Early Earth haze similar to Titan may have been UV shield for planet

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Washington, June 4 (ANI): A new study shows a thick organic haze that covered the Earth several billion years ago, similar to that on Saturn's largest moon, Titan, may have provided ultraviolet shield for planet.

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.

Apart from acting as a UV shield, the haze must have prevented the planet from freezing over by allowing gases like ammonia to build up.

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.

"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," he added.

"Methane is the key to make this climate model run, so one of our goals now is to pin down where and how it originated," said Professor Brian Toon.

If Earth's earliest organisms didn't produce the methane, it may have been generated by the release of gasses during volcanic eruptions either before or after life first arose-a hypothesis that will requires further study, he said.

"We still have a lot of research to do in order to refine our new view of early Earth," said Wolf.

"But we think this paper solves a number of problems associated with the haze that existed over early Earth and likely played a role in triggering or at least supporting the earliest life on the planet."

The study is being published in the June 4 issue of Science. (ANI)

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