Analysis of gaseous ammonia (NH3) absorption in the visible spectrum of Jupiter - Update
Analysis of gaseous ammonia (NH3) absorption in the visible spectrum of Jupiter - Update
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DOI：
10.1016/j.icarus.2017.11.031
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发表时间：
2018-03
期刊：
影响因子：
3.2
通讯作者：
P. Irwin;N. Bowles;A. Braude;R. Garland;S. Calcutt;Phillip A. Coles;S. Yurchenko;J. Tennyson
中科院分区：
文献类型：
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作者：
P. Irwin;N. Bowles;A. Braude;R. Garland;S. Calcutt;Phillip A. Coles;S. Yurchenko;J. Tennyson
为支持美国航天局/朱诺号使命，利用甚大望远镜多单元光谱探测器仪器在0.48-0.93微米光谱范围内对木星的可见/近红外反射光谱进行了观测。这些光谱包含气态氨（NH3）的光谱特征，如果我们有关于其吸收光谱的可靠信息，就可以确定云顶上方的丰度。虽然在这个光谱范围内有许多NH3吸收数据的来源，但它们涵盖了小的子范围，这些子范围不一定重叠，并且已经从各种来源确定。因此，在对整个可见光/近红外范围的反射率进行建模时，这些不同来源的一致性存在相当大的不确定性。在本文中，我们分析了木星的VLT/MUSE观测，以确定氨吸收数据的来源是最可靠的。我们发现，带模型系数的Bowles等人。（2008）通常提供MUSE范围内的可靠性和波长覆盖的最佳组合。这些条带数据似乎与Yurchenko等人的ExoMOL氨谱线数据一致。（2011），在它们重叠的波长处，但这些后者的数据不包括在0.79和0.765 μm处的氨吸收带，这在我们的MUSE观测中是突出的。然而，我们发现乐队的数据Bowles等人。（2008）在波长小于0.758 µm时不可靠。在较短波长下，我们发现Lutz和Owen（1980）的实验室观测提供了0.552 µm和0.648 µm附近氨吸收的位置和形状的良好指示，但它们的吸收强度似乎与Bowles等人的波段数据不一致。（2008）在更长的波长下。最后，我们发现Giver等人的0.648 μm吸收带的线数据与我们的实验结果一致。（1975）不适合对这些数据进行建模，因为它们只占谱带吸收的17%，并且不能可靠地扩展到木星大气中发现的低温和H2/He加宽条件。这项工作不仅对太阳系行星物理学具有重要意义，而且对未来提出的对围绕其他恒星运行的类彗星行星的观测也具有重要意义，例如美国宇航局计划中的宽视场红外巡天望远镜（WFIRST）。
Observations of the visible/near-infrared reflectance spectrum of Jupiter have been made with the Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) instrument in the spectral range 0.48–0.93 µm in support of the NASA/Juno mission. These spectra contain spectral signatures of gaseous ammonia (NH3), whose abundance above the cloud tops can be determined if we have reliable information on its absorption spectrum. While there are a number of sources of NH3absorption data in this spectral range, they cover small sub-ranges, which do not necessarily overlap and have been determined from a variety of sources. There is thus considerable uncertainty regarding the consistency of these different sources when modelling the reflectance of the entire visible/near-IR range. In this paper we analyse the VLT/MUSE observations of Jupiter to determine which sources of ammonia absorption data are most reliable. We find that the band model coefficients of Bowles et al. (2008) provide, in general, the best combination of reliability and wavelength coverage over the MUSE range. These band data appear consistent with ExoMOL ammonia line data of Yurchenko et al. (2011), at wavelengths where they overlap, but these latter data do not cover the ammonia absorption bands at 0.79 and 0.765 µm, which are prominent in our MUSE observations. However, we find the band data of Bowles et al. (2008) are not reliable at wavelengths less than 0.758 µm. At shorter wavelengths we find the laboratory observations of Lutz and Owen (1980) provide a good indication of the position and shape of the ammonia absorptions near 0.552 µm and 0.648 µm, but their absorption strengths appear inconsistent with the band data of Bowles et al. (2008) at longer wavelengths. Finally, we find that the line data of the 0.648 µm absorption band of Giver et al. (1975) are not suitable for modelling these data as they account for only 17% of the band absorption and cannot be extended reliably to the cold temperatures and H2/He-broadening conditions found in Jupiter’s atmosphere. This work is of significance not only for solar system planetary physics, but also for future proposed observations of Jupiter-like planets orbiting other stars, such as with NASA’s planned Wide-Field Infrared Survey Telescope (WFIRST).