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The Titan haze revisted: Magnetospheric energy sorces quantitative tholin yieldsWe present laboratory measurements of the radiation yields of complex organic solids produced from N2/CH4 gas mixtures containing 10 or 0.1% CH4. These tholins are thought to resemble organic aerosols produced in the atmospheres of Titan, Pluto, and Triton. The tholin yields are large compared to the total yield of gaseous products: nominally, 13 (C + N)/100 eV for Titan tholin and 2.1 (C + N)/100 eV for Triton tholin. High-energy magnetospheric electrons responsible for tholin production represents a class distinct from the plasma electrons considered in models of Titan's aiglow. Electrons with E greater than 20 keV provide an energy flux approximately 1 x 10(exp -2) erg/cm/sec, implying from our measured tholin yields a mass flux of 0.5 to 4.0 x 10(exp -14) g/sq cm/sec of tholin. (The corresponding thickness of the tholin sedimentary column accumulated over 4 Gyr on Titan's surface is 4 to 30 m). This figure is in agreement with required mass fluxes computed from recent radiative transfer and sedimentation models. If, however, theses results, derived from experiments at approximately 2 mb, are applied to lower pressure levels toward peak auroral electron energy deposition and scaled with pressure as the gas-phase organic yields, the derived tholin mass flux is at least an order of magnitude less. We attrribute this difference to the fact that tholin synthesis occurs well below the level of maximum electron energy depositon and to possible contributions to tholis from UV-derived C2-hydrocarbons. We conclude that Tita tholin, produced by magnetospheric electrons, is alone sufficient to supply at least a significant fraction of Titan's haze-a result consistent with the fact that the optical properties of Titan tholin, among all proposed material, are best at reproducing Titan's geometric albedo spectrum from near UV to mid-IR in light-scattering models.
Document ID
19950053521
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Thompson, W. Reid (Cornell Univ. Ithaca, NY, United States)
Mcdonald, Gene D. (Cornell Univ. Ithaca, NY, United States)
Sagan, Carl (Cornell Univ. Ithaca, NY, United States)
Date Acquired
August 16, 2013
Publication Date
December 1, 1994
Publication Information
Publication: Icarus
Volume: 112
Issue: 2
ISSN: 0019-1035
Subject Category
ASTROPHYSICS
Funding Number(s)
CONTRACT_GRANT: NAGW-1896
CONTRACT_GRANT: NAGW-3273
Distribution Limits
Public
Copyright
Other