Miniaturized Inductively Coupled Plasma Mass Spectrometer (ICPMS) for Trace Element Analysis

Trace elements, which are defined by abundances of <1000 ppmw in geological materials, serve as extraordinarily sensitive tracers of a variety of planetary processes including (but not limited to): i) biomineralization; ii) meteoritic infall (i.e., source of exogenous organic compounds); iii) hydrothermal activity and/or aqueous alteration; iv) weathering, erosion and sedimentation; and, v) magmatism, which in turn reflects local pressure, temperature and redox conditions in planetary interiors. In the commercial realm, trace elements are most commonly measured via inductively coupled plasma mass spectrometry (ICPMS) techniques, where a high-temperature (10,000 K) plasma effectively serves to atomize and ionize both solid (e.g., crystalline minerals or amorphous glasses) and liquid materials (e.g., water samples or chemical extracts). However, traditional modes of in situ chemical analysis available for planetary exploration, such as laser desorption mass spectrometry (LDMS; e.g., the MOMA investigation on the ExoMars rover) and laser-induced breakdown spectroscopy (LIBS; e.g., ChemCam on the Curiosity rover), are challenged to meet the limits-of-detection that enable the accurate quantitation of trace element abundances. Here, we propose to develop a miniaturized ICPMS that integrates a novel, self-sustaining low-pressure plasma source with an advanced prototype quadrupole mass spectrometer (QMS) based on the heritage design of the LADEE NMS and MAVEN NGIMS spaceflight instruments. The low-pressure operation of the plasma will simplify the design of the interface between the source and quadrupole mass analyzer, as well as reduce pumping requirements, thereby circumventing the need for multiple differential pumping regions found in commercial instruments. A laboratory demonstration of the end-to-end system, which will deliver quantitative, ppmw-level measurements of large ion lithophile elements (e.g., Rb and Sr), high-field strength elements (e.g., the lanthanides), and other transition metals (e.g., redox-sensitive V and Cu) in synthetic (NIST reference materials) and natural silicate materials (Clay Mineral Society phyllosilicates and USGS basaltic glasses) will validate this concept as TRL 4 at the end of the period of performance. The low maturity of the innovative ICP, and the unproven interface between this source and a spaceflight QMS system, define an entry TRL 1. The mission-enabling capabilities that will be realized through this effort will support assessments of planetary habitability, provide context for geochronology measurements, and offer insights into the dynamics of planetary surfaces (including atmospheric inputs) and interiors (and potential tectonic activity). Thus, this technology addresses multiple mission focus areas described in the NASA Decadal Survey and Science Plan. As encouraged by the Planetary Science Division, this effort leverages an emerging technology supported by the Small Business Innovative Research (SBIR) program. More »