Lecturer: Josh Colwell, University of Central Florida
Dr. Joshua Colwell is a Planetary Scientist and Professor of Physics at the University of Central Florida. Since 2011 he has been Associate Chair of the Department of Physics, Assistant Director of the Florida Space Institute, and Director of the Center for Microgravity Research at UCF. He came to UCF in 2006 from the Laboratory for Atmospheric and Space Physics at the University of Colorado where he earned his Ph.D. in Astrophysical, Planetary and Atmospheric Sciences.
His research interests are in the origin and evolution of the solar system with a particular emphasis on planet formation, asteroids, planetary rings, comets, and interplanetary dust. He is a Co-Investigator on the Ultraviolet Imaging Spectrograph on the Cassini mission, a spacecraft orbiting and exploring Saturn from 2004-2017. He studies the structure and dynamics of Saturn’s rings with data from Cassini. His experiments have flown on the Space Shuttle, the International Space Station, suborbital rockets, parabolic airplane flights, and he is developing a CubeSat for launch in 2018.
An avid Trekkie, his other interests include running, writing and movies. He is the author of “The Ringed Planet”, produces and hosts the astronomy podcast “Walkabout the Galaxy”, and he was a comet advisor for, and actor in, the Dreamworks picture “Deep Impact”.
Topic: Electrostatic surface properties of NEAs
The prospect of electrostatic levitation of dust near planetary surfaces was first seriously explored in the lead up to the initial robotic and human expeditions to the Moon. The absence of an atmosphere allows for the possibility of large local electric fields that can loft small particles leading to transport or loss from the object completely. Intriguing observations of the lunar horizon by the Surveyor landers were interpreted as showing dust particles within a meter of the surface near local sunset (Rennilson and Criswell 1974). Other Apollo observations also suggested that dust was mobile, particularly near sunrise and sunset (Colwell et al. 2007 for a review). Lee (1996) showed that the regolith size distribution of small asteroids could be altered by selective removal of small particles by electrostatic effects. The observations of smooth “ponds” in the floors of some craters on the asteroid Eros by the NEAR/Shoemaker spacecraft were suggested to be the result of electrostatic transport of dust (Robinson et al. 2001). Models have shown that dust may be preferentially transported into craters (Colwell et al. 2005, Hughes et al. 2008), and electrostatic transport likely acts in concert with gravitational transport triggered by impacts leading to downslope movement. I’ll review the theoretical work and observational evidence for electrostatic modification of regolith on asteroids and moons.
Recommended Readings:
Lee, P. 1996. Icarus 124, 181-194.
Colwell et al. 2005. Icarus 175, 159-169.
Hughes et al. 2008. Icarus 195, 630-648.
Hartzell and Scheeres 2013. J. Geophys. Res. 118, 116-125.
Recorded talk: click to view