Geoscience Reference
In-Depth Information
1.6
1.4
1.2
1
0.8
0.9
1.2
1.5
1.8
2.1
2.4
Wavelength (micron)
Fig. 2.
) along with the
previous observations of S(IV)-type asteroid 584 Semiramis (denoted by squares) and L6
ordinary chondrite Paranaiba (denoted by diamonds) normalized to the unity at 1.0
µ
m.
The mean values for every 10 data points are plotted with their error bars of standard
deviation.
Reflectance spectra of Karin (the first set:
×
,andthelastset:
◦
Figure 2 shows normalized reflectance spectra of Karin (the first set
and the last set) along with those of S(IV)-type asteroid 584 Semiramis
and L6 ordinary chondrite Paranaiba. The first set's spectrum of Karin
matches well the spectrum of S(IV) class asteroid. In contrast, the last
set's spectrum (blue) of Karin, which has a relatively gentle slope at the
wavelength shorter than 1.6
µ
m, matches (within noise of our spectrum) a
typical normalized spectrum of L6 ordinary chondrite. The first set seems to
be the reddened spectrum of the last set by space weathering. Laboratory
simulations of space weathering also showed relatively intense reddening at
wavelength shorter than 1.6
µ
m.
8
,
17
4. Discussions
Our result indicates that Karin has two different surfaces, reddened and
un-reddened surfaces, and the difference among spectra would reflect the
degree of space weathering. The mature and fresh surfaces' spectra strongly
stand up for the idea that space weathering is responsible for the mis-
matches between asteroid types and meteorite classes. Our result supports
the idea that S-type asteroids are parent bodies of ordinary chondrites.
1
At
rotational phase of 0.35, which is the boundary between the first set and
the second set, abrupt shift in the degree of space weathering is observed.
