We report the serendipitous discovery of an elliptical shell of CO associated with the faint stellar object SSTc2d J163134.1-240060 as part of the "Ophiuchus Disk Survey Employing ALMA" (ODISEA), a project aiming to study the entire population of protoplanetary disks in the Ophiuchus Molecular Cloud from 230GHz continuum emission and ^12^CO(J=2-1), ^13^CO(J=2-1) and C^18^CO(J=2-1) lines readable in Band 6. Remarkably, we detect a bright ^12^CO elliptical shape emission of ~3"x4" toward SSTc2d J163134.1-240060 without a 230GHz continuum detection. Based on the observed near-IR spectrum taken with the Very Large Telescope (KMOS), the brightness of the source, its three-dimensional motion, and Galactic dynamic arguments, we conclude that the source is not a giant star in the distant background (>5-10kpc) and is most likely to be a young brown dwarf in the Ophiuchus cloud, at a distance of just ~139pc. This is the first report of quasi-spherical mass loss in a young brown dwarf. We suggest that the observed shell could be associated with a thermal pulse produced by the fusion of deuterium, which is not yet well understood, but for a substellar object is expected to occur during a short period of time at an age of a few Myr, in agreement with the ages of the objects in the region. Other more exotic scenarios, such as a merger with planetary companions, cannot be ruled out from the current observations.

Cone search capability for table J/ApJ/938/54/fits (Summary of the VLT-KMOS spectrum of SSTc2d J163134.1-240060 (Data behind Figure 3))