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The massive red supergiant Antares (alpha Sco AdoublePoint M1 Iab) is an excellent star to test theoretical models of mass loss because its distance comma age comma stellar parameters comma mass-loss rate comma and interstellar reddening are well established. The early-M supergiants pose a particular challenge for models of mass loss driven by radiation pressure on molecules and-or dustdoublePoint The circumstellar molecular abundances and dust-to-gas mass ratios are lower than for later-M spectral-types comma but they still manage to drive massive winds. We request deep FUV and NUV observations to perform an extremely sensitive test for the most robust circumstellar molecule comma CO comma by observing its Fourth-Positive electronic bands against the FUV continuum of the M supergiant Antares. These observations will enable us measure any CO present in the outflow comma and to place upper-limits on the effective radiation acceleration it can provide. The proposed observations will also provide an invaluable dataset for Antares comma the oft neglected southern twin of Betelgeuse comma and our nearest Type II supernova progenitor.