Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufm.p51f..04a&link_type=abstract
American Geophysical Union, Fall Meeting 2003, abstract #P51F-04
Astronomy and Astrophysics
Astrophysics
5700 Planetology: Fluid Planets, 5749 Origin And Evolution, 5770 Tidal Forces
Scientific paper
Introduction: We evaluate the tidal disruption of planetary embryos from dynamical, geophysical and meteoritical perspectives. It is widely believed that the present population of asteroids (and thus most meteorites) derive from material that survived intense (99.9%) mass depletion in the protoplanetary disk between Earth and Jupiter. According to this scenario, about one in a thousand bodies survived scattering, close encounters and mergers to become the ancestors of the present main belt and the precursors of meteorites. Close tidal encounters were inevitable, because a deep Roche encounter near a growing planet is about as likely as accretion onto the same planet. Process and Implications: This "long march" took its toll on the survivors, which begat the present asteroids and meteorites. Specifically, for very weak bodies (rubble piles, or those with deep regolith) and for gravity-dominated bodies with viscosity less than (ν lim ˜ √ {G}ρ 3/2 R2~1011 poise for 100 km radius), an encounter with periapsis <~0.5 Rroche results in catastrophic removal of half the original mass [1]. Even partially molten silicate bodies have sufficiently low viscosity to undergo disruptive tidal deformation. Abundant mantle water at this early phase lowers viscosity and enhances disruption energetics. Our dynamical calculations show that a few percent of the surviving primordial asteroids underwent catastrophic tidal disruption during encounters with the transitory main-belt embryos [c.f. 2], if a majority were either partially molten or rubble piles during the first ~3 Ma. Melting and differentiation of asteroid parent bodies took place during this time [3], so planetary mantles may have been tidally stripped in a process that may have been as common as giant collisions. Tidal disruption produces a symmetric chain of fragments. In models of tidal disruption [1], differentiated bodies pull apart into one or more central cores almost devoid of mantle rock, flanked by core-free bodies of diminishing size away from the center. The process need only occur a few times to resolve dilemmas associated with iron and stony-iron meteorites and their parent bodies. Thermodynamics: Tidal disruption induces pressure-release melting and brings core and mantle material into sudden close association across wide surface area. Silicate and iron mix as the core and deep mantle are brought, in the course of hours, to low pressure. Melts degas abruptly and generate turbulence. The shock-free disruption and mixing of parent materials can explain highly varying cooling rates within a single meteorite taxonomic type, and mantle-removal of classic M-type asteroids such as Psyche and Kleopatra without invoking intense impact bombardment that would have easily removed Vesta's crust. We also contemplate a planetary precursor phase where accretion and gravitational equilibrium are sporadically upset by pressure release events and violent degassing. References: [1] Asphaug, E. and W. Benz 1996, Icarus 121, 225-248. [2] Morbidelli, A. et al. 2000, MAPS 35, 1309-1320. [3] Keil, K. 2000, P&SS 48, 887-903.
Agnor Craig
Asphaug Erik
Petit Jerome
Rivkin Andrew
Williams Quentin
No associations
LandOfFree
Tidal Disruption of Primordial Planetary Bodies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Tidal Disruption of Primordial Planetary Bodies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tidal Disruption of Primordial Planetary Bodies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1426278