Ancient Asteroids Enriched in Refractory Inclusions
Abstract
Calcium- and aluminum-rich inclusions (CAIs) occur in all classes of chondritic meteorites and contain refractory minerals predicted to be the first condensates from the solar nebula. Near-infrared spectra of CAIs have strong 2-micrometer absorptions, attributed to iron oxide–bearing aluminous spinel. Similar absorptions are present in the telescopic spectra of several asteroids; modeling indicates that these contain ∼30 ± 10% CAIs (two to three times that of any meteorite). Survival of these undifferentiated, large (50- to 100-kilometer diameter) CAI-rich bodies suggests that they may have formed before the injection of radiogenic 26Al into the solar system. They have also experienced only modest post-accretionary alteration. Thus, these asteroids have higher concentrations of CAI material, appear less altered, and are more ancient than any known sample in our meteorite collection, making them prime candidates for sample return.
Get full access to this article
View all available purchase options and get full access to this article.
Supplementary Material
File (sunshine.som.pdf)
- Download
- 134.93 KB
References and Notes
1
2
A. J. Brearley, R. H. Jones, in Reviews In Mineralogy, Vol. 36, Planetary Materials, J. J. Papike, Ed. (Mineralogic Society of America, Washington, DC, 1998), pp. 3-1–3-398.
3
T. H. Burbine, M. J. Gaffey, J. F. Bell, Meteorit. Planet. Sci.27, 424 (1992).
4
Other common Fe-bearing silicates that have strong absorptions in the near infrared (38). Although pyroxene spectra have absorptions in the 2-μm region, they have even stronger features near 1 μm. Conversely, olivine spectra lack 2-μm absorptions and are instead characterized by a complex feature at 1 μm. It is on this basis (a strong 2-μm absorption in the absence of a stronger 1-μm feature) that spinel is spectrally identified.
5
6
H. C. Connolly Jr., S. J. Desch, R. D. Ash, R. H. Jones, in Meteorites and the Early Solar System II, D. S. Lauretta, H. Y. McSween Jr., Eds. (Univ. of Arizona Press, Tucson, AZ, 2006), pp. 383–397.
7
M. E. Zolenskyet al., Science314, 1735 (2006).
8
F. J. Ciesla, Science318, 613 (2007).
9
G. J. MacPherson, D. A. Wark, J. T. Armstrong, in Meteorites and the Early Solar System, J. F. Kerridge, M. S. Matthews, Eds. (Univ. of Arizona Press, Tucson, AZ, 1988), pp. 746–807.
10
The Smithsonian Allende sample USNM 3509 was sectioned into large slices, and refractory inclusions were identified and cored. Thin and thick sections were made from half of the objects, and reference materials were preserved for future study. Thin sections were analyzed by the Cameca SX50 electron microprobe at the Lunar and Planetary Laboratory at the University of Arizona to quantify major and minor element abundances. While avoiding contamination from the matrix, material from the other half of the objects was cored out, ground into <38-μm-size powders, and sent to Brown University for spectral measurements at the NASA-Keck Reflectance Experiment Laboratory (RELAB) facility (40). All spectra were measured with 5-nm resolution at a standard viewing geometry of 30° incidence, 0° emission.
11
S. Xu, R. P. Binzel, T. H. Burbine, S. J. Bus, Icarus115, 1 (1995).
12
S. J. Bus, R. P. Binzel, Icarus158, 106 (2002).
13
J. T. Rayner, P. M. Onaka, M. C. Cushing, C. Michael, W. D. Vacca, Proc. SPIE5492, 1498 (2004).
14
In the Bus visible asteroid taxonomy, objects with a steep red spectral slope at wavelengths up to 0.75 μm, which are then relatively flat, are classified as L types (41).
15
S. J. Bus, thesis, Massachusetts Institute of Technology, (1999).
16
V. Zappalà, Ph. Bendjoya, A. Cellino, P. Farinella, C. Froeschlé, Icarus116, 291 (1995).
17
Whereas the Henan and Watsonia families are roughly the same distance from the sun, the mean orbits of asteroids making up these two families are markedly different in both eccentricity and inclination. The mean proper elements for the Henan family are ∼2.73 astronomical units (AU) (ranging from 2.69 to 2.76 AU), e ∼ 0.07, and sin(i) ∼ 0.06 (where e is eccentricity and i is inclination), compared with the Watsonia family at ∼2.77 AU (ranging from 2.74 to 2.80 AU), e ∼ 0.16, and sin(i) ∼0.29. This corresponds to a difference in orbital velocity between these families of over 6 km/s, making it highly unlikely these two families can be linked to a single parent body. 234 Barbara is a distinct asteroid located at 2.39 AU.
18
E. A. Cloutis, J. M. Sunshine, R. V. Morris, Meteorit. Planet. Sci.39, 545 (2004).
19
J. M. Sunshine, E. A. Cloutis, Lunar Planet. Sci.XXXI, 1640 (1999).
20
E. A. Cloutis, M. J. Gaffey, Icarus105, 568 (1993).
21
E. Jarosewich, Meteoritics25, 323 (1990).
22
B. Hapke, Theory of Reflectance and Emittance Spectroscopy (Cambridge Univ. Press, New York, 1993).
23
To calculate the single-scattering albedo of each component, we employed Hapke's two-stream approximation assuming no opposition effect, isotropic scattering, and that all components have the same density and particle size (22). Once converted to single-scattering albedo, mixing is linear and relative abundances can be estimated using a least-squares solution (42, 43).
24
M. J. S. Beltonet al., Science265, 1543 (1994).
25
J. Veverkaet al., Science289, 2088 (2000).
26
H. Yanoet al., Science312, 1350 (2006).
27
Asteroid spectra are routinely measured relative to a given wavelength, as in Fig. 3, where data are normalized to 0.55 μm. Absolute albedos are obtained from the Infrared Astronomical Satellite (IRAS) Supplemental IRAS Minor Planet Survey database, as archived in the NASA Planetary Data System data set IRAS-A-FPA-3-RDR-IMPS-V6.0.
28
29
Although the spectrum of 2448 Sholokhov is not uniquely interpretable, its presence within the same family as several spinel-rich asteroids (the Watsonia family) makes it a stronger candidate for representing spectral slope in modeling these CAI-rich asteroids than any existing theoretical method or potential laboratory analog.
30
A. Das, G. Srinivasan, Lunar Planet. Sci.XXXVIII, 1338 (2007).
31
A. J. G. Jurewicz, D. W. Mittlefehldt, J. H. Jones, Geochim. Cosmochim. Acta57, 2123 (1993).
32
R. E. Grimm, H. Y. McSween Jr., Icarus82, 244 (1989).
33
A. S. Rivkin, D. E. Trilling, L. A. Lebofsky, Bull. Am. Astron. Soc.30, 1023 (1998).
34
G. J. MacPherson, A. M. Davis, E. K. Zinner, Meteoritcs30, 365 (1995).
35
S. Sahijpal, J. N. Goswami, Astrophys. J.509, L137 (1998).
36
C. J. Allègre, G. Manhès, C. Göpel, Geochim. Cosmochim. Acta59, 1445 (1995).
37
Y. Amelin, A. N. Krot, I. D. Hutcheon, A. A. Ulyanov, Science297, 1678 (2002).
38
J. B. Adams, in Infrared and Raman Spectroscopy of Lunar and Terrestrial Materials, C. Karr, Ed. (Academic Press, San Diego, CA, 1975), pp. 91–116.
39
L. Grossman, Geochim. Cosmochim. Acta39, 433 (1975).
40
C. M. Pieters, T. Hiroi, Lunar Planet. Sci.XXXV, 1720 (2004).
41
S. J. Bus, R. P. Binzel, Icarus158, 146 (2002).
42
J. F. Mustard, C. M. Pieters, J. Geophys. Res.92, E617 (1987).
43
B. E. Clark, J. Geophys. Res.100, 14443 (1995).
44
B. E. Clark, B. Hapke, C. Pieters, D. Britt, in Asteroids III, W. F. Bottke Jr., A. Cellino, P. Paolicchi, R. P. Binzel, Eds. (Univ. of Arizona Press, Tucson, AZ, 2003), pp. 585–599.
45
B. Hapke, J. Geophys. Res.106, 10039 (2001).
46
This research was funded in part by NASA grants NNX06AH69G (J.M.S.), NNG05GF39G (H.C.C.), and NNG06GF56G (T.J.M. and L.M.L.) and NSF grant AST-0307688 (S.J.B.). We thank T. Hiroi for carefully collecting our spectra of CAIs and Allende samples at RELAB, K. Domanik for assistance with the electron microprobe at Lunar and Planetary Laboratory, and R. Binzel and two anonymous reviewers for suggestions that improved this report.
(0)eLetters
eLetters is a forum for ongoing peer review. eLetters are not edited, proofread, or indexed, but they are screened. eLetters should provide substantive and scholarly commentary on the article. Embedded figures cannot be submitted, and we discourage the use of figures within eLetters in general. If a figure is essential, please include a link to the figure within the text of the eLetter. Please read our Terms of Service before submitting an eLetter.
Log In to Submit a ResponseNo eLetters have been published for this article yet.
Information & Authors
Information
Published In
Science
Volume 320 | Issue 5875
25 April 2008
25 April 2008
Copyright
American Association for the Advancement of Science.
Article versions
You are viewing the most recent version of this article.
Submission history
Received: 18 December 2007
Accepted: 6 March 2008
Published in print: 25 April 2008
Notes
Supporting Online Material
www.sciencemag.org/cgi/content/full/1154340/DC1
Fig. S1
Table S1
References and Notes
Authors
Metrics & Citations
Metrics
Article Usage
Altmetrics
Citations
Cite as
- J. M. Sunshine et al.
Export citation
Select the format you want to export the citation of this publication.
Cited by
- Precious and structural metals on asteroids, Planetary and Space Science, 225, (105608), (2023).https://doi.org/10.1016/j.pss.2022.105608
- Olivine origination in lunar Das crater through three-dimensional numerical simulation, Icarus, 391, (115333), (2023).https://doi.org/10.1016/j.icarus.2022.115333
- The Nature of Low-albedo Small Bodies from 3 μm Spectroscopy: One Group that Formed within the Ammonia Snow Line and One that Formed beyond It, The Planetary Science Journal, 3, 7, (153), (2022).https://doi.org/10.3847/PSJ/ac7217
- Compositions of carbonaceous-type asteroidal cores in the early solar system, Science Advances, 8, 37, (2022)./doi/10.1126/sciadv.abo5781
- Spectral reflectance variations of aubrites, metal‐rich meteorites, and sulfides: Implications for exploration of (16) Psyche and other “spectrally featureless” asteroids, Meteoritics & Planetary Science, 57, 8, (1570-1588), (2022).https://doi.org/10.1111/maps.13891
- Experimental phase function and degree of linear polarization curve of olivine and spinel and the origin of the Barbarian polarization behaviour, Monthly Notices of the Royal Astronomical Society, 517, 4, (5463-5472), (2022).https://doi.org/10.1093/mnras/stac2895
- Composition of inner main-belt planetesimals, Astronomy & Astrophysics, 665, (A83), (2022).https://doi.org/10.1051/0004-6361/202244099
- Negative polarization properties of regolith simulants, Astronomy & Astrophysics, 665, (A49), (2022).https://doi.org/10.1051/0004-6361/202243844
- Asteroid taxonomy from cluster analysis of spectrometry and albedo, Astronomy & Astrophysics, 665, (A26), (2022).https://doi.org/10.1051/0004-6361/202243587
- The Calern Asteroid Polarisation Survey, Astronomy & Astrophysics, 665, (A66), (2022).https://doi.org/10.1051/0004-6361/202142960
- See more
Loading...
View Options
Check Access
Log in to view the full text
AAAS login provides access to Science for AAAS Members, and access to other journals in the Science family to users who have purchased individual subscriptions.
- Become a AAAS Member
- Activate your AAAS ID
- Purchase Access to Other Journals in the Science Family
- Account Help
Log in via OpenAthens.
Log in via Shibboleth.
More options
Register for free to read this article
As a service to the community, this article is available for free. Login or register for free to read this article.
Buy a single issue of Science for just $15 USD.