A SUBLIME 3D Model for Non-LTE Emission from Cometary and Icy Moon Atmospheres

在它的早期历史中，太阳被埋在一个尘埃和气体的碎片盘中，这个碎片盘延伸到冥王星的轨道之外。彗星形成于这个圆盘的外部区域，在那里它们保持不变，直到与另一个物体的引力相遇，它们以一个高度偏心的轨道向太阳靠近。因此，彗星核提供了一个关键的窗口，可以追溯到行星形成的最早阶段。这个小组将研究彗星和行星冰卫星的物理过程和化学组成。他们将使用新的计算工具来解释彗星重要样本的高分辨率无线电/亚毫米图像，以获得对彗星核化学的新见解，他们将研究木星和土星冰冷卫星的大气层。这些冰冷卫星的大气羽流可以揭示隐藏的地下海洋的成分，这可能为生命提供潜在的栖息地。该项目将通过一个暑期研究实习项目，指导来自少数民族大学院校的本科生。这笔拨款将基于开源的谱线建模引擎，开发一套新的谱线建模套件（SUBLIME），适用于低密度大气/彗星和冰冷卫星的外大气层。此代码将准确地解决分子的激发和辐射传递在三维。该模型将三维蒙特卡罗辐射传递和激励编码与参数化最优估计（检索）引擎相结合。通过量子化学计算，包括构建详细的势能面和随后的分子动力学求解，将生成CO-CO、HCN-H2O和CH3-OH-H2O体系的新的碰撞速率。该模型将应用于ALMA对彗星和冰冻卫星大气的观测，以了解它们的物理过程和化学丰度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In its early history, the Sun was embedded in a debris disk of dust and gas that extended beyond the orbit of Pluto. Comets formed in the outer regions of this disk, where they remain unchanged until a gravitational encounter with another object sends them in towards the Sun in a highly eccentric orbit. Cometary nuclei thus provide a crucial window back in time to the earliest stages of planet formation. This team will investigate the physical processes and chemical makeup of comets and planetary icy moons. They will use new computational tools to interpret high-resolution radio/submillimeter images of a significant sample of comets to gain new insights into the chemistry of cometary nuclei, and they will study the atmospheres of the icy moons of Jupiter and Saturn. Atmospheric plumes from these icy moons can reveal the compositions of hidden, sub- surface oceans, which might provide potential habitats for life. The PI will mentor undergraduate students from minority-serving university institutions through a summer research internship program. The grant will produce a new spectral line modeling suite (SUBLIME), based on the open source Line Modeling Engine, adapted for low-density atmospheres/exospheres of comets and icy moons. This code will accurately solve the molecular excitation and radiation transfer in three dimensions. The model will combine a 3D Monte Carlo radiative transfer and excitation code with a parameterized optimal estimation (retrieval) engine. New collisional rates for CO-CO, HCN-H2O and CH3-OH-H2O systems will be generated via quantum chemical calculations, including the construction of detailed potential energy surfaces and subsequent solving of the molecular dynamics. The model will be applied to ALMA observations of cometary and icy moon atmospheres to gain understanding of their physical processes and chemical abundances.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.