Frank Asaro, a nuclear chemist known for his work on the asteroid impact theory and mass extinctions, as well as for determining the origins of archaeological artifacts around the world, and for his work on alpha decay, passed away on June 10, 2014 at the age of 86. He was for many years a scientist at the Environmental Energy Technologies Division (EETD) of Lawrence Berkeley National Laboratory (Berkeley Lab), and prior to that, in the former Nuclear Chemistry Division.
Asaro is most famous for being a member of the team that proposed the mass extinctions that took place 65 million years ago were caused by Earth’s collision with an asteroid. The impact threw a cloud of dust into the atmosphere so thick that it obscured the sun, suppressed photosynthesis, and caused a massive die-off, including the demise of the dinosaurs. University of California Berkeley physicist and Nobel Prize winner Luis Alvarez, geologist Walter Alvarez (his son), Asaro, and Helen Michel analyzed rock samples collected by Walter in Italy and other locations from the Cretaceous-Paleogene (also known as the Cretaceous-Tertiary) boundary layer of the Earth’s crust. The samples contained a clay layer enriched in the element iridium by 600 times the normal concentration found on Earth.
Puzzling over a number of possible explanations for the enrichment, they concluded, in a classic paper published in the journal Science in 1980, that this iridium had extraterrestrial origins and was deposited when the mixture of dust and ash from the impact of an iridium-enriched asteroid settled. The team used neutron activation analysis (NAA) to measure the concentration of iridium in the layer. Their report caused a sensation in the scientific world and among the public. Asaro was expert in NAA and, with Michel, performed laboratory analysis of samples brought from around the world.
The paper caused a sensation in both the scientific community and among the general public, but over time, much more evidence has come to light to support the theory, including the discovery in 1990 of direct evidence of for the asteroid’s impact in a crater in Mexico in 1990. In 2010 an international panel of experts in geology, paleontology and related fields published the results of their exhaustive review, ruling in favor of the asteroid theory.
Asaro later designed and named the Luis Alvarez Iridium Coincidence Spectrometer specifically to measure trace iridium. Asaro set the standard for measurement of this and other trace elements in the field of archaeometry.
Applying Chemistry and Physics to Archaeology in the 1960s
In the 1950s, with Isadore Perlman, his doctoral thesis advisor at UC Berkeley, Asaro helped to develop neutron activation analysis into a technology precise enough to determine the origins of archaeological artifacts by measuring their chemical compositions. Neutron activation analysis uses the gamma ray emissions of radioactive chemical elements in irradiated pottery samples to accurately measure the abundances of elements in the sample.
The unique composition of an artifact provided a chemical signature that archaeologists could use to help determine the provenance, or point of origin of artifacts—the quarry where, for example, the clay in a shard of pottery came from. Knowing the origin helps archaeologists understand patterns of mobility, trade, wealth and settlement in ancient civilizations. The paper they published on NAA in 1969 became a landmark, the field’s most heavily cited reference.
Although he was best known for his work on the iridium layer and the asteroid theory of extinction, Asaro spent a considerable fraction of his career applying NAA to archaeological studies.
With Michal Artzy, Perlman and Asaro demonstrated in 1967 that an innovative Late Bronze Age style of pottery known as Palestinian bichrome, long considered to have been manufactured in Palestine, was actually manufactured in Cyprus and exported to Palestine.
In 1973, Asaro and colleagues studied the Colossi of Memnon, two 50-foot quartzite statues near Luxor. The statue-guardians of Pharaoh Amenhotep III were built before 1,200 B.C. In 27 B.C., the north statue fell during an earthquake. The damage was repaired in 200 A.D. by order of Roman emperor Septimius Severus. Archaeologists had long thought that the quartzite for the original statue had come from a quarry 100 miles away near Aswan. Asaro’s team showed that the original rock for the statues came from quarries in Cairo, 420 miles away—an amazing distance to transport so much weight at that time—and that the Romans used stone from the nearer Aswan quarry to repair the statue.
Drake’s Plate—A bona fide fake
Next to the extinction research, Asaro may best known for demonstrating that “Drake’s Plate,” a metal plaque that was purportedly left by Sir Francis Drake when his ship the Golden Hinde landed on the California coast in 1579, was actually a fake.
In 1936, the plate was reported found in Marin County, and acquired for the Bancroft Library at UC Berkeley by Herbert E. Bolton, the Library’s Director from 1920 to 1940. Bolton believed that Drake landed somewhere along the Marin coast, and when the inscribed brass plate turned up, he and other experts of the time authenticated it and put it on display at the Bancroft. However, over the decades, rumors began to circulate that the plate was a fake.
In 1977, Asaro and Michel applied neutron activation analysis to the plate and determined that the brass was probably manufactured between the last half of the nineteenth century and the early part of the twentieth, proving that California’s best known artifact was a fake. Just who was behind the hoax was not established until 2003 when historians published an article in California History pointing the finger at a group of Bolton’s distinguished friends. The authors argued that the fake artifact was a practical joke that went out of control when Bolton prematurely authenticated the plate before they could reveal the truth to him privately.
65-Million Year Journey Began in 1927
Frank Asaro was born July 31, 1927, and grew up in Escondido, California, the son of an avocado farmer, Nicolo Asaro, and Annie Asaro. He earned his undergraduate degree and PhD in chemistry at UC Berkeley. He studied alpha decay processes in nuclear chemistry for his doctorate under the supervision of Perlman, who was also the head of the Lawrence Berkeley National Lab’s Chemistry Division. Asaro worked with Perlman another 14 years studying nuclear structure. They conducted groundbreaking work that contributed evidence to support the now accepted unified model of the nucleus. In 1967, Perlman became interested in archaeology, and Asaro changed directions along with him.
“How good was Perlman at choosing new fields?” Asaro later said. “I thought I would take three months off to do this. I made that decision in 1967, and I’m still doing this work [some 40] years later.”
Even after his retirement from Berkeley Lab in 1991, Asaro continued to work “just for the fun of it.” With archaeologist David Adan-Bayewitz of Bar-Ilan University in Israel, he employed neutron activation analysis to investigate a series of archaeological and historical problems. One of their first research projects contributed crucial analytical evidence for solving the century-old problem of identifying the Roman-period settlement of Shikhin. When Adan-Bayewitz and Asaro encountered difficulties distinguishing the element compositions of nearby pottery production sites employing NAA, they enlisted the help of Robert Giauque, and together showed that high-precision X-ray fluorescence measurements could be more effective, in certain cases, than those of NAA for studies of local trade. XRF does not require a particle accelerator, and is easier to use. For many years the team employed both measurement techniques concurrently in their research.
At about the same time, in the early 2000’s, Asaro continued development work on NAA and achieved a breakthrough in measurement precision for several elements, particularly iron. The high-precision capabilities helped the group demonstrate that the element compositions of pottery vessels from two production workshops only 200 meters apart, at the same Roman-period settlement, could by clearly distinguished.
In the course of his measurements, Asaro noticed what he thought to be unusually high concentrations of silver in two pottery samples. No one before had ever paid any attention to silver in ancient pottery, and they decided to investigate whether silver concentrations might be meaningful. Asaro distrusted the existing measurements of silver, so he developed a new coincidence technique of silver analysis by NAA, which he used to check NAA and X-ray fluorescence measurements. This enabled the research team to study silver concentrations in about 1,300 pottery vessels from about 40 sites in Israel and, with Kathleen Slane, also in ancient Corinth in Greece. The researchers demonstrated that anomalously high silver concentrations were found only at urban sites and were context-related. Asaro considered this work to be potentially as important as the work on the iridium anomaly.
“The most intricate study dealt with archaeological evidence for contact with Jerusalem in the first century, before the city was destroyed by the Roman army in 70 CE,” says Adan-Bayewitz. In order to be able to assign with confidence a Jerusalem-area origin to ceramic oil lamps from settlements located more than 100 miles from that city, the team employed three statistical approaches. In one of these, Asaro classified lamps to subgroups, which included samples with nearly identical composition. No comparably tight pottery provenance groups had ever been published. These Jerusalem-related subgroups eventually included more than 200 samples. Asaro told Adan-Bayewitz that this was the best provenance work he had ever done. This project, in which soil micromorphologist Moshe Wieder also participated, showed that at Jewish settlements far from Jerusalem, in contrast with non-Jewish settlements, there had been a pronounced preference for lamps specifically from the Jerusalem area.
Asaro’s work shows us that the past is not necessarily a closed book. People leave traces of themselves in the effect they have on others, and the unique chemical compositions of their artifacts, read from traces of energy that Asaro learned how to use, tell stories of human time and movement.
Asaro was the loving husband of the late Lucille Asaro (née Lavezo) and is survived by his sister Marie (Scudder) and four children Frank, Antonina, Catherine, and Marianna.
Services will be held on Thusday, June 19, 2014 from 1:00-3:00 pm at the Sunset View Cemetery, 101 Colusa Ave, El Cerrito, CA 94530, (510) 525-5111
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