KArMars: A Breadboard Model for In Situ Absolute Geochronology Based on the K-Ar Method Using UV-Laser-Induced Breakdown Spectroscopy and Quadrupole Mass Spectrometry

We present a breadboard prototype to perform in situ dating applicable to planetary exploration. Based on the K-Ar dating method and using instruments inspired by flight-proven analytical components, 'KArMars' ablated a geological sample under high vacuum with a quadrupled ultraviolet (UV at 266 nm) Nd:YAG laser. During ablation, the K content of the target material was given by laser-induced breakdown spectroscopy and the released Ar-40 was measured with a quadrupole mass spectrometer. Because K was measured as a concentration and Ar-40 as a count of atoms, these values were converted using the ablated mass given by the product of the density and the ablated volume. The uncertainties of the age measurement were < 15%. The quality of the K-Ar measurements was enhanced by the advantages of UV laser ablation such as the minimisation of thermal effects on argon diffusion. This work demonstrates that a specialised instrument inspired by this set-up could provide in situ absolute geochronology with sufficient precision for scientific investigations, particularly where the crater density counting provides higher uncertainties on Mars.