HR: 09:30h
AN: P11A-07    [PDF]
TI: Color-Reflectance Trends in the Mare: Implications for Mapping FeO Using Multispectral Imaging of the Moon
AU: * Wilcox, B B
EM: bbwilcox@higp.hawaii.edu
AF: University of Hawaii, HIGP, 2525 Correa Rd, POST 504, Honolulu, HI 96822 United States
AU: Lucey, P G
EM: lucey@higp.hawaii.edu
AF: University of Hawaii, HIGP, 2525 Correa Rd, POST 504, Honolulu, HI 96822 United States
AU: Gillis, J J
EM: gillis@higp.hawaii.edu
AF: University of Hawaii, HIGP, 2525 Correa Rd, POST 504, Honolulu, HI 96822 United States
AB: Clementine-based FeO measurements provide a new resource for mapping mare basalts and cryptomare. These FeO estimates are based on algorithms that are intended to minimize the effect of maturity that strongly affects reflectance and ratio images, and maximize the effect of iron. The algorithms are based on an observation that terrains with plausibly uniform composition but varying maturity seem to form radial patterns on a plot of reflectance versus 950/750nm ratio. This behavior was parameterized using a simple rotational algorithm that placed the origin near the apparent convergence point of these trends. The technique is successful in the sense that there is a high degree of correlation between FeO estimates and measurements using lunar samples and Lunar Prospector data, and in most terrains the effects of maturity, for example owing to the presence of small craters, are minimized to $<$1% FeO. More recently, it has been reported that some mare show subparallel, not radial trends, and this observation has been used to call into question the validity of the entire method of FeO derivation. To confirm these new observations and investigate in more detail the maturity trends in the mare, we acquired data for the multiple maria: Procellarum, Frigoris, Nectaris, and Tranquillitatis. On the whole, spectra from ~20 representative fresh craters from each of the maria do produce maturity trends that formed radial patterns. Scatter plots from Mare Frigoris, however, show maturity trends that are subparallel to the other maria, as suggested by previous workers. This subparallel behavior leads to apparent FeO anomalies being present in these areas associated with fresh craters. These FeO anomalies are plausibly real, as it is not known that Frigoris is uniform in FeO content with depth. A mare surface dusted with highland debris should show non-radial trends as FeO content declines with distance from the crater. Or, thin lava flows of varying compositions should also lead to non-radial trends. In other words, local deviations from radial behavior do not necessarily invalidate the accuracy of FeO estimates. Our efforts will be to document additional mare regions that do not exhibit maturity trends that originated from a single common point. We will also present model results to constrain what variables other than stratigraphy (i.e. mineralogy, grain size, Mg\#) can account for the differences observed and results of semi-empirical corrections.
DE: 5400 PLANETOLOGY: SOLID SURFACE PLANETS
DE: 5410 Composition
DE: 5464 Remote sensing
DE: 5480 Volcanism (8450)
DE: 5494 Instruments and techniques
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting