  The superrotation of the atmosphere of Venus requires a large torque on the
up- per atmosphere. Mechanisms for providing a net balancing of this through
waves or ionospheric motions to other parts of the atmosphere have been
proposed but all have difficulties. Here we demonstrate that the albedo
gradient from the day to night side of the cloud layer allows a gradient of
light pressure that is sufficient to provide an external torque to drive this
flow.
