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

最近发现，在低压环境下用光照射物体表面，可以有效地从尘床上扬起小颗粒。这种意想不到的行为是基于两个微妙的影响。第一种是固态温室效应：受光照的尘床的最高温度位于地表以下。第二种效应是热泳：具有冷热两面的稀薄气体中的粒子被拖向冷热两面。这导致颗粒在一定的压力和光强范围内抬升。这些要求在后期的原行星盘和火星表面得到满足。作为一种侵蚀机制，这种效应有可能彻底摧毁靠近年轻恒星的星子，并回收其物质在其他位置形成行星或促进原有原行星的生长。这一过程可能有助于将火星表面的颗粒提升到大气中，并在火星的尘埃循环中发挥重要作用。在系统的研究中，我们探讨了这种新的侵蚀和抬升机制。我们在实验室实验和计算机模拟中研究了不同参数（材料、粒度、孔隙率、气体性质、辐射等）对颗粒升程的影响。结果应用于原行星盘和行星的形成。分析了其作为火星扬尘机制的意义。以火星为例，在火星探测过程中，灰尘可能会通过阳光产生，也可能在技术上用于清除敏感表面上的灰尘。

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.