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.     

天文学的重大革命

用红外线观测天空,天空则是现了另一番景象,在可见光中看到的朦胧而暗淡的古老星体,在红外光线中射出夺目的光辉;习以为常的星系也显示出不相同的形象;尘埃遮掩的区域发出耀眼的光彩,揭示着星体诞生的地方.天文学家老早就知道红外观测能打开一扇观测宇宙的新窗户.在一定波长—恰好比可见光长3～10倍——尘埃会变成透明状态,这就使研究人员能发现暗藏的星系中心,红外天空图展现出了那     

重新规划机队维修:是猛兽还是包袱?

航空公司要求MRO供应商不仅提供飞机大修业务,还希望获得更为有效的机队维修项目。这一切对于MRO供应商来说,可能需要面临更多的风险,但收益也会增加。     

模拟生命

纵观热带雨林这一地球上最丰富多彩的生态系统,科学家一直在思考,40多亿年来,覆盖我们这个荒芜星球表面的众多化学物质是如何从原始混沌态转化为连贯有序的生化态的.研究化学进化论的学者逐渐倾向于下述观点,即出现史前生命并非是不可能的.使用计算机实验手段,通过模拟原始生命的产生过程,我们可以清楚地看到,化学物质是如何首次搅起古老地表的生物潮,并逐渐发展进化为复杂的生化态,由此产生从微生物直至人类等一系列生命模式.     

全球飞机MRO供应商排名:ST宇航列榜首

根据Overhaul＆Maintenance杂志每两年一次的飞机维修业调查,新加坡科技宇航公司(ST宇航)成为排名第一的全球飞机机体MRO供应商。 尽管经济恢复缓慢和“9·11”恐怖袭击事件对全球民航业带来灾难性的影响,在过去的两年通过采购和合资的方式,ST宇航公司和汉莎技术公司     

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.     

声响:UFO的特征吗(上)

UFO现象多有强光但无声响,带有叮当声和呼啸声的UFO现象当然引发了争论和关注。 不明飞行物的目击报道已经不少了,但目击报道中提到声响的却为数不多,而这正是几年来我致力调查研究的焦点。我之所以把飞行现象和声响现象结合在一起探讨,是因为在70年代我曾经耳闻目睹了这种复合的UFO现象。那次经历启动了我的研究。而广泛的合作和巨大的兴趣使这项研究取得了进展。 那时我居住在加拿大安大略省南部的一个名叫奥尔顿的偏僻山镇中。该镇所在地区当时已有几起UFO目击事件发生。从1975年3月3日开始,我和邻居都看到了一种天空现象:明亮的白光、红光和绿光在夜空中作着难以置信的飞行表演,有几何角度     

MRO市场重现勃勃生机

MRO市场近3年来首次呈现上扬态势,但航空公司持续削减成本使得这种增长要经受考验。本文的预 测数据来自SAI和BACK两家咨询公司     

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。