Usually when the U.S. Army Chemical Materials Activity Recovered Chemical Materiel Directorate (CMA RCMD) receives a call to assess an item of interest, there is a good chance a chemical warfare agent is involved.
However, in the past several months, CMA RCMD, which is based at Aberdeen Proving Ground, has been supporting the National Park Service in partnership with Idaho National Laboratory to help in the identification of 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 during the early Eocene epoch 52 million years ago are notable for both abundance and exceptional detail of preservation.
Park Manager Arvid Aase explained the reason for the exceptional preservation is that the lake had a layer of low-oxygen saltwater and a microbial mat at the bottom. When dead creatures sank to the lake bottom, the mat grew over them and held them in place.
“While being saline at the bottom, it was fresh at the top where things were living, so freshwater microbes weren’t down there to decompose the [dead creatures], and nothing was living down there to scavenge on them,” Aase said. “It was that unique combination of conditions that allowed the fossils to be created in great abundance and very well preserved.”
Aase estimates 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 collected fossils are fish, searchers do occasionally uncover a fossilized mammal. The Fossil Butte National Monument Museum recently acquired a fossil from a private collection, first unearthed in the late 1980s.
Aase said the original collector damaged the fossilized Hyopsodus wortmani as they were preparing it, resulting in little interest from other collectors. Though it was missing both front forearms, it was still the most complete fossil of its kind, so the museum acquired it.
About five years ago, searchers dug up the fossil of a hyaenodontid, a family of carnivorous mammals that evolved and then went extinct. Aase, who is also the museum curator, described the fossil as a small, tree-climbing mammal the size of a squirrel with long fingers and a long tail.
Though this is the most complete specimen of a hyaenodontid fossil, so little is known of this still-uncertain species that once fully prepared, the museum may make history in discovering an entirely new species. It is missing its hip and both hind limbs, which fossil hunters overlooked during digging the previous year.
As the original fossil owners began preparing it, they realized the animal was lying on its back.
“So, they’re preparing the lower part of the skull and the belly of the critter, and that’s the least interesting part of the vertebra. And one hand is hidden behind the head,” Aase said.
Aase and his team were at a crossroads. If they tried to chip away the back side of the fossil to reveal the hand, they might damage what was there.
Luckily, the museum had a working relationship with Idaho National Laboratory, whose scientists previously used high-resolution X-ray microscopy to produce fossil images. Aase hoped the laboratory could help reveal hidden details of these fossils. The most promising technology had an unlikely partner in this mystery – the U.S. Army.
The Chemical Materials Activity Recovered Chemical Materiel Directorate provides centralized management and direction to the Department of Defense for safe and environmentally compliant assessment and destruction of recovered chemical warfare materiel.
When an item of concern is recovered, RCMD deploys its proven assessment technologies to determine whether the munition contains chemical agent or is explosively configured without opening the item. The first step in this process involves digital radiography and computed tomography, more commonly known as the DRCT.
Developed in partnership with Idaho National Laboratory, 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 whether a liquid fill is present, as well as the item’s explosive potential, without opening the munition, greatly reducing risk to emergency responders and the public.
The DRCT could analyze the fossil as it does potential recovered chemical warfare materiel, to reveal its true nature.
Aase said a scan of the Hyopsodus wortmani would allow them to see details of the unprepared surface imbedded in the rock, but the purpose of the fossil scan is twofold: to see details of the covered portions; and to determine whether preparation of the specimen should be halted, and instead flipped to prepare it from the other side. How well preserved is the hand tucked below the head?
The X-ray microscopy Idaho National Laboratory experts provided 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 through and get good data,” said Bill Chuirazzi, a research scientist at the laboratory. Chuirazzi then approached his colleague, Zack Thompson, a physicist whose work supports the DRCT technology – the same one the Army uses to assess recovered munitions.
A fellow history buff, Kelso Horne, director of the Army Chemical Materials Activity and treaty implementing agent for the Chemical Weapons Convention, said he is excited the Chemical Materials Activity can help the National Park Service while also serving the Army.
“Usually, the operations and technology we support means looking back in time to understand the conditions and parameters that a munition at an Army range might hold,” Horne said. “However, when we were presented with an opportunity by our partners at Idaho National Laboratory to use prehistoric data to improve our systems and possibly make history – well, that was one we needed to take.”
Computed tomography systems come in all shapes and sizes, but the system used by CMA RCMD is designed to look 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 CMA RCMD granted permission for its DRCT system to be used in the fossil analysis, with the understanding that any technological advances they may achieve 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 do a solid for them, but also develop a low-projection computed-tomography algorithm that CMA RCMD can use to assess recovered chemical weapons,” he said.
Once Idaho National Laboratory had the Army’s permission, they still needed to devise a way to hold the fossil without damaging it during the painstaking imaging process. Brian Gross, a design engineer at the laboratory, 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 permitted to handle the fossil, a testament to its rarity.
Thompson said he had to “Frankenstein” a DRCT system for the fossil imaging, using a modular set-up consisting of a flat panel X-ray detector and mount like the Army uses to assess recovered munitions, and an X-ray generator with a smaller focal spot to theoretically achieve sharper imaging. While the set-up took only 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 see inside a recovered munition, operators set up the scan, press a button, and the rotation stage spins, capturing 20 to 30 high-quality X-ray images of the munition and its contents. During the fossil imaging process, Thompson had software programs open on two separate computers – one to control the rotation of the fossil by half-degree increments, and the other to capture each image.
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“Zack had to manually click and capture every image. So, when we were taking hundreds of images, it was really two days of me just talking to Zack, so we didn’t fall asleep, and him just taking the data,” said Chuirazzi.
The modular DRCT system Thompson assembled captured 787 2D radiograph images of the Hyopsodus wortmani fossil and 683 images of the smaller hyaenodontid fossils. The next challenge was to figure out how to reconstruct those 2D images into a 3D volume, so Chuirazzi introduced another laboratory colleague to the project.
Rahul Reddy Kancharla is a post-doctoral researcher at the laboratory whose doctoratal 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 turn over the codes to Thompson and Chuirazzi for potential Army applications.
Aase has high hopes for the technological possibilities that could bring a species of the past into the present not only for visitors to the museum – but the paleontological world.
“If the scanning is good enough quality, we can actually get a 3D cast of this critter and hand it to a kid,” Aase said.
Although the Recovered Chemical Materiel Directorate does not require 3D images for all recovered munitions to determine their contents, the technology may have applications for Army operations in the future. These research and development partnerships with national laboratories like Idaho National Laboratory ensure CMA RCMD will continue as the Army’s leader in the development of safe, proven, non-intrusive technologies to assess and destroy chemical warfare materiel.
“None of this could have been accomplished without the right subject matters in the right place and our decades-long partnership with Idaho National Laboratory,” Horne said. “Only through partnership and expertise could we serve our nation’s priorities and advance paleontological finds, as well as our Army technology.”