Simulation of Lunar Craters: a Blow-hole Theory

Abstract

RECENT reports of volcanic activity on the Moon1 have stimulated us to repeat an accidental observation made many years ago by one of us (A. G. G.). During rapid evacuation of a quantity of magnesium carbonate in a flask, a number of blow-holes appeared as the occluded gas escaped, leaving a pattern of rings, some with central ‘pimples’, closely resembling lunar craters. In the present work, we have repeated this experiment (Fig. 1). We have also put a quantity of dry powder (sand, salt, magnesium oxide or magnesium carbonate) in a 5-l. flask, which was continuously evacuated; a small flow of air was admitted at the bottom of the flask by a small hole. Various forms of blow-hole were observed. In many cases, a marked ring, with steep inner edge and less steep outer edge, was formed by the fountain of small particles; sometimes, when the air was cut off, a small pimple remained at the centre of the fountain as it collapsed (Fig. 2). The form of the ‘crater’ varied rather with type of powder, especially its angle of slip, and the depth, and with the rate of flow of gas.