标题： JWST 揭示木卫二表面近期改性的光谱示踪物 显示英文标题

标题： JWST Reveals Spectral Tracers of Recent Surface Modification on Europa

摘要： 木卫二经历了多种地质过程，暴露了内部来源的物质，这些物质受到木星磁层中捕获的带电粒子的强烈辐射。 先前对木卫二上水冰的光谱分析依赖于波长>2.5微米处信噪比较低的数据，限制了对3.1微米菲涅尔峰的评估，该峰是暴露的晶体冰的特征。 我们报告了使用詹姆斯·韦布空间望远镜上的NIRSpec光谱仪（1.48 - 5.35微米）收集的高信噪比数据对水冰光谱特征的新测量结果。 这些数据揭示了一个狭窄的3.1微米晶体水冰菲涅尔峰，主要位于塔拉和鲍威斯区域的南纬地区。 我们的分析表明，在这些低纬度区域暴露的晶体冰可能由持续的热（再）结晶作用维持，其速度超过了木卫二风化层顶部10微米范围内带电粒子的非晶化作用，在短时间内（<15天）。 我们还测量了位于约1.5微米、1.65微米和2.0微米处的水冰特征，以及一个宽广的3.6微米水冰连续峰，所有这些特征在北纬地区都更强，与在南纬地区识别出的3.1微米菲涅尔峰形成对比。 这些结果支持了木卫二风化层中的水冰呈垂直分层的假设，其中非晶态冰颗粒主导其暴露表面，除了塔拉和鲍威斯区域。 我们还发现之前检测到的4.38微米13O2特征几乎只存在于塔拉和鲍威斯区域的南纬地区，很可能来源于含碳物质的内部来源。 显示英文摘要

摘要： Europa has been modified by a variety of geologic processes, exposing internally-derived materials that are heavily irradiated by charged particles trapped in Jupiter's magnetosphere. Prior spectral analysis of H2O ice on Europa relied on low signal-to-noise data at wavelengths >2.5 microns, limiting assessment of a 3.1 micron Fresnel peak that is diagnostic of exposed crystalline ice. We report new measurements of H2O ice spectral features using high signal-to-noise data collected by the NIRSpec spectrograph (1.48 - 5.35 microns) on the James Webb Space Telescope. These data reveal a narrow 3.1 micron crystalline H2O ice Fresnel peak, which is primarily located at southern latitudes in Tara and Powys Regiones. Our analysis indicates that crystalline ice exposed in these low-latitude regiones is likely sustained by ongoing thermal (re)crystallization outpacing charged particle amorphization of the top 10 microns of Europa's regolith over short timescales (<15 days). We also measured H2O ice features centered near 1.5 microns, 1.65 microns, and 2.0 microns, and a broad 3.6 micron H2O continuum peak, which are all stronger at northern latitudes, in contrast to the 3.1 micron Fresnel peak identified at southern latitudes. These results support the hypothesis that H2O ice in Europa's regolith is vertically stratified, with amorphous ice grains dominating its exposed surface, except in Tara and Powys Regiones. We also find that a previously detected 4.38 micron 13O2 feature is present almost exclusively at southern latitudes in Tara and Powys Regiones, likely derived from an internal source of carbon-bearing material.