Answering the question of whether life ever existed on Mars is a key goal of both NASA's and ESA's imminent Mars rover missions. The obfuscatory effects of oxidizing salts, such as perchlorates and sulfates, on organic matter during thermal decomposition analysis techniques are well established. Less well studied are the transformative effects of iron oxides and (oxy)hydroxides, which are present in great abundances in the martian regolith. We examined the products of flash pyrolysis–gas chromatography–mass spectrometry (a technique analogous to the thermal techniques employed by past, current, and future landed Mars missions) which form when the cyanobacteria Arthrospira platensis are heated in the presence of a variety of Mars-relevant iron-bearing minerals. We found that iron oxides/(oxy)hydroxides have transformative effects on the pyrolytic products of cyanobacterial biomolecules. Both the abundance and variety of molecular species detected were decreased as iron substrates transformed biomolecules, by both oxidative and reductive processes, into lower fidelity alkanes, aromatic and aryl-bonded hydrocarbons. Despite the loss of fidelity, a suite that contains mid-length alkanes and polyaromatic hydrocarbons and/or aryl-bonded molecules in iron-rich samples subjected to pyrolysis may allude to the transformation of cyanobacterially derived mid-long chain length fatty acids (particularly unsaturated fatty acids) originally present in the sample. Hematite was found to be the iron oxide with the lowest transformation potential, and because this iron oxide has a high affinity for codeposition of organic matter and preservation over geological timescales, sampling at Mars should target sediments/strata that have undergone a diagenetic history encouraging the dehydration, dihydroxylation, and oxidation of more reactive iron-bearing phases to hematite by looking for (mineralogical) evidence of the activity of oxidizing, acidic/neutral, and either hot or long-lived fluids.

中文翻译：

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闪蒸热解过程中氧化铁对蓝藻生物分子的转化：对火星生命探测任务的影响

回答火星上是否曾经存在生命的问题是 NASA 和 ESA 即将进行的火星漫游者任务的关键目标。在热分解分析技术过程中，氧化盐（如高氯酸盐和硫酸盐）对有机物的混淆作用已得到充分证实。研究较少的是氧化铁和（氧）氢氧化物的转化作用，它们在火星风化层中大量存在。我们研究了快速热解-气相色谱-质谱（一种类似于过去、现在和未来登陆火星任务所采用的热技术的技术）的产物，这些产物是在蓝藻节旋藻在各种与火星相关的含铁矿物存在的情况下加热。我们发现氧化铁/（氧）氢氧化物对蓝藻生物分子的热解产物具有转化作用。由于铁底物通过氧化和还原过程将生物分子转化为保真度较低的烷烃、芳香烃和芳基键合烃，因此检测到的分子种类的丰度和多样性都降低了。尽管失去了保真度，但在经过热解的富含铁的样品中包含中长链烷烃和多环芳烃和/或芳基键合分子的套件可能暗示蓝藻衍生的中长链脂肪酸（特别是不饱和脂肪酸）的转化。脂肪酸）最初存在于样品中。