Estancia La Aurora, Salto
On 17–18 February 1977, rancher Ángel María Tonna and his foreman at La Aurora, on the Daymán river by the Salto–Paysandú bridge, reported a fiery disc hovering behind the barn; a dog that ran at it was found dead.
1977 CE · -31.45, -57.91 · status: disputed
The account
The ranch had already been the scene of powerful lights since 1976, with reports of burned trees and vegetation and of animals dying. Tonna described an object like two plates rim to rim; his arm was affected but recovered. The case was reported to the US group APRO and became Uruguay's most famous UFO case. Radiation readings were claimed by a local doctor and by Japanese engineers from the Salto Grande dam. A rumour that astronaut Neil Armstrong visited the ranch was later shown to be false.
The sceptical view
The Uruguayan Air Force and other researchers called the phenomenon ball lightning or a purely meteorological event. Uruguayan researcher Eduardo Rodríguez has noted that the original 1976–77 events were never investigated at the time and Tonna was never formally interviewed.
The researched reading
A rancher’s report of a fiery disc that killed his dog. Ball lightning or an atmospheric light is the leading explanation, but the original events were never properly investigated.
| Explanation | Weight | Why |
|---|---|---|
| A poorly understood natural phenomenon | 30% | The Uruguayan Air Force and other researchers called the phenomenon ball lightning or a meteorological event; ball lightning remains poorly understood and could explain a fiery hovering light. |
| Something known, misidentified | 15% | Lights near a dam and river could be construction work, vehicles or bright planets. |
| Perception, memory or mind | 15% | Witnesses primed by earlier events at the ranch may have interpreted ordinary lights as a craft. |
| A hoax or fabrication | 12% | Claims such as the Armstrong visit were false, and radiation readings were never verified. |
| Genuinely anomalous | 12% | A dead dog, burned vegetation and the rancher’s arm injury are physical claims not fully explained, but the case was never formally investigated. |
| A known natural phenomenon | 10% | Lightning, fire or burning vegetation explain the scorched trees and dead animals. |
| Secret human technology | 6% | Military testing near the Salto Grande dam construction is a small possibility. |
Official position: The Uruguayan Air Force called it ball lightning or a meteorological event.