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.
Highlights
Humankind has studied the heavens for millennia and, until the 1960s, all observations of extraterrestrial bodies were made remotely, with either optical or spectroscopic measurements
X-ray fluorescence analysis is an integral part of the function of the CheMin instrument, as it is a prerequisite for the generation of twodimensional diffraction patterns from individual wavelengths (e.g. Co K 6.925 keV)
The miniaturized X-ray diffraction (XRD)/X-ray fluorescence (XRF) instrument CheMin has excelled on Mars, returning diffraction data comparable in many respects with data available on Earth
Summary
Humankind has studied the heavens for millennia and, until the 1960s, all observations of extraterrestrial bodies were made remotely, with either optical or spectroscopic measurements. Humankind has studied crystalline materials since the beginning of time, but it was not until the discovery of X-ray diffraction (XRD) that we learned about the ordered atomic arrangements that characterize such solids. Parrish as early as 1960 [Das Gupta et al, 1966; references in Blake (2000)], but it was not until the development of CCD X-ray detectors that it became practical to produce a miniaturized low-power X-ray diffraction instrument. Vaniman et al (1991) and Blake et al (1992) proposed similar concepts that included either a position-sensitive or a CCD X-ray detector, and these two teams combined in 1992, leading to the current CheMin instrument on Mars Science Laboratory (MSL). CheMin’s first XRD analysis on Mars coincided with the 100th anniversary of the discovery of XRD by von Laue
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
