The Diversity of Extrasolar Terrestrial Planets J. Bond, D. Lauretta & D. O’Brien IAU Symposium th August 2009

Chemistry meets Dynamics Most dynamical studies of planetesimal formation have neglected chemical constraints Most chemical studies of planetesimal formation have neglected specific dynamical studies This issue has become more pronounced with studies of extrasolar planetary systems which are both dynamically and chemically unusual Combine dynamical models of extrasolar terrestrial planet formation with chemical equilibrium models of the condensation of solids in the protoplanetary nebulae

Dynamical simulations reproduce the terrestrial planets Use very high resolution n-body accretion simulations of terrestrial planet accretion (e.g. O’Brien et al. 2006) for 10 known extrasolar planetary systems Incorporate dynamical friction Start with Mars-mass embryos located interior to the known giant planets. All known planets are assumed to be in their current orbits Neglects mass loss

Equilibrium thermodynamics predict bulk compositions of planetesimals Use spectroscopic photospheric abundances of 16 elements: H, He, C, N, O, Na, Mg, Al, Si, P, S, Ca, Ti, Cr, Fe, Ni Assign each embryo a composition based on formation region Adopt the P-T profiles of Hersant et al (2001) at 7 time steps (0.25 – 3 Myr) Assume no volatile loss during accretion, homogeneity and equilibrium is maintained

Solar System Testing “Ground tested” on Solar System simulations of O’Brien et al (2006) – good agreement Volatile enriched See Bond et al (2009) Icarus

Extrasolar “Earths” Terrestrial planets formed in ALL systems studied Most <1 Earth-mass within 2AU of the host star Often multiple terrestrial planets formed Migration may alter some of these simulations... stay tuned!

Extrasolar “Earths” HD72659 – 0.95 M SUN G star, [Fe/H] = M J planet at 4.16AU Gl777A – 1.04 M SUN G star, [Fe/H] = M J planet at 0.13AU 1.50 M J planet at 3.92AU HD – 1.00 M SUN G star, [Fe/H] = M J planet at 1.05AU 1.02 M J planet at 2.68AU

HD72659

1.03 M Earth at 0.95AU

Gl777A

1.10 M Earth at 0.89AU 0.27 wt% C

HD108874

0.46 M Earth at 0.38AU 27 wt% C 66 wt% C

HD M Earth at 0.38AU

Gl777 SiC SiO MgSiO 3 + SiO 2 MgSiO 3 + Mg 2 SiO 4 Mg 2 SiO 4 + MgO HD72659 HD108874

Terrestrial Planets may be very different in ESP systems Terrestrial planets may be common Geology of these planets may be unlike anything we see in the Solar System –Earth-like planets –Carbon as major rock-forming mineral Composition varies with ‘primordial’ chemical enrichments Implications for detection, planetary processes, atmospheric composition....