A newborn asteroid 832 Karin with old and new surfaces – SUBARU spectroscopy

Abstract

The mismatch between reflectance spectra of most common asteroids (S-type asteroids) and most common meteorites (ordinary chondrites) is thought to be caused by space weathering. Recent study of celestial mechanics has led to the discovery of a young group of S-type asteroids, “Karin cluster group”, which is thought to be remnants of a collisional breakup only 5.8 million years ago. We performed near-infrared spectroscopy of the brightest asteroid 832 Karin among this cluster group. For different rotational phases of Karin, we derived different spectra such as reddened spectrum like that of S-type asteroid and unreddened spectrum like that of ordinary chondrites. These findings indicate that a part of Karin may retain spectrally mature surface of its parent body. Although Karin might have formed from gravitational accumulation from catastrophic collision of its parent body, there would be some color heterogeneity on its surface if Karin collected materials which derived the weathered surface of the parent body.