hazy skies on early Earth could have provided a substantial source of organic material useful for emerging life on the planet. In a study published in the Proceedings for the National Academy of Sciences (Vol 103, No 48), a research team of the University of Colorado at Boulder measured organic particles produced from the kind of atmospheric gases thought to be present on early Earth.
Laboratory experiments modelled conditions measured by the Huygens probe on Saturn's moon, Titan, according to Margaret Tolbert, one of the study's authors. "It turns out that organic haze can form over a wide range of methane and carbon dioxide concentrations," said Tolbert. "This means that hazy conditions could have been present for many millions or even a billion years on Earth, while life was evolving."
According to co-author Melissa Trainer, the study was the first to measure the chemical properties of aerosols by irradiating methane and carbon dioxide with ultraviolet light. "We found that you can make a lot of organic material virtually out of thin air," said Trainer.
Scientists believe the atmospheric chemistry of Titan might hold clues to understanding climate on Earth when life was just forming. Titan has organic aerosol particles that form through photochemical processes when sunlight reacts with methane gas, she said.
According to the study, a similar haze hanging over early Earth could have supplied more than 100 million tonnes of organic material to the planet's surface each year. "As these particles settled out of the skies, they would have provided a global source of food for living organisms," said Trainer.
The haze layer could also have shielded living organisms from harmful ultraviolet rays and helped regulate Earth's early climate, according to the study. The haze may have contributed to the geological record on Earth by depositing organic carbon into some of the planet's most ancient rocks, said Alexander Pavlov, a study co-author.
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