Smoggy skies 'created life on Earth'By Roger Highfield, Science Editor
Last Updated: 2:00am GMT 11/11/2006
Hazy, smoggy skies on baby Earth could have provided the chemical building blocks of the very first life on our planet, according to a study of one of Saturn's moons.
Primordial Earth likely had a layer of atmospheric haze, similar to the one currently on the moon Titan, that may have served as the principal reservoir of lifeÂ’s building blocks, according to the study in the Proceedings of the National Academy of Sciences.
One of TitanÂ’s most striking features is its thick hazy layer of organic aerosols, which arises from chemical reactions between the methane and nitrogen molecules high in the atmosphere, driven by ultraviolet light.
Prof Margaret Tolbert at the University of Colorado and colleagues mimicked TitanÂ’s chemistry by using UV lamps in various simulated atmospheres.
The researchers found that a methane-nitrogen mix would produce multiple types of long-chain hydrocarbons, including some aromatic compounds such as benzene.
The predicted products match well with some of the known components observed by the Huygens probe to Saturn. The researchers then added carbon dioxide gas to the mix to see if conditions that were probably present on early Earth would produce a similar haze.
"It turns out that organic haze can form over a wide range of methane and carbon dioxide concentrations," said Prof Tolbert. "This means that hazy conditions could have been present for many millions or even a billion years on Earth while life was evolving."
The researcher calculate that Earth could have produced more than100 million tons of aerosols each year, and thus these organic chemicals in the haze could have served as the primary ingredients for primitive life.
According to co-author Melissa Trainer "As these particles settled out of the skies, they would have provided a global source of food for living organisms. We found that you can make a lot of organic material virtually out of thin air."
In addition to serving as a source of organic material, a haze layer over Earth could have shielded living organisms from harmful UV rays and helped to regulate EarthÂ’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 planetÂ’s most ancient rocks, said Alexander Pavlov, a co-author of the report at the University of Arizona.
"Our paper is the first but necessary step which suggests that the total mass of organics derived photochemically could have been comparable to the total mass of organics in ancient sediments," he said.