Science: Test’s Aftermath

After a few days delay to conceal the workings of their detection systems, U.S. authorities began last week to release a few details about the 30-megaton nuclear test in the Soviet Arctic. A 30-megaton explosion is not easy to hide. The island of Novaya Zemlya adjoins the international waters of the Barents Sea, and U.S. airplanes were presumably cruising near the Soviet test range. U.S. submarines were probably watching through periscopes, just as Russian submarines keep track of U.S. rocket shots from Cape Canaveral. Besides such eye and camera witnesses, the U.S. had a varied array of instruments to measure vibrations in the earth, air and ocean. The light given off by the explosion can tell a great deal about the size, height and development of the fireball. Analysis of the radioactive residue caught by filters on high-flying airplanes can reveal the composition of the Russian explosive and trace its nuclear reactions.

Local Fallout. Not much of this information has been made public, but besides estimating the power of the Russian blast at 30 megatons, the U.S. confirmed the fact that it took place at 12,000 ft. above the ground. The bomb was carried aloft by a rocket, perhaps, or, more likely, suspended from a captive balloon. However it was hoisted, the bomb’s height was carefully chosen to minimize local fallout. If the fireball did not touch the ground before it stopped expanding, little or none of its radioactive material would mix with pulverized soil blown out of its massive crater.

Soviet citizens living south of the test area have reason to hope that the fireball actually did clear the ground. If it did, most of its fission products were carried into the stratosphere, from which they will fall gradually over several years, covering a broad zone around the Northern Hemisphere. If the fireball touched the ground, its local fallout would seriously contaminate a cigar-shaped region many hundreds of miles downwind. U.S. weathermen calculated that the north winds blowing just after the Soviet test would carry local fallout southward into Soviet Russia down to the latitude of Leningrad.

Unwelcome Cloud. Even if the blast gave no local fallout, it surely created some fission products that stayed below the stratosphere to drift with the winds of the lower atmosphere until rain or snow brought them down. By studying their charts, U.S. meteorologists figured that this cloud of tropospheric fallout moved southward into Russia, then swung eastward to cross Siberia. At week’s end, it was heading across to the U.S. (see map) near Oregon and Idaho where rain was expected to wash some of its radioactive debris to earth.

The cloud crossing U.S. territory may or may not have lost most of its radioactive intensity. There was no immediate reason for alarm, said the U.S. Public Health Service, but the PHS is taking no chances. The unwelcome cloud, and all the clouds that may follow it, will be watched attentively. U.S. air, water, milk and other foodstuffs will be examined continuously for a possibly dangerous content of Soviet radioactivity.