Introduction: X-ray diffraction (XRD) is a gen-eral purpose technique used for definitive, quantitativemineralogical analysis. The MSL CheMin instrument(Fig. 1), the first XRD instrument flown in space, es-tablished the quantitative mineralogy of the Mars soil[1], characterized the first habitable environment onanother planet [2], and provided the first in-situ evi-dence of Martian silicic volcanism [3]. CheMin is nowemployed in the characterization of the depositionaland diagenetic environments of lacustrine mudstonesthat comprise the lower strata of Mt. Sharp [4].

Fig. 1: The MSL CheMin instrument (left) and ex-

ample of 2D XRD data (right). Resolution is ~0.3°2θ.

Conventional powder XRD requires samples com-prised of small grains presented in random orienta-tions. In CheMin, sample cells are vibrated to causeloose powder to flow within the cell, relaxing the re-quirement for fine-grained samples [5]. Nevertheless,CheMin still requires substantial sample preparation.Deployment of XRDs on smaller missions will requiresimpler sample preparation and decreased instrumentsize and complexity. It is also desirable to improve 2resolution to enhance the instrument’s capability to re-solve complex mineralogies. Efforts in these directionsare underway.

XRD with Limited Sample Preparation: XTRA(Extraterrestrial Regolith Analyzer) is intended to an-alyze fines in as-delivered surface regolith, withoutsample preparation [6]. Fine-grained regolith coats thesurfaces of most airless bodies in the solar system, andbecause this fraction is comminuted from the rocky re-golith, it can often be used as a proxy for the surfaceas a whole. XRTA uses a CCD in direct illuminationfor the collection of XRD and XRF signal from a sam-ple scooped and placed in a cell. XTRA can be config-ured in transmission or reflection geometry using vi-brated cells for as-delivered powders, allowing direct

analysis of materials scooped at the surface.

Fig. 2: XTRA proof of concept prototype operating invacuum (X-ray tube, vibrated reflection sample cells,CCD and electronics).

XRD without Sample Preparation: Hybrid-XRD(HXRD) is a concept under development to analyzerocks or soils without sample preparation [7]. If thematerial is sufficiently fine-grained, a powder XRDpattern is obtained, similar to CheMin or XTRA.With coarse-grained crystals, the whitebremsstrahlung radiation of the tube is diffracted intosingle crystal Laue patterns. Unlike typical Laue ap-plications, HXRD analyzes the energy of each Lauespot, enabling the measurement of single crystalBragg diffractions. (Fig. 3). Dedicated crystallo-graphic software has been developed for identificationof minerals responsible for the Laue patterns (Fig 4).

High resolution XRD: With CheMin and any ofthe previously described XRD concepts, instrumentresolution suffers from the system miniaturization andis limited to about 0.3°2θ. A planetary XRD based onGuinier geometry is under development to provide acompact high resolution instrument. This designhinges on the use of a parafocusing geometry with acurved 2D detector to cover the angular range of inter-est. A substantial gain in resolution has been demon-strated with a basic proof-of-concept instrument (fig.5). Both reflection and transmission geometries can bedeveloped with the Guinier design and are being ex-plored as part of a PICASSO funded project.

Development of High TRL Components: Rapidand cost-effective development of flight instrumentsrequires the availability of mature technologies of thecritical components. High TRL subsystems are beingdeveloped for future XRD instruments in collaborationwith industry partners who can provide expertise in

NEW DEVELOPMENTS IN X-RAY DIFFRACTION FOR PLANETARY EXPLORATION. P. C. Sarrazin1,D. F. Blake2, M. Gailhanou3, J. Chen4 , P. Dera5, R. T. Downs6, and T. F. Bristow2, 1 SETI Institute, Mountain View,CA 94043 (psarrazin@seti.org), 2 Exobiology Branch, NASA Ames Research Center, Moffett Field, CA 94035, 3

CNRS, IM2NP UMR, Marseille, France, 4 Baja Technology, Tempe, AZ, 5 HIGP, Univ. of Hawai i, Honolulu, HI, ˈ 6

Geosciences, Univ. Arizona, Tucson AZ 85721-0077.

2554.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)

design and manufacturing of flight sub-systems. Spe-cial full-frame and frame-transfer X-ray CCD detec-tors are being developed with e2V (UK); some detec-tors featuring internally cooled packages (Fig. 6a).Custom FPGA based electronics for low noise CCDoperation with embedded data processing capabilitiesare under development with Baja Technology (Fg 6b).Miniature microfocused X-ray tubes capable of opera-tion >10W are being developed by RTW of Germany(Fig. 6c), with power supplies developed by Battel En-gineering (Fig. 6d).

Fig. 3: HXRD proof of concept prototype featuring 4direct illumination CCD detectors for improved cov-erage of the reciprocal space.

Fig. 4: Crystallographic analysis code developed forthe HXRD instrument allows mineral identificationswith the “color Laue” XRD approach.

Deployment Opportunities: XRD instrumentswill be proposed for future landed instrument opportu-nities on planets and planetesimals. Instruments willbe tailored to the specific mission constraints and willbe comprised of combinations of the features andflight hardware presented above.

References: [1] Science, 341, 1238932; doi:10.1126/science. 1238932, [2] Science, 10.1126/science.1243480. [3] PNAS: doi: 10.1073/pnas.1607098113 [4] Science, 356 eaah6849 DOI:10.1126/science.aah6849 [5] LPSC 35 #1794 (2004) [6] IEEE Aerospace Confer-

ence, Big Sky, MO, March, 2012. Paper #2.0905 [7] LPSC 40 #1496 .

Fig. 5: Guinier proof of concept breadboard in reflec-tion geometry (100mm focusing diameter); XRD pat-tern of LaB6 standard showing <0.18°2θ resolution.Ray tracing simulations have shown possible improve-ment of this figure in this geometry.

Fig 6: Example of flight components under develop-ment with industrial partners: A. X-ray CCD in flightpackage with internal peltier cooler (e2V); B. CCDcontrol electromnics (Baja Technlogies); C. miniaturemicrofocused X-ray tube (RTW); D. X-ray tube powermodule with HVPS stage (Battel Engineering).

Acknowledgements: The authors are grateful forsupport from NASA/ARC’s Center Innovation Fundand NASA’s PICASSO program (grant #NNX15AM95G).

2554.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)