Meteoritics & Planetary Science, Volume 42, Number 12 (2007)http://hdl.handle.net/10150/6412412024-03-28T20:25:09Z2024-03-28T20:25:09ZAn integrated geophysical and geological study of the Monturaqui impact crater, ChileUgalde, H.Valenzuela, M.Milkereit, B.http://hdl.handle.net/10150/6563752021-02-18T02:22:36Z2007-01-01T00:00:00ZAn integrated geophysical and geological study of the Monturaqui impact crater, Chile
Ugalde, H.; Valenzuela, M.; Milkereit, B.
The Monturaqui impact crater (350-370 m in diameter and 0.1 Ma old), located in a remote area in northern Chile, was surveyed in December 2003 with detailed geophysics (gravity and magnetics), topography, petrophysics, and geology. The geology of the Monturaqui area is characterized by a basement of Paleozoic granites overlain by Pliocene ignimbrite units. No impact breccia was found in the area. The granites are the main lithology affected by the impact. Although the granite samples analyzed did not show evidence of shock metamorphism, quartz, and to a lesser extent feldspar and biotite grains from impactite samples exhibit different degrees of shock, ranging from planar microdeformation and cleavage to the development of intense planar deformation features (PDFs) and diaplectic glasses in some grains. The differential GPS survey allowed the creation of a detailed digital elevation model of the crater. Its dimensions are 370 m along the eastwest direction, 350 m along the north-south direction, and ~34 m deep. The crater exhibits a circular morphology with a preferred northwest-southeast elongation that coincides with the steepest slopes (~35 degrees) on the southeast edge. The newly acquired gravity data shows a negative anomaly of ~1 mGal at the center and allowed the creation of a 3-D model with a RMS error of <0.1 mGal, which supports the predictions of a fracturing-induced low-density granitic layer on top of the unfractured basement.
2007-01-01T00:00:00ZMineralogical composition of (25143) Itokawa 1998 SF36 from visible and near-infrared reflectance spectroscopy: Evidence for partial meltingAbell, P. A.Vilas, F.Jarvis, K. S.Gaffey, M. J.Kelley, M. S.http://hdl.handle.net/10150/6563762021-02-18T02:23:00Z2007-01-01T00:00:00ZMineralogical composition of (25143) Itokawa 1998 SF36 from visible and near-infrared reflectance spectroscopy: Evidence for partial melting
Abell, P. A.; Vilas, F.; Jarvis, K. S.; Gaffey, M. J.; Kelley, M. S.
In March 2001, asteroid (25143) Itokawa, the target of the Japanese Hayabusa spacecraft mission, was in a favorable viewing geometry for ground-based telescopic study. Visible/nearinfrared (VNIR) spectra (~0.48 to 0.9 micrometers) obtained on March 24, 26, and 27 UT, and near-infrared (NIR) spectra (~0.75 to 2.5 micrometers) obtained on March 10, 11, 12, 23, and 24 UT collectively show absorption features centered near 1.0 and 2.0 m, which are indicative of olivine and pyroxene. Analyses of these absorption features indicate an abundance ratio of olivine to pyroxene of approximately 75:25 +/- 5, respectively, with no significant variation in the relative abundance of these minerals across its surface on a regional scale. The band center positions indicate that the mean pyroxene chemistry is ~Wo(14 5)Fs(43 5). There appear to be at least two pyroxene components: primarily a low-Ca orthopyroxene accompanied by a spectrally significant (~15-20%) high Fe-rich pigeonite phase. The mean pyroxene composition is significantly more Fe-rich than the Fs1426 range found in ordinary chondrites. These pyroxene compositions are suggestive of phases crystallized from partial melts. This would indicate that the parent body of (25143) Itokawa reached temperatures sufficient to initiate partial melting (~1050 to 1250 degrees C), but that it did not attain the degree of melting required for significant melt mobilization and efficient segregation of the basaltic melt component from the unmelted residual olivine portion. Itokawas spectral band parameters place it near the S(III)/S(IV) boundary, but within the S(III) taxonomic field. In meteoritic nomenclature, Itokawa would be most analogous to an olivine-rich primitive achondrite. Alternatively, if the high Fs value is not related to partial melting, then Itokawa could also represent a rare atypical LL chondrite, or a previously unsampled oxidized Fe-rich chondritic-like assemblage.
2007-01-01T00:00:00ZBook Review: The Surface of Mars, Michael H. CarrByrne, S.http://hdl.handle.net/10150/6563782021-02-18T02:24:02Z2007-01-01T00:00:00ZBook Review: The Surface of Mars, Michael H. Carr
Byrne, S.
Book Review: The Surface of Mars, Michael H. Carr. New York: Cambridge University Press (2006).
2007-01-01T00:00:00ZBook Review: Volcanism on Io: A Comparison with Earth, Ashley DaviesRadebaugh, J.http://hdl.handle.net/10150/6563772021-02-18T02:23:25Z2007-01-01T00:00:00ZBook Review: Volcanism on Io: A Comparison with Earth, Ashley Davies
Radebaugh, J.
Book Review: Volcanism on Io: A Comparison with Earth, Ashley Davies. Cambridge: Cambridge University Press (2007).
2007-01-01T00:00:00Z