The PROCESS experiment: exposure of amino acids in the EXPOSE-E experiment on the international space station and in laboratory simulations

To understand the chemical behavior of organic molecules in the space environment, amino acids and a dipeptide in pure form and embedded in meteorite powder were exposed in the PROCESS experiment in the EXPOSE-E facility mounted on the European Technology Exposure Facility (EuTEF) platform on board the International Space Station (ISS). After exposure to space conditions for 18 months, the samples were returned to Earth and analyzed in the laboratory for reactions caused by solar UV and cosmic radiation. Chemical degradation and possible racemization and oligomerization, the main reactions caused by photochemistry in the vacuum ultraviolet domain (VUV, wavelength range 100-200?nm for photon energy from 6.2 to 12.4?eV) were examined in particular. The molecules were extracted and derivatized by silylation and analyzed by gas chromatograph coupled to a mass spectrometer (GC-MS) to quantify the rate of the degradation of the compounds. Laboratory exposure in several wavelength ranges from UV to VUV was carried out in parallel in the Cologne Deutsches Zentrum für Luft- und Raumfahrt (DLR) Center and Centre de biophysique moléculaire (CBM) laboratories. The results show that resistance to irradiation is a function of the chemical nature of the exposed molecules and the wavelengths of the UV light. The most altered compounds were the dipeptide, aspartic acid, and aminobutyric acid. The most resistant were alanine, valine, glycine, and aminoisobutyric acid. Our results also demonstrate the protective effect of meteorite powder, which reemphasizes the importance of exogenic contribution to the inventory of prebiotic organics on early Earth.     

The PROCESS experiment: amino and carboxylic acids under Mars-like surface UV radiation conditions in low-earth orbit

The search for organic molecules at the surface of Mars is a top priority of the next Mars exploration space missions: Mars Science Laboratory (NASA) and ExoMars (ESA). The detection of organic matter could provide information about the presence of a prebiotic chemistry or even biological activity on this planet. Therefore, a key step in interpretation of future data collected by these missions is to understand the preservation of organic matter in the martian environment. Several laboratory experiments have been devoted to quantifying and qualifying the evolution of organic molecules under simulated environmental conditions of Mars. However, these laboratory simulations are limited, and one major constraint is the reproduction of the UV spectrum that reaches the surface of Mars. As part of the PROCESS experiment of the European EXPOSE-E mission on board the International Space Station, a study was performed on the photodegradation of organics under filtered extraterrestrial solar electromagnetic radiation that mimics Mars-like surface UV radiation conditions. Glycine, serine, phthalic acid, phthalic acid in the presence of a mineral phase, and mellitic acid were exposed to these conditions for 1.5 years, and their evolution was determined by Fourier transform infrared spectroscopy after their retrieval. The results were compared with data from laboratory experiments. A 1.5-year exposure to Mars-like surface UV radiation conditions in space resulted in complete degradation of the organic compounds. Half-lives between 50 and 150?h for martian surface conditions were calculated from both laboratory and low-Earth orbit experiments. The results highlight that none of those organics are stable under low-Earth orbit solar UV radiation conditions.     

Formation of replicating saponite from a gel in the presence of oxalate: implications for the formation of clay minerals in carbonaceous chondrites and the origin of life

The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Moreover, there is a strong correlation in the occurrence of clay minerals and the presence of polar organic molecules. It has been shown in laboratory experiments at low temperature and ambient pressure that polar organic molecules, such as the oxalate found in meteorites, can catalyze the crystallization of clay minerals. In this study, we show that oxalate is a robust catalyst in the crystallization of saponite, an Al- and Mg-rich, trioctahedral 2:1 layer silicate, from a silicate gel at 60°C and ambient pressure. High-resolution transmission electron microscopy analysis of the saponite treated with octadecylammonium (n(C)=18) cations revealed the presence of 2:1 layer structures that have variable interlayer charge. The crystallization of these differently charged 2:1 layer silicates most likely occurred independently. The fact that 2:1 layer silicates with variable charge formed in the same gel has implications for our understanding of the origin of life, as these 2:1 clay minerals most likely replicate by a mechanism of template-catalyzed polymerization and transmit the charge distribution from layer to layer. If polar organic molecules like oxalate can catalyze the formation of clay-mineral crystals, which in turn promote clay microenvironments and provide abundant adsorption sites for other organic molecules present in solution, the interaction among these adsorbed molecules could lead to the polymerization of more complex organic molecules like RNA from nucleotides on early Earth.     

非对称多站在目标跟踪中的精度几何递变

现有靶场测量系统的笛氏坐标精确度估计取决于目标的位置以及测量仪器的数量、位置和精确度等因素。本报告分析了测量仪器的非对称布站问题。这是以往研究成果的推广,并且处理了更为一般性的问题。研究结果证明,对于测角仪器,当测站布局为非对称时,误差估计与所用的方位参考系有一定的关系。导出了几类布站几何的误差表达式,并为某类布站几何找出了最优的几何布站方案。     

天基网互操作的研究

天基网工操作专家组(SNIP)的研究工作是三方联合研究项目,由美国NASA局联空间局(ESA)和日本宇宙事业开发团(NASDA)联合参与。SNIP正在研究三个空间局中继卫星系统的互操作问题。 该项研究可分成两个阶段:第一阶段研究S波段(2GHz)互操作,第二阶段研究Ka波段(20/30GHz)的互操作(除了S波段外)。 从1985年开始,SNIP在NASA、ESA和NASDA进行了一系列双边磋商。1987年,SNIP组建了一个工作组,规定和研究用于确保数据中继系统国际兼容性的操作方案和一系列技术问题。此后,举行了一系列专家组和工作组会议,继续进行研究。 由于互操作会带来一系列操作运行和经济上的好处,所以三个空间局都很感兴趣。最近取得的大进展使互操作越发接近现实。本文将介绍SNIP研究工作的历史和现状。     

全新概念的空军联队——美国空军的366复合联队简介

为了适应美国未来的国防任务,美空军最近组建了一支全新概念的空军联队——366复合联队,以探索美国空军在未来作战环境中的适应性和灵活性。它和传统的美空军联队最大的不同在于:这支联队的编制不是固定的,根据不同任务组成不同数量飞机的编队;联队不是由单一机种而是由五种不同机种组成。每一次新组成的联队既可独立承担任务,也可随作战形势的需要,随时吸收其他联队、其他军种空中力量和盟国的空中力量形成以该联队为核心(桨毂),其他空中力量为辅助力量(辐条)的综合空中打击力量。美空军认为,这种新的复     

Quantitative electrocardiography during extended space flight

To assess the effects of prolonged space flight on the electrophysiological properties of the heart, vectorcardiograms (VCG) were obtained on the Skylab crews at regular intervals during flight and the pre- and postflight periods. The VCG signals were telemetered from Skylab and analyzed by digital computer. Conventional 12-lead electrocardiograms were derived from the VCG signals by a lead transformation program. Standardized exercise loads were incorporated into the experiment protocol to increase the sensitivity of the VCG for effects of deconditioning and to detect susceptibility for arrhythmias. In Skylab II, 24 preflight, 21 inflight, and 19 postflight experiments were analyzed. Statistically significant inflight changes observed in two or more crew members included: decreased resting heart rate, increased QRS duration, anterior shift QRS vector, increased QRS vector magnitude, anterior shift T vector, and increased T vector magnitude. One astronaut had occasional premature ventricular contractions (PVC) during the pre- and postflight phases. He had a single episode of multiple PVC's during heavy-load exercise testing in flight. A second astronaut had no arrhythmia during pre- or inflight testing. On postflight day 21 he had multiple PVC's and salvos of ectopic ventricular beats. He has had no recurrence of the arrhythmia. With the exception of the cardiac arrhythmias, no deleterious electrophysiological changes were observed during Skylab II.