Bacterial growth at the high concentrations of magnesium sulfate found in martian soils

The martian surface environment exhibits extremes of salinity, temperature, desiccation, and radiation that would make it difficult for terrestrial microbes to survive. Recent evidence suggests that martian soils contain high concentrations of MgSO? minerals. Through warming of the soils, meltwater derived from subterranean ice-rich regolith may exist for an extended period of time and thus allow the propagation of terrestrial microbes and create significant bioburden at the near surface of Mars. The current report demonstrates that halotolerant bacteria from the Great Salt Plains (GSP) of Oklahoma are capable of growing at high concentrations of MgSO? in the form of 2 M solutions of epsomite. The epsotolerance of isolates in the GSP bacterial collection was determined, with 35% growing at 2 M MgSO?. There was a complex physiological response to mixtures of MgSO? and NaCl coupled with other environmental stressors. Growth also was measured at 1 M concentrations of other magnesium and sulfate salts. The complex responses may be partially explained by the pattern of chaotropicity observed for high-salt solutions as measured by agar gelation temperature. Select isolates could grow at the high salt concentrations and low temperatures found on Mars. Survival during repetitive freeze-thaw or drying-rewetting cycles was used as other measures of potential success on the martian surface. Our results indicate that terrestrial microbes might survive under the high-salt, low-temperature, anaerobic conditions on Mars and present significant potential for forward contamination. Stringent planetary protection requirements are needed for future life-detection missions to Mars.     

英国防部发起新型航空母舰的竞争

日前，英国国防部向全球航空航天制造商发起了价值244亿美元、为英国海军制造两艘航空母舰的竞标活动。有6家公司参与了竞标，它们是波音、英国宇航防御系统、洛克希德、马丁、马可尼电子系统、雷神和汤姆逊一CSF公司。这6家公司都具有较强的海军系统综合能力。但英国政府坚持，新型航空母舰必须在英国制造。计划的第一阶段是在今年秋季选出3家承包商进行初步研究，台问价值830万美元。然后再从中选出两家公司进行减少风险的研究，台同价值3300万美元。最终承包商的确定预计将在2001年，第一艘航空母舰计划于2012年投入使用。该项目由国防…