Science Seminars

The role of electrostatic dust transport in shaping the surfaces of airless bodies

Speaker: Xu Wang (LASP)
Date: Thursday, Oct 12, 2017
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

Airless bodies, unlike our Earth, are directly exposed to solar UV radiation and solar wind plasma. Fine dust particles on their regolith are charged and may be mobilized due to electrostatic forces. Electrostatic dust transport is a long-standing problem and has been hypothesized to explain a number of unusual planetary phenomena, for example the so-called “lunar horizon glow”, the intermittently appearing radial spokes in Saturn’s rings, and the dust ponds observed on Asteroid 433 Eros and Comet 67P. However, until recently, no charging theories could explain the physical processes behind these observations.
Our recent lab experiments fundamentally advanced the understanding of this five-decades long problem. We developed and experimentally validated a new “patched charge model”, which explains how dust particles gain sufficiently large charges to get lofted from the surface. It has been shown that the emission and re-absorption of photo and/or secondary electrons inside microcavities below the regolith surface can result in large negative charges collected by surrounding dust particles. The intense repulsive forces between these negatively charged dust particles cause them to move and lift off the surface. The detailed characteristics of dust charging and hopping dynamics will be presented, including the slow-motion videos.
As a consequence of these dust activities, the features of the exposed surfaces are shown to be significantly changed. I will report several experiments showing that these dust activities eliminate existing or create new surface features. Our lab results indicate that electrostatic dust transport may be efficient in shaping the surfaces of airless bodies, such as the surface morphology and porosity as well as the space weathering effect.
Motivated by our lab breakthroughs, we are now developing the Cubsat Electrostatic Dust Analyzer (CEDA) for in situ measurements of electrostatically lofted dust particles on a surface of small airless bodies (e.g., asteroids, Phobos, or Deimos). I will briefly talk about the status of this dust sensor development.