詹姆斯·韦伯空间望远镜（JWST）观测木卫四： leading半球富CO₂地形与H₂O冰全球分布模式
Callisto from JWST: CO2-rich terrain on the leading hemisphere and global patterns of H2O ice
AI总结：
本研究利用JWST绘制木卫四H₂O、CO₂及4.57μm光谱特征分布图，发现其H₂O冰分布存在半球二分性，固相CO₂在特定撞击坑附近富集，气相CO₂呈斑块分布且与固相CO₂无明显关联。
AI中文摘要：
我们呈现了詹姆斯·韦伯空间望远镜（JWST）观测到的木卫四表面H₂O、CO₂以及4.57μm光谱特征的分布图。在假设为结晶冰的简化前提下，通过测量leading和trailing半球3.1μm菲涅尔峰的波段参数，绘制了H₂O冰的分布图。我们利用JWST对木卫四的新观测数据（以太阳系最大多环撞击盆地瓦尔哈拉为中心），更新了Cartwright等人（2024）最初提出的CO₂固相、CO₂气相以及4.57μm特征的波段深度分布图。我们的H₂O冰分布图显示，trailing半球的菲涅尔峰呈现靶心状模式，在低纬度地区强度较弱；而在leading半球，其强度与撞击事件相关。这种二分现象可能与木星磁层等离子体撞击trailing半球有关。我们的固相CO₂分布图显示，在洛夫恩/海姆达尔撞击坑附近区域出现CO₂富集，该区域可能是木卫四表面最大的非辐射分解CO₂储库。气相CO₂则呈现斑块状空间分布，与固相CO₂无明显相关性。
英文摘要：
We present maps of H2O, CO2, and a 4.57 um spectral feature across Callisto's surface observed using the James Webb Space Telescope (JWST). H2O ice was mapped by measuring band parameters of the 3.1 um Fresnel peak across the leading and trailing hemispheres under a simplified assumption of crystalline ice. We update the CO2 solid-phase, CO2 gas, and 4.57 um feature band depth maps originally presented in Cartwright et al. (2024) with a new JWST observation of Callisto centered on Valhalla, the largest multi-ring impact basin in the solar system. Our H2O ice map shows that the Fresnel peak on the trailing hemisphere exhibits a bullseye pattern that is weaker at low latitudes, and on the leading hemisphere its strength is associated with impacts. This dichotomy is possibly related to the Jovian magnetospheric plasma impinging on the trailing hemisphere. Our solid-phase CO2 map reveals an enhancement in the vicinity of the Lofn/Heimdall impact craters, a region that may be the largest reservoir of non-radiolytic CO2 on Callisto's surface. The gas-phase CO2 exhibits a patchy spatial distribution and does not clearly correlate with solid CO2.
