X‐ray computed tomography of extraterrestrial rocks eradicates their natural radiation record and the information it contains

Journal Article · Mon Aug 13 00:00:00 EDT 2018 · Meteoritics and Planetary Science

DOI:https://doi.org/10.1111/maps.13183· OSTI ID:1464290

Sears, Derek W. G.  ^[1]; Sehlke, Alexander ^[2]; Friedrich, Jon M.  ^[3]; Rivers, Mark L. ^[4]; Ebel, Denton S. ^[5]

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1. NASA Ames Research Center/BAER Institute Mountain View California 95035 USA
2. NASA Ames Research Center/USRA Mountain View California 95035 USA
3. American Museum of Natural History New York New York 10024 USA, Department of Chemistry Fordham University Bronx New York 10458 USA
4. Center for Advanced Radiation Sources University of Chicago Argonne Illinois 60439 USA
5. American Museum of Natural History New York New York 10024 USA

Abstract The radiation record of extraterrestrial rocks provides important insights into their thermal and radiation history. For meteorites this relates to their orbits, thermal history, terrestrial age, preatmospheric size and shape, and possibly cosmic ray exposure age. For meteorites from the Moon and Mars, the radiation record allows insights into transit times. For Martian surface samples, the radiation record enables estimates of their sedimentary age. Despite this, there is a growing tendency to artificially expose these samples to large radiation doses by the use of X‐ray computed tomography ( CT ) imaging, often as part of their initial examination. In order to understand the effect of synchrotron micro CT on meteorites, we placed samples of the Bruderheim L6 chondrite in the CT imaging port of the Advanced Photon Source at the Argonne National Laboratory, Argonne, Illinois. Monoenergetic X‐ray beams of 25 and 46 keV and a high flux broad spectrum beam were used. The synchrotron CT procedure exposed the samples to radiation doses significantly higher than the natural doses observed for meteorites (1670 to ~10,000 Gyr, compared to ~1000 Gyr for natural samples). It is clear that CT imaging, whether using a laboratory system as in our previous report or using the synchrotron source, makes measurement of the natural radiation record of the samples impossible. Samples should not be placed in a CT scanner without due consideration of the loss of unique information for these valuable extraterrestrial samples.

• Sponsoring Organization: USDOE
• Grant/Contract Number: DE‐FG02‐94ER14466; DE‐AC02‐06CH11357
• OSTI ID: 1464290
• Journal Information: Meteoritics and Planetary Science, Journal Name: Meteoritics and Planetary Science Vol. 53 Journal Issue: 12; ISSN 1086-9379
• Publisher: Wiley-Blackwell
• Country of Publication: United States
• Language: English