Influence of the gravitational vertical on geometric visual illusions

The occurrence of geometric orientation illusions and the perception of ambiguous figures were analyzed in 24 subjects during static body tilt relative to gravity on Earth. Results showed that illusions such as the Rock's diamond/square, the Ponzo illusion, and orientation contrast illusions occurred less frequently, and that depth reversal of ambiguous figures took more time when subjects were lying on their side or supine compared to upright, thus suggesting that the gravitational reference plays a significant role in these “visual” illusions. The structure of images, our representation of the environment, and orientation relative to gravity are all integral parts in interpreting visual images. In a weightless environment where no gravitational reference can be used, it is expected that similar alterations in visual perception will occur.     

COSAC onboard Rosetta: a bioastronomy experiment for the short-period comet 67P/Churyumov-Gerasimenko

The COSAC (Cometary Sampling and Composition Experiment) onboard the Rosetta mission is a combined gas chromatograph (GC)-mass spectrometer (MS). It is situated on Philae, the lander of the mission, which is intended to land on the nucleus of comet 67P/Churyumov- Gerasimenko. The purpose of the experiment is to analyze the volatile fraction of soil samples retrieved by a drill. For investigation, the samples will be pyrolysed, and the emanating gases fed into a GC, into an MS, or the combination of both. In the first part of this paper, the bioastronomical relevance of such measurements is outlined. In the second part the details of the hardware and its performance are described.     

Magnetic Field Fluctuations in the Solar Wind, Foreshock and Magnetosheath： Cluster Data Analysis

46 magnetosheath crossing events from the two years (2001.2-2003.1) of Cluster magnetic field measurements are identified and used to investigate the characters of the magnetic field fluctuations in the regions of undisturbed solar wind, foreshock, magnetosheath. The preliminary results indicate the properties of the plasma turbulence in the magnetosheath are strongly controlled by IMF orientation with respect to the bow shock normal. The amplitude of the magnetic field magnitude and direction variations behind quasi-parallel bow shock are larger than those behind quasi-perpendicular bow shock. Almost purely compressional waves are found in quasi-perpendicular magnetosheath.     

Survival of Bacillus pumilus spores for a prolonged period of time in real space conditions

To prevent forward contamination and maintain the scientific integrity of future life-detection missions, it is important to characterize and attempt to eliminate terrestrial microorganisms associated with exploratory spacecraft and landing vehicles. Among the organisms isolated from spacecraft-associated surfaces, spores of Bacillus pumilus SAFR-032 exhibited unusually high resistance to decontamination techniques such as UV radiation and peroxide treatment. Subsequently, B. pumilus SAFR-032 was flown to the International Space Station (ISS) and exposed to a variety of space conditions via the European Technology Exposure Facility (EuTEF). After 18 months of exposure in the EXPOSE facility of the European Space Agency (ESA) on EuTEF under dark space conditions, SAFR-032 spores showed 10-40% survivability, whereas a survival rate of 85-100% was observed when these spores were kept aboard the ISS under dark simulated martian atmospheric conditions. In contrast, when UV (>110?nm) was applied on SAFR-032 spores for the same time period and under the same conditions used in EXPOSE, a ～7-log reduction in viability was observed. A parallel experiment was conducted on Earth with identical samples under simulated space conditions. Spores exposed to ground simulations showed less of a reduction in viability when compared with the "real space" exposed spores (～3-log reduction in viability for "UV-Mars," and ～4-log reduction in viability for "UV-Space"). A comparative proteomics analysis indicated that proteins conferring resistant traits (superoxide dismutase) were present in higher concentration in space-exposed spores when compared to controls. Also, the first-generation cells and spores derived from space-exposed samples exhibited elevated UVC resistance when compared with their ground control counterparts. The data generated are important for calculating the probability and mechanisms of microbial survival in space conditions and assessing microbial contaminants as risks for forward contamination and in situ life detection.     

Microbial stowaways: inimitable survivors or hopeless pioneers?

Abstract The resiliency of prokaryotic life has provided colonization across the globe and in the recesses of Earth's most extreme environments. Horizontal gene transfer provides access to a global bank of genetic resources that creates diversity and allows real-time adaptive potential to the clonal prokaryotic world. We assess the likelihood that this Earth-based strategy could provide survival and adaptive potential, in the case of microbial stowaways off Earth. Key Words: Bacillus-Horizontal gene transfer-Bacteria-Earth Mars-Evolution. Astrobiology 12, 710-715.     

径向导叶内流动分离特性的试验研究和控制

采用接触式探针和粒子图象测速技术(PIV)对导叶式离心泵径向导叶内流场的流动特性进行了研究。基于圆柱形微型三孔探针测试结果对5种流量下导叶的压力恢复能力进行了评估,测孔位置覆盖了导叶进出口截面和主线截面。压力恢复系数的理论值和试验值表明当流量大于导叶设计流量时导叶内产生了较大的静压损失。2C/2D PIV 可视化试验的研究结果表明大流量下导叶叶片压力面发生了流动分离。设计了不同参数组合的涡流发生器来对流动分离现象进行控制,试验研究了6种方案对模型泵大流量工况下性能的影响,获得一组最佳方案,并分析了采用该方案后导叶内的流动特性。     

Preservation of martian organic and environmental records: final report of the Mars biosignature working group

The Mars Science Laboratory (MSL) has an instrument package capable of making measurements of past and present environmental conditions. The data generated may tell us if Mars is, or ever was, able to support life. However, the knowledge of Mars' past history and the geological processes most likely to preserve a record of that history remain sparse and, in some instances, ambiguous. Physical, chemical, and geological processes relevant to biosignature preservation on Earth, especially under conditions early in its history when microbial life predominated, are also imperfectly known. Here, we present the report of a working group chartered by the Co-Chairs of NASA's MSL Project Science Group, John P. Grotzinger and Michael A. Meyer, to review and evaluate potential for biosignature formation and preservation on Mars. Orbital images confirm that layered rocks achieved kilometer-scale thicknesses in some regions of ancient Mars. Clearly, interplays of sedimentation and erosional processes govern present-day exposures, and our understanding of these processes is incomplete. MSL can document and evaluate patterns of stratigraphic development as well as the sources of layered materials and their subsequent diagenesis. It can also document other potential biosignature repositories such as hydrothermal environments. These capabilities offer an unprecedented opportunity to decipher key aspects of the environmental evolution of Mars' early surface and aspects of the diagenetic processes that have operated since that time. Considering the MSL instrument payload package, we identified the following classes of biosignatures as within the MSL detection window: organism morphologies (cells, body fossils, casts), biofabrics (including microbial mats), diagnostic organic molecules, isotopic signatures, evidence of biomineralization and bioalteration, spatial patterns in chemistry, and biogenic gases. Of these, biogenic organic molecules and biogenic atmospheric gases are considered the most definitive and most readily detectable by MSL.     

Thyrotropin receptor and membrane interactions in FRTL-5 thyroid cell strain in microgravity

The aim of this work was to analyze the possible alteration of thyrotropin (TSH) receptors in microgravity, which could explain the absence of thyroid cell proliferation in the space environment. Several forms of the TSH receptor are localized on the plasma membrane associated with caveolae and lipid rafts. The TSH regulates the fluidity of the cell membrane and the presence of its receptors in microdomains that are rich in sphingomyelin and cholesterol. TSH also stimulates cyclic adenosine monophosphate (cAMP) accumulation and cell proliferation. Reported here are the results of an experiment in which the FRTL-5 thyroid cell line was exposed to microgravity during the Texus-44 mission (launched February 7, 2008, from Kiruna, Sweden). When the parabolic flight brought the sounding rocket to an altitude of 264?km, the culture media were injected with or without TSH in the different samples, and weightlessness prevailed on board for 6 minutes and 19 seconds. Control experiments were performed, in parallel, in an onboard 1g centrifuge and on the ground in Kiruna laboratory. Cell morphology and function were analyzed. Results show that in microgravity conditions the cells do not respond to TSH treatment and present an irregular shape with condensed chromatin, a modification of the cell membrane with shedding of the TSH receptor in the culture medium, and an increase of sphingomyelin-synthase and Bax proteins. It is possible that real microgravity induces a rearrangement of specific sections of the cell membrane, which act as platforms for molecular receptors, thus influencing thyroid cell function in astronauts during space missions.     

Preservation of microbial lipids in geothermal sinters

Lipid biomarkers are widely used to study the earliest life on Earth and have been invoked as potential astrobiological markers, but few studies have assessed their survival and persistence in geothermal settings. Here, we investigate lipid preservation in active and inactive geothermal silica sinters, with ages of up to 900 years, from Champagne Pool, Waiotapu, New Zealand. Analyses revealed a wide range of bacterial biomarkers, including free and bound fatty acids, 1,2-di-O-alkylglycerols (diethers), and various hopanoids. Dominant archaeal lipids include archaeol and glycerol dialkyl glycerol tetraethers (GDGTs). The predominance of generally similar biomarker groups in all sinters suggests a stable microbial community throughout Champagne Pool's history and indicates that incorporated lipids can be well preserved. Moreover, subtle differences in lipid distributions suggest that past changes in environmental conditions can be elucidated. In this case, higher archaeol abundances relative to the bacterial diethers, a greater proportion of cyclic GDGTs, the high average chain length of the bacterial diethers, and greater concentrations of hopanoic acids in the older sinters all suggest hotter conditions at Champagne Pool in the past.