Distribution of the Shearing Stresses in the Silicate Mantle of Venus

The shearing stresses in the silicate mantle of Venus are calculated. The maximum shearing stresses, of about 13.6 bar, act in the equatorial plane at the liquid core boundary. These stresses rapidly diminish with distance from the mantle-core boundary, and in the upper mantle of the planet they are about 1-3 bar. Stresses in the planet's polar planes are approximately half of what they are in the equatorial plane. In view of the low level of stresses in the Venusian interior, the conclusion is drawn that the planet's interior deeper than its lithosphere is aseismic. An estimate is made of Venus' rotation paleoperiod (16.9 +0.3, -0.4 days), which shows that at some earlier time the planet rotated considerably faster. Also, shearing stresses in the silicate mantle of Mars are calculated.