During the Vietnam War, the United States dropped more than 8 million tons of bombs and sprayed 74 million liters of Agent Orange and other herbicides in Vietnam, Cambodia, and Laos. Nearly 50 years after the war’s end, the deadly impacts of these campaigns persist: Unexploded ordnance continues to maim and kill, while hot spots of dioxin, a potent toxin in the herbicides, might still be contributing to cancers and birth defects today. Now, using declassified military satellite photos, scientists have identified the likely locations of these hidden dangers, which could help direct remediation and cleanup efforts based on research, presented on December 11, 2024 at the annual conference of the American Geophysical Union (AGU)

Identifying these risky areas in the modern landscape is challenging. Tenacious vegetation growth has long since hidden the scars of war, and historical records of bombing and herbicide spraying are both incomplete and imprecise. That’s why Philipp Barthelme, a graduate student in geoscience at the University of Edinburgh, and his colleagues turned to declassified satellite photos from the KH-9 HEXAGON and KH-4a/b CORONA missions, which were sharp enough to reveal details as small as 0.6 meters.

Although the satellite data alone cannot identify unexploded bombs, the researchers surmised they are most likely to be found in regions that were heavily bombarded. The craters from the exploded bombs stand out in the satellite images as bright white splotches. The researchers used machine learning, a kind of artificial intelligence, to pinpoint more than 500,000 such craters in Vietnam’s Quang Tri province, which was the most heavily bombed during the war, as well as a region near the borders of Vietnam, Laos, and Cambodia.

In collaboration with the nonprofit Conflict and Environment Observatory, Barthelme also used satellite data to study herbicide spraying in southern Laos. The U.S. sprayed these compounds in secretive wartime campaigns to destroy crops and improve visibility by defoliating the lush jungles. However, the dioxin in the herbicides killed and debilitated hundreds of thousands of people…The zones of defoliation from the herbicides appear in satellite data as bright, sinuous lines….

Excerpts from Maya Wei-Haas, Declassified satellite photos reveal impacts of Vietnam War, Science, Dec. 14, 2024