Barnes et al. have just published Data Release 6 of The Three-mm Ultimate Mopra Milky Way Survey (ThrUMMS). The Data Release consists of complete data cubes and various moments of line emission (¹²CO, ¹³CO, C¹⁸O) from molecular clouds, across 60 degrees × 2 degrees of the Fourth Quadrant of the Milky Way at a resolution of 72 arcseconds in galactic latitude and longitude, and 0.09 km/s in velocity. The team compute cubes and moments of the lines’ opacity, excitation temperature, and column density and reevaluated Galactic rotation parameters for the fourth quadrant. The team report two previously unrecognised features of the molecular cloud population: widespread ripples in the midplane of wavelength 4 kpc and amplitude 50 pc, potentially generated by the last perigalactic passage of the Sagittarius dwarf galaxy; and three distant, massive molecular structures, the Far Ara Clouds, two of which exhibit an exceptional velocity gradient, possibly lying near the Galactic bar’s far end or in a gas-rich dwarf galaxy 20~300 kpc beyond the disk. The images above are colour-composite plots of the integrated intensity mosaics in galactic coordinates in the three iso-CO lines, using red for ¹²CO, green for ¹³CO, and blue for C¹⁸O. The wide variations in line ratios across the Galactic plane are evident from the varying colors in this image.