SOLID3: a multiplex antibody microarray-based optical sensor instrument for in situ life detection in planetary exploration

The search for unequivocal signs of life on other planetary bodies is one of the major challenges for astrobiology. The failure to detect organic molecules on the surface of Mars by measuring volatile compounds after sample heating, together with the new knowledge of martian soil chemistry, has prompted the astrobiological community to develop new methods and technologies. Based on protein microarray technology, we have designed and built a series of instruments called SOLID (for "Signs Of LIfe Detector") for automatic in situ detection and identification of substances or analytes from liquid and solid samples (soil, sediments, or powder). Here, we present the SOLID3 instrument, which is able to perform both sandwich and competitive immunoassays and consists of two separate functional units: a Sample Preparation Unit (SPU) for 10 different extractions by ultrasonication and a Sample Analysis Unit (SAU) for fluorescent immunoassays. The SAU consists of five different flow cells, with an antibody microarray in each one (2000 spots). It is also equipped with an exclusive optical package and a charge-coupled device (CCD) for fluorescent detection. We demonstrated the performance of SOLID3 in the detection of a broad range of molecular-sized compounds, which range from peptides and proteins to whole cells and spores, with sensitivities at 1-2?ppb (ng?mL?1) for biomolecules and 10? to 103 spores per milliliter. We report its application in the detection of acidophilic microorganisms in the Río Tinto Mars analogue and report the absence of substantial negative effects on the immunoassay in the presence of 50?mM perchlorate (20 times higher than that found at the Phoenix landing site). Our SOLID instrument concept is an excellent option with which to detect biomolecules because it avoids the high-temperature treatments that may destroy organic matter in the presence of martian oxidants.     

Lava cave microbial communities within mats and secondary mineral deposits: implications for life detection on other planets

Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai'i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai'i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai'i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies.     

A two-tiered approach to assessing the habitability of exoplanets

In the next few years, the number of catalogued exoplanets will be counted in the thousands. This will vastly expand the number of potentially habitable worlds and lead to a systematic assessment of their astrobiological potential. Here, we suggest a two-tiered classification scheme of exoplanet habitability. The first tier consists of an Earth Similarity Index (ESI), which allows worlds to be screened with regard to their similarity to Earth, the only known inhabited planet at this time. The ESI is based on data available or potentially available for most exoplanets such as mass, radius, and temperature. For the second tier of the classification scheme we propose a Planetary Habitability Index (PHI) based on the presence of a stable substrate, available energy, appropriate chemistry, and the potential for holding a liquid solvent. The PHI has been designed to minimize the biased search for life as we know it and to take into account life that might exist under more exotic conditions. As such, the PHI requires more detailed knowledge than is available for any exoplanet at this time. However, future missions such as the Terrestrial Planet Finder will collect this information and advance the PHI. Both indices are formulated in a way that enables their values to be updated as technology and our knowledge about habitable planets, moons, and life advances. Applying the proposed metrics to bodies within our Solar System for comparison reveals two planets in the Gliese 581 system, GJ 581 c and d, with an ESI comparable to that of Mars and a PHI between that of Europa and Enceladus.     

祖父航天员的感受

格奥尔吉·格列奇科是一位物理学博士,1931年5月25日生于列宁格勒。1975年1月参加“联盟17”飞船飞行,并与“礼炮4”号空间站对接,飞行29天。1977年12月10日乘“联盟26”号飞船与“礼炮—6”号空间站对接,与同伴尤里·罗曼年科在轨道上度过了96天,打破了当时由美国“天空实验室”4号机组人员创下的84天的飞行记录。1985年9月第二次上天飞行,“联盟T14”号飞船与“礼炮7—联盟T13”联合体对接,飞行8天。这时,他可能是世界上第一位祖父航天员。     

ESA再入探测器的某些空气热动力问题

给出了两种不同的再入飞行器:充气的再入和下滑演示器(IRDT)和Huygens.两者的任务都涉及在靠近轨道的条件下再入并均已于2005年完成.概述了IRDT的使命和具体设计问题,综述了IRDT最近飞行的初步结果和ESTEC估计Huygens受到的辐射通量采用的方法.     

美空军为新的预警卫星计划辩护

美空军为新的预警卫星计划辩护当国会议员提出本世纪结束后会出现导弹预警覆盖空白的担忧时，空军最高层官员在今年３月中进行的国会听证会上为五角大楼新的导弹预警卫星的最新计划辩护。经数个月争论后，国防官员现打算用一种新的称为“警报”（ＡＬＡＲＭ）的系统来取代...     

法国调整军用航天计划

法国调整军用航天计划法国政府于今年４月下旬宣布了６年国防预算计划，它表明法国提出的许多军用航天计划在未能吸引其它欧洲伙伴国家参加的情况下遭到大幅度的削减。导弹预警卫星和窃听卫星的方案已束之高阁，至少要等到法国经济恢复和其它欧洲国家更愿意接受这些方案的...     

空间站紧急财政援助计划遭冷遇

美航宇局在今后４年内还要另支付俄罗斯航天局６６亿美元的计划在国会得到勉强接受。一些美国国会议员都不愿意为保持俄罗斯在国际空间站的作用再提供更多的联邦资金。法律工作者再次提出疑问，美航宇局是否应中止俄罗斯参与的空间站建造工作，特别是目前俄处于严重的经...     

在SA条件下利用GPS的轨道确定和点定位

GPS精度控制(SA)措施降低了GPS标准定位业务(SPS)非差分用户的定位精度。常说的SPS可达精度在正常条件下为100米(2DRMS)。在缺乏更多具体条件下,许多未来的SPS用户在他们的规划中采用了100米这一精度值,但多数情况下,是夸大了实际定位误差。在本文中,我们针对轨道用户星的点定位和动力学轨道确定来研究SA带来的误差。要使SA带来的误差减至最小,非差分用户有几种选择:扩大接收视场;观测尽可能多的GPS卫星;在时间上平滑误差;选用独立计算的GPS精密轨道星历(如NASA和美国测绘局计算的),而不采用广播星历。仿真计算表明,3维点位误差可保持在30米,并且在几小时内能平滑到3米。