Volumetric 3D Analysis of Martian Polymict Breccia "Black Beauty" (NWA 7034) and NWA 10567

Introduction: The martian meteorite “Black Beauty” (NWA 7034) has been classified as a polymict breccia enriched in water (6000 ppm+ OH) in recent studies by Agee, McCubbin, and others [1-4]. However, 3-dimensional analysis of the interior mineral interrelationships has been limited by lack of suitable nondestructive evaluation (NDE) techniques at relevant “whole-rock” scales [2]. On the basis of recent work with x-ray computed tomography (xCT) of lunar samples [6-10] it is now possible to measure sub-micron 3D relationships associated with whole-rock interior mineral phases [11]. Here we report on preliminary 3D observations (volumetric) of internal phases within “Black Beauty” (BB) using xCT systems at NASA GSFC and the US Army Research Laboratory (ARL). In addition we report on first-ever xCT results for the shergottite NWA 10567 [13]. Volumetric data segmentation is used to quantify mineral-phase geometric distributions and relationships at different scales (< 5 m to 25 m). A 213 g specimen of BB and 45 g piece of NWA 10567 were provided to us via a collaboration with the Dr. Jay Piatek Collection in support of SPD-1 and Mars Sample Return (part of M2M initiative). Instruments: The GSFC NDE facility includes a NorthStar X5000 xCT with voxel resolution as fine as ~ 2-5 m depending on sample size, together with a Keyence Model VK-x250 laser confocal microscope (LCM). In a collaboration with the US Army Research Lab (MMSD), a Zeiss Xradia 520 Versa xCT system is also being used for higher volumetric resolution down to < 1 m/voxel. These non-destructive evaluation studies of martian and lunar meteorites were motivated by the pathfinding work of Ketcham, Zeigler, Agee, and others [8-10,1,2] who identified key questions that only 3D measurements could address at very high resolution and with new computational analysis methods. Our focus here is on multi-scale 3D analysis of a waterrich martian meteorite at 125 m scales using software analysis methods enabled by VG Studio, CTan, MountainsMap, CTVox, and others including RHSeg3D by Tilton [12]. Approach: xCT imaging of sample NWA 7034 was conducted at both the GSFC and ARL NDE facilities at two different voxel scales: (1) ~ 25 m/voxel for whole-sample context [6], and (2) at 1-5 m/voxel for focused analysis of specific sub-regions in which spherical clasts with reaction zones were accessible [11]. In addition, xCT imaging of NWA 10567 was conducted at multiple scales for comparison (Fig. 2) given its classical shergottite composition [13]. The objective was to first examine the 3D volumetric characteristics of the entire 213 g sample for geometric contxt. Given that BB represents a martian polymict breccia with abundant water, our aim is to characterize 3D geometry of oxides (& ilmenite) at multiple-scales, to extend the work by McCubbin [2]. Methodology: We have identified spherical clasts with reaction zones near the surface of the BB sample and used our synoptic GSFC xCT scan data to target the ARL Zeiss Xradia xCT measurements to the most distinctive regions of interest. Figure 1 illustrates the “whole-rock” xCT scan conducted at the GSFC NDE facility, with the brighter grey scales representing higher density (higher atomic number) phases. The overall sample reveals clearly-visible phases up to ~ 3 mm in diameter as well as apparent cracks and larger clasts, all within a finer-grained silicate matrix. The largest of the spherical inclusions (clasts) is ~ 3 mm in diameter within this meteorite (see Figs. 1,3).