论文标题
通过HST光谱图像和伽利略磁场数据的联合分析来限制欧罗巴的下验证大气
Constraining Europa's subsolar atmosphere with a joint analysis of HST spectral images and Galileo magnetic field data
论文作者
论文摘要
我们通过结合两组观测值来限制欧罗巴的脆弱大气层：在1304Å处的氧气排放和1356Å的氧气从哈勃太空望远镜（HST）光谱图像和galileo磁场的最接近相遇中的氧气排放。我们描述了欧罗巴的三种中性气体种类的大气：全球分子（$ \ mathrm {o_2} $）和原子氧（O），以及局部水（$ \ m m i \ mathrm {h_2o} $）作为近乎供应的羽流和稳定的分布集中在月球落后的尾巴上。我们基于OI1356Å与OI1304Å的比率的组合建模（2021年）和磁场数据的排放量使我们能够对$ \ Mathrm {O_2} $的密度和位置产生约束，并在Emopa's Altereere的$ \ Mathrm {o_2} $和$ \ MATHRM {H_2O} $中得出约束。我们证明，$ 50 \％的$ \％$ $ \ MATHRM {O_2} $以及$ 50 \％$和$ 75 \％$ $ \％$的$ \ Mathrm {h_2o} $从Roth（2021）共同解释HST和Galileo测量。这些值以$ \ mathrm {o} $的列密度为条件，接近$ 6 \ times10^{16}〜\ mathrm {m}^{ - 2} $由Roth（2021）衍生而来的，以及在较强的稳定稳定的稳定$ \ Mathrm {H_2O} $ subsolare ysolare ysolare ysolare compoint comport。我们的分析得出的列密度为$ 1.2 \ times10^{18}〜\ mathrm {m}^{ - 2} $ for $ \ mathrm {o_2} $，和$ 1.5 \ times10^{19}}〜\ mathrm {Mathrm {m} \ times10^{19}〜\ mathrm {m}^{ - 2} $在$ \ mathrm {h_2o} $的subsolar Point上。然而，这两个列密度仍然位于罗斯（2021）的不确定性内。我们的结果为Europa的稳定$ \ mathrm {H_2O} $氛围提供了其他证据。
We constrain Europa's tenuous atmosphere on the subsolar hemisphere by combining two sets of observations: oxygen emissions at 1304 Å and 1356 Å from Hubble Space Telescope (HST) spectral images, and Galileo magnetic field measurements from its closest encounter, the E12 flyby. We describe Europa's atmosphere with three neutral gas species: global molecular ($\mathrm{O_2}$) and atomic oxygen (O), and localized water ($\mathrm{H_2O}$) present as a near-equatorial plume and as a stable distribution concentrated around the subsolar point on the moon's trailing hemisphere. Our combined modelling based on the ratio of OI 1356 Å to OI 1304 Å emissions from Roth (2021) and on magnetic field data allows us to derive constraints on the density and location of $\mathrm{O_2}$ and $\mathrm{H_2O}$ in Europa's atmosphere. We demonstrate that $50\%$ of the $\mathrm{O_2}$ and between $50\%$ and $75\%$ of the $\mathrm{H_2O}$ abundances from Roth (2021) are required to jointly explain the HST and Galileo measurements. These values are conditioned on a column density of $\mathrm{O}$ close to the upper limit of $6 \times10^{16}~\mathrm{m}^{-2}$ derived by Roth (2021), and on a strongly confined stable $\mathrm{H_2O}$ atmosphere around the subsolar point. Our analysis yields column densities of $1.2 \times10^{18}~\mathrm{m}^{-2}$ for $\mathrm{O_2}$, and $1.5 \times10^{19}~\mathrm{m}^{-2}$ to $2.2 \times10^{19}~\mathrm{m}^{-2}$ at the subsolar point for $\mathrm{H_2O}$. Both column densities however still lie within the uncertainties of Roth (2021). Our results provide additional evidence for the existence of a stable $\mathrm{H_2O}$ atmosphere at Europa.
