The Sandia Base Green Fireball File: Los Alamos, LaPaz, and the 1948-1950 New Mexico Investigation

Source file: DOW-UAP-D017_General_Correspondence_Of_Sandia.pdf Originating agency: Department of Energy (legacy AEC / Sandia Base) — compiled by the 17th District Office of Special Investigations (USAF), Sandia Base, the Atomic Energy Commission / Atomic Energy Security Service, and Fourth Army Control markings: Originally SECRET and CONFIDENTIAL (declassified, authority NW 91526 / NND 58378) Date range: April 1949 file cover through May 1950 (sightings tabulated December 1948 – May 1950; some reference incidents from 1947) Page count: 116 (all read) PURSUE Release: 2

Summary

This document is a 116-page bound compilation of the original government investigation into the New Mexico "green fireballs" — the wave of unexplained luminous aerial phenomena observed over the nation's most sensitive nuclear-weapons installations between December 1948 and the spring of 1950. Despite the modern DOW-prefixed filename, the contents are entirely a product of the post-war atomic complex: Sandia Base (Albuquerque), Los Alamos, Kirtland Field, the Atomic Energy Commission, the Armed Forces Special Weapons Project (AFSWP), Fourth Army, and the 17th District Office of Special Investigations (OSI) of the U.S. Air Force.

The file assembles, in roughly chronological layers: a 1949 Sandia Base classified-documents-library cover sheet titled "Unidentified Flying Objects" (File No. 333.5); the comprehensive 17th District OSI "Summary of Observations of Aerial Phenomena in the New Mexico Area, December 1948 – May 1950" (dated May 25, 1950) signed by Lt. Col. Doyle Rees, with its master tabulation of more than 200 numbered sightings; the analyzed photograph of Sighting No. 175 taken at Datil, New Mexico; the serial "Anomalous Luminous Phenomena" reports of Dr. Lincoln LaPaz of the University of New Mexico Institute of Meteoritics; the February 16, 1949 trip report by Commander Richard Mandelkorn describing the Los Alamos scientific conference held under the codename Project "Grudge"; the copper-particle airborne-collection studies of Dr. W. D. Crozier of the New Mexico School of Mines; and supporting Fourth Army "Unusual Lights" summaries from Camp Hood, Texas. Together they constitute the single most important primary-source body for the founding era of official U.S. UAP concern.

Research Article

Why this file matters

This is, in effect, the origin file of the entire modern phenomenon of official anxiety about unidentified objects over nuclear sites. Beginning around December 5, 1948, observers — including Atomic Energy Security Service (AESS) inspectors at Los Alamos, AEC security agents at Sandia, military pilots, airline pilots, and ordinary citizens — began reporting brilliant green, horizontally-moving fireballs over the New Mexico atomic installations. Because the phenomena clustered over Los Alamos, Sandia, and Kirtland, the matter was treated not as an astronomical curiosity but as a potential security threat, and it was investigated at the highest scientific levels available to the United States at the time. The file's recurring refrain — that "the continued occurrence of unexplained phenomena of this nature in the vicinity of sensitive installations is cause for concern" — is the through-line of the whole investigation.

The OSI Summary and the master sighting tabulation (the May 1950 report)

The spine of the file is the 17th District OSI's "Summary of Observations of Aerial Phenomena in the New Mexico Area, December 1948 – May 1950," dated May 25, 1950, and signed by Lt. Col. Doyle Rees, District Commander. Its body is a multi-page tabulation listing more than 200 individually numbered sightings, each with columns for date, time, number of observers, reliability, location, direction of flight, altitude, color, train/trail, duration, sound, shape, apparent size, apparent speed, and manner of disappearance. Each sighting is given one of three evaluations: (1) "Green Fireball Phenomena," (2) "Disk" or Variation, or (3) Probably Meteoric.

The geographic concentration is striking: Los Alamos, Sandia Base, Albuquerque, Alamogordo, Holloman, Las Vegas (NM), Roswell, Vaughn, and Tucumcari recur constantly, alongside a cluster of "Unusual Lights" over the Camp Hood / Killeen Base "Q" Area in Texas (an atomic-weapons storage site). The colors are overwhelmingly green, blue-green, and greenish-white. The summary explicitly notes that its observers "include scientists, Special Agents of the Office of Special Investigations (IG) USAF, airline pilots, military pilots, Los Alamos Security Inspectors, military personnel, and many other persons of various occupations whose reliability is not questioned."

The summary records that conferences were held at Los Alamos on February 17, 1949 and again on October 14, 1949 to discuss the phenomena, attended by representatives of the Fourth Army, the Armed Forces Special Weapons Project, the University of New Mexico, the Federal Bureau of Investigation, the U.S. Atomic Energy Commission, the University of California, the U.S. Air Force Scientific Advisory Board, the Geophysical Research Division of Air Materiel Command, and OSI. As the summary states: "A logical explanation was not proffered with respect to the origin of the green fireballs. It was, however, generally concluded that the phenomena existed and that they should be studied scientifically until these occurrences have been satisfactorily explained."

Dr. Lincoln LaPaz and the case against meteors

The scientific heart of the file is the series of "Anomalous Luminous Phenomena" reports written by Dr. Lincoln LaPaz, Director of the University of New Mexico's Institute of Meteoritics and an internationally respected meteoriticist who served the OSI as a voluntary consultant. The file preserves several of these serial reports (the Second/Third Reports of December 1948, the Fourth Report of February 21, 1949, the Sixth Report of August 17, 1949, and the Seventh Report of May 23, 1950).

Across these reports LaPaz builds a meticulous case that the green fireballs were not ordinary meteors. In his December 20, 1948 report he listed ten differences between the green fireballs and typical meteors: their unusual horizontal paths; their very low height (roughly 8 to 10 miles, versus 40+ miles for meteors); a velocity less than that of meteors but greater than V-2 rockets or jet planes; the absence of the violent noises that accompany low meteorite falls; their instantaneous full brightness rather than the gradual brightening of meteors; their pronounced tendency to approach from the northern half of the sky; their curious association with known meteor showers; their vivid green color (which by laboratory test "seems to be identical with that given off by copper salts in the blowpipe flame," with a wavelength near 5,218 Angstroms); their duration of 2 to 3 seconds; and the complete absence of any train of sparks or dust cloud.

LaPaz reduced the real path of the December 12, 1948 fireball using corresponding observations from a station near Starvation Peak (Bernal) and a station within the Los Alamos reservation, finding a nearly horizontal path roughly 25 miles long at an altitude of about 8 to 10 miles, with the backward extension of the path passing "almost centrally across the Los Alamos reservation." His Fourth Report describes the great fireball of January 30, 1949 — within one minute of its appearance an eyewitness telephoned to report it, and "within twelve hours after the fireball appeared, more than 100 eyewitness accounts had been obtained." LaPaz determined that fireball traversed "a nearly horizontal path approximately 143 miles long at a velocity of from seven to fourteen miles per second."

The Soviet-missile hypothesis

The file's most geopolitically charged content is LaPaz's Seventh Report (May 23, 1950), in which he offers his most explicit interpretation. He notes that the time interval during which most green fireballs were sighted in New Mexico (roughly 5 p.m. to 11 p.m. MST) corresponds to roughly 7 a.m. to 1 p.m. in the Ural region of the USSR. "Since missiles moving with velocities of the order of those found for the green fireballs would travel from the southern Urals to New Mexico in less than 15 minutes," he wrote, "a possible interpretation of the concentration of sightings... is that the green fireballs result from guided missiles launched from bases in the Urals in the morning hours before cloudiness due to convection or blinding afternoon dust storms can interfere with non-radar tracking."

Quoting his own February 20, 1950 letter to Dr. P. H. Wyckoff, LaPaz concluded the fireballs fell into one of two categories: "Those of the first category (the majority) are meteorite falls of unusual, but certainly not of impossible, magnitude, frequency and other characteristics; those of the second category (the minority) are U.S. guided missiles undergoing tests in the neighborhoods of the sensitive installations they are designed to defend. This interpretation of the latter category is the one that I proposed in answer to a question raised by Dr. Teller at the first Los Alamos conference on February 17, 1949." He then stressed: "even if my interpretation of the unconventional fireballs is the correct one, it is obvious that those in position to confirm it should refuse to do so," and warned of "the imperative necessity of immediate investigation of the unconventional green fireballs, in case you are in possession of information proving that they are not U.S. missiles."

The Los Alamos conference and Project "Grudge"

One of the most remarkable documents is the four-page "Report of Trip to Los Alamos, New Mexico, 16 February 1949" by Commander Richard S. Mandelkorn, U.S.N., of the Research and Development Division, Sandia Base — explicitly subtitled Project "Grudge." It records a conference convened to ask Los Alamos's nuclear scientists to explain the green fireballs. The attendees read as a roster of the Manhattan Project: for Los Alamos, N. E. Bradbury (the laboratory director), Marshall Holloway, Fred Reines, John Manley, and Edward Teller, with Elmo Morgan (AEC), Sidney Neuberger (Security), and others; for Fourth Army, Major William A. Godsoe and Major Wynn; for the USAF, Captain Neef; and for the University of New Mexico, Dr. Lincoln LaPaz.

Captain Neef opened by stating that the question "had been classified military SECRET under the name, Project 'Grudge.'" LaPaz described the characteristics of the phenomena and his own observation of the "Starvation Peak Incident." Then, per the report, "Mr. Teller then took over the discussion and showed that a material object travelling with the velocity of the subject phenomenon (about eight miles per second) would have to have a mass of about twenty grams" to produce the observed light, and that such an object passing through the atmosphere at 8 to 10 miles altitude "would produce a loud noise easily audible ten kilometers from the source. No sound has been observed. Therefore, Mr. Teller has the tentative opinion they are not material objects passing through the air." The conferees found "it was almost incredible that a large object such as a guided missile or informer vehicle could pass through the atmosphere at a velocity of seven to eight miles per second without producing a loud noise."

Mandelkorn's conclusion preserves the genuine uncertainty of the moment: "It is my belief that these phenomena... are deserving of serious consideration until their source and meaning have been satisfactorily explained. Although Mr. Teller's discussion tends to disprove the hypothesis that guided missiles or informer vehicles are responsible, there is cause for concern of the continued occurrences of unexplainable phenomena of this nature in the vicinity of sensitive installations."

The Crozier copper-particle studies

The file also contains a distinct scientific sub-investigation: the attempt by Dr. W. D. Crozier and Ben K. Seely of the New Mexico School of Mines to physically collect airborne particles associated with the green fireballs, in particular to test LaPaz's hypothesis that the fireballs deposited copper-bearing dust. Their report, "An Attempt to Collect Airborne Particles Associated with the Fireball of July 24, 1949," documents impactor collections at Socorro and along Highway 84, finding scattered copper-bearing particles and even "three quite remarkable particles that gave very strong cobalt indications" in the form of "perfect spheres." Their conclusion was cautiously negative: "it seems very hazardous to draw any definite conclusion associating the copper-bearing particles collected with the fireball of July 24. There still is, however, a residuum of possibility of such associations." A B-25 from Kirtland Field was even used on August 8, 1949 to attempt an airborne collection above 23,000 feet.

The Datil photograph (Sighting No. 175)

The file includes a genuine photograph — one of the few physical-evidence items in the early UAP record. It is captioned "Sighting No. 175, Photograph of Unknown Aerial Phenomena taken at Datil, New Mexico by Cpl Lertis E. Stanfield, Holloman Air Force Base, New Mexico on 24 and 25 Feb 1950." LaPaz analyzed it and concluded that the object's angular diameter was approximately 1/4 of a degree and its angular velocity greater than half a degree per minute, and on that basis: "the object seen by Stanfield was not the moon (for the angular diameter is too small), it was not Venus or any other planet (for the angular diameter was too large), and it was not a bright fixed star slightly out of focus (for the observed rate of motion is double that due to the diurnal rotation of the earth)."

Significance

For an archive tracing the official and institutional handling of UAP, this file is a cornerstone primary source — arguably the single most consequential body of material in PURSUE Release 2. It documents that the United States' nuclear-weapons establishment took unidentified aerial phenomena seriously enough to convene its most senior physicists, commission a respected meteoriticist, run airborne particle-collection flights, and circulate SECRET summaries among the AEC, the FBI, Fourth Army, and Air Materiel Command. It contains a named, reasoned scientific argument that the objects were not meteors; an explicit (if guarded) hypothesis that some were Soviet guided missiles; and Edward Teller's counter-argument that they were not material objects at all. It is the institutional seedbed of Project Twinkle and of the entire post-war pattern of UAP activity over sensitive installations.

Key People

Locations

Incidents

Notable Quotes

"A logical explanation was not proffered with respect to the origin of the green fireballs. It was, however, generally concluded that the phenomena existed and that they should be studied scientifically until these occurrences have been satisfactorily explained. Further, that the continued occurrence of unexplained phenomena of this nature in the vicinity of sensitive installations is cause for concern." — OSI Summary, May 25, 1950 (Lt. Col. Doyle Rees)

"The horizontal nature of the paths of most of the December fireballs is most unusual. Genuine meteors are rarely observed to move in horizontal paths." — Dr. Lincoln LaPaz, Anomalous Luminous Phenomena report

"By laboratory test this peculiar color seems to be identical with that given off by copper salts in the blowpipe flame. If this identification is correct, the wave length of the radiation from the green fireballs is near λ = 5,218Å." — Dr. Lincoln LaPaz, Seventh Report

"Those of the first category (the majority) are meteorite falls of unusual, but certainly not of impossible, magnitude... those of the second category (the minority) are U.S. guided missiles undergoing tests in the neighborhoods of the sensitive installations they are designed to defend." — Dr. Lincoln LaPaz, quoting his Feb. 20, 1950 letter to Dr. Wyckoff (Seventh Report)

"even if my interpretation of the unconventional fireballs is the correct one, it is obvious that those in position to confirm it should refuse to do so." — Dr. Lincoln LaPaz, Seventh Report

"Mr. Teller then took over the discussion and showed that a material object travelling with the velocity of the subject phenomenon (about eight miles per second) would have to have a mass of about twenty grams... Therefore, Mr. Teller has the tentative opinion they are not material objects passing through the air." — Mandelkorn, Report of Trip to Los Alamos, Feb. 16, 1949

"Although Mr. Teller's discussion tends to disprove the hypothesis that guided missiles or informer vehicles are responsible, there is cause for concern of the continued occurrences of unexplainable phenomena of this nature in the vicinity of sensitive installations." — Mandelkorn, Project "Grudge" report

"Dr. LaPaz stated that on the basis of the results... the object seen by Stanfield was not the moon (for the angular diameter is too small), it was not Venus or any other planet (for the angular diameter was too large), and it was not a bright fixed star slightly out of focus (for the observed rate of motion is double that due to the diurnal rotation of the earth)." — Analysis of Sighting No. 175 (Datil photograph)

"it seems very hazardous to draw any definite conclusion associating the copper-bearing particles collected with the fireball of July 24. There still is, however, a residuum of possibility of such associations." — Crozier & Seely, particle-collection report