and the first known oxidation event (2 billion years ago).
A Warm Breath of Carbon Dioxide The model showed that a partial pressure of only 2.9 millibars of CO2 would have been needed during the late Archaean and early Proterozoic periods in order to bring the surface temperature of the Earth above freezing. This result, although contrary to previous studies, agrees with current geological data. For this period of time, the contradictions of the "faint young sun problem" disappear. The result improves our understanding of how carbon dioxide in the aosphere can affect the global temperature of Earth. Today, carbon dioxide levels on Earth are increasing, primarily as a result of human activities. This increase is one of the most important causes of climate change on Earth. Understanding how carbon dioxide affected the ancient climate of Earth might provide clues about the future of Earth's climate and global biosphere. Related Links Institute for Planetary Research Explore The Early Earth at TerraDaily.com
Single Boulder May Prove Connection Betweeen Antarctica And North America
Washington DC (SPX) Jul 21, 2008The team's find, they argue, provides physical evidence that confirms the so-called southwestern United States and East Antarctica (SWEAT) hypothesis. |
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