Reflectance Spectra of Members of Very Young Asteroid
Reflectance Spectra of Members of Very Young Asteroid Families
40th Lunar and Planetary Science Conference, The Woodlands TX, USA.
Poster #2258. Poster Session I, Tues., 24 March 2009.
C.R. Chapman, B. Enke, W.J. Merline, D. Nesvorn, P.M. Tamblyn, & E.F. Young (SwRI, Boulder CO)
Introduction: Several asteroid families or clusters have very
young dynamical ages . The Veritas family of C-type
asteroids, Karin cluster within the S-type Koronis family, and the
Iannini cluster (S-type) formed about 8.3, 5.8, and <5 My ago,
respectively. A family associated with Datura is extremely
young, 0.45 My . If space weathering modifies asteroid
spectra on timescales comparable to or longer than several My,
then we may expect different spectra for members of these
recently formed families than for older families. We use the
SpeX instrument on the IRTF (in low-resolution prism mode) to
study infrared reflectance spectra of members of these young
families. We observe selected young asteroids, controls (e.g.
members of the Themis family and non-Karin members of the
Koronis family), and G-type comparison stars.
Observations: Spectra were obtained on 11 nights between
June 2005 and July 2006. Although the sky quality was
generally good, we had some difficulty characterizing extinction
resulting in slight uncertainties in the overall slopes of spectra.
Also there is jitter for faint asteroids beyond 2m and near the m and near the
1.4 and 1.9m water bands. An average spectrum is calculated m and near the m water bands. An average spectrum is calculated
for each asteroid each night. Nightly averages are then
averaged to yield spectra shown in the bottom half of this poster
for asteroids observed on multiple nights. Averages for each
asteroid family are shown in white-on-black immediately below.
Discussion: The timescale for space weathering processes
that modify reflectance spectra of S-type asteroids is an
important issue . It can be seen that spectra for the young
Iannini and Karin family asteroids are slightly less red (and/or
have shallower bands) than typical Koronis members, which may
be a subtle reflection of their comparative youth. However, if
space weathering modifies ordinary chondrite-like spectra to
mature S-type spectra (like the Koronis family), then the Iannini
and Karin family asteroids are near the end of their spectral
evolution after only a few million years. The very young asteroid
Datura is a Q-type with a deep 1m and near the m band and has only begun to
evolve toward S-type maturity.
Assuming that the Veritas and Themis families are of the
same inherent composition, then the different average spectra
for these families may reflect space weathering trends. Whereas
Themis spectra show a U-like shape in this wavelength range,
the young Veritas members tend to show a slightly bluish slope
with a hint of an inverted U-like shape, as has been previously
noted [4,5]. It is possible that the effects of space weathering are
more prominent at these longer wavelengths for C-types than for
The goals of our project are to study, with various
telescopic techniques, the physical properties of members of very young dynamical
families. These families, identified by D. Nesvorny and his colleagues, were formed
at discrete and well-determined times less than 10 million years ago. Most asteroid
families are believed to be hundreds of millions or even billions of years old. Our
expectation is that young families, as compared with typical families, may provide
clues to processes that presumably take place on relatively short timescales.
Processes in which we are interested include space weathering, temporary
preservation of near-surface volatiles, satellite formation and evolution, the
Yarkovsky Effect (which we can help to calibrate), and understanding the initial/early
configurations of asteroid families as a check on hydrocode simulations and other
theoretical insights concerning the formation of families.
Our approach is to observe known members of
the Karin cluster (a=2.87 AU, e=0.044, i=2.1), the Veritas family (a=3.17 AU, e=0.065,
i=9.3), the Iannini cluster (a=2.64 AU, e=0.267, i=12.2), and younger families like
Datura, plus controls (e.g. non-Karin members of the Koronis family, also small
members of the C-type Themis family), using a variety of telescopes, instruments,
and techniques. Our approach is to make coordinated space-based and groundbased observations of relevant family members, obtaining low- and mediumresolution spectrophotometry, radiometry, adaptive optics imaging, and lightcurve
photometry. In this poster we present our final reductions for IR reflectance spectra
obtained with SpeX on the IRTF during June 2005 through July 2006.
Some members of our
team, observing with the
IRTF SpeX remotely from
the Boulder, Colorado,
offices of SwRI, from
back-left to front-right:
Bill Merline, Clark
Chapman, Eliot Young,
and Peter Tamblyn.
References:  Nesvorny D. et al. (2003) Ap.J. 591, 486-49m water bands. An average spectrum is calculated 7.  Nesvorny D. et al.
(2006) Science 312, 149m water bands. An average spectrum is calculated 0.  Chapman C.R. (2004) Ann. Rev. EPS 32, 539m water bands. An average spectrum is calculated -567.
 Chapman C.R. (2008) ACM #839m water bands. An average spectrum is calculated 1.  Ziffer J. (2008) AAS/DPS#40, #60.06.
Average spectra for asteroids, grouped by family. All
spectra are from 0.8 to 2.45m and near the m, normalized to 1.0
reflectance at 1.5m and near the m (but vertically displaced by 0.2).
Within each part of the figure, asteroid numbers from
top to bottom are: Datura: 1270. Iannini: 1547, 151032,
4652, 81550, 87239m water bands. An average spectrum is calculated . Karin: 10783, 832. Koronis: 1289m water bands. An average spectrum is calculated ,
1423, 167, 208, 2574, 3032, 311, 4863, 5338, 534.
Veritas (Part 1): 1079m water bands. An average spectrum is calculated 3, 1086, 15066, 19m water bands. An average spectrum is calculated 845, 2147,
28022, 28546, 29m water bands. An average spectrum is calculated 89m water bands. An average spectrum is calculated 1. Veritas (Part 2): 31743, 49m water bands. An average spectrum is calculated 0,
49m water bands. An average spectrum is calculated 622, 559m water bands. An average spectrum is calculated 2, 559m water bands. An average spectrum is calculated 4, 6343, 7612. Themis: 1027, 2114,
229m water bands. An average spectrum is calculated 7, 359m water bands. An average spectrum is calculated 1, 4470, 468, 49m water bands. An average spectrum is calculated 2, 656, 859m water bands. An average spectrum is calculated 1, 9m water bands. An average spectrum is calculated 0.
Photo by Y Chapman.
This work is supported primarily by the NASA Planetary Astronomy Program.
Comparison of S-like families: Koronis exhibits trends for slightly
more weathering than Iannini (which has a slightly deeper 1m and near the m band,
measured between 0.9m water bands. An average spectrum is calculated m and near the m and 1.4m and near the m) or than Karin (less reddened
overall). But the differences from Koronis are subtle and not the same
for Karin and Iannini. Datura has a deep 1m and near the m band and resembles a
mostly unweathered, olivine-rich ordinary chondrite.
Concluding Thoughts The extremely young Datura family is represented by a fresh, olivine-rich spectrum with
a deep 1 micron band, suggesting little space weathering. The small, dynamically young S-type asteroid families
(Karin and Iannini) have evolved rather far toward mature S-type reflectance characteristics in the 0.8 2.5
micron region in just a few million years. There may be less rapid spectral evolution exhibited by Veritas family
members, provided that their inherent carbonaceous mineralogy is similar to that of Themis family members.
For these C-type families, the differences in spectral slope are opposite in our wavelength range from the
differences observed in the visible.
Environmental and Disposal Liabilities Intranet Reporting System ... Add a New EDL Site Fill out Liability page (Slide 19) List known Responsible Parties (RPs) (other than self) Record the percentage (if known) of the total cleanup costs (including all RPs)...
Sample return from C-type asteroids. The only samples of C-type asteroids currently available are from meteorites. To . understand and . make scientific . use of the samples that will be returned in . future missions, we . need a...
Please follow the catering guidelines below when placing an order. If you need additional information, contact the Food and Nutrition Services Department at (314) 331-6115 or (314) 401-9870. All catering requests must be submitted by email. To book a catering...
The Flower-class corvette was originally designed for offshore patrol work, and was not ideal as an antisubmarine escort; they were really too short for open ocean work, too lightly armed for antiaircraft defence, and little faster than the merchantmen they...
2.17 describe how experiments involving the reactions of elements such as copper, iron and phosphorus with air can be used to determine the percentage by volume of oxygen in air. Experiment with copper. This can be demonstrated by the reactionof...
Gato de Fernando Botero Imagen en wikimediacommons.org (bouar y soonsoon) Escultura en Madrid de Joan Miró Compara estas esculturas en relación con: la utilización de formas reales o recreadas el uso de volumen lleno o vacío Weding de Wien Cobbenhagen...
Arial Geneva Wingdings Blank Presentation Ethical Decision-Making in Pediatrics "Every interaction between a doctor and a patient has a moral component." Pediatrics vs. Adult Care: What are the important differences?
Ready to download the document? Go ahead and hit continue!