The haze and methane distributions on Neptune from HST-STIS spectroscopy
The haze and methane distributions on Neptune from HST-STIS spectroscopy
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DOI：
10.1016/j.icarus.2010.08.013
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发表时间：
2011-01-01
期刊：
影响因子：
3.2
通讯作者：
Tomasko, Martin G.
中科院分区：
文献类型：
--
作者：
Karkoschka, Erich;Tomasko, Martin G.
我们分析了 2003 年 8 月 3 日用哈勃 STIS 摄谱仪获取的海王星数据立方体。数据以 0.1 角秒的空间分辨率覆盖整个午后半球，波长在 300 到 1000 nm 之间，分辨率为 1 nm。导航精度为 0.004 弧秒和 0.05 海里。我们通过辐射传输计算约束垂直气溶胶结构。紫外线数据证实在 370 nm 波长处存在光学深度为 0.04 的平流层雾霾。明亮、离散的云，在纬度-40度和30度附近最为丰富，其顶部靠近对流层顶。如果它们具有光学厚度，则它们覆盖了观察到的圆盘的 1.7%。南部和北部云层云顶上方的甲烷丰度分别为 0.0026 和 0.0017 km-am，与 Sromovsky 等人早期的观测结果相同。 (Sromovsky, LA., Fry, P.M., Dowling, T.E., Baines, K.H., Limaye, S.S., [2001b]. Icarus 149, 459-488)。除了这些云之外，对流层上层基本上是晴朗的。在 1.4 条层下方，垂直均匀的雾度至少延伸至 10 条，光学深度为 0.10-0.16/条，具体取决于纬度。雾霾颗粒在波长超过 600 nm 时很亮，但在紫外线附近变暗，赤道地区比中高纬度地区更暗。纬度-60度附近的暗带是由可见光中单次散射反照率减少0.01引起的，接近于1。甲烷和氢吸收的比较与目前认为甲烷在类似于 1.5 巴层以下的纬度和高度上均匀混合的观点相矛盾。 0.04 +/- 0.01 的甲烷混合比仅在低纬度地区是均匀的。在南部高纬度地区，与低纬度值相比，它大约在 1.2 和 3.3 巴层之间凹陷。最大抑制因子在 1.8 条时类似于 2.7。我们提出了在整个阳光照射的地球上进行 2 个纬度采样的模型，使观测到的反射率达到 2.8% rms。 (C) 2010 Elsevier Inc. 保留所有权利。
We analyzed a data cube of Neptune acquired with the Hubble STIS spectrograph on August 3, 2003. The data covered the full afternoon hemisphere at 0.1 arcsec spatial resolution between 300 and 1000 nm wavelength at 1 nm resolution. Navigation was accurate to 0.004 arcsec and 0.05 nm. We constrained the vertical aerosol structure with radiative transfer calculations. Ultraviolet data confirmed the presence of a stratospheric haze of optical depth 0.04 at 370 nm wavelength. Bright, discrete clouds, most abundant near latitudes -40 degrees and 30 degrees, had their top near the tropopause. They covered 1.7% of the observed disk if they were optically thick. The methane abundance above the cloud tops was 0.0026 and 0.0017 km-am for southern and northern clouds, respectively, identical to earlier observations by Sromovsky et al. (Sromovsky, LA., Fry, P.M., Dowling, T.E., Baines, K.H., Limaye, S.S., [2001b]. Icarus 149, 459-488). Aside from these clouds, the upper troposphere was essentially clear. Below the 1.4-bar layer, a vertically uniform haze extended at least down to 10 bars with optical depth of 0.10-0.16/bar, depending on the latitude. Haze particles were bright at wavelengths above 600 nm, but darkened toward the ultraviolet, at the equator more so than at mid and high latitudes. A dark band near -60 degrees latitude was caused by a 0.01 decrease of the single scattering albedo in the visible, which was close to unity. A comparison of methane and hydrogen absorptions contradicted the current view that methane is uniformly mixed in latitude and altitude below the similar to 1.5-bar layer. The 0.04 +/- 0.01 methane mixing ratio is only uniform at low latitudes. At high southern latitudes, it is depressed roughly between the 1.2 and 3.3-bar layers compared to low-latitude values. The maximum depression factor is similar to 2.7 at 1.8 bars. We present models with 2 latitude sampling across the full sunlit globe that fit the observed reflectivities to 2.8% rms. (C) 2010 Elsevier Inc. All rights reserved.