Back in the 1960s, the US and India schemed to plant a
surveillance device on the Nanda Devi peak so they could observe
China's for possible nuclear bomb tests.
Spies scaled the mountain to put the device there, but at the final
camp, a blizzard forced them to descend, leaving the
nuclear-powered device hidden somewhere around the camp.
Next spring they returned to complete the job, but they found the
device missing, along with its plutonium rods. It was suspected
that an avalanche caused the ledge, holding the device, to be
sheared off into the ice fields below. The US spent years searching
for the contraption but to no avail.
In 2005, traces plutonium-239, an isotope that does not occur
naturally, was found in a water sample from the Himalayan mountain
range.
Which means... one day the Ganges River might be polluted by four
pounds of radioactive material...
