Comparing atmospheric haze of Titan and early Earth

One of the most alluring features of Saturn’s moon Titan is its thick layer of organic haze, which is formed from photochemistry between the methane and nitrogen gas in the high atmosphere. Although the recent Cassini/Huygens probe documented some of the organic constituents of Titan’s atmosphere, the exact composition remains shrouded in the haze. Melissa Trainer et al. mimicked Titan’s chemistry by using a deuterium lamp to irradiate various simulated atmospheres. In analyzing particle production, the authors observed the formation of multiple long-chain hydrocarbons and aromatics principally ranging from 28 to 109 atomic mass units. Overall, the aerosol properties matched well with documented data. Because Earth may have had a similar haze in its infancy, Trainer et al. next performed experiments within atmospheres that might have resembled early Earth (methane and carbon dioxide). The authors found that a significant haze layer could indeed have been produced, containing biotic precursors such as aldehydes and carboxylic acids. Earth’s aerosol production may have totaled a calculated 1014 g per year. Such a magnitude suggests that these haze particles could have served as a primary source of surface organic material, allowing life to f lourish globally and not just in localized environments. — N.Z.