Examining natural rock varnish and weathering rinds with laser-induced breakdown spectroscopy for application to ChemCam on Mars

Abstract

A laser-induced breakdown spectroscopy (LIBS) instrument is traveling to Mars as part of ChemCam on the Mars Science Laboratory rover. Martian rocks have weathered exteriors that obscure their bulk compositions. We examine weathered rocks with LIBS in a martian atmosphere to improve interpretations of ChemCam rock analyses on Mars. Profile data are analyzed using principal component analysis, and coatings and rinds are examined using scanning electron microscopy and electron probe microanalysis. Our results show that LIBS is sensitive to minor compositional changes with depth and correctly identifies rock type even if the series of laser pulses does not penetrate to unweathered material.

Chemistry of fracture‐filling raised ridges in Yellowknife Bay, Gale Crater: Window into past aqueous activity and habitability on Mars

“…Lanza et al . [, ] also noted this characteristic LIBS coating signature. These trends with depth in the LIBS data can be explained by a combination of natural sample heterogeneities but also the physical interaction of the laser with the target.…”

“…While LIBS has been used for investigating layers and performing depth profiles in numerous industrial and pharmaceutical applications, as well as with painted artwork [ Vadillo and Laserna , ; St‐Onge and Sabsabi , ; Madamba et al ., ; Kim et al ., ], its use in investigating complex, geological coatings or multilayered mineral deposits has been limited [cf. Cousin , ; Lanza et al ., ; Meslin et al ., (C. Lefebvre, et al, Depth‐resolved chemical mapping of rock coatings using Laser‐Induced Breakdown Spectroscopy: Implications for geochemical investigations on Mars, submitted to Planetary and Space Science , 2014)].…”

“…By using multiple laser shots at a given location, the laser can effectively be used to remove dust on the surface or drill down into a sample and generate plasmas at increasing depths with each successive shot. Therefore, the LIBS technique is particularly well suited for investigating surface coatings on solid materials and performing chemical depth profiles [e.g., Vadillo and Laserna , ; St‐Onge and Sabsabi , ; Lanza et al ., , ]. The rate of penetration, i.e., the amount of ablated material, with each laser shot is dependent on both laser (e.g., power, beam diameter, and pulse rate) and target (e.g., density, hardness, and cohesiveness) characteristics.…”

Insights into microbial involvement in desert varnish formation retrieved from metagenomic analysis

“…Desert varnish is a mostly inorganic coating, covering rocks predominantly in arid and semiarid regions (Hunt, 1954;Dorn, 1998;Lanza et al, 2012). It is composed mainly of clay minerals ( 60%) and manganese and iron oxyhydroxides (20%-30%) (Dorn, 1991;Grote and Krumbein, 1992).…”

Chemometrics in laser‐induced breakdown spectroscopy

“…It has become a research focus in the spectral field with the development of laser and optical detection techniques. Compared with conventional analytical tools, LIBS demonstrates some substantial advantages with regards to being rapid, real‐time, on‐site, and nondestructive while allowing remote detection without complicated sample preparation procedures as well as simultaneous multicomponent analysis . Because of these advantages, LIBS technology has been widely used in process analysis and in the control of industrial manufacturing, food supervision, environmental monitoring, historical relic identification, and space exploration .…”