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

在它的早期历史中，太阳被嵌在尘埃和气体的碎片圆盘中，这些碎片延伸到冥王星的轨道之外。彗星在这个圆盘的外部区域形成，在那里它们保持不变，直到与另一个物体的引力相遇，将它们送进高度偏心的轨道上的太阳。因此，彗核为回到行星形成的最早阶段提供了一个至关重要的窗口。该团队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一个重要彗星样本的高分辨率无线电/亚毫米图像，以获得对彗核化学的新见解，他们还将研究木星和土星冰冷卫星的大气。来自这些冰冷卫星的大气羽流可以揭示隐藏的亚表面海洋的组成，这些海洋可能为生命提供潜在的栖息地。PI将通过暑期研究实习计划指导少数族裔服务大学的本科生。这笔赠款将产生一个新的谱线建模套件(SUPRIME)，该套件基于开源的谱线建模引擎，适用于低密度的彗星和冰冷卫星的大气层/外球层。该程序将精确地求解分子激发和辐射传输的三维问题。该模型将结合一个3D蒙特卡罗辐射传输和激发程序和一个参数化的最优估计(检索)引擎。CO-CO、HCN-H2O和CH3-OH-H2O体系的新碰撞速率将通过量子化学计算产生，包括构建详细的势能面和随后的分子动力学求解。该模型将应用于ALMA对彗星和冰冷月球大气的观测，以了解它们的物理过程和化学丰度。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.