The Astromaterials X-Ray Computed Tomography Laboratory at Johnson Space Center
Ryan A. Zeigler, Poorna Srinivasan, Lindsay P. Keller, Francis McCubbin, and Daniel M. Coleff
Astromaterials Research and Exploration Division, NASA JSC, Mailcode XI, 2101 NASA Parkway, Houston, TX 77058
Overview: The Astromaterials Acquisition and Curation Office at NASA’s Johnson Space Center (hereafter JSC curation)is the past, present, and future home of all of NASA’s astromaterials sample collections. JSC curation currently houses all orpart of nine different sample collections. Our primary goals are to maintain the long-term integrity of the samples and ensurethat the samples are distributed for scientific study in a fair, timely, and responsible manner, thus maximizing the return oneach sample. Part of the curation process is planning for the future, thus we also perform fundamental research in advanced
curation initiatives. Advanced Curation is tasked with developing procedures, technology, and data sets necessary for curating
new types of sample collections, or getting new results from existing sample collections [1]. As part of these advanced curation
efforts we are augmenting our analytical facilities. A micro X-ray computed tomography (micro-XCT) laboratory dedicated tothe study of astromaterials came online within the JSC Curation office this summer, and we plan to add additional facilities
that will enable non-destructive (or minimally-destructive) analysesof astromaterials in the near future (micro-XRF, confocal imaging
Raman Spectroscopy). These facilities will be available to: (1)develop sample handling and storage techniques for future sample
return missions, (2) be utilized by PET for future sample return
missions, (3) be used for retroactive PET-style analyses of ourexisting collections, and (4) for periodic assessments of the existing
sample collections. Here we describe the new micro-XCT system, aswell as some of the ongoing or anticipated applications of theinstrument.
Instrument: We have installed a Nikon XTH 320 micro-XCTsystem in JSC curation. It has four interchangeable X-ray sources:
180 kV nano focus transmission source, 225 kV reflection sourcewith multi-metal target (Mo, W, Ag, Cu), a 225 kV rotating target(W) reflection source, and a 320 kV reflection source. The system
also has a 16-bit, 400 mm2 (2000 x 2000 pixel) CCD detector, aswell as a heavy-duty stage that will accommodate large (up to 30cm) and heavy (up to 100 kg) samples. The multiple sources, highresolution detector, and large stage allow us the flexibility toanalyze a wide range of sample sizes. The 180 kV transmission
source will allow for high resolution (submicron) scans on smallsamples (less than ~5 mm), whereas the 225 kV and 320 kV sources
will allow scans of larger samples at resolutions on the order of 10s
or 100s of microns per voxel depending on the sample size. The
maximum size high-density rock sample that can be scanned has yet
to be determined, but test scans on basalt samples >15 cm indiameter have been successful.
Discussion: High-intensity XCT scanners have been used to
study astromaterials (and other geologic samples) for over 15 years[2-3], and the practice is becoming ever more prevalent. They havea wide range of scientific uses, including (but certainly not limitedto) measuring porosity, determining the modal abundance and 3D
distribution of phases inside samples, and identification of fabrics
or strain patterns in samples. In addition to their use for research,
Figure 1: Slices of the micro-CT scan of sample 14321,1404.
Brightness of the phases are proportional to x-ray attenuation (aXCT scans have increasingly been utilized as a part of themeasure of composition and density of the phase). Yellow arrows
astromaterials curation process, beginning with meteorites [4-5],
highlight interesting feldspathic (top) and mafic (bottom) clasts.
Sample is ~ 6 cm in diameter.
and more recently with the Apollo samples [6]. Their utility inFigure 2: Single 2D slice of the micro-CT scan of ungrouped achondrite NWA 11119 showing the igneous textures and major mineralogical phases
within the sample. Sample is ~ 3 cm long.

curation lies in their ability to non-destructively map out the phases and voids within a sample. As an example, we havescanned several large Apollo polymict breccias, and we were able to identify and tentatively classify the lithologies in theseclasts. The samples can then be subdivided, either through sawing or careful chipping, and those “new” clasts made available
to scientists. In addition to the myriad curatorial uses, we have begun to use the XCT system as an integral part of coordinatedanalyses of astromaterials. Two examples of this are the mapping of textures within ungrouped achondrite NWA 11119(Figure 2), as well as a newly acquired unclassified carbonaceous chondrite from Morocco (Figure 3). In each case, the XCTscans were able to characterize the major phases with the meteorites, and identify areas of interest for additional higherresolution study (e.g., by TEM). The penetrative nature of the XCT scans allows for astromaterials samples to be analyzed
within sealed low-density containers, preserving the pristinity of the samples. The XCT technique is not completely nondestructive, however. A recent study by [7] has shownthat XCT scans of meteorites can alter the naturalradiation dose of the sample. The number of techniques
where this is applicable (e.g., thermo-luminescence) islimited, however. Never-theless, XCT scans could
cause damage for other types of studies (e.g., organics),
and we plan to undertake extensive studies to fully
characterize the impact XCT scans have on the samples.
In the meantime, the percentage of any one sample thatis studied by XCT will be limited to ensure that noirreparable damage is done to an entire sample.
References [1] McCubbin et. al. (2017) ThisSymposium, [2] McCoy et al. (2002) EPSL 246, 102108. [3] Zolensky et al. (2014) MAPS 49, 1997-2016.
[4] Almeida et al. (2014), MAPS 77 abstract #5033. [5]Smith C. L. (2013) MAPS 76, abstract #5323. [6]Zeigler (2014) 45th LPSC, abstract #2665. [7] Sears, etal. (2016) MAPS 51.4, 833-838.

Figure 3: Single slice of the micro-CT scan of an unclassified Moroccan
carbonaceous chondrite. Large dark grey areas are large zoned CAIs. Sample is~4 cm in diameter.