ELECTROSTATIC CHARGING PROPERTIES OF SIMULATED LUNAR DUST

The charge on grains of simulated lunar regoliths (MLS-1 and JSC-1) has been measured in a plasma containing thermal electrons with a few electron volts temperature and a second population of nearly monoenergetic fast electrons with energy variable from 15 to 100 eV. The measured charges are similar to that on glass microspheres of the same diameter. Both the glass and the simulated lunar samples showed multiple charge states in a finite electron energy range, that might help the theoretical models suggesting active electrostatic dust transport on the Moon. The measurements can be well described by a charging model which includes currents due the background thermal plasma, monoenergetic fast electrons and secondary electrons.