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

• Applicant: Professor Dr. Gerhard Wurm
• Subject Area: Astrophysics and Astronomy
• Term: from 2008 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 53838542

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.

• DFG Programme: Research Grants