Usually when the US Army Chemical Materials Activity Recovered Chemical Materiel Directorate (CMA RCMD) receives a call to assess an item of interest, there is a good chance that a chemical warfare agent is involved.
However, in recent months, the CMA RCMD, which is based at the Aberdeen Proving Ground, has supported the National Park Service in collaboration with the Idaho National Laboratory to help identify an extremely rare fossil.
The National Park Service website describes Fossil Butte National Monument in southwestern Wyoming as “America’s aquarium in stone.” Fossilized fish, birds, reptiles and mammals that once populated the area in and around a large freshwater lake in the early Eocene epoch 52 million years ago are remarkable for both abundance and exceptional detail of preservation.
Park manager Arvid Aase explained that the reason for the extraordinary protection is that the lake had a layer of low-oxygen salt water and a microbial mat at the bottom. As dead creatures sank to the bottom of the lake, the mat grew over them and held them in place.
“While it was salt water at the bottom, it was fresh at the top where things lived, so freshwater microbes weren’t down there to decompose [dead creatures], and nothing lived down there to cut them down,” said Aase. “It was the unique combination of conditions that allowed the fossils to be created in great abundance and very well preserved.”
Aase estimates that fossil hunters collect about 100,000 well-preserved fossils each year from private quarries outside the park. “And that’s not counting the broken ones,” he adds.
Although most of the fossils collected are fish, searchers occasionally uncover a fossilized mammal. The Fossil Butte National Monument Museum recently acquired a fossil from a private collection that was only unearthed in the late 1980s.
Aase said the original collector damaged the fossilized Hyopsodus wortmani while preparing it, resulting in little interest from other collectors. Although it was missing both forearms, it was still the most complete fossil of its kind, so the museum acquired it.
About five years ago, prospectors dug up the fossil of a hyaenodontid, a family of carnivorous mammals that evolved and then became extinct. Aase, who is also a museum curator, described the fossil as a small tree-climbing mammal about the size of a squirrel with long fingers and a long tail.
Although this is the most complete specimen of a hyaenodontid fossil, so little is known about this still uncertain species that, once fully prepared, the museum can make history with the discovery of an entirely new species. It is missing the hip and both hind limbs, which fossil hunters overlooked during the dig the previous year.
When the original owners of the fossil began to prepare it, they realized that the animal was lying on its back.
“So, they prepare the lower part of the skull and the abdomen of the animals, and that’s the least interesting part of the vertebra. And one hand is tucked behind the head,” Aase said.
Aase and his team were at a crossroads. If they tried to chip the back of the fossil to reveal the hand, they could damage what was there.
Fortunately, the museum had a collaboration with the Idaho National Laboratory, whose scientists previously used high-resolution X-ray microscopy to produce fossil images. Aase hoped the lab could help reveal hidden details about these fossils. The most promising technology had an unlikely partner in this mystery – the US Army.
The Directorate for Recovered Chemical Materiel for Chemical Materials Activity provides centralized management and guidance to the Ministry of Defense for the safe and environmentally friendly assessment and destruction of recovered chemical warfare materiel.
When a problem is recovered, the RCMD uses its proven assessment technologies to determine whether the munition contains chemical agents or is explosively configured without opening the item. The first step in this process involves digital radiography and computed tomography, more commonly known as DRCT.
Developed in collaboration with the Idaho National Laboratory, the DRCT uses X-ray technology to vertically scan a recovered munition on a rotating platform, producing a high-quality 2D or 3D digital image of its interior or cross-section. This determines the presence of a liquid charge, as well as the explosive potential of the item, without opening the ammunition, greatly reducing the risk to emergency personnel and the public.
The DRCT could analyze the fossil, as it does potentially recovered chemical warfare material, to reveal its true nature.
Aase said that a scan of Hyopsodus wortmani would allow them to see details of the unprepared surface embedded in the rock, but the purpose of the fossil scan is twofold: to see details of the covered parts; and to determine whether the preparation of the sample should be stopped and instead turned to prepare it from the other side. How well preserved is the hand hidden under the head?
The X-ray microscopy provided by the Idaho National Laboratory experts was not a suitable candidate for the hyaenodontid fossil.
“First of all, the sample in the rock was too big, but also because the fossil itself was big, it was too thick for our X-rays to really penetrate and get good data,” said Bill Chuirazzi, a researcher at the lab. Chuirazzi then turned to his colleague, Zack Thompson, a physicist whose work underpins the DRCT technology—the same one the Army uses to evaluate recovered munitions.
A history buff, Kelso Horne, director of the Army Chemical Materials Activity and treaty implementing agent for the Chemical Weapons Convention, said he is excited that the Chemical Materials Activity can help the National Park Service while also serving the Army.
“Typically, the operations and technology we support means we look back in time to understand the conditions and parameters that a munition on an Army range can accommodate,” Horne said. “But when we were presented with an opportunity by our partners at the Idaho National Laboratory to use prehistoric data to improve our systems and possibly make history — well, it was one we had to take.”
Computed tomography systems come in all shapes and sizes, but the system used by CMA RCMD is designed to see through the metal shell of a munition, as well as the thick stainless steel container in which it is safely stored – similar to the fossil in the rock.
Thompson added that the CMA RCMD authorized its DRCT system to be used in the fossil analysis, with the understanding that any technological advances they might make would be handed over to the Army in its modernization efforts.
“Part of what we can do with the data is not just image a fossil for the Park Service to make a solid one for them, but also develop a low-projection computed tomography algorithm that CMA RCMD can use to assess recovered Chemical weapons.” he said.
Once the Idaho National Laboratory had the Army’s permission, they still had to devise a way to hold the fossil without damaging it during the painstaking imaging process. Brian Gross, a design engineer at the lab, used photos and measurements provided by Aase and 3D printing to create a custom holder for the fossil.
“Brian designed a 3D-printed holder that fit the unique fossil like a glove, and it plugged right into Zack’s system and held this thing in place,” Chuirazzi said, though only Aase was allowed to handle the fossil, a testimony about its rarity.
Thompson said he had to “Frankenstein” a DRCT system for the fossil imaging, using a modular setup consisting of a flat-panel X-ray detector and mount, which the Army uses to evaluate recovered munitions, and an X-ray generator with a smaller focal point to theoretically achieve sharper imaging. While the setup only took about two hours, it was the imaging itself that was far more labor intensive than a standard Army assessment operation.
When the Army uses the DRCT system to look inside a recovered munition, operators set up the scan, press a button, and the rotary stage spins, taking 20 to 30 high-quality X-rays of the munition and its contents. During the fossil imaging process, Thompson had software programs open on two separate computers—one to control the fossil’s rotation in half-degree increments, and the other to capture each image.
The morning sun
Daily
Get your morning news in your email inbox. Get all the best news and sports from baltimoresun.com.
“Zack had to manually click and capture every image. So when we took hundreds of images, it was really two days of me just talking to Zack, so we didn’t fall asleep, and he just took the data,” Chuirazzi said.
The Thompson modular DRCT system collected 787 2D radiographs of the Hyopsodus wortmani fossil and 683 images of the smaller hyaenodontid fossils. The next challenge was figuring out how to reconstruct these 2D images into a 3D volume, so Chuirazzi introduced another lab colleague to the project.
Rahul Reddy Kancharla is a post-doctoral researcher at the lab whose doctoral studies involved limited-angle reconstruction—creating detailed imaging from a limited number of X-ray angles. Kancharla is now developing an algorithm to reconstruct 2D fossil images into a 3D volume to validate his codes for the National Park Service. The actual rendering of 3D images is still weeks, possibly months away, but if successful, he will then hand over the codes to Thompson and Chuirazzi for potential Army applications.
Aase has high hopes for the technological possibilities that can bring a species from the past into the present not only for visitors to the museum – but the palaeontological world.
“If the scan is good enough quality, we can actually get a 3D cast of this creature and hand it to a child,” Aase said.
Although the Directorate of Recovered Chemical Materiel does not require 3D imaging of all recovered munitions to determine their content, the technology may have applications for Army operations in the future. These research and development partnerships with national laboratories such as the Idaho National Laboratory ensure that CMA RCMD will continue as the Army’s leader in the development of safe, proven, non-intrusive technologies to assess and destroy chemical warfare agents.
“None of this could have been accomplished without the right subjects in the right place and our decades-long partnership with the Idaho National Laboratory,” Horne said. “Only through partnership and expertise could we serve our nation’s priorities and advance paleontological discoveries as well as our Army technology.”