Early Earth's Atmosphere Like Titan's

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Early Earth May Have Had An Atmosphere Similar To Titan's

The University of Colorado at Boulder press release is reproduced below:

Early Earth Haze May Have Spurred Life, According To New CU-Boulder Study

Hazy skies on early Earth could have provided a substantial source of organic material useful for emerging life on the planet, according to a new study led by the University of Colorado at Boulder.

In a study published in the Proceedings for the National Academy of Sciences the week of Nov. 6, the research team measured organic particles produced from the kind of atmospheric gases thought to be present on early Earth. The laboratory experiment modeled conditions measured by the Huygens probe on Saturn's moon, Titan, last year during the NASA-European Space Agency's Cassini mission, according to Margaret Tolbert of CU-Boulder's Cooperative Institute for Research in Environmental Sciences, one of the study's authors.

The researchers mimicked Titan's hazy skies by exposing methane gas to an ultraviolet lamp, then added carbon dioxide gas to the mix to see if conditions that were probably present on early Earth would produce a similar organic haze. "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 of CU-Boulder's Laboratory for Atmospheric and Space Physics, 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, who completed her doctoral degree in CU-Boulder's chemistry and biochemistry department at CU in May 2006 under Tolbert.

Scientists believe the atmospheric chemistry of Titan might hold valuable clues to understanding the climate on Earth when life was just forming, said Trainer. Titan is an unusual solar system moon in that it has an atmosphere -- in this case one thick with 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 Earth early in its history could have supplied more than 100 million tons 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.

Previous efforts to understand early life on Earth have focused on extreme environments like hydrothermal vents, where energy and nutrients are plentiful, said Tolbert. The new study shows that such a high-energy food source could have been produced globally early in Earth's history, possibly expanding the habitable domain for early life, she said.

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 Earth's early climate, according to the study. The haze may have contributed to the geologic record on Earth by depositing organic carbon into some of the planet's most ancient rocks, said Alexander Pavlov, a study co-author and former LASP researcher now at the University of Arizona. Organic carbon is believed by scientists to be of biological origin.

Other authors on the study included LASP's Owen Toon, H. Langley Dewitt and Jose Jimenez of CIRES, and Christopher McKay of NASA's Ames Research Center in Moffett Field, Calif.

"It's exciting to see that the early Earth experiments produced so much organic matter," said Carl Pilcher, director of NASA's Astrobiology Institute, headquartered at NASA Ames. "An organic haze produced this way on early Earth could have contributed to the formation and sustenance of life."

The study was funded by the NASA Solar System Exploration Division's Exobiology program and the NASA Astrobiology Institute. CIRES is a joint research endeavor of CU-Boulder and the National Oceanic and Atmospheric Administration.

Source: UCB Press Release

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NASA Study Shows Titan and Early Earth Atmospheres Similar

The Ames Research Center press release is reproduced below:

November 6, 2006

John Bluck
NASA Ames Research Center, Moffett Field, Calif.
Phone: (650) 604-5026/9000
E-mail: jbluck@mail.arc.nasa.gov

Adriana Raudzens Bailey
University of Colorado, Boulder
Phone: 303-492-6289
E-mail: adrianar@cires.colorado.edu

RELEASE: 06_81AR

NASA Study Shows Titan and Early Earth Atmospheres Similar

Organic haze in the atmosphere of Saturn's moon, Titan, is similar to haze in early Earth's air -- haze that may have helped nourish life on our planet-- according to a NASA Astrobiology Institute study released Nov. 6, 2006.

Study scientists simulated both the atmospheric conditions of early Earth and those of present-day Titan. Their study, "Organic Haze on Titan and the Early Earth," describing the scientists' work, appears in Proceedings of the National Academy of Sciences. The principal author is Melissa Trainer, a NASA Astrobiology Institute postdoctoral fellow at the University of Colorado, Boulder.

"It's exciting to see that the early Earth experiments produced so much organic matter," said Carl Pilcher, director of the NASA Astrobiology Institute, at NASA Ames Research Center, Moffett Field, Calif. "An organic haze produced this way on early Earth could have contributed to the formation and sustenance of life."

According to the study's researchers, their experiments help scientists interpret observations of Titan's atmosphere from NASA's Cassini mission, while also showing how a major source of organics could have been produced on Earth billions of years ago.

The researchers reported that the aerosols produced in the laboratory could serve as analogs for the observed haze in Titan's atmosphere. The scientists also estimated that aerosol production on early Earth could have served as a primary source of organic material to the surface.

"This paper shows one of the ways in which the study of other worlds can help us understand Earth," said Chris McKay, a scientist at NASA Ames and one of the study's co-authors. "Titan has a thick organic haze layer, and this work started out to understand the chemistry of that alien organic haze. Then we realized that we could apply the same approach to the organic haze on early Earth."

"We hope to determine how the organics were made and their chemical nature," McKay observed. The scientists reported that when sunlight hits an atmosphere of methane and nitrogen, like the atmosphere of Titan today, aerosol particles form. When an atmosphere also contains carbon dioxide, as in the atmosphere of ancient Earth, different kinds of aerosols form.

The scientists used a special ultraviolet-light lamp to produce particles in the simulated atmospheres, and measured the chemical composition, size and shape of the resulting particles.

"It's somewhat similar to the smog in Los Angeles," Trainer explained. "Today's haze on Earth is also created photochemically, which means sunlight powers chemical reactions in the atmosphere. However, the early atmosphere of Earth had different gases present, so chemical composition of the early haze is very different than the haze we have today. There also would have been a lot more of it."

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Source: NASA/ARC Press Release 06_81AR

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The Photochemistry of CH4 and CO2 Illustration

The photochemistry of CH4 and CO2 may have produced an organic haze layer on the early Earth.

Image is an illustrative composite prepared by Melissa G. Trainer using images of Titan and Earth, courtesy of NASA/JPL-Caltech.

+ View High Resolution Image

Source: NASA - Ames Research Center - Multimedia