A miniature laser ablation time-of-flight mass spectrometer for in situ planetaryexploration

Abstract

We report the development and testing of a miniature mass spectrometer and ion sourceintended to be deployed on an airless planetary surface to measure the elemental andisotopic composition of rocks and soils. Our design concentrates at this stage onthe proposed BepiColombo mission to the planet Mercury. The mass analyser isan axially symmetric reflectron time-of-flight design. The ion source utilizes alaser induced plasma, which is directly coupled into the mass analyser. Laserablation gives high spatial resolution, and avoids the need for sample preparation.Our prototype instrument has a demonstrated mass resolutionm/Δm (FWHM) in excess of 600 and a predicted dynamic range of better than four orders ofmagnitude. Isotopic fractionation effects are found to be minor. We estimate that a flightinstrument would have a mass of 500 g (including all electronics), a volume of650 cm3 and could operate on 3 W power.