Department of Plant Pathology, University of Florida , Space Life Sciences Lab, Kennedy Space Center, USA.
Astrobiology. 2011 Jun;11(5):477-85. doi: 10.1089/ast.2011.0615.
Endospores of Bacillus subtilis HA101 were applied to a simulated Mars Exploration Rover (MER) wheel and exposed to Mars-normal UV irradiation for 1, 3, or 6 h. The experiment was designed to simulate a contaminated rover wheel sitting on its landing platform before rolling off onto the martian terrain, as was encountered during the Spirit and Opportunity missions. When exposed to 1 h of Mars UV, a reduction of 81% of viable endospores was observed compared to the non-UV irradiated controls. When exposed for 3 or 6 h, reductions of 94.6% and 96.6%, respectively, were observed compared to controls. In a second experiment, the contaminated rover wheel was rolled over a bed of heat-sterilized Mars analog soil; then the analog soil was exposed to full martian conditions of UV irradiation, low pressure (6.9 mbar), low temperature (-10°C), and an anaerobic CO(2) martian atmosphere for 24 h to determine whether endospores of B. subtilis on the contaminated rover wheel could be transferred to the surface of the analog soil and survive martian conditions. The experiment simulated conditions in which a rover wheel might come into contact with martian regolith immediately after landing, such as is designed for the upcoming Mars Science Laboratory (MSL) rover. The contaminated rover wheel transferred viable endospores of B. subtilis to the Mars analog soil, as demonstrated by 31.7% of samples showing positive growth. However, when contaminated soil samples were exposed to full martian conditions for 24 h, only 16.7% of samples exhibited positive growth-a 50% reduction in the number of soil samples positive for the transferred viable endospores.
枯草芽孢杆菌 HA101 的芽孢被应用于模拟的火星探测车（MER）车轮上，并暴露于火星正常的紫外线下 1、3 或 6 小时。该实验旨在模拟污染的探测车轮停放在其着陆平台上，然后滚落到火星地形上的情况，这种情况在“勇气号”和“机遇号”任务中遇到过。当暴露于 1 小时的火星紫外线时，与未经过紫外线照射的对照相比，可存活芽孢的数量减少了 81%。当暴露 3 或 6 小时时，与对照相比，分别减少了 94.6%和 96.6%。在第二个实验中，污染的探测车轮在经过加热消毒的火星模拟土壤床上滚动；然后将模拟土壤暴露于完整的火星紫外线照射、低压（6.9 毫巴）、低温（-10°C）和无氧 CO2 火星大气条件下 24 小时，以确定枯草芽孢杆菌的芽孢是否可以从污染的探测车轮转移到模拟土壤表面并在火星条件下存活。该实验模拟了探测车轮在着陆后可能立即与火星风化层接触的情况，例如为即将到来的火星科学实验室（MSL）探测车设计的情况。污染的探测车轮将枯草芽孢杆菌的可存活芽孢转移到火星模拟土壤中，31.7%的样本显示出阳性生长证明了这一点。然而，当污染土壤样本暴露于完整的火星条件下 24 小时时，只有 16.7%的样本显示出阳性生长，转移的可存活芽孢的土壤样本阳性数量减少了 50%。
