|
Isotopic compositions of cometary matter
returned by Stardust.
McKeegan K. D., Aléon J., Bradley J., Brownlee D.,
Busemann H., Butterworth A., Chaussidon M., Fallon S., Floss
C., Gilmour J., Gounelle M., Graham G., Guan Y., Heck P. R.,
Hoppe P., Hutcheon I. D., Huth J., Ishii H., Ito M.,
Jacobsen S. B., Kearsley A., Leshin L. A., Liu M.-C., Lyon
I., Marhas K., Marty B., Matrajt G., Meibom A., Messenger
S., Mostefaoui S., Mukhopadhyay S., Nakamura-Messenger K.,
Nittler L., Palma R., Pepin R. O., Papanastassiou D. A.,
Robert F., Schlutter D., Snead C. J., Stadermann F. J.,
Stroud R., Tsou P., Westphal A., Young E. D., Ziegler K.,
Zimmermann L., and Zinner E. (2006)
Science 314, 1724-1728.
doi:10.1126/science.1135992
ABSTRACT
Hydrogen, carbon, nitrogen, and oxygen isotopic
compositions are heterogeneous among comet 81P/Wild 2
particle fragments; however, extreme isotopic anomalies are
rare, indicating that the comet is not a pristine aggregate
of presolar materials. Nonterrestrial nitrogen and neon
isotope ratios suggest that indigenous organic matter and
highly volatile materials were successfully collected.
Except for a single 17O-enriched circumstellar
stardust grain, silicate and oxide minerals have oxygen
isotopic compositions consistent with solar system origin.
One refractory grain is 16O-enriched, like
refractory inclusions in meteorites, suggesting that Wild 2
contains material formed at high temperature in the inner
solar system and transported to the Kuiper belt before comet
accretion.
|