Field Museum Obtains Mass of Rare Meteorite

Thu, 08/22/2013 - 06:37 -- pheck

The main mass of the rare Sutter's Mill meteorite after the Smithsonian Institution cut it and divided among five academic institutions: the Smithsonian Institution, American Museum of Natural History, The Field Museum of Chicago, Arizona State University and UC Davis. The 205 gram mass is the largest stone recovered from the meteorite that exploded over California's Sierra foothills in April 2012. Photo credit: Smithsonian Institution.

The main mass of a rare meteorite that exploded over California’s Sierra foothills in April 2012 will be preserved for current and future scientific discoveries, thanks to the collaborative efforts of five U.S. academic institutions.

It has found a permanent home among: The Field Museum of Natural History in Chicago, the Smithsonian Institution’s National Museum of Natural History in Washington, D.C., American Museum of Natural History in New York City, Arizona State University in Tempe, and the University of California, Davis. Together, the institutions have successfully acquired the biggest known portion of the Sutter’s Mill meteorite.

The meteorite is considered to be one of the rarest types to hit the Earth -- a carbonaceous chondrite containing cosmic dust and presolar materials that helped form the planets of the solar system.

Its acquisition signifies enhanced research opportunities for each institution and ensures that future scientists can study the meteorite for years to come.

“I am fortunate to be able to study this interesting, rare and unique meteorite. We will preserve pristine pieces of it at The Field Museum for future generations of scientists who will be armed with analytical tools which we can only dream of today," said Philipp R. Heck, PhD, The Field Museum’s Robert A. Pritzker Associate Curator.

The meteorite formed about 4.5 billion years ago. While it fell to Earth roughly the size of a minivan before exploding as a fireball, less than 950 grams have been found. Its main mass weighs just 205 grams (less than half a pound) and is about the size of a human palm.

The main mass was X-rayed by CT scan at the UC Davis Center for Molecular and Genomic Imaging. This was the first time a meteorite acquisition was CT scanned before its division among a consortium of institutes, allowing prior knowledge of each piece’s contents. Then it was cut into five portions, reflective of each institution’s investment, before being delivered to the institutions.

The portion of the main mass acquired by each institution includes:
• American Museum of Natural History: 34 percent
• Smithsonian Institution’s National Museum of Natural History: 32 percent
• The Field Museum of Natural History: 16 percent
• Arizona State University: 13 percent
• UC Davis: 5 percent

When the meteorite landed near Sutter’s Mill, the gold discovery site that sparked the California Gold Rush, it spurred a scientific gold rush of sorts, with researchers, collectors and interested citizens scouring the landscape for fragments of meteorite. The institutions that have acquired the main mass were among those that acted on this rare scientific opportunity to gain insights about the origins of life and the formation of the planets.

At The Field Museum, Dr. Heck prepared a polished section of the meteorite that he and his colleagues first studied with a scanning electron microscope to prepare a petrographic description and produce high-quality X-ray maps to determine its chemical composition. The Field Museum team also prepared a micro-CT scan of one of its pieces and used mass spectrometry to identify presolar stardust.

Involvement from the other institutions included:
• UC Davis, located 60 miles west of Sutter’s Mill, provided local outreach and education for meteorite donations, and confirmed for the original discoverer of the meteorite’s main mass that it was carbonaceous chondrite. The university also X-rayed the meteorite and determined its age and chemical composition.
• The Smithsonian Institution cut the mass into five portions.
• The American Museum of Natural History worked closely with UC Davis geology professor Qing-zhu Yin to secure specimens of Sutter's Mill right after its fall, and performed nondestructive computed tomography (CT) scans of several specimens kindly loaned by their finders. These scans were used to determine the density of several samples to very high accuracy, confirming the type of meteorite represented by Sutter's Mill.
• The Field Museum of Natural History found several presolar stardust grains in two smaller pieces of Sutter’s Mill donated by private meteorite collector Terry Boudreaux. Presolar stardust grains are the oldest solid samples available to any lab and are essentially time capsules from before the solar system formed 4.6 billion years ago.
• Arizona State University’s Meenakshi Wadhwa, director of the Center for Meteorite Studies, was contacted by Robert Haag, the private collector who owned the main mass. She then contacted the other institutions to initiate its joint acquisition.

More information:
- Download photos of the meteorite mass:
- Video: meteorite’s divided portions:
- Video: 3-D scan of Sutter’s Mill meteorite fragment: