Venus Upper Clouds and the UV Absorber From MESSENGER/MASCS Observations
Venus Upper Clouds and the UV Absorber From MESSENGER/MASCS Observations
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DOI：
10.1002/2017je005406
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发表时间：
2018-01-01
影响因子：
4.8
通讯作者：
Sanz-Requena, J. F.
中科院分区：
文献类型：
--
作者：
Perez-Hoyos, S.;Sanchez-Lavega, A.;Sanz-Requena, J. F.
关于金星大气层最有趣的长期问题之一是未知紫外线吸收剂的起源和分布，负责在金星光谱的近紫外线和蓝色范围内检测到的吸收带。在这项工作中，我们使用的数据收集的水星大气和表面成分光谱仪（MASCS）摄谱仪上的水星表面，空间环境，地球化学和测距（信使）使命在2007年6月第二次金星飞越来解决这个问题。光谱范围从0.3米到1.5米，包括一些气态H2O和CO2带，以及部分SO2吸收带和紫外吸收的核心。我们使用的NEMESIS辐射传输代码和检索套件调查赤道大气中的粒子的垂直分布，并检索假想的紫外线吸收剂的折射率，假设是很好地混合与金星的小模式1粒子。结果表明，赤道大气是均匀的，云顶（单位光学厚度的高度）在地面以上752公里处。紫外吸收中心在0.340.03m，半峰全宽为0.140.01m。我们的值与以前的候选人的紫外线气溶胶吸收剂，其中二氧化硫（S2 O）和二氧化硫（S2 O2）提供最好的协议与我们的results.Plain语言摘要金星的大气层是完全被云层覆盖，它的云是非常反射在大多数可见光波长，除了近紫外线，其中吸收剂的来源不明强烈吸收太阳辐射。这样一个神秘的吸收器提供了与许多大气特征的对比，这些特征的动态可以从图像中跟踪，并且它在地球的能量预算中也有很大的作用。但是，到今天为止，我们还不清楚它是由什么组成的。在这项工作中，我们分析了在第二次金星飞越水星表面，空间环境，地球化学和测距（信使号）航天器在其路线上的水星，在2007年。利用数值代码，我们再现了金星赤道大气反射的光，并反演了金星高层大气中粒子的分布，云层顶部距地表约75公里。我们还检索了令人困惑的吸收体的吸收光谱，并将其与一些先前提出的候选人。虽然没有发现完美的匹配，含硫物质（S2 O和S2 O2）提供了最好的协议。毫无疑问，要确定金星的紫外线吸收剂还有很长的路要走，但这项工作提供了大量的光谱限制。
One of the most intriguing, long-standing questions regarding Venus's atmosphere is the origin and distribution of the unknown UV absorber, responsible for the absorption band detected at the near-UV and blue range of Venus's spectrum. In this work, we use data collected by Mercury Atmospheric and Surface Composition Spectrometer (MASCS) spectrograph on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission during its second Venus flyby in June 2007 to address this issue. Spectra range from 0.3m to 1.5m including some gaseous H2O and CO2 bands, as well as part of the SO2 absorption band and the core of the UV absorption. We used the NEMESIS radiative transfer code and retrieval suite to investigate the vertical distribution of particles in the equatorial atmosphere and to retrieve the imaginary refractive indices of the UV absorber, assumed to be well mixed with Venus's small mode1 particles. The results show a homogeneous equatorial atmosphere, with cloud tops (height for unity optical depth) at 752km above surface. The UV absorption is found to be centered at 0.340.03m with a full width at half maximum of 0.140.01m. Our values are compared with previous candidates for the UV aerosol absorber, among which disulfur oxide (S2O) and dioxide disulfur (S2O2) provide the best agreement with our results.Plain Language Summary The atmosphere of Venus is fully cloud covered, and its clouds are very reflective in most visual wavelengths, with the exception of the near ultraviolet, where an absorber of unknown origin strongly absorbs solar radiation. Such a mysterious absorber provides contrast to many atmospheric features whose dynamics can be tracked from images, and it also has a substantial role in the energy budget of the planet. But, as of today, we have no clear idea what it is made of. In this work, we have analyzed spectra taken during the second Venus flyby of MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft on its route to Mercury, in 2007. Using a numerical code, we have reproduced the light reflected by the equatorial atmosphere of the planet and retrieved the distribution of particles in the upper atmosphere of Venus, with a cloud top of some 75km above the surface. We have also retrieved the absorption spectrum of the puzzling absorber and compared it with some previously proposed candidates. While no perfect match is found, sulfur-bearing species (S2O and S2O2) provide the best agreement. There is still a long way to undoubtedly identify Venus's UV absorber, but this work provides substantial spectral constraints.