Microphysical modeling of comets and planetesimals

我们最近在实验室实验中发现了与彗星中观测到的物理性质相匹配的宏观高孔率尘埃集合体，并对彗核进行了新的近距离观测，受此启发，这一建议旨在详细描述彗核近表面层和彗核与彗星之间的过渡区的物理过程。在这个项目中，我们将对彗星类似物的气体渗透性和热性质以及松散束缚的尘埃颗粒与稀薄气体流动的动力学相互作用进行到目前为止尚不可行的实验室实验。这些实验结果将被用来校准我们新的彗星表面和核与彗核之间过渡区的热物理模型，它将包括对彗核外层的改进的形态描述，改进的对核和彗发中的质量和能量传递的处理，以及彗星表面附近的尘埃加速模型。作为一个副作用，我们还将更好地描述原行星盘中的尘埃相互作用，这涉及到与彗星中存在的非常相似的物理性质。通过结合实验(IGEP)和理论/观测(MPS)小组的专业知识，我们的模型将涵盖我们目前拥有的彗核附近的物理过程和彗星的原行星前体--行星小星/彗星的完整图景。

Motivated by our recent results from laboratory experiments on the formation of macroscopic highporosity dust aggregates with physical properties matching those observed in comets and by new close-up observations of cometary nuclei, this proposal intends to derive at a detailed description of the physical processes in the near-surface layers of a cometary nucleus and the transition region between nucleus and coma. In this project, we will perform so far unfeasible laboratory experiments on the gas permeability and thermal properties of cometary analogs as well as on the dynamical interactions of loosely-bound dust grains with rarefied-gas flows. These experimental results will then be used to calibrate our new thermophysical model of the cometary surface and the transition region between nucleus and coma, which will consist of an improved morphological description of the outer layers of the cometary nucleus, an improved treatment of mass and energy transfer in the nucleus and in the coma, and a model of the dust acceleration in the vicinity of the cometary surface. As a side-effect, we will also arrive at a better description of the dust-dust interaction in protoplanetary disks, which involves very similar physical properties as those present in comets. By combining the expertise of an experimental (IGEP) and a theoretical/observational (MPS) group, our model will encompass the complete picture that we currently have of the physical processes close to a cometary nucleus and of protoplanetary precursors of comets, the planetesimals/cometesimals.