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1.
Elements usually considered volatile are key constituents (C, N, O) of the pre-solar grains identified in primitive meteorites
and/or key diagnostic elements (noble gases). Their isotopic compositions generally are unlike anything seen in matter of
solar-system origin. The large variations are indicative of the various stellar sources and various processes of nucleosynthesis
by which they were created.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
J-P de Vera G Horneck P Rettberg S Ott 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(8):1236-1243
Complementary to the already well-studied microorganisms, lichens, symbiotic organisms of the mycobiont (fungi) and the photobiont (algae), were used as "model systems" in which to examine the ecological potential to resist to extreme environments of outer space. Ascospores (sexual propagules of the mycobiont) of the lichens Fulgensia bracteata, Xanthoria elegans and Xanthoria parietina were exposed to selected space-simulating conditions (up to 16 h of space vacuum at 10(-3) Pa and UV radiation at 160 nm < or = lambda < or = 400 nm), while embedded in the lichen fruiting bodies. After exposure, the ascospores were discharged and their viability was tested as germination capacity on different culture media including those containing Mars regolith simulant. It was found that (i) the germination rate on media containing Mars regolith simulant was as high as on other mineral-containing media, (ii) if enclosed in the ascocarps, the ascospores survived the vacuum exposure, the UV-irradiation as well as the combined treatment of vacuum and UV to a high degree. In general, 50 % or more viable spores were recovered, with ascospores of X. elegans showing the highest survival. It is suggested that ascospores inside the ascocarps are well protected by the anatomical structure, the gelatinous layer and the pigments (parietin and carotene) against the space parameters tested. 相似文献
3.
两台F136原型机近日达到静态试验的里程碑,这是GE和罗-罗公司为期10年的F-35联合攻击战斗机(JSF)备用发动机开发计划的一部分。GE/罗—罗战斗机发动机小组刚刚在邻近辛辛那提市的GE交通运输部门的高空试验台完成了舰载型和常规起降型F-35的F136所必需的试验。前不久还完成了追加的最终功率校准工程试验。 相似文献
4.
Onofri S de la Torre R de Vera JP Ott S Zucconi L Selbmann L Scalzi G Venkateswaran KJ Rabbow E Sánchez Iñigo FJ Horneck G 《Astrobiology》2012,12(5):508-516
Cryptoendolithic microbial communities and epilithic lichens have been considered as appropriate candidates for the scenario of lithopanspermia, which proposes a natural interplanetary exchange of organisms by means of rocks that have been impact ejected from their planet of origin. So far, the hardiness of these terrestrial organisms in the severe and hostile conditions of space has not been tested over extended periods of time. A first long-term (1.5 years) exposure experiment in space was performed with a variety of rock-colonizing eukaryotic organisms at the International Space Station on board the European EXPOSE-E facility. Organisms were selected that are especially adapted to cope with the environmental extremes of their natural habitats. It was found that some-but not all-of those most robust microbial communities from extremely hostile regions on Earth are also partially resistant to the even more hostile environment of outer space, including high vacuum, temperature fluctuation, the full spectrum of extraterrestrial solar electromagnetic radiation, and cosmic ionizing radiation. Although the reported experimental period of 1.5 years in space is not comparable with the time spans of thousands or millions of years believed to be required for lithopanspermia, our data provide first evidence of the differential hardiness of cryptoendolithic communities in space. 相似文献
5.
Ulrich Ott 《Space Science Reviews》1991,56(1-2):23-29
Data on the composition of the Martian atmosphere obtained by instruments aboard the Viking spacecraft are not of sufficient accuracy to address important questions regarding the composition and history of Mars. Laboratory analyses of gases trapped in glassy phases of shergottite meteorite EETA 79001 yield precise data, but it remains to be ascertained that these gases constitute unfractionated Martian atmosphere. Return from Mars of a gas sample for laboratory analysis appears preferable to another in situ measurement, especially if rocks of documented origin will become available for gas analysis as well. 相似文献
6.
基于性能的后勤保障(PBL)是美国国防部提出并大力推广的装备保障新理念.它强调将保障作为一个综合的、可承受的性能包来购买,以便优化系统的战备完好性.经过多年的推广,PBL在使用中取得了较好的效果. 相似文献
7.
Kallenbach R. Robert F. Geiss J. Herbst E. Lammer H. Marty B. Millar T.J. Ott U. Pepin R.O. 《Space Science Reviews》2003,106(1-4):319-376
Volatile isotope abundances are tracers for the evolutionary processes of the solar system. At the same time they carry information
on the galactic nucleosynthetic sources, from which solar matter originates. This working group report summarizes the present
knowledge and addresses unresolved issues regarding fractionation of isotopes of volatile elements in the solar system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Ulrich Ott 《Space Science Reviews》2007,130(1-4):87-95
Small amounts of pre-solar “stardust” grains have survived in the matrices of primitive meteorites and interplanetary dust
particles. These grains—formed directly in the outflows of or from the ejecta of stars—include thermally and chemically refractory
carbon materials such as diamond, graphite and silicon carbide; as well as refractory oxides and nitrides. Pre-solar silicates,
which have only recently been identified, are the most abundant type except for possibly diamond. The detailed study with
modern analytical tools, of isotopic signatures in particular, provides highly accurate and detailed information with regard
to stellar nucleosynthesis and grain formation in stellar atmospheres. Important stellar sources are Red Giant (RG) and Asymptotic
Giant Branch (AGB) stars, with supernova contributions apparently small. The survival of those grains puts constraints on
conditions they were exposed to in the interstellar medium and in the early solar system. 相似文献
9.
Space Science Reviews - 相似文献
10.
Microbial rock inhabitants survive hypervelocity impacts on Mars-like host planets: first phase of lithopanspermia experimentally tested 总被引:3,自引:0,他引:3
Horneck G Stöffler D Ott S Hornemann U Cockell CS Moeller R Meyer C de Vera JP Fritz J Schade S Artemieva NA 《Astrobiology》2008,8(1):17-44
The scenario of lithopanspermia describes the viable transport of microorganisms via meteorites. To test the first step of lithopanspermia, i.e., the impact ejection from a planet, systematic shock recovery experiments within a pressure range observed in martian meteorites (5-50 GPa) were performed with dry layers of microorganisms (spores of Bacillus subtilis, cells of the endolithic cyanobacterium Chroococcidiopsis, and thalli and ascocarps of the lichen Xanthoria elegans) sandwiched between gabbro discs (martian analogue rock). Actual shock pressures were determined by refractive index measurements and Raman spectroscopy, and shock temperature profiles were calculated. Pressure-effect curves were constructed for survival of B. subtilis spores and Chroococcidiopsis cells from the number of colony-forming units, and for vitality of the photobiont and mycobiont of Xanthoria elegans from confocal laser scanning microscopy after live/dead staining (FUN-I). A vital launch window for the transport of rock-colonizing microorganisms from a Mars-like planet was inferred, which encompasses shock pressures in the range of 5 to about 40 GPa for the bacterial endospores and the lichens, and a more limited shock pressure range for the cyanobacterium (from 5-10 GPa). The results support concepts of viable impact ejections from Mars-like planets and the possibility of reseeding early Earth after asteroid cataclysms. 相似文献