An estimate of the prevalence of biocompatible and habitable planets

A Monte Carlo computer model of extra-solar planetary formation and evolution, which includes the planetary geochemical carbon cycle, is presented. The results of a run of one million galactic disc stars are shown where the aim was to assess the possible abundance of both biocompatible and habitable planets. (Biocompatible planets are defined as worlds where the long-term presence of surface liquid water provides environmental conditions suitable for the origin and evolution of life. Habitable planets are those worlds with more specifically Earthlike conditions). The model gives an estimate of 1 biocompatible planet per 39 stars, with the subset of habitable planets being much rarer at 1 such planet per 413 stars. The nearest biocompatible planet may thus lie approximately 14 LY distant and the nearest habitable planet approximately 31 LY away. If planets form in multiple star systems then the above planet/star ratios may be more than doubled. By applying the results to stars in the solar neighbourhood, it is possible to identify 28 stars at distances of < 22 LY with a non-zero probability of possessing a biocompatible planet.     

浅析亚洲复合材料市场及复合材料低成本制造技术

复合材料是新材料领域的重要组成部分,与传统材料相比,复合材料具有可设计性强,比强度、比模量高,抗疲劳断裂性能好,结构功能一体化等一系列优越性能。现代高科技的发展离不开复合材料,复合材料对现代科学技术的发展有着十分重要的作用。复合材料的研究深度和应用广度,及其生产发展的速度和规模,已成为衡量一个国家科学技术先进水平的重要标志之一。     

Iron-sulfide-bearing chimneys as potential catalytic energy traps at life's emergence

The concept that life emerged where alkaline hydrogen-bearing submarine hot springs exhaled into the most ancient acidulous ocean was used as a working hypothesis to investigate the nature of precipitate membranes. Alkaline solutions at 25-70°C and pH between 8 and 12, bearing HS(-)±silicate, were injected slowly into visi-jars containing ferrous chloride to partially simulate the early ocean on this or any other wet and icy, geologically active rocky world. Dependent on pH and sulfide content, fine tubular chimneys and geodal bubbles were generated with semipermeable walls 4-100?μm thick that comprised radial platelets of nanometric mackinawite [FeS]±ferrous hydroxide [～Fe(OH)(2)], accompanied by silica and, at the higher temperature, greigite [Fe(3)S(4)]. Within the chimney walls, these platelets define a myriad of micropores. The interior walls of the chimneys host iron sulfide framboids, while, in cases where the alkaline solution has a pH>11 or relatively low sulfide content, their exteriors exhibit radial flanges with a spacing of ～4?μm that comprise microdendrites of ferrous hydroxide. We speculate that this pattern results from outward and inward radial flow through the chimney walls. The outer Fe(OH)(2) flanges perhaps precipitate where the highly alkaline flow meets the ambient ferrous iron-bearing fluid, while the intervening troughs signal where the acidulous iron-bearing solutions could gain access to the sulfidic and alkaline interior of the chimneys, thereby leading to the precipitation of the framboids. Addition of soluble pentameric peptides enhances membrane durability and accentuates the crenulations on the chimney exteriors. These dynamic patterns may have implications for acid-base catalysis and the natural proton motive force acting through the matrix of the porous inorganic membrane. Thus, within such membranes, steep redox and pH gradients would bear across the nanometric platelets and separate the two counter-flowing solutions, a condition that may have led to the onset of an autotrophic metabolism through the reduction of carbon dioxide.     

邛海:水与火的缠绵

仙女梳妆时在大凉山的绵亘中遗失了她的镜子,于是便有了层峦叠嶂间的这一汪翡翠般的水域.传说在山民淳朴而炽烈的情感中沉淀成一种浪漫,在这个属火民族的注释下,水与火的交融便化做缠绵的图腾.……     

CCSDS AOS建议介绍

本文简介了ＡＯＳ建议制订的背景及其特点，较为详细地描述了其结构与业务，并阐述了与之相关的虚拟信道复用、等时业务的实现等问题。     

SLE服务在测控设备中的应用研究

针对CCSDS(空间数据系统咨询委员会)建议的SLE(空间链路扩展)服务并不完全适应现有测控设备运行管理体系和数据交互体系的问题,在介绍SLE服务体系和我国航天测控设备运行管理体系的基础上,对测控设备接口关系、SLE业务对现有测控设备的要求以及SLE服务在测控通信领域的发展等方面进行了重点研究,提出了应用SLE服务的测控设备接口方案和相关设备设计要求,并建议逐步在深空站等具备条件的地面站配置和使用自主开发的SLE服务。     

Terraforming Mars: conceptual solutions to the problem of plant growth in low concentrations of oxygen

The widespread growth of higher plants on Mars following ecopoiesis has often been invoked as a method of generating atmospheric oxygen. However, one issue that has been overlooked in this regard is the fact that terrestrial plants do not thrive under conditions of low oxygen tension. A review of the relevant botanical literature reveals that the high oxygen demands of root respiration could limit the introduction of most plants on Mars until after terraforming has raised the atmospheric pO2 to 20-100 mbar. A variety of physiological strategies are discussed which, if it is possible to implement them in a genetically engineered plant specifically designed for life on Mars, might allow this problem to be overcome.     

A microbial oasis in the hypersaline Atacama subsurface discovered by a life detector chip: implications for the search for life on Mars

The Atacama Desert has long been considered a good Mars analogue for testing instrumentation for planetary exploration, but very few data (if any) have been reported about the geomicrobiology of its salt-rich subsurface. We performed a Mars analogue drilling campaign next to the Salar Grande (Atacama, Chile) in July 2009, and several cores and powder samples from up to 5?m deep were analyzed in situ with LDChip300 (a Life Detector Chip containing 300 antibodies). Here, we show the discovery of a hypersaline subsurface microbial habitat associated with halite-, nitrate-, and perchlorate-containing salts at 2?m deep. LDChip300 detected bacteria, archaea, and other biological material (DNA, exopolysaccharides, some peptides) from the analysis of less than 0.5?g of ground core sample. The results were supported by oligonucleotide microarray hybridization in the field and finally confirmed by molecular phylogenetic analysis and direct visualization of microbial cells bound to halite crystals in the laboratory. Geochemical analyses revealed a habitat with abundant hygroscopic salts like halite (up to 260?g kg(-1)) and perchlorate (41.13?μg g(-1) maximum), which allow deliquescence events at low relative humidity. Thin liquid water films would permit microbes to proliferate by using detected organic acids like acetate (19.14?μg g(-1)) or formate (76.06?μg g(-1)) as electron donors, and sulfate (15875?μg g(-1)), nitrate (13490?μg g(-1)), or perchlorate as acceptors. Our results correlate with the discovery of similar hygroscopic salts and possible deliquescence processes on Mars, and open new search strategies for subsurface martian biota. The performance demonstrated by our LDChip300 validates this technology for planetary exploration, particularly for the search for life on Mars.     

CCSDS AOS数据保护途径的研究

本文旨在探讨一种适合于贯彻CCSDS AOS建议的我国TDRSS的数据保护途径，内容主要包括实施数据保护层次的选择、实现数据加密业务与加密认证业务的具体方法和进行密钥分配与管理的方法，并分析了数据保护对AOS的影响，提出了对我国TDSS数据安全问题的建议。