The search for signs of life is a major objective in the exploration of Mars. Of particular interest are chemical biosignatures such as biomolecules. However, molecular biosignatures are susceptible to extreme environmental conditions such as heat, ionising radiation and strong oxidants. Therefore, a knowledge of the stability of possible biosignature molecules under present and past conditions on Mars is important, as well as the nature of possible alteration products. In the light of the long volcanically active history of Mars, we have studied the thermal behaviour of selected biological compounds, namely, haemin (an iron porphyrin closely related to the haem prosthetic group), cytochrome c (a small protein) and lecithin (a mixture of phospholipids). Samples were exposed to temperatures up to 900°C under an inert atmosphere of nitrogen, either in neat form or in mineral matrices. The matrix materials used were sodium chloride, gypsum (CaSO4 ⋅ 2H2O), Ca-montmorillonite (STx-1b), the Martian regolith simulant JSC Mars-1A and some mixtures thereof. Key results are: (1) The onset of significant decomposition for haemin, cytochrome c and lecithin occurs around 240°C. At slightly higher temperatures the disappearance of all characteristic infrared spectral bands indicates complete decomposition and loss of the primary biosignatures. (2) Haemin stoichiometrically releases CO2 and HCl during the initial thermal decomposition phase, at the end of which the iron porphyrin core is still intact. High-temperature products of haemin include graphite, α-iron and cementite (Fe3C). (3) Neat lecithin forms long-chain polyphosphates at 500°C, whereas lecithin‒NaCl mixtures form diphosphate (pyrophosphate). As these anions are absent and rare, respectively, in minerals, they may potentially serve as secondary biosignatures. (4) Heating a mixture of NaCl and JSC Mars-1A at 800°C in the presence of lecithin produces the aluminosilicate mineral sodalite (Na8[AlSiO4]6Cl2), which however appears to be of limited use as a secondary biosignature.

寻找生命迹象是探索火星的主要目标。特别感兴趣的是化学生物印记，例如生物分子。然而，分子生物印记易受极端环境条件的影响，例如热、电离辐射和强氧化剂。因此，了解火星当前和过去条件下可能的生物特征分子的稳定性以及可能的改变产物的性质非常重要。鉴于火星长期的火山活动历史，我们研究了选定生物化合物的热行为，即血红素（一种与血红素辅基密切相关的铁卟啉）、细胞色素c（一种小蛋白质）和卵磷脂（磷脂的混合物）。样品在氮气惰性气氛下暴露在高达 900°C 的温度下，无论是纯净形式还是矿物基质。使用的基质材料是氯化钠、石膏 (CaSO 4 ⋅ 2H 2 O)、钙蒙脱石 (STx-1b)、火星风化层模拟物 JSC Mars-1A 及其一些混合物。主要结果是：(1) 血红素、细胞色素c和卵磷脂的显着分解发生在 240°C 左右。在稍高的温度下，所有特征红外光谱带的消失表明主要生物特征完全分解和丢失。(2) 海民按化学计量释放 CO 2和 HCl 在初始热分解阶段，在该阶段铁卟啉核心仍然完好无损。血红素的高温产品有石墨、α-铁和渗碳体（Fe 3 C）。(3) 纯卵磷脂在 500°C 时形成长链聚磷酸盐，而卵磷脂-NaCl 混合物形成二磷酸盐（焦磷酸盐）。由于这些阴离子在矿物质中分别不存在和稀有，因此它们有可能作为次要生物印记。(4) 在卵磷脂存在的情况下，将 NaCl 和 JSC Mars-1A 的混合物在 800°C 下加热会产生铝硅酸盐矿物方钠石（Na 8 [ AlSiO 4 ] 6 Cl 2），但其作为二次方钠石的用途似乎有限生物印记。