In-Situ Geochronology using Resonance Ionization

We are developing a miniature laser ablation resonance ionization mass spectrometer for in-situ isotopic measurements on Mars and other solid bodies, with a focus on Rb-Sr geochronology. Using a lab instrument built from off-the-shelf components, we have achieved a precision that is within a factor of four of that required to support Rb-Sr geochronology (87Sr/86Sr to ±0.0002 required, ±0.0008 demonstrated). These results were obtained with fewer resonance lasers than anticipated (2 instead of 3) at power levels lower than expected (15 μJ blue & 2 mJ green versus 5 mJ blue & 5 mJ green). Ongoing laboratory work focuses on continuing to increase the precision and accuracy of the instrument, as well as automating the measurement process. New theoretical work on a multi-pass resonance ionization mirror system indicates that it may be possible to reduce power levels for the blue and green lasers even further, reducing their cost, power, and mass requirements. A miniature laser ablation system has been completed, and work is proceeding on a miniature mass spectrometer, both consistent with space flight mass, power, and volume requirements.