根据2010年4月登载在《应用和环境微生物学》Applied and Environmental Microbiology上的研究表示，宇宙飞船上携带的常见细菌很可能会在火星严酷的环境中存活很长一段时间，并在不经意间造成污染。
探寻火星生命是美国国家航空航天局（NASA）火星探测计划和天体生物研究所的长期目标。为了保护火星表面的原始环境，防止其遭到破坏，前往火星的宇宙飞船都要接受消毒处理。
尽管如此，消毒却仅仅是减少了细菌的数量。最近的一项研究显示，各种微生物群在飞船着陆时就留在了火星。航天器的消毒设备只能保证除适应能力极强的细菌外其他都不能存活，这些能够存活的细菌包括不动杆菌、芽孢杆菌、大肠杆菌、葡糖球菌和链球菌。
中佛罗里达大学的研究人员复制了一个同火星相似的环境模型，并模拟了包括干燥、低气压、低温以及紫外线辐射等恶劣环境。在长达一星期的研究中，研究人员发现大肠杆菌是一个潜在污染物，它很有可能在火星存活，但在紫外线辐射下的浅地层尘土中或飞船防紫外线生态龛的阻挡下，它不会在火星表面生长。
“如果确认了微生物能在火星上长期存活的可能性，那么过去和未来的火星探测工作也许会让微生接种物掺杂着地球生物播种在火星上，”研究人员说，“这样一来，一种新的微生物种类多样性就该被研究，以便确定它们在火星长期生存的潜力。”（生物谷Bioon.com）
生物谷推荐原文出处：
Applied and Environmental Microbiology doi:10.1128/AEM.02147-09
Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens
Bonnie J. Berry,1 David G. Jenkins,1 and Andrew C. Schuerger2*
Department of Biology, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816,1 Department of Plant Pathology, University of Florida, Bldg. M6-1025, Space Life Sciences Lab, Kennedy Space Center, Florida 328992
Escherichia coli and Serratia liquefaciens, two bacterial spacecraft contaminants known to replicate under low atmospheric pressures of 2.5 kPa, were tested for growth and survival under simulated Mars conditions. Environmental stresses of high salinity, low temperature, and low pressure were screened alone and in combination for effects on bacterial survival and replication, and then cells were tested in Mars analog soils under simulated Mars conditions. Survival and replication of E. coli and S. liquefaciens cells in liquid medium were evaluated for 7 days under low temperatures (5, 10, 20, or 30°C) with increasing concentrations (0, 5, 10, or 20%) of three salts (MgCl2, MgSO4, NaCl) reported to be present on the surface of Mars. Moderate to high growth rates were observed for E. coli and S. liquefaciens at 30 or 20°C and in solutions with 0 or 5% salts. In contrast, cell densities of both species generally did not increase above initial inoculum levels under the highest salt concentrations (10 and 20%) and the four temperatures tested, with the exception that moderately higher cell densities were observed for both species at 10% MgSO4 maintained at 20 or 30°C. Growth rates of E. coli and S. liquefaciens in low salt concentrations were robust under all pressures (2.5, 10, or 101.3 kPa), exhibiting a general increase of up to 2.5 orders of magnitude above the initial inoculum levels of the assays. Vegetative E. coli cells were maintained in a Mars analog soil for 7 days under simulated Mars conditions that included temperatures between 20 and –50°C for a day/night diurnal period, UVC irradiation (200 to 280 nm) at 3.6 W m–2 for daytime operations (8 h), pressures held at a constant 0.71 kPa, and a gas composition that included the top five gases found in the martian atmosphere. Cell densities of E. coli failed to increase under simulated Mars conditions, and survival was reduced 1 to 2 orders of magnitude by the interactive effects of desiccation, UV irradiation, high salinity, and low pressure (in decreasing order of importance). Results suggest that E. coli may be able to survive, but not grow, in surficial soils on Mars.
