ELECTROSTATIC CHARGING PROPERTIES OF SIMULATED LUNAR DUST

The charge on grains of simulated lunar regoliths (MLS-1 and JSC-1) ha s been measured in a plasma containing thermal electrons with a few el ectron volts temperature and a second population of nearly monoenerget ic fast electrons with energy variable from 15 to 100 eV. The measured charges are similar to that on glass microspheres of the same diamete r. Both the glass and the simulated lunar samples showed multiple char ge states in a finite electron energy range, that might help the theor etical models suggesting active electrostatic dust transport on the Mo on. The measurements can be well described by a charging model which i ncludes currents due the background thermal plasma, monoenergetic fast electrons and secondary electrons.