IN-SITU GEOCHRONOLOGY ON MARS BY LASER INDUCED BREAKDOWN SPECTROSCOPY

Laser-induced breakdown spectroscopy is explored for the development of an in-situ K-Ar geochronology instrument for Mars. Potassium concentrations in five prepared standard basaltic glasses and equivalent rock samples in their natural form are quantified using the potassium doublet at 766.49 and 769.90 nm (²P_3/2 → ²S_1/2 and ²P_1/2 → ²S_1/2, respectively). Measurement precision varies from 0.5 – 5.5 (% RSD) over the 3.6 to 0.025 % potassium by weight for the standard glass samples, and little additional precision is achieved above 20 laser shots at 5 locations. For the glass standards, the detection limit for potassium is approximately 40 ppm, while the relative error of prediction is 1.5%. Measurements of the rock samples showed larger variations in signal due to sample heterogeneity. Relative errors of prediction are on the order of 10%.