AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Chemical Composition of Ions During Laboratory Simulations of Titan’s Haze Formation
JENNIFER BERRY, Melissa Ugelow, Margaret Tolbert, Eleanor Browne, University of Colorado, Boulder
Abstract Number: 224 Working Group: Extraterrestrial Aerosols: from Mars to Titan and Beyond
Abstract Understanding the chemistry of organic haze formation in the N2/CH4 atmosphere of Saturn’s largest moon, Titan, has been an active area of research due to the fundamental role of the haze on Titan’s climate and the possible connection to the chemistry of early Earth. Haze formation on Titan is initiated by UV photons and energetic electrons and results in a complex series of ion-neutral and radical reactions leading to higher molecular weight hydrocarbons and nitrogen containing species. Measurements of both neutral and ionic species in Titan’s atmosphere have been made by the Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS). A long history exists of laboratory studies focusing on both fundamental ion-neutral reactions and on the composition of haze particles produced from the complex chemistry that occurs upon the irradiation of N2/CH4 mixtures. However, there has been little experimental work on the role of ion chemistry in haze production. Here, we present results using an Aerodyne/Tofwerk Atmospheric Pressure interface Time-of-Flight Mass Spectrometer (APi-ToF-MS) to study ion chemical composition and relative abundance during the formation of aerosols. This high-resolution instrument (R ~9000) allows for in-situ identification of the exact mass of positive ions from 1 to >1700 m/z during the irradiation of different concentrations of CH4 in N2. We observe the growth of ions that vary in saturation and carbon number during aerosol formation. Families of CxHy+, CxHyNw+, CxNw+, and HyNw+ are detected with increasing saturation at higher masses during the irradiation of CH4/N2 mixtures. No ions containing nitrogen are observed during the irradiation of CH4/Ar mixtures. We compare the APi-ToF-MS measurements to Aerosol Mass Spectrometer (AMS) data in order to explore connections between ion chemistry and haze formation.