We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Using HED meteorites to interpret neutron and gamma-ray data from asteroid 4 Vesta.
- Authors
Beck, Andrew W.; Lawrence, David J.; Peplowski, Patrick N.; Prettyman, Thomas H.; McCoy, Timothy J.; McSween, Harry Y.; Toplis, Michael J.; Yamashita, Naoyuki
- Abstract
Here, we construct a comprehensive howardite, eucrite, and diogenite ( HED) bulk chemistry data set to compare with Dawn data. Using the bulk chemistry data set, we determine four gamma-ray/neutron parameters in the HEDs (1) relative fast neutron counts (fast counts), (2) macroscopic thermal neutron absorption cross section (absorption), (3) a high-energy gamma-ray compositional parameter ( Cp), and (4) Fe abundance. These correspond to the four measurements of Vesta made by Dawn's Gamma Ray and Neutron Detector ( GRa ND) that can be used to discern HED lithologic variability on the Vestan surface. We investigate covariance between fast counts and average atomic mass (<A>) in the meteorite data set, where a strong correlation ( r2 = 0.99) is observed, and we demonstrate that systematic offsets from the fast count/<A> trend are linked to changes in Fe and Ni concentrations. To compare the meteorite and GRa ND data, we investigate and report covariance among fast counts, absorption, Cp, and Fe abundance in the HED meteorite data set. We identify several GRa ND measurement spaces where the Yamato type B diogenites are distinct from all other HED lithologies, including polymict mixtures. The type B's are diogenites that are enriched in Fe + pigeonite + diopside ± plagioclase, relative to typical, orthopyroxenitic diogenites. We then compare these results to GRa ND data and demonstrate that regions north of ~70°N latitude on Vesta (including the north pole) are consistent with type B diogenites. We propose two models to explain type B diogenite compositions in the north (1) deposition as Rheasilvia ejecta, or (2) type B plutons that were emplaced at shallow depths in the north polar region and sampled by local impacts. Lastly, using principal component ( PC) analysis, we identify unique PC spaces for all HED lithologies, indicating that the corresponding GRa ND measurables may be used to produce comprehensive lithologic maps for Vesta.
- Subjects
METEORITES; NEUTRONS; NEUTRON capture; ANALYSIS of covariance; ABSORPTION
- Publication
Meteoritics & Planetary Science, 2015, Vol 50, Issue 8, p1311
- ISSN
1086-9379
- Publication type
Article
- DOI
10.1111/maps.12467