ADHESION AND COHESION MECHANISMS OF LUNAR DUST ON THE MOONS SURFACE

This review is based on many publications from the US and some from th e former Soviet Union. It briefly describes the sources of lunar dust. The problems posed to the past Apollo missions are summarized. The ph ysical properties of lunar soils, such as cohesion, angle of repose, a ngle of friction, and bearing capacity, as reported by scientists from these two nations, are compared. The composition of lunar soils is de scribed in terms of acidic and basic components. Since lunar soils are mainly silicates, we are the first to point out the importance of the Lewis acid-base interaction to the cohesion and adhesion of lunar dus t. The adhesion of lunar dust is similar to that of a xerographic deve loper. For the adhesion between lunar dust and dissimilar materials, b oth van der Waals and electrostatic interactions can be the driving fo rce, depending on the size of the dust particles. For particles smalle r than 50 mu m, van der Waals interaction predominates, while for thos e larger than 50 mu m, electrostatic interaction controls. For the ele ctrostatic interaction, lunar dust should charge positively. If lunar dust is pre-charged, e.g, by solar wind, the electrostatic interaction should predominate regardless of the size of the particles. It is imp ortant to note that for the electrostatic interaction, both electronic and ionic mechanisms can influence charge exchange. Thus, the Lewis t ype acid-base interaction can also affect the charge exchange. Experim ental work with a simulated lunar dust is recommended for the elucidat ion of the adhesion and cohesion mechanisms. Before that, all methods of control of lunar dust are, at best, speculative.