Tholin

The dissociation and ionisation products react with one another in lower layers of the atmosphere to give more complex compounds such as benzene and similar organic molecules with masses between 100 and 350 Da, which are converted to organic anions (20-8,000 Da), which then in turn lead to tholins. 

It is assumed that tholins also played an important role in the PAH world hypothesis. The PAH world could have existed as a pre-RNA world on the primeval Earth. It is suggested that PAHs can undergo stacking, thus forming structures to which nucleobases are chemically bound (to OH functions which are formed by photochemical derivatisation of the PAHs). The PAH stacks replace the more complex phosphate-D-ribose-phosphate chains in the nucleic acids (Ehrenfreund et al., 2006). 

These new results only became possible when the groups of H. Waite and B. Magee at the South West Research Institute (SWRI) in San Antonio, Texas, combined analytical data obtained from two different instruments. These are the ion and neutral mass spectrometer (INMS), which obtained data on small to medium-sized molecules in the upper atmosphere of Titan (950-1,150 km) and the Cassini plasma spectrometer (CAPS), which also registered particles from tholins, both positive (100-350 Da) and negative ions (20-8,000 Da) (Waite et al., 2007 Atrey, 2007). 

Steady state Simple calculations for the reactions at the beginning of the processes for tholin formation... 

Tholin A term used in planetary science to refer generally to organic heteropolymers the reddish tar-like organic residue created in simulations of the action of ultraviolet radiation on gases typically found in planetary environments... 

Sagan C, Khare BN. Tholins organic chemistry of interstellar grains and gas. Nature 1979 277 102-7. 

One important group of colour indicators is derived from 1 10 phenan-tholine (orrAo-phenanthroline) which forms a 3 1 complex with iron(II). The complex known as ferroin undergoes a reversible redox reaction accompanied by a distinct colour change... 

These low-albedo materials are also relatively spectrally featureless. Comparisons with the spectra of meteorites suggest that some of this material is similar to the opaque carbonaceous material found in carbonaceous chondrites (Gaffey et al., 1993 Johnson and Fanale, 1973) and to material referred to as tholins (carbon-rich material formed in laboratory experiments containing complex solid hydrocarbons such as polycyclic aromatic hydrocarbons (Cmikshank et al., 1991)). It is generally assumed that satellite surfaces contain a mixture of ices and silicate material, probably hydrated, mixed with similar dark carbon-rich material. However, detailed identification of these constituents is difficult due to the paucity of distinctive spectral features and to the fact that even relatively small amounts of these compounds mixed with brighter silicate materials and/or ices produce a dark mixture and reduce or eliminate the spectral contrast from absorptions in the higher-albedo materials. 

Although lapetus extreme hemispheric albedo contrast has been recognized essentially from the time of its discovery, the nature and origin of the dark material that dominates the leading hemisphere is still uncertain. Spectrally, the dark material resembles some low-albedo, red asteroids. This material is believed to be similar to hydrocarbon-rich materials produced in laboratory experiments, known as tholins, which are opaque, contain PAHs and are spectrally red (Cmikshank et al., 1991). Tholins are also candidates for at least some of the dark, non-ice constituents on Ganymede and Callisto. Unfortunately, spectra in the 3-5 p,m region where these material have some spectral features are not yet available for Saturn satellites. 

The interior and atmospheric composition of the Jovian planets and Titan differ from our terrestrial planets in particular, Jovian planets and Titan contain complex organic solids named tholins [152]. Sagan et al. [153] diermochemically... 

The combination of GC x GC with TOFMS has considerable potential for the study of samples of astro-biological significance, for example in the study of complex hydrocarbon mixtures extracted from Late Archean sediments [31] or in characterizing the products of laboratory synthesis of Titan tholins [32]. Presented here is the general principles of two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-TOFMS) analysis for the... 

Pyrolysis of Murchison Thermochemolysis of Murchison HyPy Pyrolysis of Tholins... 

Tholins are complex organics that form via photolysis reaction in the atmosphere of Titan, the largest moon of Saturn, which produces a thick reddish-brown haze. As for the material reported here tholin material can be produced in the laboratory by cold plasma discharge in a nitrogen-methane mixture. 

The main products released upon pyrolysis of a tholin sample are nitriles, dinitriles, benzonitriles, pyrroles, and... 

FIGURE 18.4 Total ion chromatograms from GC x GC-TOFMS (contour and surface plots) of products released upon pyrolysis of tholin sample. P, pyrrole BN, benzonitrile. 

McGuigan, M.,Waite, J.H., Imanaka, H., Sacks, R.D. (2006) Analysis of Titan tholin pyrolysis products by comprehensive two-dimensional gas chromatography-time-of-flight... 

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