Non-racemic amino acids in the Murray and Murchison meteorites

Conception of the 'Chirality-Experiment' on ESA's mission ROSETTA to comet P46/Wirtanen

In the last years extraterrestrial scenarios for the origin of homochirality in biological structures received considerable attention in the topical literature: Rubenstein and Bonner postulated a rapidly rotating neutron star emitting circularly polarised synchrotron radiation responsible for the first asymmetric synthesis; the group of Bailey published the observation of circular polarisation caused by Mie scattering from aligned dust grains in the Orion OMC-1 star-formation region that might provide an enantioselective effect on prochiral or racemic organic molecules. Rikken and Raupach observed a magnetochiral effect and considered extraterrestrial magnetic fields of sufficient strengths to introduce biomoleculars parity violation. With the aim to investigate these hypotheses among other theories describing the origin of biological asymmetry, our laboratory participates in the conception and development of ROSETTA's COSAC Experiment, that is designed to identify organic molecules in the cometary matter in situ. Within COSAC's 'Chirality Module' enantiomers will be separated gas chromatographically with the help of capillary columns coated with chirally active liquid films. This technique will allow the separation of specific chiral organic compounds out of the analysed cometary matter into their enantiomeric constituents. Both thermo conductivity and mass spectrometric detectors will be used to determine each enantiomer's amount and therefore the corresponding enantiomeric excesses. As a consequence of COSAC's 'Chirality-Experiment' far-reaching results are expected to investigate the various hypotheses about the first asymmetric synthesis.

Circular polarisation in star-forming regions: possible implications for homochirality

Our discovery of high degrees of circular polarisation in some star-forming regions provides an attractive mechanism for the origin of homochirality. The largest degrees of circular polarisation, so far observed at near-infrared wavelengths, are thought to arise from the scattering of stellar radiation from aligned dust grains and are calculated to extend down to UV wavelengths. The extent of the region where circularly polarised light (CPL) of a single handedness originates is very large, and it is likely that the whole of a planetary system would see a single handedness of CPL also. We present the observational data, models of the scattering that leads to the production of CPL, and a model for the origin of homochirality. We also discuss briefly future laboratory and space-based experiments.