Gravity studies of Aphrodite Terra on Venus

Four gravity profiles across Aphrodite Terra are studied and investigated morphologically. Results provide evidence for an isostatic state for western Aphrodite and Ulfrun Regio at mean crustal thicknesses (T) of 50-30 km, differing from previous results. The graben area of middle Aphrodite is not in isostatic equilibrium, and deficit masses are indicated. Atla Regio to the east is regionally Airy compensated with T = 50 km, and the mountains Nokomis, Maat, and Ozza Montes are locally undercompensated. Atla Regio, Beta Regio, and the isostatic disturbed zones in the middle of Aphrodite have been associated with recent volcanism, according to observation of the concentrations of electrical discharges in these areas. Results give a T of 50 km for Aphrodite Terra. (R.R.)