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The THS Experiment: Simulating Titans Atmospheric Chemistry at Low Temperature (200K)In Titan's atmosphere, composed mainly of N2 (95-98%) and CH4 (2-5%), a complex chemistry occurs at low temperature, and leads to the production of heavy organic molecules and subsequently solid aerosols. Here, we used the Titan Haze Simulation (THS) experiment, an experimental setup developed at the NASA Ames COSmIC simulation facility to study Titan's atmospheric chemistry at low temperature. In the THS, the chemistry is simulated by plasma in the stream of a supersonic expansion. With this unique design, the gas is cooled to Titan-like temperature ( approximately 150K) before inducing the chemistry by plasma, and remains at low temperature in the plasma discharge (approximately 200K). Different N2-CH4-based gas mixtures can be injected in the plasma, with or without the addition of heavier precursors present as trace elements on Titan, in order to monitor the evolution of the chemical growth. Both the gas- and solid phase products resulting from the plasma-induced chemistry can be monitored and analyzed using a combination of complementary in situ and ex situ diagnostics. A recent mass spectrometry[1] study of the gas phase has demonstrated that the THS is a unique tool to probe the first and intermediate steps of Titan's atmospheric chemistry at Titan-like temperature. In particular, the mass spectra obtained in a N2-CH4-C2H2-C6H6 mixture are relevant for comparison to Cassini's CAPS-IBS instrument. The results of a complementary study of the solid phase are consistent with the chemical growth evolution observed in the gas phase. Grains and aggregates form in the gas phase and can be jet deposited on various substrates for ex situ analysis. Scanning Electron Microscopy images show that more complex mixtures produce larger aggregates. A mass spectrometry analysis of the solid phase has detected the presence of aminoacetonitrile, a precursor of glycine, in the THS aerosols. X-ray Absorption Near Edge Structure (XANES) measurements also show the presence of imine and nitrile functional groups, showing evidence of nitrogen chemistry. These complementary studies show the high potential of THS to better understand Titan's chemistry and the origin of aerosol formation.
Document ID
20160014794
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Sciamma-O'Brien, Ella
(Bay Area Environmental Research Inst. Petaluma, CA, United States)
Upton, Kathleen
(California Inst. of Tech. Pasadena, CA, United States)
Beauchamp, Jack L.
(California Inst. of Tech. Pasadena, CA, United States)
Salama, Farid
(NASA Ames Research Center Moffett Field, CA United States)
Contreras, Cesar Sanchez
(Bay Area Environmental Research Inst. Petaluma, CA, United States)
Bejaoui, Salma
(Oak Ridge Associated Universities Moffett Field, CA, United States)
Foing, Bernard
(European Space Agency Paris, France)
Pascale, Ehrenfreund
(Space Policy Inst. Washington, DC, United States)
Date Acquired
December 22, 2016
Publication Date
August 3, 2015
Subject Category
Astrophysics
Report/Patent Number
ARC-E-DAA-TN24743
Meeting Information
Meeting: IAU XXIX General Assembly
Location: Honolulu,HI
Country: United States
Start Date: August 3, 2015
End Date: August 14, 2015
Sponsors: International Astronomical Union
Funding Number(s)
CONTRACT_GRANT: NNH06CC03B
CONTRACT_GRANT: NNX14AR61A
WBS: WBS 399131.02.06.03.27
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Laboratory
Astrophysics
Cosmic
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