J/AJ/152/54 Spectroscopy of main-belt Ch/Cgh-type asteroids (Vernazza+, 2016)
Compositional homogeneity of CM parent bodies.
Vernazza P., Marsset M., Beck P., Binzel R.P., Birlan M., Cloutis E.A.,
DeMeo F.E., Dumas C., Hiroi T.
<Astron. J., 152, 54-54 (2016)>
=2016AJ....152...54V 2016AJ....152...54V (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Spectroscopy ; Spectra, infrared
Keywords: meteorites, meteors, meteoroids - methods: data analysis -
methods: laboratory: solid state - methods: observational -
minor planets, asteroids: general - techniques: spectroscopic
Abstract:
CM chondrites are the most common type of hydrated meteorites, making
up ∼1.5% of all falls. Whereas most CM chondrites experienced only
low-temperature (∼0°C-120°C) aqueous alteration, the existence
of a small fraction of CM chondrites that suffered both hydration and
heating complicates our understanding of the early thermal evolution
of the CM parent body(ies). Here, we provide new constraints on the
collisional and thermal history of CM-like bodies from a comparison
between newly acquired spectral measurements of main-belt Ch/Cgh-type
asteroids (70 objects) and existing laboratory spectral measurements
of CM chondrites. It first appears that the spectral variation
observed among CM-like bodies is essentially due to variations in the
average regolith grain size. Second, the spectral properties of the
vast majority (unheated) of CM chondrites resemble both the surfaces
and the interiors of CM-like bodies, implying a "low" temperature
(<300°C) thermal evolution of the CM parent body(ies). It follows
that an impact origin is the likely explanation for the existence of
heated CM chondrites. Finally, similarly to S-type asteroids and (2)
Pallas, the surfaces of large (D>100km) - supposedly primordial -
Ch/Cgh-type main-belt asteroids likely expose the interiors of the
primordial CM parent bodies, a possible consequence of impacts by
small asteroids (D<10km) in the early solar system.
Description:
We conducted an extensive spectroscopic survey in the near-infrared
range of 70 main-belt Ch/Cgh-type asteroids and 4 Ch/Cgh-type families
and combined these measurements with available visible wavelength
spectra.
New data presented here are near-infrared asteroid spectral
measurements for Ch- and Cgh-type asteroids from 0.7-2.5µm obtained
using SpeX, the low- to medium-resolution near-IR spectrograph and
imager on the 3m NASA InfraRed Telescope Facility (IRTF) located on
Mauna Kea, HI. Observing runs were conducted remotely primarily from
the Observatory of Paris-Meudon, France between 2010 April and 2012
January. The spectrograph SpeX, combined with a 0.8*15arcsec slit, was
used in the low-resolution prism mode for acquisition of the spectra
in the 0.7-2.5µm wavelength range. In order to monitor the high
luminosity and variability of the sky in the near-IR, the telescope
was moved along the slit during the acquisition of the data so as to
obtain a sequence of spectra located at two different positions (A and
B) on the array.
In addition, we complemented our data set with additional
near-infrared spectra retrieved from the Small Main-Belt Asteroid
Spectroscopic Survey (SMASS) database (http://smass.mit.edu/).
Combining these near-infrared measurements with available visible
wavelength spectra (Bus, 1999PhDT........50B 1999PhDT........50B; Lazzaro et al.,
2004Icar..172..179L 2004Icar..172..179L) allows for the first time an extensive visible
and near-infrared (VNIR) spectral database of main-belt Ch and Cgh
types with D>45km (78% or 49/63 of all Ch and Cgh types listed in
SMASS; see Table1).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 70 Observational circumstances and spectral parameters
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See also:
B/astorb : Orbits of Minor Planets (Bowell+ 2014)
J/ApJ/741/68 : Main Belt asteroids with WISE/NEOWISE. I. (Masiero+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Asteroid Asteroid number (1)
7- 17 A11 "Y:M:D" Date Observing date (near-infrared) (2)
19- 26 F8.4 km Diam [14/227] Diameter (3)
28- 34 F7.5 --- pV [0.03/0.18] Albedo (3)
36- 46 F11.8 um-1 Slope [-0.1/0.23] Spectral slope over the visible
and near-infrared range
48- 57 F10.8 --- Depth [0.001/0.087] The 0.7µm band depth
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Note (1): The signal-to-noise ratio for most asteroid spectra is generally above
100, and above 50 for all objects.
Note (2): For observations reported here, we give the observation date (UT). All
near-infrared (NIR) data were obtained using the NASA InfraRed Telescope
Facility (IRTF) at Mauna Kea, Hawaii.
Note (3): Albedo and diameters were taken from IRAS and/or WISE (Masiero et al.
2011, Cat. J/ApJ/741/68; 2012ApJ...759...14M 2012ApJ...759...14M).
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 22-Sep-2016