A series of laboratory experiments was carried out in order to generate a diagnostic spectrum for polycyclic aromatic hydrocarbons (PAHs) of astrobiological interest in the context of the Martian South Polar Residual Cap (SPRC), to establish PAH spectral features more easily detectable in CO₂ ice (mixed with small amounts of H₂O ice) than the previously reported absorption feature at 3.29 µm in order to constrain their detectability limit. There is currently no existing literature on PAH detection within SPRC features, making this work novel and impactful given the recent discovery of a possible subglacial lake beneath the Martian South Pole. Although they have been detected in Martian meteorites, PAHs have not been detected yet on Mars, possibly due to the deleterious effects of ultraviolet radiation on the surface of the planet. SPRC features may provide protection to fragile molecules, and this work seeks to provide laboratory data to improve interpretation of orbital remote sensing spectroscopic imaging data. We also ascertain the effect of CO₂ ice sublimation on organic spectra, as well as provide PAH reference spectra in mixtures relevant to Mars. A detectability limit of ∼0.04% has been recorded for observing PAHs in CO₂ ice using laboratory instrument parameters emulating those of the Compact Reconnaissance Imaging Spectrometer for Mars, with new spectral slope features revealed between 0.7 and 1.1 µm, and absorption features at 1.14 and most sensitively, at 1.685 µm. Mars regolith analog mixed with a concentration of 1.5% PAHs resulted in no discernible organic spectral features. These detectability limits measured in the laboratory are discussed and extrapolated to the effective conditions on the Mars South Polar Cap in terms of dust and water ice abundance and CO₂ ice grain size for both the main perennial cap and the H₂O ice-dust sublimation lag deposit.

中文翻译：

---

火星南极实验室类似物中有机分子的检测极限

进行了一系列实验室实验，以便在火星南极残留帽 (SPRC) 的背景下生成具有天体生物学意义的多环芳烃 (PAH) 的诊断光谱，以建立更容易在 CO _{2 中}检测到的 PAH 光谱特征冰（与少量 H ₂O 冰）比之前报道的 3.29 µm 处的吸收特征，以限制其可检测性极限。目前没有关于 SPRC 特征中 PAH 检测的现有文献，鉴于最近在火星南极下方发现了一个可能的冰下湖，这使得这项工作具有新颖性和影响力。尽管已在火星陨石中检测到 PAH，但在火星上尚未检测到 PAH，这可能是由于紫外线辐射对行星表面的有害影响。SPRC 特征可以为脆弱分子提供保护，这项工作旨在提供实验室数据，以改进对轨道遥感光谱成像数据的解释。我们还确定了 CO ₂的影响有机光谱上的冰升华，以及提供与火星相关的混合物中的 PAH 参考光谱。使用模拟火星紧凑型侦察成像光谱仪的实验室仪器参数观察 CO ₂冰中多环芳烃的可检测性极限为 ~0.04% ，新的光谱斜率特征显示在 0.7 和 1.1 µm 之间，吸收特征为 1.14 和最灵敏，在 1.685 µm。火星风化层模拟物与浓度为 1.5% 的多环芳烃混合导致没有可辨别的有机光谱特征。讨论了实验室测量的这些可检测性极限，并将其外推到火星南极盖上灰尘和水冰丰度以及 CO ₂的有效条件主要多年生盖层和 H ₂ O 冰尘升华滞后沉积物的冰粒大小。