Contact forces between sub-micrometer ice particles in protoplanetary environments

在过去的几十年里，行星形成的研究在理论、观测和实验方面都有了迅速的发展。行星形成的第一阶段是由碰撞控制的。它是两个粒子之间接触的强度，决定了粒子是通过粘附生长还是被破坏。因此，量化接触水平的相互作用是所有行星形成的进一步建模的最基本的。特别是像硅酸盐这样的耐火材料，迄今为止在实验室中进行了广泛的研究。然而，在原行星盘的外部区域，巨行星的核心应该是由水冰主导的。水冰接触物理学的描述纳米和微米尺度的低温下与行星形成的应用只是最近才开始，虽然非常基本的基本接触力和扭矩目前知之甚少。直到最近，由于热梯度力显微镜的发展，它们的测量才变得可行。在拟议的项目中，我们将建立这种技术，并对纳米至微米尺寸的水冰颗粒接触进行系统的测量。这将提供第一个实验数据库，用于模拟冰冷的小行星形成的早期阶段。

Research on planet formation saw a rapid evolution during the last few decades with respect to theory, observation and experiment. The first phases of planet formation are governed by collisions. It is the strength of the contacts between two particles, which decides if particles grow by sticking or are destroyed. Therefore, to quantify the interaction at the contact level is most fundamental for all further modeling of planet formation. Especially refractory materials like silicates were extensively studied in the laboratory so far. However, the outer regions of protoplanetary disks where cores of giant planets are supposed to be formed are dominated by water ice. The description of water ice contact physics on nanometer and micrometer size scale at low temperatures with application to planet formation only started recently and though very basic the underlying contact forces and torques are currently poorly known. Their measurement only recently became feasible by the development of a thermal gradient force microscope. In the proposed project we will establish this technique and carry out systematic measurements on nanometer to micrometer size water ice particle contacts. This will provide a first experimental database for modeling the early phases of icy planetesimal formation.