San Francisco State University
Who it subcontracts to
No subawards reported under its lunar awards.
Who it works for
FERROMAGNETIC RESONANCE STUDIES OF THE DUAL LASER WEATHERED SAMPLES (TASK 2.3) SCOPE OF WORK THE PROPOSED RESEARCH IN THIS SCOPE OF WORK IS PART OF TASK 2.3, WHICH AIMS TO PROVIDE COORDINATED AND DETAILED CHEMICAL, PETROLOGICAL, SPECTRAL, AND MAGNETIC STUDIES OF THE DUAL LASER WEATHERED SAMPLES FROM TASK 1.1. THESE ANALYSES WILL SERVE AS A METRIC FOR SIMULANT-REGOLITH REPRODUCIBILITY AND AS A CONTROL FOR ASSESSING VARIABILITY OF THESE PROPERTIES IN RESPONSE TO ENVIRONMENTAL INFLUENCES. THE MAGNETIC PROPERTIES OF THE LUNAR SOILS ARE THE FOCUS OF CO-I ICHIMURA"S RESEARCH BECAUSE OF THE INTENSITY OF THE FERROMAGNETIC RESONANCE SIGNAL IS ONE OF THE KEY METRICS USED TO ASSESS THE MATURITY OF LUNAR SOILS AND SOIL SIMULANTS. OBJECTIVES/SIGNIFICANCE: FERROMAGNETIC RESONANCE (FMR) IS USED TO DETERMINE A MEASURE OF THE SPACE WEATHERING MATURITY OF A REGOLITH SAMPLE, IS/FEO, WHERE IS IS THE MASS-WEIGHTED FMR INTENSITY AND FEO IS THE WEIGHT PERCENTAGE OF IRON OXIDE IN THE REGOLITH.1 THE FMR OF LUNAR SOILS ORIGINATES FROM SINGLE DOMAIN NANOPHASE METALLIC IRON PARTICLES (NPFE0) THAT FORM DURING THE REDUCTION OF IRON OXIDES AS THE CUMULATIVE RESULT OF WEATHERING. THE NORMALIZATION OF IS TO THE WT% FEO IS REQUIRED SINCE THE AMOUNT OF METALLIC IRON IS RELATED TO BOTH THE DEGREE OF WEATHERING AND THE AMOUNT OF IRON OXIDE IN THE ORIGINAL, UN-WEATHERED, REGOLITH. THE IS/FEO MATURITY INDEX OF LUNAR SOILS INCREASES STEADILY WITH THE DURATION OF SURFACE EXPOSURE. IN THE CONTEXT OF LABORATORY EXPERIMENTS AIMED AT REPRODUCING THE EFFECTS OF SPACE WEATHERING, SUCH AS LASER IRRADIATION AND PARTICLE BOMBARDMENT OF LUNAR ANALOGS, AN IMPORTANT CRITERION IS WHETHER IS/FEO MATURITY INCREASES SYSTEMATICALLY WITH EXPOSURE. FMR WILL BE USED TO ADDRESS TWO MAIN SCIENCE OBJECTIVES: (1) TO PLACE THE LABORATORY WEATHERED HIGHLAND SOIL ANALOGS ON THE IS/FEO MATURITY INDEX AS A FUNCTION OF EXPOSURE METHOD. (2) TO COMPARE MAGNETIC ANISOTROPY PARAMETERS OF LABORATORY WEATHERED HIGHLAND SOIL ANALOGS TO THOSE FROM TWENTY-ONE HIGHLAND LUNAR SOILS RANGING FROM IMMATURE TO MATURE SPECIMENS WITH <5 WT% FEO. THE USE OF MAGNETIC, SPECTRAL, AND COMPOSITIONAL PARAMETERS TO ITERATE WITH TASK 1.1 WILL ENSURE THAT THE LUNAR HIGHLANDS SIMULANT APPROXIMATES THE MINERALOGY AND PARTICLE SIZE DISTRIBUTIONS OF LUNAR HIGHLAND SOILS.2"6 ONCE THE EXPERIMENTAL SIMULANTS AND LUNAR SAMPLES ARE SHOWN TO REPLICATE THE PROPERTIES EXHIBITED BY AN EQUATORIAL REGOLITH,2,7"9 THE SAME ANALYSES WILL BE USED TO CHARACTERIZE WHETHER THESE PROPERTIES ARE MODIFIED BY DUAL LASER WEATHERING AT POLAR TEMPERATURES AND WITH VOLATILES PRESENT. EXTENDING THE STATE OF KNOWLEDGE: MULTIPLE STUDIES HAVE USED LASER IRRADIATION TO SIMULATE THE IMPACT-INDUCED COMPONENT OF SPACE WEATHERING.10"19 IRON NANOPARTICLES (I.E., NPFE0) PRODUCED BY LASER IRRADIATION ARE DETECTED BY TEM AND/OR FMR WITHIN THE UPPERMOST THIN AMORPHOUS LAYERS OF SOME TARGETS.13,14,20 AS AGGLUTINITIC GLASS AND NANOPHASE IRON METAL ARE THE PRIMARY CAUSES OF SPECTRAL ALTERATION OF THE VISIBLE AND NEAR INFRARED SPECTRUM,21"25 AND MAIN COMPONENT OF THE MAGNETIC PROPERTIES OF LUNAR SOILS [16, 17, 19-21],23,24,26"28 THE INABILITY OF LASER WEATHERING EXPERIMENTS TO PRODUCE AGGLUTINATES IS MAJOR LIMITATION OF THE CURRENT METHOD. WITHOUT NPFE0 BEARING AGGLUTINATES, THESE SAMPLES DO NOT POSSESS THE PROPER FMR SIGNATURE. OUR PRELIMINARY FMR INTENSITY MEASUREMENTS OF HIGHLAND SOILS 61501, 64421, 67511, WITH CORRESPONDING IS/FEO VALUES OF 53, 83, AND 8.8, YIELD A CURVE FOR MATURITY TO WHICH A LASER IRRADIATED HIGHLANDS REGOLITH ANALOG WAS COMPARED. WITH INCREASING LASER IRRADIATION OF OUR HIGHLANDS REGOLITH ANALOG, THE SPECTRA INCREASINGLY REDDEN, DARKEN, AND LOSE SPECTRAL CONTRAST " UP TO A POINT. THE ESTIMATED IS/FEO VALUE FOR THIS LASER IRRADIATED HIGHLANDS SOIL ANALOG, FOR WHICH THE OPTICAL SPECTRUM NO LONGER CHANGES, IS 7! THIS IS/FEO VALUE IS LOWER THAN ANY OF THE ACTUAL LUNAR SOILS THAT WE HAVE ANALYZED, WHICH EMPHASIZES THE NEED FOR A SPACE WEATHERIN