Fractal Organic Hazes Provided an Ultraviolet Shield for Early Earth

The Archean Earth (3.8 to 2.5 billion years ago) was probably enshrouded by a photochemical haze composed of fractal aggregate hydrocarbon aerosols. The fractal structure of the aerosols would have had a strong effect on the radiative properties of the haze. In this study, a fractal aggregate haze w...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2010-06, Vol.328 (5983), p.1266-1268
Main Authors: Wolf, E.T, Toon, O.B
Format: Article
Language:English
Subjects:
Aerosols
Ammonia
Atmospheric aerosols
Cooling
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fractals
Gases
Geological time
Hydrocarbons
Monomers
Optical thickness
Particle mass
Radius of a sphere
Stratigraphy
Ultraviolet radiation
Wavelengths
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Summary:The Archean Earth (3.8 to 2.5 billion years ago) was probably enshrouded by a photochemical haze composed of fractal aggregate hydrocarbon aerosols. The fractal structure of the aerosols would have had a strong effect on the radiative properties of the haze. In this study, a fractal aggregate haze was found to be optically thick in the ultraviolet wavelengths while remaining relatively transparent in the mid-visible wavelengths. At an annual production rate of 10¹⁴ grams per year and an average monomer radius of 50 nanometers, the haze would have provided a strong shield against ultraviolet light while causing only minimal antigreenhouse cooling.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1183260