Optical Properties of Venusian Clouds

翻译后摘要：尽管多年的研究，金星的大气层是不是很好地理解。当研究金星大气层的光谱时，在大约320 - 500 nm处有一个尚未解释的吸收区域（Pérez-Hoyos等人，2018年）。这对应于光谱的蓝色到紫外区域，或“近紫外”，尽管不同作者对确切范围的引用不同（例如参见Pollack等人，1980;Frandsen，Wennberg，& Kjaergaard，2016;Ekonomov et al.，1984;Limaye等人，2019).这种吸收被认为发生在金星的上层云层中，由H2SO 4/H2O混合物的液滴组成。该吸收不能通过单独的液滴或通过包含SO2气体来解释，因此已经提出了与液滴或气体混合的另外的颗粒或气溶胶吸收剂（Ekonomov等人，1984; Pollack等人，1980).虽然已经提出了几个候选者，但没有任何化学物质被最终证明符合观测到的金星吸收模式和大气化学。该项目将研究含有候选吸收剂的硫酸液滴的光学特性。这将首先在大量液体或气溶胶分布中进行，然后使用光学镊子在单个液滴中进行。该项目还将考虑液滴中吸收剂候选物的物理和更一般的光学性质，包括真实的折射率和保持球形的能力。在金星上观察到了光辉图案--当光线被内部反射时，在球形液滴中产生的一系列同心彩色光环（Laven，2005）。所观察到的辉光表明液滴中存在吸收剂颗粒。颗粒必须完全在液滴内，因为将颗粒附着到液滴表面会导致光泽变形，这是没有观察到的。一些候选者不可能插入到液滴中，因此，无论它们与检测到的光学性质和吸收是否一致，都不可能成为吸收体（Petrova，2018）。LMD（Le Atomatoire de Météorologie Dynamique）金星大气模型全面模拟了金星的云。实验室实验中有希望的候选者的物理、化学和光学特性可以包括在模型中，以模拟它们在金星大气中的行为，从而检查它们是否适合作为候选者。除了有助于缩小搜索范围或加强识别吸收体的证据外，在模型中包括已确认的吸收体将提高其模拟实际行为以解决其他问题的能力，如果没有一个候选者似乎足以提供所有检测到的吸收，计算机模拟将特别有用。然后，将使用模型将联合收割机候选吸收剂以可变的数量和配对组合起来，看看是否有任何有希望的吸收剂。如果预测到有希望的候选混合物，则可以开始混合物的实验测试，并且该过程可以迭代地进行以确定吸收剂比率。

Abstract: Despite many years of study, the atmosphere of Venus is not well understood. When the spectrum of light from Venus's atmosphere is examined, there is an as yet unexplained region of absorption at approximately320 -500nm (Pérez-Hoyos et al., 2018). This corresponds to the blue to ultraviolet region of the spectrum, or "near-UV", although the exact range is quoted differently by different authors, (see for example Pollack et al., 1980;Frandsen, Wennberg, & Kjaergaard, 2016;Ekonomov et al., 1984;Limaye et al., 2019).The absorption is believed to occur in the upper cloud layer of Venus, which consists of droplets of anH2SO4/H2O mixture. The absorption cannot be explained by the droplets alone, or by the inclusion of SO2 gas, and so an additional particulate or aerosol absorber mixed in with the droplets or gas has been proposed (Ekonomov et al., 1984; Pollack et al., 1980).Although several candidates have been suggested, no chemical species has been conclusively proven to fit the observed absorption pattern and atmospheric chemistry of Venus. This project will examine the optical properties of sulphuric acid droplets containing candidate absorbers. This will be done initially in bulk liquid or aerosol distributions, and then in single droplets using optical tweezers. The project will also consider the physical and more general optical properties of the absorber candidates in droplets, including real refractive index and ability to maintain a spherical shape. Glory patterns -a series of concentric coloured rings of light produced in spherical droplets when light is internally reflected (Laven, 2005)-have been observed on Venus. The observed glories suggest the presence of absorber particles in the droplets. The particles must be entirely within the droplets as attaching particles to the droplet surface would result in distortion of the glory, which is not observed. Some candidates are impossible to insert into droplets and so, regardless of their agreement with the optical properties and absorption detected, cannot be the absorber (Petrova, 2018).The LMD (Le Laboratoire de Météorologie Dynamique) Venus atmosphere model comprehensively models the clouds of Venus. The physical, chemical, and optical properties of promising candidates from the laboratory experiments can be included in the model to simulate their behaviour in the Venusian atmosphere and therefore to check their suitability as candidates. As well as helping narrow down the search or strengthening the evidence for the identification of the absorber, the inclusion of a confirmed absorber in the model will improve its ability to model realistic behaviour to solve other problems.Computer modelling will be particularly useful if no single candidate seems sufficient to provide all of the absorption detected. Modelling would then be used to combine candidate absorbers in variable amounts and pairings to see if any are promising. If promising candidate mixtures are predicted, experimental tests of the mixtures could begin, and the process could proceed iteratively to identify the absorber ratios.