Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089) 6230.pdf A MINIATURIZED CHEMIN XRD/XRF FOR FUTURE MARS EXPLORATION. B. Lafuente1, P. Sarrazin1, T. F. Bristow2, D. F. Blake2, M. Gailhanou3, J. Chen4, K. Thompson1, R. Walroth2, K. Zacny5, R. T. Downs6, and A. Yen7, 1SETI Institute, Mountain View, CA ([email protected]), 2Exobiology, NASA ARC, Moffett Field, CA, 3CNRS, IM2NP UMR, Marseille, France, 4Baja Technology, Tempe, AZ, 5Honeybee Robotics Spacecraft Mecha- nisms Corp., Pasadena, CA, 6Geosciences, Univ. Arizona, Tucson AZ, 7JPL, Pasadena, CA. Introduction: X-ray Diffraction (XRD) and X-ray ergy-selective detection of XRD photons in Mars’ ra- Fluorescence (XRF) analyses provide the most diag- diative environment. The CheMinX XRD geometry is nostic and complete characterization of rocks and soil based on an architecture demonstrated by hundreds of by any spacecraft-capable technique, improved upon commercial XRD instruments (Terra, commercial spin- only by sample return and analysis in terrestrial labora- off of CheMin, Fig. 1). This design resulted from a tories. In a complex sample such as a basalt, XRD can ray-tracing study of XRD geometries based on high as- definitively identify and quantify all minerals, establish pect-ratio detectors. It was found that reduced surface their individual elemental compositions and quantify area detectors can be used with no loss in throughput, the amount of the amorphous component. When cou- angular resolution or angular range, the loss in detector pled with XRF, the composition of the amorphous coverage being fully compensated for by an optimized component can be determined as well. collimator design. The MSL CheMin instrument, the first XRD instru- In its basic implementation CheMinX will provide ment flown in space, established the quantitative min- a resolution of 0.3° 2θ FWHM, slightly improved over eralogy of the Mars soil [1], characterized the first hab- CheMin’s 0.35°. A dual CCD configuration is also de- itable environment on another planet [2], and provided veloped for higher XRD resolution (0.15-0.2° 2θ the first in-situ evidence of Martian silicic volcanism FWHM based on ray tracing simulations) with no loss [3]. CheMin is now employed in the characterization of angular coverage, however at a cost in size, weight of the depositional and diagenetic environments of la- and power of the instrument. The single CCD CheM- custrine mudstones that comprise the lower strata of inX remains our focus for its ultimate miniaturization. Mt. Sharp [4]. The CheMinX design enables the use of VIS-NIR CheMin as-designed is restricted to Flagship-class spectroscopy CCD detectors in place of the large dedi- missions due to its size, mass and power. Deployment cated X-ray CCD of CheMin. As a result, the cost and of XRD/XRF on smaller (i.e., MER-class) rovers re- power requirement for CCD deep cooling are dramati- quires further miniaturization of the instrument, and cally reduced. The e2v CCD used in the Terra is also the availability of a simpler sample collection capabil- used for CheMinX, installed in an internally cooled ity than was implemented for the MSL mission. We flight-qualified package. are developing CheMinX, a new instrument benefiting from a decade of advancements in geometry design and subsystem miniaturization (Fig. 1). Fig. 2: CheMinX will use the same detector and XRD geom- etry as Terra, a commercial spin-off of CheMin. Left: Terra instrument, mass: 14.5 kg (including case, batteries and em- bedded computer), power: 75W, typical analysis time: 15 min to 1 hr, right: 2D and diffractogram XRD data. Fig. 1: The MSL CheMin instrument, 295 x260x300mm3, Sample handling: The resonant sample cells of 10.5 kg (left) vs CheMinX projected volume 2.5x smaller and CheMin are redesigned for a more compact and lower mass <5 kg (right). cost sample handling subsystem. A fixed tuning fork is CheMinX design: The XRD measurement of combined with multiple single-use cells in a CheMinX is based on the same principles as CheMin, cartridge/dispenser arrangement. A preliminary me- but uses different components and a layout optimized chanical design of CheMinX is shown in Fig. 3 com- to these components. Like in CheMin, XRD is col- pared to the CheMin sample wheel. lected by a CCD in direct illumination, critical for en- Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089) 6230.pdf CheMinX as well as other planetary XRD and XRF in- struments developed by our team [5-7]. Fig. 3: Sample handling stage of CheMin with a large wheel holding a circular array of resonant sample-cell vibrators (left) versus compact design of CheMinX with single reso- nant vibrator and single-use sample cells supplied from a cartridge (right). Chemical analysis by X-ray fluorescence: For el- emental composition, CheMin used bulk sample com- Fig 4: Example of flight components under development with positions determined by a companion instrument industrial partners: A. CheMinX X-ray CCD in flight pack- (APXS). With CheMinX, the instrument provides XRF age with internal Peltier cooler (e2V); B. CCD control elec- measurement independently using an internal Silicon tronics (Baja Tech.); C. miniature microfocused X-ray tube Drift Detector (SDD) in reflection geometry. These 25kV-5W (RTW); D. X-ray tube power module with 25kV-5W spectra are quantified using Fundamental Parameters HVPS (Battel Engineering). (FP) approaches and calibrated spectra obtained from experiments conducted under the same conditions in Sample collection and delivery: CheMinX re- terrestrial laboratories. Depending on the background, quires the collection and delivery of powdered rock trace elements can be detected down to a few 10s of materials or soils. The identification of simpler sam- PPM, given sufficient collection time. pling technologies than those applied on MSL is criti- cal for the deployment of CheMinX on smaller rovers. Direct beam intensity monitoring: CheMinX has We are evaluating sample processing and delivery the capability to measure the direct beam intensity at technologies as part of this instrument development, Co Kα. This enables the measurement of sample ab- and will demonstrate CheMinX with powdering drills sorption, which varies with chemistry, compactness and arm prototypes developed at Honeybee Robotics. and thickness. Absorption inside the sample affects the overall diffracted intensity and the shape of the diffrac- Summary: Substantial reductions in mass, volume tion peaks, and is as such important for accurately and energy consumption relative to MSL CheMin are modeling the diffraction pattern for data interpretation. now possible for similar XRD performance (resolution The direct beam intensity measurement is obtained of 0.30-0.35° 2θ FWHM). An instrument with im- passively with a solid polycrystalline material (dia- proved resolution (0.2° 2θ FWHM) is also being devel- mond, silicon) positioned in the beam-stop structure to oped to provide better capabilities with complex min- diffract a single partially masked ring, proportional to eral assemblages and trace phases, at the cost of re- the transmitted beam intensity, on a lesser populated duced miniaturization. In both cases, the instrument region of the CCD. benefits from improved XRF performance by use of a Development of High TRL Components: rapid dedicated SDD placed in backscattering geometry. and cost-effective development of flight instruments CheMinX will provide quantitative mineralogy and el- requires the availability of mature technologies for the emental chemistry from drilled rocks and scooped soils critical components. High TRL subsystems are being on Mars. developed in collaboration with industrial partners: X- References: ray CCD detectors (Teledyne e2v), electronics for low [1] Science, 341, 1238932; doi:10.1126/science. noise CCD operation and embedded data processing 1238932, [2] Science, 10.1126/science.1243480. [3] (Baja Tech.), miniature microfocused X-ray tubes PNAS: doi: 10.1073/pnas.1607098113 [4] Science, (RTW), high-voltage power supplies (Battel Engineer- 356 eaah6849 DOI:10.1126/science.aah6849 [5] Wal- ing), piezoelectric actuators (Cedrat Technologies) etc roth et al, LPSC-49 #2233, [6] Blake et al, LPSC-50 (Fig. 4). These components will find applications in #1144 [7] Blake et al, LPSC-50 #1468..