CRATER: Characterization of Regolith And Trace Economic Resources (CRATER)

In situ laser ablation sampling enables spatially-resolved measurements (on the scale of <100 microns) of inorganic and organic composition via bond-breaking and mass removal of mineralogical matrices, and desorption/ionization of embedded organic content, respectively. High-resolution mass spectrometry empowers the separation of isobaric interferences (chemical compounds sharing the same nominal mass), including atomic (e.g., 54Cr+ versus 54Fe+), molecular (e.g., 28Si16O+ versus 12C16O2+), and organic signals (e.g., protonated phenylalanine C9H12NO2+ versus protonated triaminopurine C5H8N7+). In combination, these two analytical capabilities offer unparalleled potential to probe the chemistry of the lunar surface and subsurface. Here, we propose to develop CRATER (Characterization of Rock and Trace Economic Resources), a 7.9 kg, 47 W (active power) Orbitrap-based laser ablation mass spectrometer offering ultrahigh mass resolution (m/dm > 100,000, FWHM at mass 100) and enhanced photon-substrate coupling via deep ultraviolet (213 nm) radiation. Specifically, we will advance the following critical subsystems: 1. a dual-polarity Orbitrap mass analyzer, originally developed for commercial applications by Thermo Fisher, ruggedized for spaceflight by a consortium of French laboratories, and capable of measuring both positively- and negatively-charged ions across a range in molecular weight (20 – 1000 amu), volatility, and ionization potential; 2. a high power solid-state (Nd:Cr:YAG) laser system with continuously variable output energy (1 – 100% attenuation in 1% increments) capable of generating ≥1 mJ of deep UV light (213 nm) by quintupling the frequency of the heritage oscillator/amplifier flown on the Mercury Laser Altimeter (MLA); and, 3. an ion inlet subsystem that supports laser sampling of lunar materials (including regolith fines) under ambient conditions, and acceleration/energization/delivery of discrete ion packets into the Orbitrap analyzer. The science objectives of the CRATER investigation fall into three distinct, but related, categories: DYNAMICS OF THE MOON-FORMING EVENT: The CRATER investigation will critically assess the purported enrichment in refractory elements (e.g., Al) and depletion in volatile metals (e.g., K) in lunar surface materials relative to the cogenetic silicate Earth, and characterize chemical distinctions between regolith and subsurface samples. DEFINITION OF A "LIFE DETECTION BLANK”: The highly capable CRATER instrument will quantitatively measure prebiotic organic compounds, including amino acids and nucleobases derived primarily from the infall of cometary and/or asteroidal materials, down to pmol/mm2 concentrations, enabling provenance recognition based on diagnostic abundance patterns and the definition of an abiotic baseline for future astrobiology missions. RESOURCE EXPLORATION: The CRATER instrument will also enable resource prospecting through the generation of 2D chemical maps of economically important transition metals (e.g., Ti, Cr, Fe, and Cu) in positive ion mode, and sulfur (S) and halogens that serve as proxies for liquid water and/or solar implantation (e.g., F, Cl, and Br) in negative ion mode. Through these initiatives, the CRATER investigation addresses key science questions from all three crosscutting themes defined in the NASA Planetary Decadal Survey, as well as the evolving priorities of the Lunar Exploration Assessment Group (LEAG), as outlined in the Lunar Exploration Roadmap (2016). The activities proposed through this study support the objectives of the DALI Program, specifically: development of spacecraft-based instruments that show promise for use in future Lunar missions including expected commercial ventures; advancement of new technologies that significantly improve instrument measurement capabilities; and, demonstration of instruments for small stationary landers. More »