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Hypervelocity impacts and magnetization of small bodies in the Solar SystemThe observed magnetism of asteroids such as Gaspra and Ida (and other small bodies in the solar system including the Moon and meteorites) may have resulted from an impact-induced shock wave producing a thermodynamic state in which iron-nickel alloy, dispersed in a silicate matrix, is driven from the usual low-temperature, low-pressure, alpha, kaemacite, phase to the paramagnetic, epsilon (hcp), phase. The magnetization was acquired upon rarefaction and reentry into the ferromagnetic, alpha, structure. The degree of remagnetization depends on the strength of the ambient field, which may have been associated with a Solar-System-wide magnetic field. A transient field induced by the impact event itself may have resulted in a significant, or possibly, even a dominant contribution, as well. The scaling law of Housen et al. (Housen, K. R., R. M. Schmidt, and K. A. Holsapple 1991) for catastrophic asteroid impact disaggregation imposes a constraint on the degree to which small planetary bodies may be magnetized and yet survive fragmentation by the same event. Our modeling results show it is possible that Ida was magnetized when a large impact fractured a 125 +/- 22-km-radius protoasteroid to form the Koronis family. Similarly, we calculate that Gaspra could be a magnetized fragment of a 45 +/- 15 km-radius protoasteroid.
Document ID
19950060234
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Chen, Guangqing
(California Institute of Technology, Pasadena, CA United States)
Ahrens, Thomas J.
(California Institute of Technology, Pasadena, CA United States)
Hide, Raymond
(University of Oxford Oxford, United Kingdom)
Date Acquired
August 16, 2013
Publication Date
May 1, 1995
Publication Information
Publication: Icarus
Volume: 115
Issue: 1
ISSN: 0019-1035
Subject Category
Astrophysics
Accession Number
95A91833
Distribution Limits
Public
Copyright
Other

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