Retrograde motion? We are just passing Mars on the inside track as we speed around the Sun on a much shorter radius.
Planets closer in have to travel in their orbits at a much different speed just to keep from being drawn into the Sun. Something about conservation of energy and the sum of the vectors acting upon the object.
The key is that the shorter the radius of the orbit, the higher the velocity needs to be. Think of orbiting as throwing yourself at the ground and missing- the further you are from the surface, the lower the speed needed to clear the horizon.