Geoscience Reference
In-Depth Information
DIFFERENCE IN DEGREE OF SPACE WEATHERING
ON NEWBORN ASTEROID KARIN
TAKANORI SASAKI
∗
, SHO SASAKI, JUN-ICHI WATANABE,
TOMOHIKO SEKIGUCHI, FUMI YOSHIDA, TAKASHI ITO,
HIDEYO KAWAKITA, TETSUHARU FUSE,
NARUHISA TAKATO and BUDI DERMAWAN
Department of Earth and Planetary Science, The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
∗
takanori@eps.s.u-tokyo.ac.jp
We have carried out a near-infrared (
J
,
H
,and
K
bands) spectroscopy of
the asteroid Karin with cooled infrared spectrograph and camera for OHS on
the Subaru telescope. This asteroid is the brightest asteroid among the Karin
cluster group, which is thought to be remnants of a collisional breakup only
5.8 million years ago. For different rotational phases of Karin, we derived dif-
ferent spectra such as a reddened spectrum like that of S-type asteroid and an
un-reddened spectrum like that of ordinary chondrite. Our result supports the
idea that S-type asteroids are parent bodies of ordinary chondrites.
1. Introduction
Although S-type asteroids are the most common among the inner-part main
belt asteroids as well as near-Earth asteroids, reddened reflectance spec-
tra and derived mineralogy of S-type asteroids are different from those
of ordinary chondrites, the most common meteorites. Space weathering is
thought to be able to explain these spectral mismatches between asteroid
types and meteorite classes.
1
-
3
Recent asteroid surveys suggest strong link
between S-type asteroids and ordinary chondrites.
4
,
5
Multispectral obser-
vation of Ida by Galileo spacecraft showed that relatively fresh surface such
as crater interiors and ejecta have reflectance like ordinary chondrites.
1
Moreover NEAR-Shoemaker mission revealed, thanks to X-ray and near-
infrared spectrometer measurements, an ordinary chondrite composition of
433 Eros despite a reddened S-type spectrum, suggesting once again that
the space weathering has altered the surface optical properties.
6
,
7
The detailed mechanism of space weathering has been remained to be
unsolved until recently, when the laboratory experiments using high-energy
∗
Corresponding author.
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