  We present a 0.5"-resolution diffraction-limited 17.7 micron image of the red
supergiant Antares obtained with the VLT mid-infrared instrument VISIR. The
VISIR image shows six clumpy dust clouds located at 0.8"--1.8" (43--96 stellar
radii = 136--306 AU) away from the star. We also detected compact emission
within a radius of 0.5" from the star. Comparison of our VISIR image taken in
2010 and the 20.8 micron image taken in 1998 with the Keck telescope reveals
the outward motions of four dust clumps. The proper motions of these dust
clumps amount to 0.2"--0.6" in 12 years. This translates into expansion
velocities (projected onto the plane of the sky) of 13--40 km/s with an
uncertainty of +/-7 km/s. The velocities of the dust clumps cannot be explained
by a simple accelerating outflow, implying the possible random nature of the
dust cloud ejection mechanism. The inner compact emission seen in the 2010
VISIR image is presumably newly formed dust, because it is not detected in the
image taken in 1998. The mass of the dust clouds is estimated to be
(3-6)x10^{-9} Msun. These values are lower by a factor of 3--7 than the amount
of dust ejected in one year estimated from the (gas+dust) mass-loss rate of
2x10^{-6} Msun/yr, suggesting that the continuous mass loss is superimposed on
the clumpy dust cloud ejection.
