小行星表面有机物的红外光谱探测方法

小行星的有机物记录了太阳系早期有机物的形成发展历史,为地球早期生命前体出现的研究提供了重要依据,对于研究生命起源和演化具有重要意义.本文综合分析了小行星表面可能存在的有机物成分、种类及其赋存状态,利用红外光谱开展地面模拟实验,探讨有机物的红外光谱特征及其影响因素.结果表明,不同类型有机物的红外光谱特征与其类型、结构、温...     

Radiation stability of organic matter in liquid and frozen H2O, NH3 and water-ammonia mixtures

The redox properties of irradiated liquid and frozen H₂O, NH₃ and H₂O/NH₃ mixtures at 298 K and 77 K, resp., towards some simple organic molecules have been checked by injecting carrierfree ¹¹C atoms and analyzing their chemical state by means of radiochromatography. The reactions and the stability of organic products versus radiation dose (in this study by MeV protons) depend on temperature, phase state, mobility of radicals, their concentration and reactivity. Especially dangerous are the reactive OH and O₂H radicals which oxidize organic material to inorganic CO₂. Highest stability has been found at low temperatures (solid state, reduced mobility of radicals) and for systems containing H-donors (H₂O/NH₃ mixtures), which reduce the concentration of oxidizing radicals. The fact that many bodies in space consist of H₂O-ice with NH₃ and CH₄ additives at temperatures between 10 and 150 K is promising in view of the survival of organic matter under high doses of radiation.     

Production and evolution of carbonaceous material by ion irradiation in space.

We review recent experimental studies concerning the evolution, driven by ion irradiation, of carbonaceous material from frozen gas to a refractory molecular solid. Under further irradiation the latter changes to a polymer-like material and ultimately to amorphous carbon. Most of the results have been obtained by "in situ" and remote IR and Raman spectroscopy. The results have been applied to demonstrate that molecular solids may be easily formed by irradiation of frozen mantles in dense interstellar clouds. Polymer-like material and amorphous carbons may result by further irradiation of organic mantles on grains in the diffuse interstellar medium. Those grains, during the aggregation to form extended bodies like comets (T-Tau phase of the Sun), are further modified. These latter are also irradiated, after the comet formation, during their long stay in the Oort cloud. In particular it has been suggested that comet may develop an ion-produced cometary organic crust that laboratory evidences show to be stable against temperature increases experienced during passages near the Sun. The comparison between the Raman spectra of some IDP (Interplanetary Dust Particles) and the Raman spectra of some ion-produced amorphous carbons, is also discussed.     

Laboratory simulation of the photoprocessing and warm-up of cometary and pre-cometary ices: production and analysis of complex organic molecules.

The possibility that the organic molecules that have been found near comets could have formed by UV photolysis of interstellar ices was investigated by simulating this process in the laboratory. It is found that oxygen rich organics containing C-OH, C-H and C=O groups are readily produced in this way. These results indicate that part of the organic material in comets may have formed by UV irradiation of ices, either in the pre-solar nebula or in the interstellar phase.     

A continual model of soil organic matter transformations for predicting soil forming dynamics inside higher plant CELSS

A continual model of humification and mineralization of soil organic matter (SOM) formed under the conditions of a Lunar base from biological waste materials is proposed. The model parameters corresponding to the conditions of several Earths climatic regions are estimated. The time necessary for the formation of organic matter in the soil based on regolith and higher plant residues has been evaluated. Soil formation under tropical conditions are shown to be the most appropriate for Lunar base CELSS due to high matter turnover rate, relatively short formation time, minimum deposited mass, and satisfactory predictability of expected soil parameters.     

Life in the solar system.

Life, defined as a chemical system capable of transferring its molecular information via self-replication and also capable of evolving, must develop within a liquid to take advantage of the diffusion of complex molecules. On Earth, life probably originated from the evolution of reduced organic molecules in liquid water. Organic matter might have been formed in the primitive Earth's atmosphere or near hydrothermal vents. A large fraction of prebiotic organic molecules might have been brought by extraterrestrial-meteoritic and cometary dust grains decelerated by the atmosphere. Any celestial body harboring permanent liquid water may therefore accumulate the ingredients that generated life on the primitive Earth. The possibility that life might have evolved on early Mars when water existed on the surface marks it as a prime candidate in a search for bacterial life beyond the Earth. Europa has an icy carapace. However, cryovolcanic flows at the surface point to a possible water subsurface region which might harbor a basic life form. The atmosphere and surface components of Titan are also of interest to exobiology for insight into a hydrocarbon-rich chemically evolving world. One-handed complex molecules and preferential isotopic fractionation of carbon, common to all terrestrial life forms, can be used as basic indicators when searching for life beyond the Earth.     

Stable carbon isotope fractionation in the search for life on early Mars.

Isotopic measurements and, more specifically, ratios of 13C to 12C in organic relative to inorganic deposits, are useful in reconstructing past biological activity on Earth. Organic matter has a lower ratio of 13C to 12C due largely to the preferential fixation of 12C over the heavier isotope by the major carbon-fixation enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase, although other factors (e.g., availability of source carbon, fixation by other carboxylating enzymes and diagenesis of organic material) also contribute to fractionation. Would carbon isotope discrepancies between inorganic and organic carbon indicate past biological activity on Mars? In order to answer this question, we analyse what is known about terrestrial biologic and abiologic carbon fixation and its preservation in the fossil record, and suggest what the isotope discrimination during possible biologic and abiologic carbon fixation on Mars might have been like. Primarily because isotopic signatures of abiotically fixed carbon overlap with those of biotic fixation, but also because heterotrophy does not significantly alter the isotopic signature of ingested carbon, fractionation alone would not be definitive evidence for life. However, a narrow range of fractionation, including no fractionation, would suggest biotic processes. Never-the-less, isotopic ratios in organic deposits on Mars would be extremely useful in analysing prebiotic, if not biotic, carbon transformations on Mars.     

Organic syntheses in gas phase and chemical evolution in planetary atmospheres

Atmospheric chemistry may be one of the important pathways to the synthesis of organic compounds in a planetary periphery. Depending on the nature of the carbon source (CH₄, CO or CO₂), the main composition of the atmosphere, and the respective roles of the various energy sources, is it possible, and to what extent, to produce organics? What kind of gaseous mixture is the most favourable to prebiotic organic syntheses? How far can the results of laboratory works be extrapolated to the case of planetary atmospheres? These questions are discussed, on the basis of several available laboratory data, and by considering the main atmospheric composition of the planets of the solar system, and the list of organic compounds which have already been dettected in their atmospheres.     

Electronmicroscopic investigations on the role of vesicle-like bodies in inner ear maculae for fish otolith growth.

The presence, morphology and possible origin of vesicle-like bodies (VBs) within the inner ear otolithic membrane of developmental stages of cichlid fish Oreochromis mossambicus and adult swordtail fish Xiphophorus helleri was analysed by means of transmission and scanning electron microscopy (TEM and SEM, respectively) employing various fixation procedures. The VBs are believed to be involved in the formation of the otolith (or statolith in birds and mammals) regarding the supply of the otolith's organic material. Increasing the osmolarity of the fixation medium decreased the number of VBs seen. Decalcification ended up in a complete disappearance of the VBs. Whilst a fixation with glutaraldehyde followed by OSO4 fixation yielded numerous VBs, only few of them were observed when the tissue was fixed with glutaraldehyde and OSO4 simultaneously. Therefore, the results strongly suggest that the VBs are fixative (i.e., glutaraldehyde) induced artifacts, so-called blisters. With this, the supply of an oto- or statolith's organic material remains obscure. Possibly, it is provided by secretion from the supporting cells as has been hypothesized earlier.     

Microgravity and musculoskeletal system of mammals.

This review surveys data in the literature and our own findings concerning the effects of weightlessness on bones and muscles of white rats flown on Cosmos biosatellites and Spacelab-3. It has been shown that the magnitude and sign of functional changes in muscles depend on their biomechanical profile. Structural and metabolic foundations of functional adaptation and its dynamics have been identified: in 5-7 day flights muscle contractility changes are mainly associated with a diminished activity of excitation-contraction coupling, in longer-term flights they are produced by changes in myosin populations specific for myofibers of different functional profile. At early flight stages (up to 1 week) osteoporosis and bone demineralization are very mild; therefore decrease in bone mechanical strength may be caused by changes in physico-chemical parameters of the collagen-crystal system. In flights of up to 3 weeks noticeable osteoporosis develops which is primarily produced by osteogenesis inhibition and which is responsible for a marked decrease of bone strength. These changes may result from uncoupling of bone resorption and remodelling processes. This uncoupling is characterized as incomplete osteogenesis and may be caused by changes in the collagen composition of the organic bone matrix. The above-mentioned adaptive changes in muscle functions of specific skeletal compartments may play a role in different responses of various bones to weightlessness.     

The seeding of life by comets.

The evidence that living organisms were already extant on the earth almost 4 Gyr ago and that early bombardment by comets and asteroids created a hostile environment up to about this time has revived the question of how it was possible for prebiotic chemical evolution to have provided the necessary ingredients for life to have developed in the short intervening time. The actual bracketed available temporal space is no more than 0.5 Gyr and probably much less. Was this sufficient time for an earth-based source of the first simple organic precursor molecules to have led to the level of the prokaryotic cell? If not, then the difficulty would be resolved if the ancient earth was impregnated by organic molecular seed from outer space. Curiously, it seems that the most likely source of such seeds was the same a one of the sources of the hostile enviroment, namely the comets which bombarded the earth. With the knowledge of comets gained by the space missions it has become clear that a very large fraction of the chemical composition of comet nuclei consists of quite complex organic molecules. Furthermore it has been demonstrated that comets consist of very fluffy aggregates of interstellar dust whose chemistry derives from photoprocessing of simple ice mixtures in space. Thus, the ultimate source of organics in comets comes from the chemical evolution of interstellar dust. An important and critical justification for assuming that interstellar dust is the ultimate source of prebiotic molecular insertion on the earth is the proof that comets are extremely fluffy aggregates, which have the possibility of breaking up into finely divided fragments when the comet impacts the earth's atmosphere. In the following we will summarize the properties of interstellar dust and the chemical and morphological structure of comets indicated by the most recent interpretations of comet observations. It will be shown that the suitable condition for comets having provided abundant prebiotic molecules as well as the water in which they could have further evolved are consistent with theories of the early earth environment.     

Prebiotic synthesis of nucleotides at the Earth orbit in presence of Lunar soil.

Modern studies now favor the fact that extraterrestrial organic molecules served as an important source of biological important substances on the primitive Earth. It is presumed that these space-made organic molecules could be transported safely to the Earth surface being associated with mineral grains. It is important to test whether nucleotides synthesized in Earth orbit could be protected by lunar surface regolite. The phosphorylation of adenosine, uridine and thymidine has been studied with respect of their further transformations and degradation in presence of mineral bed. After retrieval, HPLC analysis is used to identify all the mononucleotides of certain nucleosides. It has been shown, that exposure of the investigated nucleosides as dry films in space conditions in the presence of Lunar soil increases the yield of synthesized nucleotides in 1.1-3.0 times as compared with the exposure of the same samples in absence of Lunar soil. To identify and evaluate the principal source of energy in open space responsible for nucleotide synthesis reaction laboratory experiments were performed. It has been shown, that vacuum ultra violet (VUV 145 nm) radiation promotes nucleotide synthesis more effectively than ultra violet (UV 254 nm) while the presence of Lunar soil increases reaction yield in 1.5-2.0 times. Formation of 5'-mononucleotides seemed to be the most effective reaction both in flight and in laboratory experiments. Protective action of lunar soil on synthesized nucleotides against UV radiation has been shown in open Space conditions.     

Search for organic molecules in the outer solar system

Recent developments of millimeter astronomy have led to the discovery of more and more complex molecules in the interstellar medium. In a similar way, attempts have been made to detect complex molecules in the atmospheres of the most primitive bodies of the Solar System, i.e. outer planets and comets, as well as in Titan's atmosphere. An important progress has been achieved thanks to the continuous development of infrared astronomy, from the ground and from space vehicles. In particular, an important contribution has come from the IRIS-Voyager infrared spectrometer with the detection of prebiotic molecules on Titan, and some complex organic molecules on Jupiter and Saturn. Another important result has been the observation of carbonaceous material in the immediate surroundings of Comet Halley's nucleus. In the near future, the search for organic molecules in the outer Solar System should benefit from the developments of large millimeter antennae, and in the next decade, from the operation of infrared Earth-orbiting spacecrafts (ISO, SIRTF).     

Analog environments for a Europa lander mission

This paper reviews the utility of analog environments in preparations for a Europa lander mission. Such analogs are useful in the demonstration and rehearsal of engineering functions such as sample acquisition from an icy surface, as well as in the exercise of the scientific protocols needed to identify organic, inorganic and possible biological impurities in ice. Particular attention is drawn to Antarctic and Arctic analog sites where progress in these latter areas has been significant in recent years.     

Material balance and diet in bioregenerative life support systems: connection with coefficient of closure.

Bioregenerative life support systems (BLSS) with different coefficients of closure are considered. The 66.2% coefficient of closure achieved in "BIOS-3" facility experiments has been taken as a base value. The increase in coefficient of closure up to 72.6-93.0% is planned due to use of soil-like substrate (SLS) and concentrating of urine. Food values were estimated both in a base variant ("BIOS-3"), and with increases in the coefficient of closure. It is shown that food requirements will be more fully satisfied by internal crop production with an increase in the coefficient of closure of the BLSS. Changes of massflow rates on an 'input-output' and inside BLSS are considered. Equations of synthesis and degradation of organic substances in BLSS were examined using a stoichiometric model. The paper shows that at incomplete closure of BLSS containing SLS there is a problem of nitrogen balancing. To compensate for the removal of nitrogen from the system in urine and feces, it is necessary to introduce food and a nitrogen-containing additive.     

国外低吸收辐射比有机温控涂层发展概况

长期以来,低吸收辐射比有机温控涂层是人们着重研究的一类重要的卫星被动温控涂层,这类涂层应具有低的太阳吸收率α_s,以及高的热辐射率ε_n,即涂层必须有低α_s/ε_n值。而旦,涂层在宇宙环境中应保持该性能的长期稳定性。本文概述固外低α_s/ε_有机温控涂层的研制情况。     

Plants--rhizospheric organisms interaction in a manmade system with and without biogenous element limitation.

The effect has been studied of inoculation of seeds of wheat with two species of rhizospheric microorganisms--Pseudomonas fluorescens and Pseudomonas putida--on young plant growth with complete and with nitrogen deficit mineral nutrition. With complete mineral medium, plants grown from seeds inoculated with bacteria of Pseudomonas genus (experiment plants) have been found to have better growth over plants not inoculated with these bacteria (control plants). The experiment plants had increased transpiration and their biomass had higher organic nitrogen content. With nitrogen deficit medium, the plants inoculated with bacteria and those without them, have not revealed changes in growth. Neither case demonstrated competition of microorganisms with plants for nitrogen sources.     

The formation of organic molecules in astronomical ices.

An absorption feature at 3.4 micrometers has been observed in various lines-of-sight through the diffuse interstellar medium. Its position and width lead to an identification with the C-H stretching mode of solid organic material. A possible mechanism for the production of organic solids in the interstellar medium is UV photoprocessing of icy mantles which accrete on dust grains in dense clouds. Furthermore, thermally induced reactions involving formaldehyde molecules in the mantles could be an important source of organics. Laboratory simulation of these processes shows that a large variety of oxygen- and nitrogen-rich species may be produced. It is shown that the occurrence of periodic transient heating events plays an important role in the production of organic material in the ice mantles. Finally, it is pointed out how future missions like the Infrared Space Observatory (ISO) as well as analysis of comet material by Rosetta may be able to clarify the nature and evolution of interstellar organics.     

Assessing the feasibility of involving gaseous products resulting from physicochemical oxidation of human liquid and solid wastes in the cycling of a bio-technical life support system

The study addresses the possible ways of involving gaseous products produced by “wet” incineration of human wastes mixed with H₂O₂ in an alternating electric field in the cycling of the physical model of a bio-technical life support system (BTLSS). The resulting gas mixture contains CO₂ and O₂, which are easily involved in the cycling in the closed ecosystem, and NH₃, which is unacceptable in the atmosphere of the BTLSS. NH₃ fixation has been proposed, which is followed by nitrification and involvement of the resulting products in the mass exchange of the closed system. Experiments have been performed to show that plants can be grown in the atmosphere resulting from the closing of the gas loop that includes a physicochemical installation and a growth chamber with plants representing the phototrophic compartment of the BTLSS. The results of the study suggest the conclusion that the proposed method of organic waste oxidation can be a useful tool in creating a physical model of a closed-loop integrated BTLSS.     

Chemical evolution and the origin of life.

During the last three decades major advances have been made in our understanding of the formation of carbon compounds in the universe and of the occurence of processes of chemical evolution. 1) Carbon and other biogenic elements (C,H,N,O,S and P) are some of the most abundant in the universe. 2) The interstellar medium has been found to contain a diversity of molecules of these elements. 3) Some of these molecules have also been found in comets which are considered the most primordial bodies of the solar system. 4) The atmospheres of the outer planets and their satellites, for example, Titan, are actively involved in the formation of organic compounds which are the precursors of biochemical molecules. 5) Some of these biochemical molecules, such as amino acids, purines and pyrimidines, have been found in carbonaceous chondrites. 6) Laboratory experiments have shown that most of the monomers and oligomers necessary for life can be synthesized under hypothesized but plausible primitive Earth conditions from compounds found in the above cosmic bodies. 7) It appears that the primitive Earth had the necessary and sufficient conditions to allow the chemical synthesis of biomacromolecules and to permit the processes required for the emergence of life on our planet. 8) It is unlikely that the emergence of life occurred in any other body of the solar system, although the examination of the Jovian satellite Europa may provide important clues about the constraints of this evolutionary process. Some of the fundamental principles of chemical evolution are briefly discussed.