Scientists are using decades-old radioactive glass discovered covering the ground after the first nuclear test bomb explosion to explore ideas on the Moon’s genesis some 4.5 billion years ago.
In a recent study, Professor James Day of the Scripps Institution of Oceanography at the University of California, San Diego, and colleagues looked at the chemical makeup of zinc and other volatile elements found in the trinitite, a green-colored glass that was created when radioactive materials were exposed to the high temperatures produced by the 1945 plutonium bomb explosion.
The test samples used for analysis were gathered at the Trinity test site in New Mexico between 10 meters (30 feet) and 250 meters (800 feet) from the epicenter.
The glass nearest to the detonation site was low in volatile elements like zinc when compared to samples taken farther away. The zinc that was present was enriched in the heavier and less reactive isotopes of these elements, which are distinct atomic mass versions of these elements with the same chemical characteristics.
Zinc and other volatile substances, which vaporize at high temperatures, “dried out” more quickly close to the explosion than they did farther away. The results were released in the journal Science Advances’ Feb. 8 (2017) issue.
We used what was a history-changing event to scientific benefit, obtaining new and important scientific information from an event over 70 years ago that changed human history forever.
Professor James Day
“The results show that evaporation at high temperatures, similar to those at the beginning of planet formation, leads to the loss of volatile elements and to enrichment in heavy isotopes in the leftover materials from the event,” said Day, a Scripps geoscientist and lead author of the study. “This has been conventional wisdom, but now we have experimental evidence to show it.”
Scientists have long hypothesized that comparable chemical processes occurred when Earth collided with a planetary body the size of Mars, producing the debris that eventually gave rise to the Moon. The trinitite and lunar rocks are both substantially depleted in volatile elements and contain little to no water, according to Day and colleagues’ study of the materials.
Day’s research offers fresh proof in favor of the “giant impact scenario” of the Moon’s creation. At the New Mexico desert test site, a thin sheet of trinitite that reached about 350 meters (1,100 ft) from ground zero formed due to heat generated by the nuclear reactions.
The results of the investigation demonstrated that whether extreme temperature and pressure events occur on Earth or in space, volatile elements are subject to the same chemical processes.
“We used what was a history-changing event to scientific benefit, obtaining new and important scientific information from an event over 70 years ago that changed human history forever,” said Day, director of the Scripps Geochemistry Isotope Laboratory.
