Planet formation occurs by collisions, which can be energetic enough to cause global melting. During collisions, iron is delivered to the core of the growing planet, which has observable chemical and isotopic effects. Much of my work on planet-building has involved combining modelling of planetary dynamics with calculations of the chemical consequences. This approach can tell us things like how fast Mars formed, and how the Moon and the Earth ended up with identical isotopic signatures.
Most accretion simulations assume that all collisions result in perfect mergers, which is an oversimplification. One of my graduate students, Tina Dwyer, is now looking at what effects more realistic collisions have on the physical and isotopic makeup of the planets.
Tina has also just started to look at the extent to which imperfect accretion can affect satellite evolution. One of the reasons for doing this is that Don Korycansky and I have found that late-stage bombardment of the satellites can dramatically affect the amount of ice surviving to the present day.
Cartoon of how core formation evolves as a planet grows (taken from this article). The chemical effects of core formation depend on whether the incoming iron breaks up into cm-scale blobs or not.
Here is a list of my accretion-related papers:
· Impact-driven ice loss in outer solar system satellites: Consequences for the Late Heavy Bombardment, F. Nimmo, D.G. Korycansky Icarus 219, 508-510, 2012 Reprint
· Heterogeneous accretion, composition and core-mantle differentiation of the Earth, D.C. Rubie, D.J. Frost, U. Mann, Y. Asahara, F. Nimmo, K. Tsuno, P. Kegler, A. Holzheid, H. Palme Earth Planet. Sci. Lett. 301 31-42, 2011 Reprint
· Tungsten isotopic evolution during late-stage accretion: constraints on Earth-Moon equilibration F. Nimmo, D.P. O'Brien, T. Kleine Earth Planet. Sci. Lett. 292 363-370, 2010 Reprint
· Hf-W chronometry and the accretion and early evolution of asteroids and terrestrial planets T. Kleine, M. Touboul, B. Bourdon, F. Nimmo, K. Mezger, H. Palme, Q.-Z. Yin, S.B. Jacobsen, A.N. Halliday Geochim. Cosmochim. Acta, 73 5150-5188, 2009 Reprint (PDF)
· How rapidly did Mars accrete? Uncertainties in the Hf-W timing of core formation, F. Nimmo and T. Kleine Icarus ,191, , 497-504, 2007.Preprint (PDF)
· Formation of the Earth's core D.C. Rubie, F. Nimmo and H.J. Melosh, Treatise on Geophysics vol. 9, pp. 51-90, (G. Schubert, ed.), 2007. Email me if you want a reprint.
· The Origin of the Core F. Nimmo, Encyclopedia of Geomagnetism and Paleomagnetism, D. Gubbins and E. Herrero-Bervera, eds., Springer, pp.89-91, 2007. Preprint (PDF)
· Isotopic outcomes of N-body accretion simulations: Constraints on equilibration processes during large impacts from Hf/W observations,F. Nimmo and C.B. Agnor, Earth Planet. Sci. Lett. , 243, 26-43, 2006. Reprint (PDF)
Last Modified: 4th Sept 2012