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Review
. 2014 Oct 21;1(Pt 6):514-22.
doi: 10.1107/S2052252514021150. eCollection 2014 Nov 1.

The first X-ray diffraction measurements on Mars

David Bish  1 , David Blake  2 , David Vaniman  3 , Philippe Sarrazin  4 , Thomas Bristow  2 , Cherie Achilles  1 , Przemyslaw Dera  5 , Steve Chipera  6 , Joy Crisp  7 , R T Downs  8 , Jack Farmer  9 , Marc Gailhanou  10 , Doug Ming  11 , John Michael Morookian  7 , Richard Morris  11 , Shaunna Morrison  8 , Elizabeth Rampe  11 , Allan Treiman  12 , Albert Yen  7
Affiliations
Review

The first X-ray diffraction measurements on Mars

David Bish et al. IUCrJ. .

Abstract

The Mars Science Laboratory landed in Gale crater on Mars in August 2012, and the Curiosity rover then began field studies on its drive toward Mount Sharp, a central peak made of ancient sediments. CheMin is one of ten instruments on or inside the rover, all designed to provide detailed information on the rocks, soils and atmosphere in this region. CheMin is a miniaturized X-ray diffraction/X-ray fluorescence (XRD/XRF) instrument that uses transmission geometry with an energy-discriminating CCD detector. CheMin uses onboard standards for XRD and XRF calibration, and beryl:quartz mixtures constitute the primary XRD standards. Four samples have been analysed by CheMin, namely a soil sample, two samples drilled from mudstones and a sample drilled from a sandstone. Rietveld and full-pattern analysis of the XRD data reveal a complex mineralogy, with contributions from parent igneous rocks, amorphous components and several minerals relating to aqueous alteration. In particular, the mudstone samples all contain one or more phyllosilicates consistent with alteration in liquid water. In addition to quantitative mineralogy, Rietveld refinements also provide unit-cell parameters for the major phases, which can be used to infer the chemical compositions of individual minerals and, by difference, the composition of the amorphous component.

Keywords: Curiosity rover; Mars; X-ray diffraction; extraterrestrial mineralogy.

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Figures

Figure 1
Figure 1
Schematic diagram of the CheMin instrument and resulting XRF and XRD data.
Figure 2
Figure 2
A comparison of XRD patterns from empty Kapton (black) and Mylar (red) cells. Peaks at 25.8 and 32.1° are due to scattering from the Al light shield on the CCD detector.
Figure 3
Figure 3
XRD patterns of crushed and sieved (<150 µm) NaCl measured on the CheMin III instrument, (left) without and (right) with sonic vibration.
Figure 4
Figure 4
CheMin IV XRD data for (a) silver behenate and (b) SWa-1 smectite.
Figure 5
Figure 5
A two-dimensional X-ray diffraction pattern of the beryl:quartz standard measured on Mars.
Figure 6
Figure 6
A two-dimensional XRD pattern for the Rocknest aeolian bedform (dune).
Figure 7
Figure 7
Observed (blue, integrated from the two-dimensional image in Fig. 6 ▶) and calculated (red) plots from Rietveld refinement using data for Rocknest (∼26.4 h integration, phases listed in Table 1 ▶). The calculated background (black line) is inscribed at the base of the observed pattern and the gray pattern at the bottom is the difference plot (observed − calculated). The difference at ∼25.8° is due to scattering from the Al light shield on the CCD.
Figure 8
Figure 8
A colorized two-dimensional XRD pattern for the John Klein mudstone drill sample.
Figure 9
Figure 9
Rietveld refinement results for the John Klein mudstone (∼56.5 h integration). The vertical line near 10° 2θ represents the position of a Pearson VII profile used to model the ∼10 Å diffraction peak from a phyllosilicate. The differences near 22° 2θ are due to the 02l diffraction band from the phyllosilicate.
Figure 10
Figure 10
Rietveld refinement results for the Cumberland mudstone (∼41.1 h integration). The vertical lines near 7.4 and 10.1° 2θ represent the positions of split Pearson VII profiles used to model the ∼10 Å and ∼14 Å diffraction peaks from phyllosilicates. The differences near 22° 2θ are due to the 02l diffraction band from the phyllosilicates.
See this image and copyright information in PMC

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