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Searching for life on Mars: selection of molecular targets for ESA's aurora ExoMars mission 总被引:1,自引:0,他引:1
Parnell J Cullen D Sims MR Bowden S Cockell CS Court R Ehrenfreund P Gaubert F Grant W Parro V Rohmer M Sephton M Stan-Lotter H Steele A Toporski J Vago J 《Astrobiology》2007,7(4):578-604
The European Space Agency's ExoMars mission will seek evidence of organic compounds of biological and non-biological origin at the martian surface. One of the instruments in the Pasteur payload may be a Life Marker Chip that utilizes an immunoassay approach to detect specific organic molecules or classes of molecules. Therefore, it is necessary to define and prioritize specific molecular targets for antibody development. Target compounds have been selected to represent meteoritic input, fossil organic matter, extant (living, recently dead) organic matter, and contamination. Once organic molecules are detected on Mars, further information is likely to derive from the detailed distribution of compounds rather than from single molecular identification. This will include concentration gradients beneath the surface and gradients from generic to specific compounds. The choice of biomarkers is informed by terrestrial biology but is wide ranging, and nonterrestrial biology may be evident from unexpected molecular distributions. One of the most important requirements is to sample where irradiation and oxidation are minimized, either by drilling or by using naturally excavated exposures. Analyzing regolith samples will allow for the search of both extant and fossil biomarkers, but sequential extraction would be required to optimize the analysis of each of these in turn. 相似文献
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Morphological, compositional, and biological evidence indicates the presence of numerous well-developed microbial hyphae structures distributed within four different sample splits of the Nakhla meteorite obtained from the British Museum (allocation BM1913,25). By examining depth profiles of the sample splits over time, morphological changes displayed by the structures were documented, as well as changes in their distribution on the samples, observations that indicate growth, decay, and reproduction of individual microorganisms. Biological staining with DNA-specific molecular dyes followed by epifluorescence microscopy showed that the hyphae structures contain DNA. Our observations demonstrate the potential of microbial interaction with extraterrestrial materials, emphasize the need for rapid investigation of Mars return samples as well as any other returned or impactor-delivered extraterrestrial materials, and suggest the identification of appropriate storage conditions that should be followed immediately after samples retrieved from the field are received by a handling/curation facility. The observations are further relevant in planetary protection considerations as they demonstrate that microorganisms may endure and reproduce in extraterrestrial materials over long (at least 4 years) time spans. The combination of microscopy images coupled with compositional and molecular staining techniques is proposed as a valid method for detection of life forms in martian materials as a first-order assessment. Time-resolved in situ observations further allow observation of possible (bio)dynamics within the system. 相似文献
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航空背景所带来的技术优势对汽车的品牌定位可能并无多大帮助,但在理念的层面上,却出现惊人的一致,那就是对"高端"的追求。航空发动机需要的是万无一失的细腻,豪华车主需要的是唯我独尊的精致,而两者,都需要最佳的服务精神。"北京国际航空展"是国内历史最久最专业的航空展。它汇聚中国航空业全部权威机构,得到航空领域相关机构的鼎力支持。历届北京航展吸引了世界14个国家及地区超过129个展商,17000名专业观众参与,北京国际航空展已经成为国内外航空产业同仁高度关注的交流和合作专业展会。第十四届北京国际航空展主题为:环保、科技、安全、商业,2011年9月21日至24日在北京举行。 相似文献
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4月,两年一度的上海车展靓丽登场。本届上海车展总规模将超过20万平方米,创下国内之最。在本届上海车展的主题"创新未来"推动下,各大车企再次在新能源汽车的研发和推广上下足工夫,纷纷在环保、绿色等字眼上大做文章。特别是在日本地震之后,日本品牌更在意"地球很危险",积极准备在车展上推出自己的绿色产品。 相似文献
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Wolfgang Schulte Stefan Hofer Peter Hofmann Hans Thiele Ralf von Heise-Rotenburg Jan Toporski Petra Rettberg 《Acta Astronautica》2007,60(12):966-973
For more than a decade Kayser-Threde, a medium-sized enterprise of the German space industry, has been involved in astrobiology research in partnership with a variety of scientific institutes from all over Europe. Previous projects include exobiology research platforms in low Earth orbit on retrievable carriers and onboard the Space Station. More recently, exobiology payloads for in situ experimentation on Mars have been studied by Kayser-Threde under ESA contracts, specifically the ExoMars Pasteur Payload. These studies included work on a sample preparation and distribution systems for Martian rock/regolith samples, instrument concepts such as Raman spectroscopy and a Life Marker Chip, advanced microscope systems as well as robotic tools for astrobiology missions. The status of the funded technical studies and major results are presented. The reported industrial work was funded by ESA and the German Aerospace Center (DLR). 相似文献
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Evidence of microbial life on Earth has been found in siliceous rock formations throughout the geological and fossil record. To understand the mechanisms of silicification and thus improve our search patterns for evidence of fossil microbial life in rocks, a series of controlled laboratory experiments were designed to simulate the silicification of microorganisms. The bacterial strains Pseudomonas fluorescens and Desulphovibrio indonensis were exposed to silicifying media. The experiments were designed to determine how exposure time to silicifying solutions and to silicifying solutions of different Si concentration affect the fossilization of microbial biofilms. The silicified biofilms were analyzed using transmission electron microscopy (TEM) in combination with energy-dispersive spectroscopy. Both bacterial species showed evidence of silicification after 24 h in 1,000 ppm silica solution, although D. indonensis was less prone to silicification. The degree of silicification of individual cells of the same sample varied, though such variations decreased with increasing exposure time. High Si concentration resulted in better preservation of cellular detail; the Si concentration was more important than the duration in Si solution. Even though no evidence of amorphous silica precipitation was observed, bacterial cells became permineralized. High-resolution TEM analysis revealed nanometer-sized crystallites characterized by lattice fringe-spacings that match the (10-11) d-spacing of quartz formed within bacterial cell walls after 1 week in 5,000 ppm silica solution. The mechanisms of silicification under controlled laboratory conditions and the implication for silicification in natural environments are discussed, along with the relevance of our findings in the search for early life on Earth and extraterrestrial life. 相似文献
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