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We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have(More)
Some of the global warming from anthropogenic greenhouse gases is offset by increased reflection of solar radiation by clouds with smaller droplets that form in air polluted with aerosol particles that serve as cloud condensation nuclei. The resulting cooling tendency, termed the indirect aerosol forcing, is thought to be comparable in magnitude to the(More)
Recent exploration by the Cassini/Huygens mission has stimulated a great deal of interest in Saturn's moon, Titan. One of Titan's most captivating features is the thick organic haze layer surrounding the moon, believed to be formed from photochemistry high in the CH(4)/N(2) atmosphere. It has been suggested that a similar haze layer may have formed on the(More)
Homogeneous freezing of nitric acid hydrate particles can produce a polar freezing belt in either hemisphere that can cause denitrification. Computed denitrification profiles for one Antarctic and two Arctic cold winters are presented. The vertical range over which denitrification occurs is normally quite deep in the Antarctic but limited in the Arctic. A 4(More)
In situ measurements of the relative humidity with respect to ice (RHi) and of nitric acid (HNO3) were made in both natural and contrail cirrus clouds in the upper troposphere. At temperatures lower than 202 kelvin, RHi values show a sharp increase to average values of over 130% in both cloud types. These enhanced RHi values are attributed to the presence(More)
Efficient, numerically stable, methods for the calculation of light-scattering intensity functions for concentrically coated spheres are discussed. Earlier forms of these equations are subject to various numerical difficulties which give rise to significant errors, especially for thin absorbing shells. The present equations are accurate for all refractive(More)