Evolution of CO on Titan

Atmospheric Structure and Composition

“…As regards N 2 , the factor ~1.5 enhancement in 15 N/ 14 N has been interpreted as due to non-thermal escape of N 2 (Lunine et al 1999) , and suggests that Titan's primitive atmosphere was 2-10 times thicker than nowadays (Niemann et al 2005) . A similar explanation, involving a massive loss of CO in Titan's early history, was put forward by Wong et al (2002) to explain the factor of ~2 higher than terrestrial 18 O/…”

“…However, even under this assumption, the OH fl uxes required to sustain the observed amounts of H 2 O and CO 2 fail to produce a ~ 40 ppm CO mixing ratio and the current chemical loss of CO exceeds its steady-state production by typically (1-2) × 10 6 cm −2 s −1 . The problem was exacerbated with the realization (Wong et al 2002) that the OH + CH 3 reaction essentially recycles water, leading to only ~2 ppm of CO in equilibrium. Suggestions to solve this dilemma included: (i) alternate external sources, such as CO contained in micrometeorites (Lara et al 1996) or delivered by cometary impacts , (ii) surface or internal sources such as oceanic evaporation or volcanic outgassing (Baines et al 2006) , and (iii) a CO abundance not in equilibrium and refl ecting a larger primordial abundance (Wong et al 2002 ;Wilson and Atreya 2004) .…”

The Origin of Water Vapor and Carbon Dioxide in Jupiter's Stratosphere

“…A possibility is that Hyperion is a significant source of dust (and hence oxygen) to Titan, as advocated by Banaszkiewicz and Krivov (1997). We finally note that in the case of Titan, photochemical models (Lara et al 1996, Wong et al 2002 require a large CO flux ((8-11) × 10 5 cm −2 s −1 ) in order to maintain the conservation of O atoms, adopting a ∼5 × 10 −5 CO mixing ratio. Evaporation from a surface ocean and steady meteoritic influx have been invoked to sustain this flux.…”

Crossed Molecular Beam Study on the Formation of Phenylacetylene and Its Relevance to Titan’s Atmosphere

“…12 Finally, PAHs are thought to be crucial building blocks leading to the formation of the orange-reddish haze layers on Saturn's moon Titan. [13][14][15][16][17][18][19][20][21] But how are PAHs formed in these extreme environments? Multiple experimental studies have been completed in the last decades, where PAHs and nanosized soot particles were observed ranging from the hydrocarbon rich flame chemistry studies [22][23][24] to the shock wave experiment of Mimura 25 and the laser ablation experiment of graphite under different quenching atmospheres by Jäger et al 26 Chemical reaction networks that model the formation of PAHs in combustion flames [27][28][29] and in the interstellar medium 30 stress the importance of the phenylacetylene molecule (C 6 H 5 CCH) in the growth of PAHs starting from an initial hydrogen abstraction/acetylene addition sequence via the phenyl radical.…”