Mathematics – Logic
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008dps....40.1612l&link_type=abstract
American Astronomical Society, DPS meeting #40, #16.12; Bulletin of the American Astronomical Society, Vol. 40, p.413
Mathematics
Logic
Scientific paper
While residing in the Kuiper Belt, an average comet (d=2 km) experiences tens to hundreds of impacts with d>8m objects over 3.5Gyr, while a typical Kuiper Belt Object (KBO) with d=200km undergoes 1x106 collisions. Durda and Stern (2000) suggest the interiors of most comet nuclei have been heavily damaged by collisions, and 1/3 of KBOs surfaces have been reworked.
We have initiated a laboratory program dedicated to investigating the chemical, mineralogical, and spectral effects that impacts have had on comets and KBOs throughout their histories. Experiments were conducted at the NASA Johnson Space Center Experimental Impact Laboratory using the Vertical Impact gun. In phase 1, 16 experiments over a range of impact speeds (2.0 - 2.8 km/s) were conducted. Targets included refractory components found in comet dust, including Mg-rich olivine (forsterite) and pyroxene (enstatite), diopside, and Fe-rich sulfides (pyrrhotite). In phase 2, low-porosity, volatile-rich targets were constructed by mixing refractory dust components plus amorphous carbon, volatiles (H2O, CO2), and organics (PAHs). Targets were then insolated with a solar simulator to generate a layered target with a volatile-free crust above the volatile-rich base, and impacted. Analyses of pre- and post-impacted materials will be presented, including a) spectral changes, using a Fourier Transform Infrared Spectrometer (FTIR, 5 - 15 um) to investigate changes in slope, band depths, band shifting, and new signatures, b) the structural/shock-induced effects of the dust, through Transmission Electron Microscope (TEM) data, and c) compositional information via X-ray Diffraction lab studies. Phase 1 experiments demonstrate that silicate targets impacted at 2.45 and 2.8 km/s have been altered, causing changes in FTIR spectra (e.g., darkening, shallowing of band depths) and clear evidence of shock (high density of planar dislocations) in TEM images.
This study was supported by a Cottrell College Science Award from Research Corporation and a NASA MUCERPI grant.
Cintala Mark J.
Keller Lindsay P.
Lederer Susan M.
Nakamura-Messenger Keiko
Olney R. D.
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