Astrobiology:实验证实细菌可在行星间传递

一些科学家相信，微生物（如图）能够在行星之间传递——当一颗陨星与另一颗天体碰撞后，前者爆炸所产生的岩石碎片最后会落到后者的表面。

据美国《科学》杂志在线报道，如今，一个国际研究小组在原则上证实了这一假设——这些“天外来客”能够在碰撞过程中幸免于难。科学家用炸药轰击包含有微生物的地球岩石，旨在模拟陨星在空中爆炸时的景象。结果表明，尽管一些细菌因此死掉，但仍有一些细菌活了下来。研究人员在2月份出版的《天体生物学》（Astrobiology）杂志上报告了这一发现。（来源：科学时报群芳）

生物谷推荐原始出处：

（Astrobiology），doi:10.1089/ast.2007.0134，Gerda Horneck, Natalia A. Artemieva

Microbial Rock Inhabitants Survive Hypervelocity Impacts on Mars-Like Host Planets: First Phase of Lithopanspermia Experimentally Tested

Gerda Horneck, Dieter Stoffler, Sieglinde Ott, Ulrich Hornemann, Charles S. Cockell, Ralf Moeller, Cornelia Meyer, Jean-Pierre de Vera, Jorg Fritz, Sara Schade, Natalia A. Artemieva.

ABSTRACT

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. Astrobiology 8, 17–44.