University of Colorado at Boulder - 03 June 2010
Fractal haze may have warmed the early EarthA new study shows a thick organic haze that enshrouded early Earth several billion years ago may have been similar to the haze now hovering above Saturn's largest moon, Titan, and would have protected primordial life on the planet from the damaging effects of ultraviolet radiation.
The University of Colorado at Boulder scientists believe the haze was made up primarily of methane and nitrogen chemical byproducts created by reactions with light, said CU-Boulder doctoral student Eric Wolf, lead study author. Not only would the haze have shielded early Earth from UV light, it would have allowed gases like ammonia to build up, causing greenhouse warming and perhaps helped to prevent the planet from freezing over.
The researchers determined the haze of hydrocarbon aerosols was probably made up of fluffy, microscopic particles shaped somewhat like cottonwood tree seeds that would have blocked UV but allowed visible light through to Earth's surface, Wolf said.
Prior to the new study, the prevailing scientific view was that the atmosphere of Earth some 3 billion years ago was primarily made up of nitrogen gas with lesser amounts of carbon dioxide, methane, hydrogen and water vapor, said Wolf. "Since climate models show early Earth could not have been warmed by atmospheric carbon dioxide alone because of its low levels, other greenhouse gases must have been involved. We think the most logical explanation is methane, which may have been pumped into the atmosphere by early life that was metabolizing it."
New Scientist - 03 June 2010
Early Faint Sun Paradox Explained?A haze of fluffy fractal-shaped particles may have helped protect early life from harmful ultraviolet radiation, a new study suggests. The aerosols could help resolve a long-standing puzzle about how the early Earth stayed warm.
Billions of years ago, the sun emitted up to 30 per cent less light than it does today. That should have made the early Earth too cold to maintain liquid water on the surface until about 2 billion years ago. But geological studies of banded iron formations and other materials that can form in water suggest liquid water pooled on the surface much earlier.
Universe Today - 03 June 2010
Countering the Early Faint SunModels of the Sun’s evolution indicate it was as much as 30 percent less luminous during Earth’s early history than it is now. But, somehow the surface of the planet was warm enough for primordial life to emerge. A new study and a look at Saturn's moon Titan has provided clues for how the Sun could have kept the early Earth warm enough. Scientists say a thick organic haze that enshrouded early Earth several billion years ago may have been similar to the haze that covers Titan and would have protected emerging life on the planet from the damaging effects of ultraviolet radiation, while warming the planet, as well.
This new study will likely re-ignite interest in a controversial experiment by scientists Stanley Miller and Harold Urey in the 1950s in which methane, ammonia, nitrogen and water were combined in a test tube. After Miller and Urey ran an electrical current through the mixture to simulate the effects of lightning or powerful UV radiation, the result was the creation of a small pool of amino acids — the building blocks of life.
- Science 04 June 2010: Vol. 328. no. 5983, pp. 1238-1239, DOI: 10.1126/science.1189196
- Science 04 June 2010: Vol. 328. no. 5983, pp. 1266-1268, DOI: 10.1126/science.1183260
- Nature 464, 744-747 (01 April 2010) | doi: 10.1038/nature08955