"When the astronauts go into space, what protects them from solar radiation (microwaves, etc.) which the ozone and atmosphere protect the Earth from?"
-
New Pathways for the Formation of Complex Organics and Prebiotic Synthesis in the Gas Phase, in Nano Clusters, and on Dust Grain Surfaces
PI: Samy El-Shall
The proposed research is focused on the physical and chemical processes that can lead to the formation of bio-forming polyatomic molecules through gas phase ion-molecule reactions, intracluster reactions, and surface reactions catalyzed by dust grains. The overall objective is to understand the general physical and chemical principles underlying the origin and early evolution of life. To understand how life can begin on a habitable planet such as the Earth, it is essential to know what organic compounds were likely to have been available. Among the key questions we plan to address in this proposal are: (1) how are simple organic compounds assembled into more complex molecular systems? and (2) what are the essential processes and pathways by which complex systems can develop those basic properties that are critical to life’s origins?
The proposed project involves the study of the polycyclic aromatic hydrocarbons (PAHs) that are present in interstellar clouds as evidenced by spectroscopy and meteorites. The PAH molecules are readily ionized and their large surfaces provide strong bonding for interstellar species such alkynes (acetylene and polyacetylenes) and polar molecules (formaldehyde, formic acid, HCN, cyanoacetylenes). The PAH surfaces can serve as catalysts for the formation of complex prebiotic organics. The thermochemistry, kinetics, and temperature effects of the gas phase and cluster reactions will be investigated using the mass-selected ion mobility technique. In the nano clusters’ regime, we will study the photochemical reactions of the PAHs within clusters of interstellar molcules including water clusters.
As to reactions on grain surfaces, we will use the LVCC method (Laser Vaporization/Controlled Condensation) to generate highly porous dust-like nanoparticles that model cosmic dust, and study their catalytic and photocatalytic reactions. Building blocks of amino acids such as HCN, ammonia, ketones and aldehydes will be adsorbed on the nanoparticle grains covered with water ice. The porosity and large surface areas of the grains create little nanovessels in which the organic molecules can pool. In the presence of ultraviolet photons, the organics can be polymerized to form more complex molecules. We will study the effects of UV radiation on the catalytic properties of the grains, and the resultant product distribution. Reaction products will be detected using temperature-programmed desorption and mass spectrometry (TPD/MS) from surface-adsorbed gas targets that have been exposed to the UV radiation.
The results of proposed work will allow one to assess the relative importance of gas phase, clusters, and grain catalyzed reactions in the formation of complex organics and in prebiotic synthesis under interstellar conditions. This will contribute to the development of new models that provide more accurate predictions of interstellar molecular abundances. This proposal is directly related to the goals of the NASA Astrobiology Program concerning the formation of complex organic molecules in space and their delivery to planetary surfaces, and investigating models of early environments in which organic chemical synthesis could occur.February 14, 2012
