[P-PS03] Small Solar System Bodies: New perspectives on the origin and evolution of the Solar System

[PPS03-P14] On the near-infrared color of Karin family asteroids

*Shigeru Takahashi¹, Fumi Yoshida^2,3, Hikaru Kubota⁴, Hideo Sagawa⁴, Takahiro IINO¹ (1.The University of Tokyo, 2.University of Occupational and Environmental Health, Japan, 3.Chiba Institute of Technology, 4.Kyoto Sangyo University)

Keywords:Asteroids, Karin family, Near-infrared spectrophotometry, Space weathering

The Karin family, a young asteroid cluster within the Koronis family, was first identified by Nesvorný et al. (2002) through a numerical method, revealing that it formed from a collisional breakup event approximately 5.8 million years ago. Since its discovery, several studies have been conducted to investigate the physical and spectral properties of its members.

In this study, we show near-infrared spectrophotometric results of the Karin family asteroids using archival ground-based data from the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea. Our study focused on five asteroids; (832) Karin, (13765) Naismith, (47640) 2000 CA30, (69880) 1998 SQ81, and the interloper (4507) Petercollins. Previous observations have suggested that (832) Karin exhibits two distinct surface types; a red surface and a non-red surface (Sasaki et al., 2004; Yoshida et al., 2004). However, the precise location of the red surface remains unclear.

By analyzing past observations in combination with our newly obtained data, we attempted to constrain the possible location of the red surface on (832) Karin. The past results indicate that while the red area was detected in 2003, it was absent in the observations in 2004 and 2006 (Chapman et al., 2007; Vernazza et al., 2007; Ito & Yoshida, 2007). Considering the rotational phase and aspect angles during these observations, we propose that the red surface may be confined to a region visible only from specific equatorial viewing geometries, possibly within a crater-like deep depression or another distinct geological feature on the asteroid’s surface.

For the other Karin family asteroids, their near-infrared colors were nearly identical to (832) Karin, with the exception of (47640) 2000 CA30, which displayed a notably different I-band reflectance. These results support the hypothesis that the Karin family asteroids share a common surface properties, consistent with their origin from a collisional breakup event approximately 5.8 million years ago (Vernazza et al., 2006). In contrast, (4507) Petercollins, which had previously been identified as an interloper in the Karin family, exhibited a significantly redder spectrum. This further supports the conclusion that (4507) Petercollins is not related to the Karin family (Nesvorný & Bottke, 2004; Vernazza et al., 2006).


References
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Ito & Yoshida PASJ 59(1), 269 (2007)
Nesvorný et al. Nature 417(6890), 720 (2002)
Nesvorný et al. Icarus 170(2), 324 (2004)
Sasaki et al. AJ 615(2) L161 (2004)
Vernazza et al A&A 460(2), 945 (2006)
Vernazza et al. Icarus 191(2), 330 (2007)
Yoshida et al. PASJ 56(6), 1105 (2004)