In 1965, at the height of Cold War anxieties over China’s nascent nuclear programme, the CIA and India’s Intelligence Bureau launched a covert mission to install a nuclear‑powered listening device high on Nanda Devi. Then the weather turned.
A long-buried Cold War secret in the Indian Himalayas is back in the spotlight: a lost nuclear-powered device, abandoned near Nanda Devi nearly 60 years ago, may still be entombed in ice above the headwaters of the Ganga.
In 1965, at the height of Cold War anxieties over China’s nascent nuclear programme, the CIA and India’s Intelligence Bureau launched a covert mission to install a nuclearpowered listening device high on Nanda Devi, India’s secondhighest peak.
The system relied on a radioisotope thermoelectric generator (RTG) fuelled by several kilograms of plutonium, meant to power sensors that would eavesdrop on Chinese missile and nuclear tests across the border.
Caught in a ferocious blizzard, the joint team cached the device on the mountain and retreated; when climbers returned the next season, the RTG and its plutonium core had vanished, likely swept away by avalanche or buried deep in the glacier.
WHAT IS RTG?
An RTG, or Radioisotope Thermoelectric Generator, is a device that makes electricity using heat from a radioactive material. The material slowly gives off heat as it naturally breaks down.
The RTG converts this heat into electricity, without any moving parts.
RTGs are often used in space missions or remote places where solar power does not work well. They are very reliable and can produce power for decades. An RTG is not a nuclear bomb and cannot explode. Its main concern is radiation safety if the material is damaged or exposed.
WHERE IS THE LOST DEVICE NOW?
Decades of subsequent Indian and American search missions have failed to locate the generator, and neither government will say exactly what became of it. Some officials and authors have speculated that an Indian team may have quietly retrieved the hardware, while others believe the unit is still locked somewhere in the unstable ice and rock of the Nanda Devi massif.
A 1978 survey by India’s Atomic Energy Commission reported no detectable plutonium contamination in local rivers, but it also could not pinpoint the device’s location, leaving its fate unresolved.
RADIOACTIVE RISK ABOVE GANGA
The stakes are high because Nanda Devi’s glaciers feed the Rishi Ganga and Dhauliganga, which join the Alaknanda and eventually the Bhagirathi to form the Ganga, lifeline to hundreds of millions downstream. Experts say an intact, wellshielded RTG buried deep in ice poses limited immediate risk, but any breach in its containment over time could release radioactive material into meltwater and sediments flowing towards heavily populated plains.
That “low probability, high impact” scenario haunts environmentalists and local communities every time a flood, avalanche or rockice collapse hits Uttarakhand’s fragile valleys.
The renewed focus on the Nanda Devi device comes amid worsening Himalayan glacier melt, more frequent disasters like the 2021 Chamoli flood, and rising scrutiny of historic nuclear and military footprints in ecologically sensitive zones.
While no radiation leak has ever been confirmed, scientists warn that continued warming and glacial retreat could eventually expose or disturb whatever remains of the RTG.
For India and the United States, the episode is also an enduring reminder of how a secret strategic gamble in the high Himalayas created a longlived environmental question mark over one of the world’s most sacred and densely reliedupon river systems.
