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| Titel |
Adsorption of Acetylene and Formation of Benzene on Cosmic Dust in Titan’s Atmosphere |
| VerfasserIn |
Victoria Frankland, Alexander James, Juan Carrillo Sanchez, Thomas Mangan, Karen Willacy, John Plane |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124612
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| Publikation (Nr.) |
 EGU/EGU2016-4071.pdf |
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| Zusammenfassung |
| The formation of the haze layers and tholins in Titan’s atmosphere is unclear. One potential
mechanism is that small precursors, such as acetylene (C2H2), adsorb onto un-ablated cosmic
dust particles as they sediment through Titan’s atmosphere. The uptake coefficient of C2H2
onto cosmic dust analogues was measured using low temperature dual flow tube
apparatus. Synthesized olivines analogues (Mg2−2nFe2nSiO4 where 1 ≥ n ≥ 0) were
used to represent the cosmic dust particles based on investigations of cometary
dust. The results indicated that the adsorption of C2H2 was independent of the
Mg:Fe ratio in the dust analogue with the mean uptake coefficient (at 181 K) as
1.7 × 10−4. In some cases, the uptake experiments were left until the surface had
become saturated with C2H2. Here, a small benzene (C6H6) mass trace was detected
indicating that cyclotrimerzation of C2H2 into C6H6 was occurring on the surface.
Further experiments using ultrahigh vacuum apparatus were used to confirm this
observation.
The rate of C6H6 (formed through C2H2 cyclotrimerization) desorbing from un-ablated
cosmic dust particles sedimenting through Titan’s atmosphere was explored using a 1D
model. The results revealed that this heterogeneous formation and desorption route was
competitive with gaseous C6H6 formation rates suggesting that the dust could be acting as a
seed for the formation of complex organic molecules (such as PAHs) and tholins and, through
this, the formation of the haze layers. |
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