Organic Material in Micrometeorites: Processes Affecting Its Delivery to Planetary Environments

Wilson, Rebecca (2010). Organic Material in Micrometeorites: Processes Affecting Its Delivery to Planetary Environments. PhD thesis The Open University.



During their delivery to Earth, extraterrestrial dust particles (EDPs) are heated via aerodynamic braking in the upper atmosphere, liberating volatile and organic species. This study investigates the influence of atmospheric entry heating on this liberation process from Murchison (an EDP analogue), in order to assess the EDP contribution of biologically significant material to the early Earth.

Experimental simulations used a filament pulse pyrolyser to flash heat Murchison, replicating early Earth EDP atmospheric entry conditions. These simulations determined that the dehydration of phyllosilicates, the decomposition of organic and carbonate materials released H2O, organic carbon and CO2, respectively. Further characterisation of the released organic species (using GCxGC-TOFMS) identified a range of aliphatic, aromatic, PAH, O-bearing, S-bearing and N-bearing species; including biomolecule precursors. Relative abundances of these organic species were dependant not only on simulation peak temperature and duration, but also on their reaction with other fragments, which may have led to their production as secondary products.

In a complimentary study, comprehensive volatile organic analysis of Antarctic micrometeorites (AMMs) identified a range of aromatic, aliphatic, N-bearing, S-bearing, S-N-bearing and O-bearing species. Variations in the distribution of AMM aromatic species in comparison to the EDP analogue (as used in simulations) are consistent with i) the liberation of species during atmospheric entry heating ii) the alteration of organic material during Antarctic weathering processes and iii) a contribution from terrestrial sources. Alternatively, these deviations could reflect a different source (parent body) composition.

This investigation demonstrates that the abundance and composition of volatile and organic species liberated and retained in EDPs during entry heating (and their subsequent atmospheric reactions), may have played a role in atmospheric and climate development. EDPs additionally served as a source of prebiotic molecules and may have provided sites for chemical evolution.

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