Ralf I.
Kaiser
*a,
Weijun
Zheng
b,
Yoshihiro
Osamura
c and
Agnes H. H.
Chang
d
aDepartment of Chemistry, University of Hawaii at Manoa, 2545 McCarthy Mall, Honolulu, HI 96822-2275, USA. E-mail: ralfk@hawaii.edu
bState Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, No. 2, North 1st Street, ZhongGuanCun, Beijing 100190, P. R. China
cKanagawa Institute of Technology, Atsugi 243-0292, Japan
dDepartment of Chemistry, National Dong Hua University, Hualien, 974, Taiwan
The symposium ‘Kuiper Belt Objects – Laboratory Studies, Models, and Observations’ at the Pacifichem 2010 in Honolulu, Hawaii, focussed on the interplay between laboratory spectroscopy, theoretical investigations, and fundamental laboratory studies on specific molecular processes, which lead to a chemical modification of KBO surfaces with the overall goal to extract generalized concepts on the chemical processing of KBO surfaces and related bodies in the outer Solar System. Four ‘radiation’ sources are considered ranging from high energy electrons and MeV nuclei (simulating GCR particles) via solar photons to thermal chemistry of open shell reactants like hydroxyl radicals and hydrogen atoms at low temperatures. In detail, Zheng et al. (DOI: 10.1039/c1cp20528e) demonstrated that an investigation of the chemistry of (suprathermal) oxygen atoms, formed in the decomposition of water molecules upon interaction with energetic electrons in the track of galactic cosmic ray particles (GCRs) yields vital laboratory data on the interacting of non-equilibrium species with water-rich KBO ices. Kim et al. (DOI: 10.1039/c1cp20658c) proposed that non-equilibrium effects of triplet carbon monoxide in nitrogen-rich ices lead to the formation of the diazirinone molecule (N2CO), which was recently characterized for the very first time spectroscopically.9 These results were amplified by Pilling et al.'s study (DOI: 10.1039/c1cp20592g) on the processing of water–carbon dioxide ices by heavy MeV particles of the galactic cosmic radiation field. Non-equilibrium effects are also induced via the photolysis of water-bearing ices as outlined by Kinugawa et al. (DOI: 10.1039/c1cp20595a) and Andersson et al. (DOI: 10.1039/c1cp21138b) utilizing sophisticated time-of-flight spectroscopy of the photofragments produced at 157 nm. Oba et al. (DOI: 10.1039/c1cp20596j), Hidaka et al. (DOI: 10.1039/c1cp20645a), and He et al. (DOI: 10.1039/c1cp21601e) showed nicely that reactions of hydroxyl radicals and hydrogen atoms can also result in a rich chemistry on KBO surfaces. Finally, Kayi et al. (DOI: 10.1039/c1cp20656g) demonstrated via electronic structure calculations that the astrobiologically relevant glycine amino acid is thermodynamically less stable by 31–37 kJ mol−1 compared to its methylcarbamic acid isomer thus raising questions of a possible photon-induced isomerization of both structures.
We hope that the timeliness of this topic in light of the currently operating New Horizon Mission (NASA) on its way to (ex-planet) Pluto and the Rosetta Mission (ESA) launched in 2004, which is currently on its route to comet 67P/Churyumov-Gerasimenko, triggers further laboratory, spectroscopy, and theoretical investigations on the stability and chemical processing of ices of Kuiper belt objects in the next decade.
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