Particle Lift by a Solid State Greenhouse Effect and Thermophoresis on Planetary and Protoplanetary Surfaces

最近发现，在低压环境中用光照射表面可以有效地将小颗粒从灰尘床中升起。这种意外的行为是基于两个微妙的影响。第一种是固态温室效应：被照亮的尘埃床的最高温度位于地表以下。第二个效应是热泳：稀薄气体中的粒子有冷的一面和热的一面，它们被拉向冷的一面。这导致在一定的压力和光强度范围内粒子提升。这些要求在晚期的原行星盘和火星表面都得到了满足。作为侵蚀机制，这种效应有可能完全摧毁靠近年轻星星的微行星，并回收其物质在其他位置形成行星，或促进先前存在的原行星的生长。这一过程可能有助于将火星表面的颗粒提升到大气层中，并在火星的尘埃循环中发挥重要作用。在一个系统的研究中，我们调查这种新的侵蚀和提升机制。我们研究了颗粒升力对不同参数（材料、颗粒尺寸、孔隙率、气体性质、辐射等）的依赖性。实验室实验和计算机模拟。结果被应用到原行星盘和行星形成。分析了火星尘埃扬升机制的意义。在火星上，尘埃可能会通过阳光而升空，也可能会在火星探测期间通过技术手段从敏感表面上清除尘埃。

It was discovered recently that illuminating a surface by light in a low pressure environment can efficiently lift small particles from a dust bed. This unexpected behaviour is based on two subtle effects. The first is a solid state greenhouse effect: the temperature maximum of an illuminated dust bed is located somewhat below the surface. The second effect is thermophoresis: particles in a rarefied gas with a warm and a cold side are dragged towards the cold side. This leads to particle lifting in a certain pressure and light intensity range. The requirements are met in late time protoplanetary disks and on the surface of Mars. As erosion mechanism, the effect has the potential to completely destroy a planetesimal close to a young star and recycle its material to form planets in other locations or to boost the growth of pre-existing protoplanets. The process might aid to lift particles from the surface of Mars into its atmosphere, and play a significant role in the planet’s cycle of dust. In a systematic study we investigate this new erosion and lifting mechanism. We study the dependency of particle lift on different parameters (material, particle size, porosities, gas properties, radiation etc.) in laboratory experiments and computer simulations. The results are applied to protoplanetary disks and planet formation. The significance as mechanism to lift dust on Mars is analyzed. In the case of Mars, dust lift-off might occur by sunlight or it might be used technologically to remove dust on purpose from sensitive surfaces during Mars exploration.