根據(jù)2010年4月登載在《應用和環(huán)境微生物學》Applied and Environmental Microbiology上的研究表示，宇宙飛船上攜帶的常見細菌很可能會在火星嚴酷的環(huán)境中存活很長一段時間,，并在不經(jīng)意間造成污染。
探尋火星生命是美國國家航空航天局（NASA）火星探測計劃和天體生物研究所的長期目標,。為了保護火星表面的原始環(huán)境,，防止其遭到破壞，前往火星的宇宙飛船都要接受消毒處理,。
盡管如此，消毒卻僅僅是減少了細菌的數(shù)量,。最近的一項研究顯示,，各種微生物群在飛船著陸時就留在了火星。航天器的消毒設備只能保證除適應能力極強的細菌外其他都不能存活,，這些能夠存活的細菌包括不動桿菌,、芽孢桿菌、大腸桿菌,、葡糖球菌和鏈球菌,。
中佛羅里達大學的研究人員復制了一個同火星相似的環(huán)境模型，并模擬了包括干燥,、低氣壓,、低溫以及紫外線輻射等惡劣環(huán)境。在長達一星期的研究中,，研究人員發(fā)現(xiàn)大腸桿菌是一個潛在污染物,，它很有可能在火星存活，但在紫外線輻射下的淺地層塵土中或飛船防紫外線生態(tài)龕的阻擋下,，它不會在火星表面生長,。
“如果確認了微生物能在火星上長期存活的可能性，那么過去和未來的火星探測工作也許會讓微生接種物摻雜著地球生物播種在火星上，”研究人員說,，“這樣一來,，一種新的微生物種類多樣性就該被研究，以便確定它們在火星長期生存的潛力,。”（生物谷Bioon.com）
生物谷推薦原文出處：
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.
