Fig. 3

Dependence of the relative production parameter on longitude. Dots are the relative production parameter of the exospheric atoms, which is the common logarithm of the ratio of production rate at a certain longitude to that at an antipodal point. The dot color represents the local time at which the observations were performed. The black solid lines in (a) and (b) are, respectively, the common logarithm of surface Mg/Si and Ca/Si abundance ratios at a certain longitude to that at an antipodal point