No. 49: Jan-Feb 1987
Following the famous mystery cloud of April 9, 1984 (SF#38), the authors of the original article in Science collected additional observations and now have this to say:
"Our conclusion is that original estimated positions were in error. Additional data, primarily from Van den Berg, place the event between the Kuriles and Sakhalin. The altitude of the center of the halo at the maximum observed size is estimated to have been greater than 200 miles, and the diameter of the halo is estimated to have been at least 380 miles. It seems unlikely that a groundbased explosion could produce this kind of effect. It is surprising to us that no official data have been provided by government agencies and that such a significant observation from a region of demonstrated military sensitivity was, and still remains, a mystery."
(McKenna, Daniel L., and Walker, Daniel A.; "Mystery Cloud: Additional Observations," Science, 234:412, 1986.)
Evidently the mystery cloud mentioned above is only one in a long series:
"Large icy clouds, similar to plumes of gas that rise over volcanoes, have appeared over islands along the coast of the Soviet Union during the past several years, baffling experts, who cannot explain what they are or what causes them.
"The clouds dissipate in a few hours vanishing as mysteriously as they appear.
"Among the plumes are a series of massive clouds that during the past four years have periodically swelled over Novaya Zemlya, the Arctic island long used by the Soviets for nuclear weapons tests.
"However, there appears to be no correlation between the clouds and known Soviet tests, which are usually detected by Western governments. Further, non-governmental scientists said the 200-mile-long plumes appear to be many times larger than the largest conceivable nuclear explosion could produce."
A NOAA satellite detected a large plume coming from the Arctic Ocean near Bennett Island, north of the Soviet Union, in 1983. Three distinct sources were found; one on the island and the other two about 9 miles offshore on the ice-covered ocean. This plume was 6 miles wide, 155 miles long, and 23,000 feet high.
(Anonymous; "'Plumes' over Soviet Isles Continue to Baffle Experts," Las Vegas Sun, July 20, 1986. Cr. T. Adams via L. Farish)