The traditional concept of racemates means an exactly 1:1 mixture of two enantiomeric molecules. Modern analytical and catalytic/preparative discoveries, first of all the Soai-reaction, make necessary a re-evaluation of this concept. The most important aspect of such a revision is the definition of the amount of an excess of one or of the other enantiomer, originating from statistical fluctuation, which can still be „tolerated” when a substance is defined as racemate. The present paper discusses the statistical view of racemates and some related problems.

  The major purpose of manned exploration on Mars is to find extraterrestrial life in either extant or extinct forms. Space agriculture is necessary to carry out such manned exploration on Mars in the long term, as it is very reasonable method to provide human beings with foods and to recycle materials. A conceptual design of space agriculture for habitation on Mars is developed by Space Agriculture Saloon. We design confined greenhouse dome to create living environment on Mars based on the constraints from planetary protection together with humanistic requirements and wellness. Hyper-thermophilic aerobic composting microbial ecology is proposed to process metabolic wastes and inedible biomass for recycling materials. A great number of bacteria were brought by human beings from the Earth to Mars. It is eventually a keen issue whether terrestrial life forms brought into Mars could prevent the forward contamination on exploration sites or not. When we plan unmanned and manned exploration of Mars, whole scenario should be carefully planned based on the requirements of astrobiology. We should avoid contamination of Mars before we could find life forms exist and well characterized, or confirm that life have never evolved on Mars. We propose an extension of the planetary protection policy, which has been discussed and issued by COSPAR and IAU at scoping the horizon of manned missions. Any planning of space agriculture or manned exploration should meet such international regulation defined and revised for the new scope.

A possibility for the prebiotic conversion of carboxylic acids and the evolutionary onset of a primitive metabolism, which may have served as a medium for the presentday metabolic pathway equipped with enzymes, was examined under submarine hydrothermal environments. We used a flow-reactor system simulating submarine hydrothermal environments for the purpose. It was found that malate, which is one of the TCA cycle member molecules, was synthesized from three other kinds of the member molecules; namely alpha ketoglutarate, succinate and fumarate, in the absence of the relevant enzymes. Furthermore, citrate was synthesized in the solution including pyruvate and all kinds of the TCA cycle member molecules. The synthesis of citrate was significantly suppressed when neither pyruvate nor one of the member molecules was present in the initial setup of the starting reaction solution. These results suggested that submarine hydrothermal environments could have played an important role for the prebiotic conversion and synthesis of carboxylic acids and for the ignition of a primitive metabolism.