1. An Artist’s Impression The young Sun gas/dust nebula solid planetesimals

2. Sequence of events 1. Nebular disk formation 2. Initial coagulation (~10km, ~10 4 yrs) 3. Runaway growth (to Moon size, ~10 5 yrs) 4. Orderly growth (to Mars size, ~10 6 yrs), gas loss (?) 5. Late-stage collisions (~10 7-8 yrs)

3. Timescale Summary Runaway growth Orderly growth Late-stage accretion (Giant impacts. Gas loss?) Dust grains ~Moon-size (planetesimal) ~Mars-size (embryo) ~Earth-size (planet) ~1 Myr ~0.1 Myr ~10-100 Myr

4. What does our Solar System consist of? The Sun 99.85% of the mass (78% H, 20% He) Nine Eight Planets Satellites (Moons) Comets, asteroids, Kuiper Belt Objects, etc.

5. Where is everything? J S U N P 1 AU is the mean Sun-Earth distance = 150 million km Nearest star (Proxima Centauri) is 4.2 LY=265,000 AU KB Me V E Ma Note log scales! Inner solar system 5 AU 1.5 AU Outer solar system 30 AU Note logarithmic scales! Me V Ma E Gas giants Ice giants Terrestrial planets

6. Basic data Distance (AU) P orbital (yrs) P rotation (days) Mass (10 24 kg) Radius (km)  (g cm -3 ) Sun--24.72x10 6 695950 1.41 Mercury0.380.2458.60.3324375.43 Venus0.720.62243.0R4.8760525.24 Earth1.00 5.9763715.52 Mars1.521.881.030.6433903.93 Jupiter5.2011.860.411899714921.33 Saturn9.5729.600.44568602680.68 Uranus19.1984.060.72R86.6249731.32 Neptune30.07165.90.67102.4247641.64 Pluto39.54248.66.39R0.01311522.05 See e.g. Lodders and Fegley, Planetary Scientist’s Companion

7. Nebular Composition Based on solar photosphere and chondrite compositions, we can come up with a best-guess at the nebular composition (here relative to 10 6 Si atoms): Data from Lodders and Fegley, Planetary Scientist’s Companion, CUP, 1998 This is for all elements with relative abundances > 10 5 atoms. Element HHeCNONeMgSiSArFe Log 10 (No. Atoms) 10.449.447.006.427.326.526.0 5.655.055.95 Condens. Temp (K) 180--78120-- 13401529674401337 Blue are volatile, red are refractory Most important refractory elements are Mg, Si, Fe, S (makes up the rocky planets)

8. Terrestrial (silicate) planets Consist mainly of silicates ((Fe,Mg)SiO 4 ) and iron (plus FeS) Mercury is iron-rich, perhaps because it lost its mantle during a giant impact (more on this later) Volatile elements (H 2 O,CO 2 etc.) uncommon in the inner solar system because of the initially hot nebular conditions Some volatiles may have been supplied later by comets Satellites like Ganymede have similar structures but have an ice layer on top (volatiles are more common in the outer nebula) Mercury Venus Earth Moon Mars Ganymede Io

9. F.Nimmo EART164 Spring 11 VenusEarthMarsTitanJupiterSaturnUranusNeptune Solar constant (Wm -2 )2620138059415.650.514.93.71.5 Obliquity ( o )17723.424.0(27)3.126.79828.3 Orbital period (years)0.6211.88(29.4)11.929.484165 Rotation period (hours)58322424.63839.910.717.216.1 Bond albedo A0.760.40.150.30.34 0.30.29 Molecular wt.  (g/mol) 432943292.22.12.6 T surface or T 1bar (K)730288220951651347672 Surface pressure (bar)921.0071.47n/a g (ms -2 )8.99.83.71.3524.210.08.811.1 T eq (K)22924521783113846048 Scale height H (km)158.5122327602820 Radius (km)605263703390257571,50060,30025,00024,800 Mass (10 24 kg)4.875.970.640.13190056887102 Useful Data Data mostly from Taylor, Appendix A