Partikelablösemechanismen auf der Marsoberfläche: Wind und lichtinduzierte Kräfte

• Antragsteller: Professor Dr. Gerhard Wurm
• Fachliche Zuordnung: Astrophysik und Astronomie
• Förderung: Förderung von 2012 bis 2019
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 225970202

Dust is ubiquitous on Mars and has many facets. Understanding the dust cycle is important for the planet’sclimate. Observations of dust bear information on the planet’s composition and its surface and atmosphere.And last but not least, due to its mechanical properties dust is critical for current and future exploration of theplanet. However, while global dust storms and local dust devils are frequently observed on Mars, it is stilldebated how dust gets entrained into the atmosphere in the first place. At the low atmospheric pressure of afew mbar, high wind speeds are needed to lift particles from the ground assuming that the same liftingmechanism is active as on Earth but typical wind speeds found on Mars are often below the threshold to raisedust. The same restriction applies to dust devil rotational and translational speeds, which are often too low.Curiously though, it was recently found that another mechanism provides additional lift for particles at theMartian surface. Due to a solid state greenhouse effect and photophoresis or a sub surface pressure increasebased on thermal creep, particles can efficiently be lifted as the surface is illuminated by the sun. This lift canbe stronger than gravity on Mars. In general, neither gas drag nor light induced forces can lift particles on theirown, as they are too weak to overcome cohesion in addition. A combination of both effects is likely capable ofproviding the required lifting force more generally and detach particles from the surface though, explaining thelarge quantity of dust in dust devils and (global) dust storms. The combined action of gas drag and lightinduced lift will be studied mostly in laboratory experiments during this project to approach this long-standingproblem.

• DFG-Verfahren: Sachbeihilfen