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快速的发展。行星形成的第一阶段受碰撞的支配。这是两个粒子之间接触的强度，决定了粒子是通过粘连生长还是被破坏。因此，量化接触水平上的相互作用对于所有行星形成的进一步模拟是最基本的。尤其是像硅酸盐这样的耐火材料，到目前为止在实验室中得到了广泛的研究。然而，原行星盘的外部区域被认为是形成巨型行星核心的地方，而这些区域主要是水冰。在纳米和微米尺度上描述低温下的水冰接触物理并应用于行星形成只是最近才开始的，虽然非常基本，但潜在的接触力和力矩目前知之甚少。直到最近，随着热梯度力显微镜的发展，他们的测量才变得可行。在拟议的项目中，我们将建立这项技术，并对纳米到微米尺寸的水冰颗粒接触进行系统测量。这将为模拟冰行星小行星形成的早期阶段提供第一个实验数据库。

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.