36th DPS Meeting, 8-12 November 2004
Session 28 Asteroid Physical Properties I
Oral, Thursday, November 11, 2004, 10:30am-12:00noon, Clark

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[28.09] Compositional Results of Binary Near-Earth Asteroid 2003 YT1: A Basaltic Achondrite

P. A. Abell (NASA Johnson Space Center), M. J. Gaffey, P. S. Hardersen (University of North Dakota)

Near-Earth Asteroid 2003 YT1 was discovered by the Catalina Sky Survey on December 18, 2003. It was later reported to be a binary object based on lightcurve observations taken at the Ondrejov Observatory and radar observations obtained from the Arecibo telescope (IAUC 8336). Arecibo radar delay-Doppler images indicate that the diameters of the primary and secondary are approximately 1000 and 180 m respectively. In addition, the radar data demonstrate that the primary is irregular in shape, in contrast to other previously imaged binary asteroids, which have been noted to be almost spherical (e.g., 1998 ST27).

Near-infrared spectral data from ~ 0.7 to 2.5 microns obtained of 2003 YT1 at the NASA Infrared Telescope Facility on May 9 and 10, 2004 UT shows well defined 1 and 2 micron features. Analyses of these features suggest that this near-Earth object has a surface assemblage dominated by orthopyroxene, perhaps with some accessory plagioclase. No detectable olivine is seen in the spectral data. The band positions of the absorption features suggest that the pyroxene chemistry is ~ Wo8Fs32. Such pyroxene chemistry and the lack of any obvious olivine content suggest that this asteroidís parent body experienced significant heating with a large amount of eutectic melt production.

The inferred pyroxene mineralogy lies near that of the diogenite-eucrite boundary and suggests that 2003 YT1 may have a compositional affinity to these basaltic achondrite meteorites. As such this binary object could plausibly represent a portion of ejected material from the surface of asteroid 4 Vesta. The fact that the primary is an irregularly shaped object and the eccentric nature of the secondaryís orbit, suggest that 2003 YT1 may be the result of fragments ejected from the surface of Vesta at low relative velocity.

This research is supported by NASA NEOO grant number NNG04GI17G.


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