Man sized blk circle w/ antennae down each side, single white light. Obj hovered over field, backed behind some trees and vanished

I saw this on my way to the schoolbus one morning. I was in the 1st or 2nd grade.  I lived on Lower Roswell Rd. in Marietta, Ga - which was a fairly rural suburb of Atlanta in '74 -  on a 2 acre tract of land bordered by a neighboring field, and about 2-300 yds beyond a recently built neighborhood subdivision called Kings Cove.  The nearest cross street is(was) Dickerson Rd.  I was walking southwesterly toward the bus stop across my yard when this object caught my attention, roughly 45 degrees off my left shoulder hovering silently over my neighbor's field.  It was a black, round, man sized object, featureless except for a single light in the middle of the circle, and two "legs" which were thin, antennae-like hanging down from each side of the circle.  About the time I became cognizant of what I was seeing the light in the middle of the circle went out.  It then backed silently and smoothly backward and upward, across my neighbor's field and positioned itself behind the pine trees which bordered this field and the back of the subdivision.  The object then vanished.