Laser time-of-flight mass spectrometry for space

We describe a miniature reflection time-of-flight mass spectrometer for in situ planetary surface analysis. The laser ablation mass spectrometer (LAMS) measures the elemental and isotopic composition of regolith materials without any sample preparation or high-voltage source extraction. The small size (<2×103 cm3) and low mass (∼2 kg) of LAMS, due to its fully coaxial design and two-stage reflectron, satisfy the very strict resource limitations of landed science missions to solar system bodies. Microscopic surface samples are obtained with a short-pulse laser focused to a spot with a diameter ∼30–50 μm. Coupled with a microimager, LAMS can interactively select and analyze a range of compositional regions (with lateral motion) and access unweathered, subsurface materials (with repeated pulses). The mass resolution is sufficient to distinguish isotopic peaks at unit masses, and the detection limits are on the order of a few ppm. The design and calibration method of a prototype LAMS device is given, including the development of preliminary relative sensitivity coefficients for major element bulk abundance measurements.