  We report new 2 cm VLBA images of the inner radio jet of M87 showing a limb
brightened structure and unambiguous evidence for a faint 3 mas long
counter-feature which also appears limb brightened. Multi-epoch observations of
seven separate jet features show typical speeds of less than a few percent of
the speed of light, despite the highly asymmetric jet structure and the
implications of the canonical relativistic beaming scenario. The observed
morphology is consistent with a two stream spine-sheath velocity gradient
across the jet, as might be expected from the recently discovered strong and
variable TeV emission as well as from numerical modeling of relativistic jets.
Considering the large jet to counter-jet flux density ratio and lack of
observed fast motion in the jet, we conclude that either the inner part of the
M87 jet is intrinsically asymmetric or that the bulk plasma flow speed is much
greater than any propagation of shocks or other pattern motions.
