Engineering topics
Publications and source records attributed to Klein, H. P..
A major argument in the claim that life had been discovered during the Viking mission to Mars is that the results obtained in the Labeled Release (LR) experiment are analogous to those observed with terrestrial microorganisms. This assertion is critically examined and found to be implausible.
The MOx instrument was developed to characterize the reactive nature of the martian soil. The objectives of MOx were: (1) to measure the rate of degradation of organics in the martian environment; (2) to determine if the reactions seen by the Viking biology experiments were caused by a soil oxidant and measure the reactivity of the soil and atmosphere: (3) to monitor the degradation, when exposed to the martian environment, of materials of potential use in future missions; and, finally, (4) to develop technologies and approaches that can be part of future soil analysis instrumentation. The basic approach taken in the MOx instrument was to place a variety of materials composed as thin films in contact with the soil and monitor the physical and chemical changes that result. The optical reflectance of the thin films was the primary sensing-mode. Thin films of organic materials, metals, and semiconductors were prepared. Laboratory simulations demonstrated the response of thin films to active oxidants.
Proposals for continuing the search for extant life on Mars are primarily predicated on the assumption that specialized environmental niches that could support a biota may exist on the planet. Before attempting any critical tests for extant organisms, either in situ or on returned samples, it is imperative to determine whether any such sites actually exist. If, through remote sensing and landed instrumentation, sites of potential biological interest are discovered and characterized, biological tests can then more effectively be planned to elicit the presence of organisms that are adapted to living in these particular environments.
Of all the other planets in the solar system, Mars remains the most promising for further elucidating concepts about chemical evolution and the origin of life. Strategies were developed to pursue three exobiological objectives for Mars exploration: determining the abundance and distribution of the biogenic elements and organic compounds, detecting evidence of an ancient biota on Mars, and determining whether indigenous organisms exist anywhere on the planet. The three strategies are quite similar and, in fact, share the same sequence of phases. In the first phase, each requires global reconnaissance and remote sensing by orbiters to select sites of interest for detailed in situ analyses. In the second phase, lander missions are conducted to characterize the chemical and physical properties of the selected sites. The third phase involves conducting 'critical' experiments at sites whose properties make them particularly attractive for exobiology. These critical experiments would include, for example, identification of organics, detection of fossils, and detection of extant life. The fourth phase is the detailed analysis of samples returned from these sites in Earth-based laboratories to confirm and extend previous discoveries. Finally, in the fifth phase, human exploration is needed to establish the geological settings for the earlier findings or to discover and explore sites that are not accessible to robotic spacecraft.
The search for evidence of life on Mars is a highly interdisciplinary enterprise which extends beyond the traditional life sciences. Mars conceivably had a pervasive ancient biosphere which may have persisted even to the present, but only in subsurface environments. Understanding the history of Mars' global environment, including its inventory of volatile elements, is a crucial part of the search strategy. Those deposits (minerals, sediments, etc.) which could have and retained a record of earlier biological activity must be identified and examined. While the importance of. seeking another biosphere has not diminished during the years since the Viking mission, the strategy for Mars exploration certainly has been modified by later discoveries. The Viking mission itself demonstrated that the present day surface environment of Mars is hostile to life as we know it. Thus, to search effectively for life on Mars, be it extant or extinct, we now must greatly improve our understanding of Mars the planet. Such an understanding will help us broaden our search beyond the Viking lander sites, both back in time to earlier epochs and elsewhere to other sites and beneath the surface. Exobiology involves much more than simply a search for extant life beyond Earth. It addresses the prospect of long-extinct biospheres and also the chemistry, organic and otherwise, which either led to life or which occurred on rocky planets that remained lifeless. Even a Mars without a biosphere would reveal much about life. How better to understand the origin and impact of a biosphere than to compare Earth with another similar but lifeless planet? Still, several relatively recent discoveries offer encouragement that a Martian biosphere indeed might have existed. The ancient Martian surface was extensively sculptured by volcanism and the activity of liquid water. Such observations invoke impressions of an ancient martian atmosphere and environment that resembled ancient Earth more than present-day Mars. Since Viking, we have learned that our own biosphere began prior to 3.5 billion years ago, during an early period when our solar system apparently was sustaining clement conditions on at least two of its planets. Also, we have found that microorganisms can survive, even flourish, in environments more extreme in temperature and water availability than had been previously recognized. The common ancestor of life on Earth probably was adapted to elevated temperatures, raising the possibility that hydrothermal systems played a central role in sustaining our early biosphere. If a biosphere ever arose on Mars, at least some of its constituents probably dwelled in the subsurface. Even today, conditions on Mars and Earth become more similar with increasing depth beneath their surfaces. For example, under the martian permafrost, the geothermal gradient very likely maintains liquid water in environments which resemble aquifers on Earth. Indigenous bacteria have recently been recovered from deep aquifers on Earth. Liquid groundwater very likely persisted throughout Mars' history. Thus, martian biota, if they ever existed, indeed might have survived in subsurface environments.
Of all the other planets in the solar system, Mars remains the most promising for further elucidating concepts about chemical evolution and the origin of life. Exobiological objectives for Mars exploration include: determining the abundance and distribution of the biogenic elements and organic compounds, detecting evidence of an ancient biota on Mars, and determining whether indigenous organisms exist anywhere on the planet. Both approved and planned missions to Mars were evaluated for their potential to contribute to the understanding of these exobiology science objectives and an exploration strategy was developed for each objective.
Mussels collected from hydrocarbon seeps in the Gulf of Mexico grow with methane as sole carbon and energy source due to a symbiotic association with methane-oxidizing bacteria. Transmission electron micrographs of mussel gills show cells with stacked intracytoplasmic membranes similar to type I methanotrophic bacteria. Methanotrophs are known to synthesize several types of cyclic triterpenes, hopanoids and methyl sterols, as well as unique monounsaturated fatty acid, double bond positional isomers that serve as biomarkers for this group. Lipid analysis of dissected mussels demonstrated the presence of these biomarkers predominantly in the gill tissue with much smaller amounts in mantle and remaining body tissues. Gill tissue contained 1150 micrograms/g dry wt. of hopanepolyol derivatives and diplopterol while the mantle tissue contained only 17 micrograms/g. The C16 monounsaturated fatty acids (16:1) characteristic of type I methanotrophic membranes dominated the gill tissue making up 53% of the total while only 5% 16:1 was present in the mantle tissue. The methyl sterol distribution was more dispersed. The predominant sterol in all tissues was cholesterol with lesser amounts of other desmethyl and 4-methyl sterols. The gill and mantle tissues contained 3461 micrograms (17% methyl) and 2750 micrograms (5% methyl) sterol per gm dry wt., respectively. Methyl sterol accounted for 44% of the sterol esters isolated from the gill, suggesting active demethylation of the methanotrophic sterols in this tissue. The use of lipid biomarkers could provide an effective means for identifying host-symbiont relationships.
A primary scientific theme for the Space Exploration Initiative (SEI) is the search for life, extant or extinct, on Mars. Because of this, concerns have arisen about Planetary Protection (PP), the prevention of biological cross-contamination between Earth and other planets during solar system exploration missions. A recent workshop assessed the necessity for, and impact of, PP requirements on the unmanned and human missions to Mars comprising the SEI. The following ground-rules were adopted: (1) Information needed for assessing PP issues must be obtained during the unmanned precursor mission phase prior to human landings. (2) Returned Mars samples will be considered biologically hazardous until proven otherwise. (3) Deposition of microbes on Mars and exposure of the crew to martian materials are inevitable when humans land. And (4) Human landings are unlikely until it is demonstrated that there is no harmful effect of martian materials on terrestrial life forms. These ground-rules dictated the development of a conservative PP strategy for precursor missions. Key features of the proposed strategy include: to prevent forward-contamination, all orbiters will follow Mars Observer PP procedures for assembly, trajectory, and lifetime. All landers will follow Viking PP procedures for assembly, microbial load reduction, and bio-shield. And, to prevent back-contamination, all sample return missions will have PP requirements which include fail-safe sample sealing, breaking contact chain with the martian surface, and containment and quarantine analysis in Earth-based laboratory. In addition to deliberating on scientific and technical issues, the workshop made several recommendations for dealing with forward and back-contamination concerns from non-scicntific perspectives.
This volume includes chapters on exobiology in space, chemical and early biochemical evolution, life without oxygen, potential for chemical evolution in the early environment of Mars, planetary protection issues and sample return missions, and the modulation of biological evolution by astrophysical phenomena. Papers are presented on the results of spaceflight missions, the action of some factors of space medium on the abiogenic synthesis of nucleotides, early peptidic enzymes, microbiology and biochemistry of the methanogenic archaeobacteria, and present-day biogeochemical activities of anaerobic bacteria and their relevance to future exobiological investigations. Consideration is also given to the development of the Alba Patera volcano on Mars, biological nitrogen fixation under primordial Martian partial pressures of dinitrogen, the planetary protection issues in advance of human exploration of Mars, and the difficulty with astronomical explanations of periodic mass extinctions.
Planetary protection (PP) issues for both a comet nucleus sample return (CNSR) mission and a Mars rover sample return (MRSR) mission are discussed, with special attention given to the PP requirements for such missions, the exobiology science objectives for the CNSR and MRSR missions, and a qualitative PP risk assessment for both mission types. A set of contamination control procedures for both missions is presented, which identify procedures for each of the mission phases (i.e., the prelaunch, launch, sample handling, transit vehicle, and earth return). Recommendations for further research and technology development are discussed.
The mechanism for synthesis of monounsaturated fatty acids under aerobic and anaerobic conditions was studied in the facultative anaerobic cyanobacterium, Oscillatoria limnetica. The hexadecenoic acid (C16:1) of aerobically grown O. limnetica was shown to contain both the delta 7 (79%) and delta 9 (21%) isomers, while the octadecenoic (C18:1) acid was entirely the delta 9 acid. Incorporation of [2-14C] acetate into the fatty acids under aerobic conditions resulted in synthesis of the delta 7 and delta 9 C16:1 and the delta 9 C18:1. Synthesis of unsaturated fatty acids in the presence of DCMU required sulfide. Anaerobic incubations in the presence of DCMU and sulfide (less than 0.003% atmospheric oxygen) resulted in a two-fold increase in monounsaturated fatty acids of both delta 7 and delta 9 C16:1 and delta 9 and delta 11 C18:1. The synthesis of these is characteristic of a bacterial-type, anaerobic pathway.
Life support systems in space travel, in closed ecological systems were studied. Topics discussed include: (1) problems of life support and the fundamental concepts of bioregeneration; (2) technology associated with physical/chemical regenerative life support; (3) projection of the break even points for various life support techniques; (4) problems of controlling a bioregenerative life support system; (5) data on the operation of an experimental algal/mouse life support system; (6) industrial concepts of bioregenerative life support; and (7) Japanese concepts of bioregenerative life support and associated biological experiments to be conducted in the space station.
A bioregenerative life support system designed to address the fundamental requirements of a functioning independent lunar base is presented in full. Issues to be discussed are associated with CELSS weight, volume and cost of operation. The fundamental CELSS component is a small, highly automated module containing plants which photosynthesize and provide the crew with food, water and oxygen. Hydrogen, nitrogen and carbon dioxide will be initially brought in from earth, recycled and their waste products conserved. As the insufficiency of buffers necessitates stringent cybernetic control, a stable state will be maintained by computer control. Through genetic engineering and carbon dioxide, temperature, and nutrient manipulation, plant productivity can be increased, while the area necessary for growth and illumination energy decreased. In addition, photosynthetic efficiency can be enhanced through lamp design, fiber optics and the use of appropriate wavelengths. Crop maintenance will be performed by robotics, as a means of preventing plant ailments.
Space research in biology is presented with emphasis on flight experiment results and radiation risks. Topics discussed include microorganisms and biomolecules in the space-environment experiment ES 029 on Spacelab-1, the preliminary characterization of persisting circadian rhythms during space flight; plant growth, development, and embryogenesis during the Salyut-7 flight, and the influence of space-flight factors on viability and mutability of plants. Consideration is also given to radiation-risk estimation and its application to human beings in space, the radiation situation in space and its modification by the geomagnetic field and shielding, the quantitative interpretation of cellular heavy-ion action, and the effects of heavy-ion radiation on the brain vascular system and embryonic development.
Space-based and space-related research in the life sciences is presented in reviews and reports. Topics examined include the long-term effects of weightlessness, cosmic chemistry and chemical and biological evolution, life-support systems for space travel, planetary protection, and the g-scale factor in gravitational biology. Consideration is given to the role of Ca ions in cytological effects of hypogravity, the organic aerosols of Titan, the role of meteorite impacts in the formation of organic molecules, prebiotic synthesis of purines and pyrimidines, atmosphere behavior of gas-closed mouse-algal systems, air and water regeneration in advanced regenerative environmental-control and life-support systems, and the influence of gravity on the development of animal systems.
The effect of oxygen on squalene epoxidase activity in Saccharomyces cerevisiae was investigated. In cells grown in standing cultures, the epoxidase was localized mainly in the 'mitochondrial' fraction. Upon aeration, enzyme activity increased and the newly formed enzyme was associated with the 'microsomal' fraction. At 0.03 percent (vol/vol) oxygen, epoxidase levels doubled, whereas the ergosterol level was only slightly increased. Cycloheximide inhibited the increase in epoxidase under these conditions. An apparent K sub m for oxygen of 0.38 percent (vol/vol) was determined from a crude particulate preparation for the epoxidase.
The stability of particulate palmitoyl-CoA desaturase preparations from anaerobically grown yeast cells was increased by exposure to low levels of oxygen. The stabilizing effect of oxygen may be based upon the increased amounts of palmitoleic acid and ergosterol that become available to the cells. These results suggest the evolutinary appearance of this system at a time when atmospheric oxygen was at a low level.