NASA · NASA-UAP-D015
Mercury Astronaut Scientific Debriefings and the Glenn Luminous Particles (1962-1963)
This file is a 216 page compilation of Project Mercury scientific debriefing material from 1962 and 1963, centered on the post flight scientific analysis of observations by John Glenn (MA-6), Scott Carpenter (MA-7), and Gordon Cooper (MA-9). Its UAP relevance is narrow and specific: it is the primary documentary record of the "luminous particles" Glenn reported on his first orbital flight (the "fireflies"), and it contains the contemporaneous NASA scientific reasoning that characterized them as particles associated with the spacecraft rather than anything extraterrestrial.
Key excerpts
“From t[h]e [velocity] considerations alone, it may be stated that the luminous [p]articles observed by Col. Glenn were not extra[t]errest[r]ial particles but were particles asso[c]iated with the spacecraft or [the] la[unching] of the booster. (lines 151 to 157)”
“Shortly before reentry, just at sunri[s]e, Carpenter performed the de[c]isi[v]e experi[m]ent of hitting the capsule walls with hi[s] hand. The blows promptly resulted i[n] the liberation of large numbers of particles. It i[s] thus clear that at least those parti[c]les observed in the MA-6 flight emanated from the capsule. (lines 1279 to 1285)”
“It i[s] con[s]idered most likely that t[h]e particles of the Glenn effect are snowflakes f[o]rmed [i]n the capsule, between the cabin bulkhead and the heat shi[e]ld by the steam exhaust from the li[f]e-support system. (lines 1387 to 1393)”
Alternative hypotheses
Ice or snow particles condensed from the life support system, plus capsule debris
the documented explanation, most probable).
Dust, waste, and insulation sweepings shed from the exterior of the capsule
Dye marker or shark repellant escaping from the capsule
Extraterrestrial particles
least probable, and rejected on the record).