类火星永久冻土条件下氨基酸的缓慢辐射分解:在火星上寻找现存生命的应用。

IF 2.6 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS
Astrobiology Pub Date : 2025-09-01 Epub Date: 2025-08-11 DOI:10.1177/15311074251366249
Alexander A Pavlov, Hannah L McLain, Kendra K Farnsworth, Daniel P Glavin, Jamie E Elsila, Jason P Dworkin, Zhidan Zhang, Christopher H House
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引用次数: 0

摘要

未来致力于寻找火星上现存生命的任务将需要清楚地了解浅层冰层下有机生物特征的降解过程。银河和太阳宇宙射线不断轰击火星表面,随着时间的推移,有机生物分子会发生转化和降解,最终摧毁生命存在的化学证据。我们进行了辐射分解实验,将水冰和硅酸盐基质中的单个氨基酸以及水冰中死亡的大肠杆菌微生物中的氨基酸暴露于伽马辐射中,作为火星表面宇宙射线暴露的代理。测定了氨基酸的辐射降解速率。我们发现,火星表面冰中的氨基酸在宇宙射线照射下可以存活5000万年以上,这远远超过了火星表面冰沉积物的预期年龄。从死亡的大肠杆菌有机物中提取的氨基酸在水冰中和分离的纯氨基酸溶解在水冰中的降解速率相似。我们发现,随着冰温的升高,非生物和生物氨基酸的辐射降解率均有所增加。蒙脱石对氨基酸的伽马辐射没有额外的保护作用。根据我们的实验,有纯冰或以冰为主的永久冻土的地点将是寻找火星上最近沉积的氨基酸的最佳地点,因此,应该被视为未来火星任务寻找现存生命的目标采样地点。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Slow Radiolysis of Amino Acids in Mars-Like Permafrost Conditions: Applications to the Search for Extant Life on Mars.

Future missions dedicated to the search for extant life on Mars will require a clear understanding of the organic biosignature degradation processes in the shallow icy subsurface. Galactic and solar cosmic rays constantly bombard the martian surface and transform and degrade organic biomolecules over time, eventually destroying chemical evidence of life. We conducted radiolysis experiments by exposing individual amino acids in H2O-ice and silicate matrices and amino acids from dead Escherichia coli microorganisms in H2O-ice to gamma radiation as a proxy for cosmic ray exposure on the martian surface. The rates of amino acid radiolytic degradation were determined. We found that amino acids in the surface ice on Mars would survive over 50 million years of cosmic ray exposure, which is far greater than the expected age of the current surface ice deposits on Mars. Amino acids from dead E. coli organic matter in H2O-ice and isolated pure amino acids dissolved in H2O-ice tend to degrade at similar rates. We found that amino acid radiolytic degradation rates increased with increasing ice temperature in both abiotic and biological amino acids. Montmorillonite did not provide additional protection against gamma radiation to amino acids. Based on our experiments, locations with pure ice or ice-dominated permafrost would be the best places to look for recently deposited amino acids on Mars and, thus, should be considered as a target sampling location for future Mars missions searching for extant life.

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来源期刊
Astrobiology
Astrobiology 生物-地球科学综合
CiteScore
7.70
自引率
11.90%
发文量
100
审稿时长
3 months
期刊介绍: Astrobiology is the most-cited peer-reviewed journal dedicated to the understanding of life''s origin, evolution, and distribution in the universe, with a focus on new findings and discoveries from interplanetary exploration and laboratory research. Astrobiology coverage includes: Astrophysics; Astropaleontology; Astroplanets; Bioastronomy; Cosmochemistry; Ecogenomics; Exobiology; Extremophiles; Geomicrobiology; Gravitational biology; Life detection technology; Meteoritics; Planetary geoscience; Planetary protection; Prebiotic chemistry; Space exploration technology; Terraforming
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