Preparing CDEX for flight to provide lunar elemental analysis and Rb-Sr dating

We have developed an instrument to assess and revise the history of the inner solar system by obtaining in-situ Rb-Sr dates on the Moon. These dates will allow us to determine the age of large lunar basalt flows and impact basins to ±20-80 Myr, and when flown to the Moon, allow us to robustly answer important science hypotheses regarding the existence of the LHB, the cratering rate from 1-3 Ga, and the age of recent geologic events such as the time of formation of Copernicus and IMPs. The instrument is called the “Chemistry and Dating EXperiment" (CDEX). CDEX is uniquely able to map the microscopic chemical context of a sample, while simultaneously determining age. The instrument measures rubidium-strontium (Rb-Sr) geochronology using laser ablation resonance ionization mass spectrometry (LA-RI-MS) for isobar free elemental separation. The RI lasers can be turned off on CDEX to assess chemistry in LA-MS mode. This instrument was the basis for Discovery and Mars 2020 proposals, and planning is underway for future CLPS, Discovery and New Frontiers opportunities. This will proposal specifically addresses instrument TRL deficiencies identified under these earlier flight proposals, and will improve the TRL of the integrated instrument from 4 to 6. We are working with commercial lander vendors to expand our previous plan developed under NASA Discovery to include CDEX operation from commercial landers, including mechanical design and conops for sample acquisition and analysis.

This proposal focuses on: 1) modification of an existing mass spectrometer electrical engineering development unit to withstand environmental testing, and to avoid detector saturation and screen unwanted signals, 2) development of a 2nd generation Sr-laser subsystem that is 6X more thermally and electrically efficient, 3) development of a 2nd generation of laser electronics that simplify Rb-Sr laser control, 4) environmental testing of the new laser subsystems, 5) integration of the lasers with the flight mass spectrometer, 6) functional testing of the integrated instrument, 7) environmental testing of the integrated instrument, and 8) assessment of accommodation for placement on commercial landers, including those from Astrobotic, Intuitive Machines, Lockheed Martin, and Deep Space Systems.

These measurements are relevant for missions to the Moon, as well as other inner solar system targets. Specifically, the instrument is relevant to the NRC DS goal of: “Determin[ing] the chronology of basin-forming impacts and constrain[ing] the period of late heavy bombardment in the inner solar system, and thus address[ing] fundamental questions of inner solar system impact processes and chronology”.