木卫二尾半球可见光光谱的内、外成因贡献
Endogenic and Exogenic Contributions to Visible-wavelength Spectra of Europa's Trailing Hemisphere
摘要：
木卫二后半球的组成反映了内源性地质表面重塑和外源性硫辐解的综合影响。使用空间分辨的可见光波长光谱的欧罗巴与哈勃太空望远镜，我们映射多个光谱特征的拖尾半球，并比较其地理分布的大规模地质，磁层轰击，和表面颜色。基于这样的比较，我们解释我们的光谱的某些方面作为指示纯外源性硫辐解产物和其他方面作为指示辐解产物形成的内源性物质和磁层硫的混合物。在我们的光谱中看到的两个反射的空间分布-向近紫外线的广泛下降和在530 nm处的明显特征-似乎与先前从地基分光光度法提出的硫同素异形体一致。然而，两个额外的功能-在360 nm处的吸收功能和在红色波长的光谱斜率-的地理更一致的内源性材料，已被硫辐解改变。我们建议辐照硫酸盐作为这种材料的潜在候选者，但我们无法确定特定的物种与现有数据。
英文摘要：
The composition of Europa's trailing hemisphere reflects the combined influences of endogenous geologic resurfacing and exogenous sulfur radiolysis. Using spatially resolved visible-wavelength spectra of Europa obtained with the Hubble Space Telescope, we map multiple spectral features across the trailing hemisphere and compare their geographies with the distributions of large-scale geology, magnetospheric bombardment, and surface color. Based on such comparisons, we interpret some aspects of our spectra as indicative of purely exogenous sulfur radiolysis products and other aspects as indicative of radiolysis products formed from a mixture of endogenous material and magnetospheric sulfur. The spatial distributions of two of the absorptions seen in our spectra -- a widespread downturn toward the near-UV and a distinct feature at 530 nm -- appear consistent with sulfur allotropes previously suggested from ground-based spectrophotometry. However, the geographies of two additional features -- an absorption feature at 360 nm and the spectral slope at red wavelengths -- are more consistent with endogenous material that has been altered by sulfur radiolysis. We suggest irradiated sulfate salts as potential candidates for this material, but we are unable to identify particular species with the available data.
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