Catastrophic Disruptions or Slow Erosion as the Dominant Mechanism for IDP Production

Details Catastrophic Disruptions or Slow Erosion as the Dominant Mechanism for IDP Production Catastrophic Disruptions or Slow Erosion as the Dominant Mechanism for IDP Production

Jul 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993metic..28q.349f&link_type=abstract

Meteoritics, vol. 28, no. 3, volume 28, page 349

Mathematics

Logic

Asteroid Belt, Interplanetary Dust Particles

Scientific paper

Evidence from the degree of entry heating [1,2] and solar flare track densities [3] suggests a large fraction of the silicate IDPs recovered from the stratosphere are derived from main-belt asteroidal parent bodies. The two dominant mechanisms by which main-belt asteroids contribute to the interplanetary dust are slow erosion and catastrophic disruption with subsequent comminution of the debris. These mechanisms produce profoundly different IDP populations. If slow erosion dominates, the IDPs sample the diversity of the asteroid population in rough proportion to the surface areas of the individual asteroids [4], although probably modified by fragmentation effects [5]. If catastrophic collisions dominate, the IDPs principlly sample the debris of a few recent disruptions. Comparison of the compositional diversity of the IDP population with that of the main-belt asteroids and with the asteroid families associated with recent disruptions should allow a choice between the two mechanisms. Diversity in the Main-Belt: Reflection spectroscopy indicates that the main-belt asteroids include primitive, metamorphic, and igneous objects showing a great range of compositional diversity within each group [6]. Likely parent bodies for most types of meteorites have been identified in the main-belt, and several types of asteroids remain without analog meteorites [6]. Many of these asteroids have relatively high albedos. Diversity of the IDPs: Both the anhydrous and the hydrated silicate IDPs have high contents of carbon [4,7] and volatiles [8]. Only 4 of 30 silicate IDPs analyzed by [4] and 2 of 11 analyzed by Thomas et al. [7] had C/Si lower than CM meteorites, suggesting that most silicate IDPs are carbonaceous chondrites [4]. The parent bodies of these carbon-rich IDPs are likely to be dark objects. Unless many higher albedo interplanetary particles are hidden among the "terrestrial" dust on the collectors, the silicate IDPs do not sample the higher albedo asteroids in proportion to their surface areas in the main belt. The lack of compositional diversity suggests the silicate IDPs principly sample only a few source types, mostly carbonaceous chondrites. Catastrophic Collision Origin: The three major dust bands, identified in the main-belt by IRAS measurements, are believed to have resulted from the catastrophic disruption of larger asteroids [9]. These dust bands are associated with the Themis, Eos, and Koronis families of asteroids (see Table 1). Two of these families are dominated by asteroids similar to carbonaceous chondrites: Themis, associated with hydrated carbonaceous chondrite material, and Eos, associated with anhydrous carbonaceous chondrite material. The Koronis family is classified as S-type, generally thought to be differentiated stony-iron bodies [6], but analog meteorites have not yet been identified. If most of the collected IDPs were derived from comminution of the debris from the catastrophic collisions responsible for the IRAS dust bands we would expect IDPs to consist principlly of carbonaceous chondrite material of both the anhydrous and hydrated types as well as S-type material of unknown chemical and mineralogical composition. The low abundance of non-carbonaceous, silicate IDPs is consistent with catastrophic collisions being the dominant dust producing mechanism in the main belt. References: [1] Flynn G. J. (1989) Icarus, 77, 287-310. [2] Brownlee D. E. et al. (1993) LPS XXIV. [3] Sandford S. A. (1986) Icarus, 68, 377-394. [4] Schramm L. S. et al. (1989) Meteoritics. [5] Flynn G. J. (1990) ACM III, 59-62. [6] Bell J. F. et al. (1989) In Asteroids II, 921-945. [7] Thomas K. L. et al. (1993) GCA, in press. [8] Flynn G. J. et al. (1993) LPS XXIV. [9] Sykes M. V. (1989) In Asteroids II, 336-367. Table 1, which appears here in the hard copy, shows dust band associations with asteroid families.

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