Science: Atomic Footprint

Since the atom bomb hit Hiroshima, Jap reports have played on the U.S. conscience with reports of weird, agonized deaths of civilians who had appeared untouched by the explosion (see MEDICINE). The plain implication: radioactivity from the bombs would go on killing men and vegetation in Hiroshima and Nagasaki for years to come.

To scotch these stories, the U.S. Army last week took 31 newsmen to see with their own eyes the first awesome footprint of man’s newest genie in the earth of New Mexico. Though the footprint was eight weeks old, it was still awesome.

The wide, flat valley dotted with greasewood, yucca and bunch grass selected as site for the test explosion is known in Manhattan Project doubletalk as “Trinity.” Most of the land once belonged to a rancher named MacDonald, whose wrecked ranch house was the first human habitation to be blasted by the terrible force of exploding atoms. Ten thousand yards from the test site are the two low, heavy-timbered buildings, banked to the roof with earth, which housed the bomb-exploding generator and observation instruments (known in atom-scientist code as “Beta” and “Ten Thousand”). Nearby stand two white-painted Sherman tanks used to examine the area immediately after the explosion—airtight and lead-lined to protect the crews from radiation—hung with mysterious instruments which the Army’s cautious scientists still refuse to explain.

Lake of Jade. Seen from the air, the crater itself seems a lake of green jade shaped like a splashy star and set in a sere disc of burnt vegetation half a mile wide. From close up the “lake” is a glistening incrustation of blue-green glass 2,400 ft. in diameter, formed when the molten soil solidified in air. The glass takes strange shapes—lopsided marbles, knobbly sheets a quarter-inch thick, broken, thin-walled bubbles, green, wormlike forms.

In the glass lake’s center, directly beneath the bomb’s exploding point, is a crater of bare earth about 15 ft. deep and 300 ft. across. Scientists told newsmen the earth here was pushed downward ten feet by the explosion’s force. Stumps of the four reinforced-concrete tower pillars that supported the bomb still stand in the crater, flaked and twisted. The rest of the tower has vanished into vapor.

Aftereffects? Major General Leslie R. Groves and Physicist J. Robert Oppenheimer, military and scientific parents of the atom bomb, parried all questions about the bomb itself. But about its aftereffects they were anxious to talk. Data on Hiroshima and Nagasaki will not be complete until scientists now on the spot have finished their tests. But all three atomic explosions, said General Groves, were “comparable” in power. Important difference was that New Mexico’s test bomb went off only 100 ft. above ground, those in Japan “much higher.” Hence the effects of their blast, heat and radiation were spread much thinner, their radioactivity dissipated more completely in the atmosphere. The explosions in Japan, General Groves asserts, were timed for higher altitude both to increase the blast and to reduce residual radioactivity. Even in New Mexico, vegetation not destroyed by the blast remained healthy, showed no aftereffects of radioactive gases.

But newsmen at Trinity last week could not leave their cars at the crater’s rim without first donning canvas overshoes to protect themselves against burns from radioactive material which might lodge in their shoes. Scientists with radiometers like long-lensed cameras found several “hot spots” near the inner crater’s edge, warned others to stay away. Reporters who enthusiastically pocketed souvenir bits of crater glass had second thoughts when someone recalled the effects of radiation on fertility. The radiometers proved that some of the souvenirs were actually still dangerous.