The Object That Followed the Crew for 24 Hours
On 9 December 1972, two days into Apollo 17's translunar coast, Commander Gene Cernan looked out his window and saw something that wasn't supposed to be there: a bright object, far from the spacecraft, flashing with precise rhythmic regularity — alternating between a brilliant flash and a dimmer one, over and over, on a clockwork cycle.
Lunar Module Pilot Jack Schmitt had already been watching it for roughly 24 hours. He had noticed it the day before but hadn't put it together. Now both men were looking at the same thing, and it was clearly not one of the nearby debris particles — there were particles close by to compare against, and this was something else entirely, distant and rotating.
Houston was called. The crew gave position marks. Mission Control tried to triangulate its location using gimbal angles and NOUN 20 spacecraft attitude readings. The object was observed, debated, and logged — and it appears in the official Apollo 17 flight transcript, timestamped and verbatim, exactly as the crew reported it.
Apollo 17 launched on 7 December 1972 — the only night launch of the Apollo programme — and remains the most recent mission to carry humans to the lunar surface. The crew were Commander Eugene "Gene" Cernan, a veteran of Gemini 9 and Apollo 10; Lunar Module Pilot Harrison "Jack" Schmitt, a geologist and the only professional scientist to walk on the Moon; and Command Module Pilot Ron Evans, who remained in lunar orbit while Cernan and Schmitt descended to the Taurus-Littrow valley.
The mission broke records across the board: longest time on the lunar surface (75 hours), longest EVAs, most samples collected. Schmitt's scientific training was considered a primary mission asset — he was trained to notice things others might not. Which makes his account of the following encounter all the more striking.
| Event 1 — The Rotating Flasher | A bright object far from the spacecraft, clearly distinct from nearby debris, rotating rhythmically and flashing alternately bright then dim. Observed by Schmitt for ~24 hours and confirmed by Cernan. Houston attempted triangulation via gimbal angles. MET 02:18:47. |
| Event 2 — Two Simultaneous Flashers | CMP Ron Evans later reported two separate objects showing the same bright/dim alternating flash pattern, widely separated. Both had consistent intensity. Evans suggested SLA (Spacecraft LM Adapter) panels but this was not confirmed. MET ~02:20:56. |
| Event 3 — Flash on the Lunar Surface | Jack Schmitt interrupted a geology report mid-sentence to call out a bright flash north of Grimaldi crater during lunar orbit. 'A thin streak of light.' Houston checked seismometers for a meteorite impact. Recorded at MET 03:15:38. |
The exchange begins at mission elapsed time 02:18:47. The spacecraft is roughly two days into translunar coast. Cernan spots the object and begins describing it to Houston, with Schmitt confirming:
"Hey, Bob, I'm looking at what — what Jack was talking about; and it's definitely not a particle that's nearby because there is another one I can look at and get a three-dimensional comparison with. It is a — it is a bright object, and it's obviously rotating because it's flashing. It's way out in the distance, as I say, because there are particles that are close by and it's obviously not one of those. It's apparently rotating in a very rhythmic fashion because the flashes come around almost — almost on time. And it's as we look back at the Earth, it's up at about 11:00 — about — oh, maybe 10 or 12 Earth diameters. I don't know whether that does you any good, but there is something out there."— CDR Gene Cernan — Apollo 17 Flight Transcript, MET 02:18:47
Houston's response is measured but engaged — they take it seriously and try to nail down a position:
"Roger. We don't doubt it, Gene. And we might work out a set of gimbal angles or something here; maybe we can get a look at it through the optics."— CAPCOM Bob Parker — Apollo 17 Flight Transcript
Cernan presses the point. He wants it understood that this is not the kind of spurious sighting that could be explained away as a nearby particle or lens flare:
"Okay. And I — I just want to emphasise that it's definitely not — not one of these particles that tends to look like a star out there. It's something physical in the distance."— CDR Gene Cernan — Apollo 17 Flight Transcript, MET 02:18:49
Houston requests a position mark. Cernan and Schmitt work together to give it: the object is at roughly 45 degrees pitched up from the spacecraft's centre window, in the XZ plane. Cernan gives a mark as it crosses the XX axis. Schmitt adds his own detail:
"One unique thing about it, Bob, is that it's got two flashes. As it comes around in — in rhythmic fashion, you get a very bright flash; and then you get a dull flash. And then it'll come around with a bright flash, and then a dull flash."— CDR Gene Cernan — Apollo 17 Flight Transcript, MET 02:18:51
"It's something physical in the distance."
— Commander Gene Cernan, Apollo 17 — 9 December 1972During the observation, Schmitt offers an explanation: the object might be the mission's spent S-IVB third stage, the 58-foot rocket body that had been jettisoned during translunar injection and was drifting ahead of them. He thought he could make out the engine bell through his monocular.
Cernan flatly disagreed. In the transcript, he says Schmitt "couldn't see the engine bell on that thing" if he had "10 monoculars." Later, Schmitt qualifies his own suggestion — noting he had been watching the object for roughly 24 hours without connecting it to the S-IVB, thinking it was "just some other particle out there." That timeline makes the S-IVB hypothesis more complicated: if Schmitt had been observing it for a full day, it would have been maintaining a consistent relative position to the spacecraft for an unusually long period.
For context: the S-IVB was intentionally crashed into the Moon during Apollo 17 to generate seismic data. Its precise trajectory was tracked by NASA throughout the mission. Whether it would have appeared as a rhythmically rotating, dual-flashing object at the described angular position has never been formally confirmed in the mission record.
Later, Evans reports a second object — then two simultaneous objects — with the same bright/dim alternating flash signature, widely separated. He suggests SLA panels (the four petals of the Spacecraft LM Adapter that separated during launch). This remains unconfirmed.
Three days later, in lunar orbit, Schmitt's observational instincts produce another unexpected report. Mid-sentence during a geology description of the Grimaldi region, he interrupts himself:
"Hey, I just saw a flash on the lunar surface! It was just out there north of Grimaldi. Just north of Grimaldi. You might see if you got anything on your seismometers, although a small impact probably would give a fair amount of visible light."— LMP Jack Schmitt — Apollo 17 Flight Transcript, MET 03:15:38
He elaborates: "a bright little flash right out there near that crater... a thin streak of light." Houston asks him to mark the location on his map and checks the seismometer network left on the surface by earlier missions. This is a documented Transient Lunar Phenomenon (TLP) — a category of unexplained optical events on the lunar surface that has been reported by observers since the 18th century.
"Hey, I just saw a flash on the lunar surface!"
— LMP Jack Schmitt, Apollo 17 — in lunar orbit, December 1972Veteran of Gemini 9 and Apollo 10. Formally reported the flashing object to Houston at MET 02:18:47. Gave position marks. Rejected the S-IVB explanation. The last human to walk on the Moon.
Professional geologist and the only scientist to walk on the Moon. Had been observing the object for approximately 24 hours before Cernan raised it. Also reported a flash on the lunar surface in orbit.
Orbited the Moon alone while Cernan and Schmitt were on the surface. Later reported seeing two simultaneous objects with identical bright/dim flash signatures, widely separated — possibly SLA panels.
Astronaut and physicist serving as capsule communicator during this leg of the mission. Responded to the crew's report: 'We don't doubt it, Gene.' Requested gimbal angles to attempt triangulation.
Apollo 17 lifts off from Kennedy Space Center at 00:33 UTC. The night launch illuminates the Florida coast for hundreds of miles. Crew: Cernan, Schmitt, Evans.
Lunar Module Pilot Jack Schmitt begins observing a flashing object from his window during translunar coast. He watches it for approximately 24 hours without formally reporting it, assuming it's 'just some other particle out there.'
Commander Cernan independently identifies the object and keys the radio. He emphasises it is clearly not a nearby debris particle, is physically distant, and is rotating rhythmically with two distinct flash levels: one bright, one dim.
CAPCOM Bob Parker requests gimbal angles and NOUN 20 spacecraft attitude data to attempt to locate the object through onboard optics. Cernan and Schmitt provide a position mark as the object crosses the XZ plane.
Schmitt suggests the object might be the mission's spent S-IVB stage. Cernan strongly disagrees — suggesting Schmitt couldn't distinguish the engine bell even with 10 monoculars. The debate is recorded verbatim in the transcript.
CMP Ron Evans calls in two separate objects with the same bright/dim alternating signature, widely separated. He suggests SLA panels but cannot confirm. Both objects maintain similar intensity and rhythm.
The spacecraft completes its translunar coast and enters lunar orbit. Cernan and Schmitt prepare to descend to Taurus-Littrow.
In lunar orbit, Schmitt interrupts a geological description to call out a bright flash north of Grimaldi crater — 'a thin streak of light.' Houston checks seismometers for a meteorite impact signature.
The full exchange is recorded in the official Apollo 17 flight transcript, published by NASA. Timestamped, verbatim, and publicly available. Not disputed or redacted.
Cernan, Schmitt and Evans all observed separate anomalous flashing objects during the mission. Each provided independent descriptions consistent with one another.
CAPCOM Bob Parker's response — 'We don't doubt it, Gene' — and the subsequent request for gimbal angles indicates Mission Control treated the sighting as a genuine object worth attempting to locate.
Cernan described a precise, clockwork alternation: bright flash, dim flash, bright flash, dim flash. This regularity is inconsistent with random debris tumbling and was noted by both crew members.
Schmitt had been watching the object for approximately 24 hours before it was formally reported. This sustained relative position to the spacecraft is difficult to account for with random debris.
When Schmitt offered the S-IVB as an explanation, Cernan disputed it immediately and vigorously. The disagreement is recorded in the transcript. No formal NASA resolution appears in the record.
Schmitt's flash report north of Grimaldi is consistent with Transient Lunar Phenomena, a long-documented but not fully explained category of optical events on the lunar surface.
Unlike some mission anomalies, there is no formal post-mission NASA analysis of the flashing objects in the publicly available Apollo 17 documentation. The transcript record stands without a definitive explanation.
Most UAP sightings from the Apollo programme involve brief visual observations — a flash, a particle, a brief glimpse of something anomalous before it passes out of frame. The Apollo 17 encounter is different in several respects.
It lasted approximately 24 hours before being formally reported, which means the object maintained a consistent angular position relative to the spacecraft for an extended period. It was observed by two crew members independently and cross-confirmed. It was precise enough in its behaviour — the alternating dual-flash cycle — to be described consistently by both Cernan and Schmitt without prompting each other. And Houston's response was to attempt to locate it, not to dismiss it.
The S-IVB explanation may ultimately be correct — it was the closest large piece of hardware following the same general trajectory. But Cernan's rejection of that explanation in real time, Schmitt's observation duration, and the fact that no formal post-mission analysis appears in the public record leaves the question open.
What is not in question is that three of NASA's most rigorously selected and trained crew members reported it, that Mission Control took it seriously, and that the exchange is preserved verbatim in the official transcript.