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为了研究冰冻天体表面撞击坑的形成与演化,开展了水冰的超高速撞击成坑实验。使用二级轻气炮发射1.0 mm直径的球形弹丸,以3 km/s、5 km/s和7 km/s速度对圆柱状冰块进行撞击。弹丸材料包括聚碳酸酯和不锈钢两种,冰块温度为253 K。实验观察到了不同弹丸和不同速度条件下,冰块中撞击坑的形貌特征。对撞击坑直径、深度和剖面形状进行了测量,并与文献中铝弹丸对水冰的撞击坑进行了比较分析。获得了水冰撞击坑特征随撞击参数的变化规律,结果表明:撞击坑直径和深度的主导机制不同,坑深主要由弹丸侵彻作用形成,而坑径主要由冰块的剥落所致;坑深比坑径具有更强的对于弹丸密度的依赖性,高密度弹丸撞击坑直径具有比低密度弹丸更强的对于撞击速度的依赖性;撞击坑体积与撞击能量成正比,高密度弹丸形成的撞击坑直径表现出“能量缩比”行为,而低密度弹丸形成的撞击坑直径表现出“动量缩比”行为。 相似文献
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Impact structures are a rare habitat on Earth. However, where they do occur they can potentially have an important influence on the local ecology. Some of the types of habitat created in the immediate post-impact environment are not specific to the impact phenomenon, such as hydrothermal systems and crater lakes that can be found, for instance, in post-volcanic environments, albeit with different thermal characteristics than those associated with impact. However, some of the habitats created are specifically linked to processes of impact processing. Two examples of how impact processing of target materials has created novel habitats that improve the opportunities for colonization are found in the Haughton impact structure in the Canadian High Arctic. Impact-shocked rocks have become a habitat for endolithic microorganisms, and large, impact-shattered blocks of rock are used as resting sites by avifauna. However, some materials produced by an impact, such as melt sheet rocks, can make craters more biologically depauperate than the area surrounding them. Although there are no recent craters with which to study immediate post-impact colonization, these data yield insights into generalized mechanisms of how impact processing can influence post-impact succession. Because impact events are one of a number of processes that can bring localized destruction to ecosystems, understanding the manner in which impact structures are recolonized is of ecological interest. Impact craters are a universal phenomenon on solid planetary surfaces, and so they are of potential biological relevance on other planetary surfaces, particularly Mars. 相似文献
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Do large craters on Mars represent sites that contain aqueous and hydrothermal deposits that provide clues to astrobiological processes? Are these materials available for sampling in large craters? Several lines of evidence strongly support the exploration of large impact craters to study deposits important for astrobiology. The great depth of impact craters, up to several kilometers relative to the surrounding terrain, can allow the breaching of local aquifers, providing a source of water for lakes and hydrothermal systems. Craters can also be filled with water from outflow channels and valley networks to form large lakes with accompanying sedimentation. Impact melt and uplifted basement heat sources in craters > 50 km in diameter should be sufficient to drive substantial hydrothermal activity and keep crater lakes from freezing for thousands of years, even under cold climatic conditions. Fluid flow in hydrothermal systems is focused at the edges of large planar impact melt sheets, suggesting that the edge of the melt sheets will have experienced substantial hydrothermal alteration and mineral deposition. Hydrothermal deposits, fine-grained lacustrine sediments, and playa evaporite deposits may preserve evidence for biogeochemical processes that occurred in the aquifers and craters. Therefore, large craters may represent giant Petri dishes for culturing preexisting life on Mars and promoting biogeochemical processes. Landing sites must be identified in craters where access to the buried lacustrine sediments and impact melt deposits is provided by processes such as erosion from outflow channels, faulting, aeolian erosion, or excavation by later superimposed cratering events. Very recent gully formation and small impacts within craters may allow surface sampling of organic materials exposed only recently to the harsh oxidizing surface environment. 相似文献
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Life and its former traces can only be detected from space when they are abundant and exposed to the planetary atmosphere at the moment of investigation by orbiters. Exposed rock surfaces present a multifractal labyrinth of niches for microbial life. Based upon our studies of highly stress-resistant microcolonial fungi of stone monument and desert rock surfaces, we propose that microbial biofilms that develop and become preserved on rock surfaces can be identified remotely by the following characteristics: (1) the existence of spectroscopically identifiable compounds that display unique adsorption, diffraction, and reflection patterns characteristic of biogenerated organic compounds (e.g., chlorophylls, carotenes, melanins, and possibly mycosporines), (2) demonstrably biogenic geomorphological features (e.g., biopitting, biochipping, and bioexfoliation), and (3) biominerals produced in association with biofilms that occupy rock surfaces (e.g., oxalates, forsterite, and special types of carbonates, sulfides, and silicates). Such traces or biosignatures of former life could provide macroscopically visible morphotypes and chemically identifiable products uniquely indicative of life. 相似文献
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Cockell CS Voytek MA Gronstal AL Finster K Kirshtein JD Howard K Reitner J Gohn GS Sanford WE Horton JW Kallmeyer J Kelly L Powars DS 《Astrobiology》2012,12(3):231-246
Although a large fraction of the world's biomass resides in the subsurface, there has been no study of the effects of catastrophic disturbance on the deep biosphere and the rate of its subsequent recovery. We carried out an investigation of the microbiology of a 1.76 km drill core obtained from the ~35 million-year-old Chesapeake Bay impact structure, USA, with robust contamination control. Microbial enumerations displayed a logarithmic downward decline, but the different gradient, when compared to previously studied sites, and the scatter of the data are consistent with a microbiota influenced by the geological disturbances caused by the impact. Microbial abundance is low in buried crater-fill, ocean-resurge, and avalanche deposits despite the presence of redox couples for growth. Coupled with the low hydraulic conductivity, the data suggest the microbial community has not yet recovered from the impact ~35 million years ago. Microbial enumerations, molecular analysis of microbial enrichment cultures, and geochemical analysis showed recolonization of a deep region of impact-fractured rock that was heated to above the upper temperature limit for life at the time of impact. These results show how, by fracturing subsurface rocks, impacts can extend the depth of the biosphere. This phenomenon would have provided deep refugia for life on the more heavily bombarded early Earth, and it shows that the deeply fractured regions of impact craters are promising targets to study the past and present habitability of Mars. 相似文献
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Vera Martinez 《Acta Astronautica》2009,64(2-3):382-390
The paper describes the main issues for the design of an appropriately planned habitat for tourists in space.Due study and analysis of the environment of space stations (ISS, MIR, Skylab) delineate positive and negative aspects of architectonical design. Analysis of the features of architectonical design for touristic needs and verification of suitability with design for space habitat.Space tourism environment must offer a high degree of comfort and suggest correct behavior of the tourists. This is intended for the single person as well as for the group. Two main aspects of architectural planning will be needed: the design of the private sphere and the design of the public sphere.To define the appearance of environment there should be paid attention to some main elements like the materiality of surfaces used; the main shapes of areas and the degree of flexibility and adaptability of the environment to specific needs. 相似文献
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Duke MB 《Acta Astronautica》2002,50(6):379-383
The Clementine mission has revived interest in the possibility that ice exists in shadowed craters near the lunar poles. Theoretically, the problem is complex, with several possible sources of water (meteoroid, asteroid, comet impact), several possible loss mechanisms (impact vaporization, sputtering, photoionization), and burial by meteorite impact. Opinions of modelers have ranged from no ice to several times 10(16) g of ice in the cold traps. Clementine bistatic radar data have been interpreted in favor of the presence of ice, while Arecibo radar data do not confirm its presence. The Lunar Prospector mission, planned to be flown in the fall of 1997, could gather new evidence for the existence of ice. If ice is present, both scientific and utilitarian objectives would be addressed by a lunar polar rover, such as that proposed to the NASA Discovery program, but not selected. The lunar polar rover remains the best way to understand the distribution and characteristics of lunar polar ice. 相似文献
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Materials blasted into space from the surface of early Earth may preserve a unique record of our planet's early surface environment. Armstrong et al. (2002) pointed out that such materials, in the form of terrestrial meteorites, may exist on the Moon and be of considerable astrobiological interest if biomarkers from early Earth are preserved within them. Here, we report results obtained via the AUTODYN hydrocode to calculate the peak pressures within terrestrial meteorites on the lunar surface to assess their likelihood of surviving the impact. Our results confirm the order-of-magnitude estimates of Armstrong et al. (2002) that substantial survivability is to be expected, especially in the case of relatively low velocity (ca. 2.5 km/s) or oblique (相似文献
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Current debates on the prevention of an arms race in outer space are dominated by the traditional perspective of international strategic balance. This article addresses the issue through the often-neglected lens of environmental protection, reviewing a number of environmental instruments as they relate to outer space. It argues that environmental protection, as a non-traditional element, is an instrumental impetus for arms control. The current regime leaves the door open for states to develop conventional orbital weapons and ground-based anti-satellite weapons (ASATs), which would have a significant adverse impact on the space environment. Thus the law of environmental protection is deficient in effectively protecting the space environment from pollution resulting from military activities. It is further argued that the space arms control regime should be strengthened for humanity's common interest in a sustainable space environment. Preferably an international treaty should be concluded to prohibit testing, deployment and use of space-based weapons and ASATs. These substantive obligations also conform to the requirements of safeguarding international peace and security, and the security interests of spacefaring countries. 相似文献
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Hypervelocity impacts on the retrieved Hubble Space Telescope (HST) solar array was investigated by our extended Direct Simulation Monte Carlo (DSMC) model and the result matches well with the measured data in most of the particle mass range. The revelation of the altitude dependence of particles flux onto the retrieved surfaces provides some insight in understanding the observed higher flux onto Mir space station relative to that onto Long Duration Exposure Facility (LDEF). Our analysis suggests that a slightly higher primary flux onto Mir space station would be possible even without taking into account the secondary impacts, as a result of the existence of the highly eccentric orbits of small-sized debris. It is, furthermore, predicted that 43% of the measured impact flux onto Mir station in PIE experiment may be from secondary impacts, and a corresponding 7% for the detectors in Echantillions experiment. 相似文献
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月球探测器软着陆动力学仿真 总被引:5,自引:0,他引:5
随着深空探测技术的发展,新型月球探测器需要在遍布石块、陨石坑和斜坡等复杂月球表面上着陆,因此有必要对月球着陆探测器的着陆性能进行评估。本文对一种四腿可展开式着陆器进行了合理简化,并用ADAMS软件建立了着陆动力学仿真模型。模型中应用子程序表达缓冲铝蜂窝和月壤的力学性质,通过在预研着陆器的仿真模型上加载,实现了系统的仿真;并得到了月球探测器以给定姿态和着陆速度在不同地面坡度和月壤物理特性下的着陆性能及一般规律,对我国月球探测器软着陆动力学研究具有一定参考价值。 相似文献
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Fluid inclusions in minerals hold the potential to provide important data on the chemistry of the ambient fluids during mineral precipitation. Especially interesting to astrobiologists are inclusions in low-temperature minerals that may have been precipitated in the presence of microorganisms. We demonstrate that it is possible to obtain data from inclusions in chemosynthetic carbonates that precipitated by the oxidation of organic carbon around methane-bearing seepages. Chemosynthetic carbonates have been identified as a target rock for astrobiological exploration. Other surficial rock types identified as targets for astrobiological exploration include hydrothermal deposits, speleothems, stromatolites, tufas, and evaporites, each of which can contain fluid inclusions. Fracture systems below impact craters would also contain precipitates of minerals with fluid inclusions. As fluid inclusions are sealed microchambers, they preserve fluids in regions where water is now absent, such as regions of the martian surface. Although most inclusions are < 5 microns, the possibility to obtain data from the fluids, including biosignatures and physical remains of life, underscores the advantages of technological advances in the study of fluid inclusions. The crushing of bulk samples could release inclusion waters for analysis, which could be undertaken in situ on Mars. 相似文献
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文章描述了一个用于航天器防护结构综合优化的独特方法——几何规划优化技术,以减小暴露于流星体和空间碎片超高速碰撞环境下的航天器防护结构系统的重量。空间碎片和流星体环境由广义加权目标函数的公式来定义。通过Wilkinson,Burch和Nysmith超高速碰撞预示模型说明几何规划的性能。表明遵循几何规划形式的超高速碰撞模型,可以进行综合非线性设计优化。 相似文献