海王星的D/H比率到底告诉了我们它的水丰度是多少？
What is Neptune's D/H ratio really telling us about its water abundance ?
摘要：
我们调查深海丰富的海王星使用一个简单的2组件（核心+信封）玩具模型。该模型的自由参数是行星中重元素的总质量（Z）、包层中Z的质量分数（f_env）和吸积积木的D/H比（D/H_build）。我们系统地搜索允许的参数空间上的网格和约束它使用海王星的散装碳丰度，D/H比，和内部结构模型。假设太阳的C/O比和彗星的D/H是形成行星的吸积构件，我们可以拟合所有的Z值（中位数约为7%），如果Z值小于15%（f_env被锁定在固体核心中），则其余的约束都可以拟合。该模型预测海王星的最大体氧丰度为65 \times太阳值。如果我们假设C/O为0.17，对应于笼形水合物的构建块，我们预测最大氧丰度为太阳值的200倍，中值为~ 140。因此，这两种情况都导致氧丰度显著低于Cavalié等人（2017）的首选值（约540倍太阳能），这是从依赖于模型的深层CO观测中推断出来的。我们简单但稳健的模型排除了这种高水丰度。我们将这种差异归因于我们对海王星内部结构或原始原太阳星云化学性质的不完全理解。
英文摘要：
We investigate the deep water abundance of Neptune using a simple 2-component (core + envelope) toy model. The free parameters of the model are the total mass of heavy elements in the planet (Z), the mass fraction of Z in the envelope (f_env), and the D/H ratio of the accreted building blocks (D/H_build ). We systematically search the allowed parameter space on a grid and constrain it using Neptune's bulk carbon abundance, D/H ratio, and interior structure models. Assuming solar C/O ratio and cometary D/H for the accreted building blocks forming the planet, we can fit all of median ~ 7%), and the rest the constraints if less than ~ 15% of Z is in the envelope (f_env is locked in a solid core. This model predicts a maximum bulk oxygen abundance in Neptune of 65 \times solar value. If we assume a C/O of 0.17, corresponding to clathrate-hydrates building blocks, we predict a maximum oxygen abundance of 200 times solar value with a median value of ~ 140. Thus, both cases lead to an oxygen abundance significantly lower than the preferred value of Cavalié et al. (2017) (~ 540 times solar), inferred from model dependent deep CO observations. Such high water abundances are excluded by our simple but robust model. We attribute this discrepancy to our imperfect understanding of either the interior structure of Neptune or the chemistry of the primordial protosolar nebula.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
