Interplanetary transfer of photosynthesis: an experimental demonstration of a selective dispersal filter in planetary island biogeography

We launched a cryptoendolithic habitat, made of a gneissic impactite inoculated with Chroococcidiopsis sp., into Earth orbit. After orbiting the Earth for 16 days, the rock entered the Earth's atmosphere and was recovered in Kazakhstan. The heat of entry ablated and heated the rock to a temperature well above the upper temperature limit for life to below the depth at which light levels are insufficient for photosynthetic organisms ( approximately 5 mm), thus killing all of its photosynthetic inhabitants. This experiment shows that atmospheric transit acts as a strong biogeographical dispersal filter to the interplanetary transfer of photosynthesis. Following atmospheric entry we found that a transparent, glassy fusion crust had formed on the outside of the rock. Re-inoculated Chroococcidiopsis grew preferentially under the fusion crust in the relatively unaltered gneiss beneath. Organisms under the fusion grew approximately twice as fast as the organisms on the control rock. Thus, the biologically destructive effects of atmospheric transit can generate entirely novel and improved endolithic habitats for organisms on the destination planetary body that survive the dispersal filter. The experiment advances our understanding of how island biogeography works on the interplanetary scale.     

Biomarker response to galactic cosmic ray-induced NOx and the methane greenhouse effect in the atmosphere of an Earth-like planet orbiting an M dwarf star

Planets orbiting in the habitable zone of M dwarf stars are subject to high levels of galactic cosmic rays (GCRs), which produce nitrogen oxides (NOx) in Earth-like atmospheres. We investigate to what extent these NO(Mx) species may modify biomarker compounds such as ozone (O3) and nitrous oxide (N2O), as well as related compounds such as water (H2O) (essential for life) and methane (CH4) (which has both abiotic and biotic sources). Our model results suggest that such signals are robust, changing in the M star world atmospheric column due to GCR NOx effects by up to 20% compared to an M star run without GCR effects, and can therefore survive at least the effects of GCRs. We have not, however, investigated stellar cosmic rays here. CH4 levels are about 10 times higher on M star worlds than on Earth because of a lowering in hydroxyl (OH) in response to changes in the ultraviolet. The higher levels of CH4 are less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% lower CH4 fluxes compared to those studies. Unlike on Earth, relatively modest changes in these fluxes can lead to larger changes in the concentrations of biomarker and related species on the M star world. We calculate a CH4 greenhouse heating effect of up to 4K. O3 photochemistry in terms of the smog mechanism and the catalytic loss cycles on the M star world differs considerably compared with that of Earth.     

Generalized input-estimation technique for tracking maneuveringtargets

A new input estimation technique for target tracking problem is proposed. Conventional input estimation techniques assume that the target maneuver level is constant within the detection window, which has been the major drawback of the techniques. The proposed technique is developed to overcome this drawback by modeling the target maneuver as a linear combination of some basic time functions. The resulting algorithm has a generalized formulation including earlier works on input estimation. A detection performance of the proposed algorithm is analyzed by investigating the detection sensitivity according to the selection of maneuver models and other design parameters such as the detection window size, measurement noise level, and sampling step size. A computer simulation study shows that the estimation performance of the proposed algorithm is comparable to Bogler's input estimation method while the computation time is greatly reduced     

Comparison of SDINS in-flight alignment using equivalent errormodels

The psi-angle model and the equivalent tilt (ET) model have been widely used for in-flight alignment (IFA) to align and to calibrate a strapdown inertial navigation system (SDINS) on a moving base. However, these models are not effective for a system with large attitude errors because the neglected error terms in the models degrade the performance of a designed filter. In this paper, with an odometer as an external aid, a velocity-aided SDINS is designed for IFA. Equivalent error models applicable to IFA with large attitude errors are derived in terms of rotation vector error and additive and multiplicative quaternion errors. It is found that error models in terms of additive quaternion error (AQE) become linear. Thus the proposed error models reduce unmodeled error terms for a linear filter. From a number of van tests, it is shown that the proposed error models effectively improve the performance of IFA     

Anomalous Cosmic Rays

We review the observed properties of anomalous cosmic rays and the present status of our knowledge of the processes by which they originate. We compiled a comprehensive set of ACR energy spectral data from various spacecraft throughout the heliosphere during the passes of Ulysses over the poles of the Sun and present first results of a detailed modeling effort. In several contributions, we discuss the questions of injection and possible pre-acceleration of pickup ions, summarize new observations on the ionic charge composition, and present new results on the composition of minor ions in ACRs.     

Geoscience for Understanding Habitability in the Solar System and Beyond

Space Science Reviews - This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences. It addresses how interactions between the interior of a planet or...     

乘波构型飞行器磁流体进气道一体化概念设计

采用准一维的磁流体方程组对设计状态下内磁流体发生器进行参数设计,利用斜激波理论设计磁流体进气道一体化的外形.以该外形为基点,对安装五对电极的内磁流体发生器采用五方程模型进行三维数值模拟,并通过调节其磁作用数以满足准一维假设下设计的进气道外形.研究表明,磁流体进气道最小出口流动均匀参数可以作为判别内发生器最优磁作用数的准则,在该磁作用数下内磁流体发生器可以有效地提高进气道的性能.      

高超声速二方程湍流模型的数值模拟对比

对基于Reynolds和Favré(密度加权)混合平均的二方程湍流模型进行了修正,同时根据数值模拟高超声速流动时必须具有高分辨率捕捉间断面与在边界层内抑制数值粘性的能力的要求,提出了新的总变差减小(TVD)格式熵修正函数.在此基础上,通过对压缩拐角的高超声速湍流的数值模拟,对基于Reynolds和Favré混合平均的二方程湍流模型,以及其它不可压缩模型及可压缩性修正模型进行了对比,显示了不同湍流模型及可压缩性修正在计算壁面压力分布和热流分布上的特点,说明了对高超声速压缩拐角型流动,湍流模型可压缩修正的必要性,得到了基于Reynolds和Favré混合平均的二方程湍流模型的计算结果最接近实验结果.      

Experiment on the <Emphasis Type="Italic">Vernov</Emphasis> satellite: Transient energetic processes in the Earth’s atmosphere and magnetosphere. Part II. First results

We present the first experimental results on the observation of optical transients, gamma-ray bursts, relativistic electrons, and electromagnetic waves obtained during the experiment with the RELEC complex of scientific equipment on the Vernov satellite.     

爆轰波-激波迎面作用后的稳定波系

本文为对当量比乙炔氧气混合气体中爆轰波与激波正面对撞产生稳定波系的实验和理论研究.实验主要以高速扫描摄影获取两波对撞的x-t纹影图,一维理论分析则基于三种热完全的组分求解两波对撞的稳定解并探寻它们的规律.实验发现透射波系包括一道激波和爆轰波,以及紧随爆轰波后的稀疏波区,这种波系情况与一维理论分析中CJ解一致.透射CJ爆轰与人射爆轰相比马赫数降低,而相对波前来流的传播速度有轻微提高,但在实验室坐标下其速度显著降低.透射波系受初始压强影响不大;初始温度提高使得爆轰波速度降低,而透射激波速度增加;对波系起实质影响作用的是入射激波强度,激波越强,则整个透射流场呈现偏向激波的趋势;理论分析还指出,稀疏波区的出现不可避免,当激波强度趋于声波时稀疏波区趋于消失,激波越强则疏波区趋于扩大.