Department of Physics and Astronomy, University College London, Gower Street, London, UK.
Department of Astronomy, Yale University, New Haven, Connecticut, USA.
Astrobiology. 2022 Sep;22(9):1029-1031. doi: 10.1089/ast.2021.0143. Epub 2022 Aug 8.
In original experiments, Bak (Wind-Driven Saltation: An Overlooked Challenge for Life on Mars. 2019;19(4):497-505) suggest a new mechanism for the destruction of spores on Mars: abrasion by wind-driven saltation. Bak found that the tumbling of spores on grain surfaces (simulating saltation) was, by far, most lethal at the outset of their experiments. They suggest that it may be sharp edges of the freshly crushed basalt particles used in their experiments that destroy the spores and that these edges abrade away over the course of each experiment. But prior Mars analogue experiments, observations of particles from terrestrial deserts, and imaging from Mars landers suggest that most martian dust has been rounded by billions of years of aeolian processes. If so, saltation on Mars is more likely well simulated by the later stages of the Bak experiments, reducing implied lethality by orders of magnitude. Experiments could test this by beginning with particles that had been already abraded. Even assuming the highest lethality found in their experiments, saltation "hop" distances on Mars suggest that abrasion would not prevent ∼1% of released spores from remaining viable while traveling hundreds or even thousands of kilometers.
在最初的实验中，Bak （Wind-Driven Saltation: An Overlooked Challenge for Life on Mars. 2019;19(4):497-505）提出了一种新的机制来解释火星上孢子的破坏：风驱动的跳跃侵蚀。Bak 发现孢子在谷物表面翻滚（模拟跳跃）时，在实验开始时的杀伤力最大。他们认为，可能是实验中使用的新鲜碎玄武岩颗粒的尖锐边缘破坏了孢子，并且这些边缘在每次实验过程中都会逐渐磨损。但是，先前的火星模拟实验、对来自地球沙漠的颗粒的观察以及火星着陆器的成像表明，大多数火星尘埃已经在数十亿年的风成过程中被磨圆。如果是这样，那么火星上的跳跃更有可能是通过 Bak 实验的后期阶段来很好地模拟，将隐含的杀伤力降低几个数量级。实验可以通过从已经磨损的颗粒开始来测试这一点。即使假设在实验中发现的最高杀伤力，火星上的跳跃“跳跃”距离表明，在数百甚至数千公里的行程中，磨损不会阻止释放的孢子中约 1%的孢子保持存活。
