The Montchaboud Vapour Ball

At twenty past ten on the night of 26 July 2012 a retired man went out onto his balcony at Montchaboud in the Isère, as he did most evenings. The sky was clear and not yet fully dark. Over the mountains to the south-south-east a mass rose into view. It was roughly round with blurred edges and seemed to swirl. It was silver-grey, a little larger than the full Moon and far fainter. It moved in a straight line and without a sound. In three to six seconds it reached the zenith, where the roof of the house hid it. He saw a few bright points below it and a turbulent trail behind. He stayed out for nearly two hours in case it returned, then wrote it all down.

What is on the record

The archive holds the case file of GEIPAN, the unit of the French space agency CNES that investigates UAP reports. It publishes the gendarmerie report and a 2014 investigation report. Because the case was so odd, GEIPAN's head went to interview the witness in October 2012.

The report works through seven explanations. A balloon on the wind would have had to be very low. The nearest wind reading also ran the wrong way. A rocket venting fuel looks like this but takes minutes to cross the sky, and no launcher or satellite was passing. A comet would have moved far too slowly. Space debris did re-enter that day, but debris burns brighter and longer. Ball lightning did not suit the calm weather. A cloud of midges near a street light would have grown as it came closer. A phosphene, a flash inside the eye, could not be checked. GEIPAN called the account "de grande qualité, très précis, bien documenté" (high quality, very precise, well documented). It still rests on one person with no photo or video.

Why it sits where it does

The page grades L0 · SINGLE ACCOUNT. GEIPAN withholds witness identities and the record calls him only "un témoin", so it carries no identified witness. Class D means GEIPAN investigated and could not explain the case, which it scores 0.75 for consistency and 0.6 for strangeness. The tier measures sourcing, not the quality of the investigation, and it is never a verdict. What crossed the sky over Montchaboud is not resolved here.