Titan's ionospheric chemistry, fullerenes, oxygen, galactic cosmic rays, the formation of exobiological molecules on and within its surfaces and lakes
Abstract
We present an updated model originally presented by Sittler et al. (2009) about the formation of aerosols within Titan's thermosphere-ionosphere that can trap incoming keV oxygen ions from Saturn's magnetosphere with primary origins from Saturn's moon Enceladus. This new model (Sittler et el., 2019) solves many of the difficulties in the original model and by developing a Galactic Cosmic Ray (GCR) model whose secondaries can penetration below Titan's surface ~ 100 m deep and reach lake beds ~ 200 m deep we have essentially closed the loop of this model and show amino acids can form on the surface, subsurface and lake beds for time scales ~ 450 Myrs. One of the key elements is that the negative ion measurements by the Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS) give evidence for formation of unsaturated anion carbon chains which can eventually become long enough to fold into fullerene C60 and C70 carbon shells, of various charge states. Based on laboratory data the fullerenes can trap incoming keV O+ magnetospheric ions that have relatively high energy collisions with the fullerenes and, once trapped, protect the oxygen atom from Titan's reducing thermosphere-ionosphere. The fullerenes then rapidly form into large aerosols and eventually settle onto Titan's surface. The cosmic rays then convert the aerosols now on Titan's surface or lake beds into tholins and precursor molecules. Then due to large > 10 km meteor impacts and cryovolcanism liquid water can form near the surface so hydrolysis can occur for time scales ~ 100-1000 years and convert the precursor molecules into amino acids such as glycine with abundances ~ 2.5 ppb to 5 ppb. We will discuss the model details and plans for future measurements and model development.
References: Sittler, E., Ali, A., Cooper, J., Johnson, R., Coates, A., Young, D., Planet. Space Sci., Vol. 57, 1547-1557, 2009. Sittler, E., Cooper, J., Sturner, S., and Ali, A., Icarus, in press, 2019.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P23D3531S
- Keywords:
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- 5210 Planetary atmospheres;
- clouds;
- and hazes;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6281 Titan;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS