Almeida, N. V.

Smith, C. L.

Sykes, D.

Zeigler, R. A.

NASA Technical Reports Server

Micro Computed Tomography and Micro X-ray Fluorescence as Tools for the Curation 
and Scientific Study of Apollo Samples. R. A. Zeigler1, N. V. Almeida2, D. Sykes3, C. L. 
Smith
2
,
1
NASA Johnson Space Center, 2101 NASA Parkway, Mail Code XI2, Houston, TX 77058, 
ryan.a.zeigler@nasa.gov. 
2
Department of Earth Sciences, Natural History Museum, London. 
3
Imaging and 
Analysis Center, Natural History Museum, London. 
 
Introduction: From 1969 to 1972, astronauts 
from six Apollo missions landed on the surface of the 
Moon and collected 382 kg of rocks, soils, and cores 
(2196 samples in total). Despite the fact that scien-
tists began studying the Apollo samples nearly 50 
years ago, new discoveries about how the Moon 
formed and evolved are still being made. In order to 
more fully understand the history of the Moon, 
“new” samples are needed in order to test the hy-
potheses raised by recent studies: (1) new FAN and 
Mg-suite samples to test the age of formation of the 
Moon and the timing of magma ocean crystallization; 
(2) new evolved lithologies to better understand the 
timing and mechanism by which tertiary crust forms 
on the Moon; (3) new igneous samples to better un-
derstand the volatile budget on the Moon; and (4) 
new igneous samples to better constrain the timing 
and intensity of the lunar dynamo. There are no 
“new” large samples within the Apollo collection that 
remain unstudied. There are a great many large 
polymict breccias within the Apollo collection that 
contain lithic clasts of igneous rocks, however. These 
polymict breccia clasts will be able to address the 
scientific questions listed above (and innumerable 
other questions). The issue then becomes how to find 
and characterize lithic clasts within polymict Apollo 
breccias without doing undue damage to the samples 
and without contaminating the samples. The answer 
to this problem is to use micro computed tomography 
(micro-CT) and micro x-ray fluorescence (mi-
cro-XRF) to map the interiors and exteriors of Apollo 
polymict breccias. 
Methodology: Micro-CT measurements are 
made by projecting a cone of high energy x-rays 
through a sample and measuring the attenuation of 
those x-rays on a CCD detector. This gives a 2D 
view of the x-ray attenuation within a sample. The 
sample is then rotated by a fraction of a degree and a 
new 2D x-ary attenuation snapshot taken. Computer 
software is then used to combine the many 2D snap-
shots taken over a full 360 degree rotation into a 3 
dimensional view of the rock. Micro-CT measure-
ments have the sensitivity to distinguish most of the 
major rock forming minerals found in Apollo sam-
ples. Given the high energy nature of the x-rays in-
volved, samples can be scanned triply bagged in 
Teflon to preserve their pristine nature. The samples 
shown in this work were scanned on the Nikon HMX 
ST 225 System at the Natural History Museum in 
London. Scans were made at 205-220 kV, 135-160 
A beam current, with an effective voxel size of 
21-44 microns. Bench top micro-XRF instruments 
use high energy x-rays to induce fluorescence in the 
near surface of a sample. They can rapidly scan large 
areas (~100 cm2) with a small pixel size (~25 um) 
and measure the semi-quantitative composition of 
largely unprepared surfaces for all elements between 
Figure 1 (left): (a) Macroscopic image of 14305,483 
slab. Area in parts b + c outlined in orange. Field of 
view is 10 cm wide. (b) X-ray RGB composite image 
of the surface of 14305,483. K = red, Al = green, Si = 
blue. White arrows denote pits in the sample. (c) X-ray 
RGB composite image of the surface of 14305,483. Ca 
= red, Mg = green, Fe = blue. 
 
https://ntrs.nasa.gov/search.jsp?R=20150020931 2019-08-31T05:34:53+00:00Z
Be and U, often with sensitivity on the order of a 
~100 ppm. The micro-XRF scans were made on an 
EDAX Orbis PC micro-XRF at Washington Univer-
sity. Samples were scanned without a protective bag 
using an accelerating voltage of 45 kV, a beam cur-
rent of 800 A, and a beam diameter of 30 m.  
Results: To date, we have made micro-CT 
scans of 10 different Apollo samples. This includes 
numerous polymict breccias (all regolith breccias 
unless otherwise noted): 14305,483 (155 g); 
14321,1404 (346 g); 15205,0 (136 g); 15405,0 (im-
pact-melt breccia; 201 g); and 60639,0 (153 g). The 
scans have been able to identify lithic and mineral 
clasts within each breccia. Of particular note is a 
mid-Ti basalt clast identified within the main mass of 
60639 (Fig. 1). This clast was identified previously 
[1], however the exact size and weight of the clast 
was unknown. Additionally, many interesting lithic 
clasts have been identified within the scans of 14321, 
a breccia known to contain numerous important lithic 
clasts [2]. In addition to the polymict breccias, sever-
al igneous samples were scanned as well (all basalts 
unless otherwise noted): 10057,19 (132 g); 
15555,1039 (66 g); 15556,215 (354 g); 70017,72 
(127 g); and 60015,180 (anorthosite, 122 g). The 
textures of these igneous samples can be seen in the 
scans, and the volume/distribution of vesicles within 
the samples is also apparent. Micro-XRF scans were 
made of sample 14305,483 (Fig. 2). The scans were 
done on unbagged sample, however (Teflon absorbs 
low energy fluorescent x-rays). The scans give the 
major element composition of numerous clasts on the 
sawn surface of the breccia. In particular, two areas 
rich in K and Si were found, suggesting that these are 
“new” evolved lithic clasts. 
Discussion: For polymict Apollo breccias, mi-
cro-CT analyses allow the entire clast population of 
relatively large samples (up to ~15-20 cm) to be 
mapped in a few hours. Although definitive identifi-
cation of lithologies based solely on micro-CT anal-
ysis is not always possible, by combining the mi-
cro-CT technique with a more quantitative technique 
like micro-XRF, definitive lithic clast identification 
is possible. The micro-CT scans can be used to de-
termine where to subdivide a large sample, and then 
these new clasts made available to scientists for more 
detailed study. Although this study concentrates on 
Apollo samples, these techniques are equally valid 
for use on meteorites. In fact, previous studies have 
already shown the efficacy of micro-CT work on 
meteorites [3-5]. This technique is likely to be used 
on future sample return missions, e.g., OSIRIS-Rex. 
References: [1] Delano J. W. (1975) PLSC, vol. 6, 15-47. 
[2] Shervais J. W. et al. (1984) Breccia Guidebook No.7 
14321.  JSC 19492 [3] Keubler K. E. et al. (1999). Icarus 
141: 96-106. [4] Almeida N. V. et al. (2014) MAPS 77: 
abstract #5033. [5] Smith C. L. (2013) MAPS 76, abstract 
#5323. 
Figure 2: (a) A 3-dimensional view of a micro-CT scan of the main mass of Apollo 16 polymict breccia 60639. The 
colors within the scan correspond to materials high x-ray attenuation values, and highlight lithic and mineral clasts 
rich in Fe-bearing minerals (e.g., pyroxene, olivine, ilmenite). The blue clasts are basalt clasts within the breccia. 
The whole sample is ~8 cm in the longest dimension. (b) A view of a single cross-sectional slice through the image 
in (a). Brighter phases are more Fe-rich, similar to a back-scattered electron image. The sub-ophitic texture of the 
basalt clast is apparent at this scale (c) An isolated view of the largest basalt clast within 60639,0. 
 


Micro Computed Tomography and Micro X-Ray Fluorescence and Tools for the Curation and Scientific Study of Apollo Samples

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