1. Planetary Geology 101 The Solar System

6. Formation of the Solar System The stages of solar system formation start with a protostar embedded in a gas cloud, then to an early star with a circumstellar disk, to a star surrounded by small "planetesimals" that are starting to clump together to a solar system like ours today.

7. Formation of the Solar System www.jwst.nasa.gov/birth.html Credit: Shu et al. 1987 protostar circumstellar disk planetesimals home

10. Structure (from the inside out) Central star Inner “terrestrial” planets Asteroid belt Outer “gas giant” planets Outer “ice giant” planets (Dwarf planets) Trans-Neptunian objects (Kuiper belt, scattered disk, Oort Cloud) Miscellaneous

11. The Sun “Yellow dwarf”, 1.4 million km in diameter Fuses 620 million tonnes/sec of H 8.3 light-minutes away

12. The Sun

13. Mercury Innermost planet, 4,880 km in diameter Very dense, with its own magnetic field Enigmatically large iron core Recent evidence for volcanism

14. Mercury

15. Venus Regarded as Earth’s “Evil Twin” Surface T: 460°C, P: 92 Bar Subject to runaway greenhouse effect Extensive resurfacing due to volcanism

16. Venus

17. Mars Diameter: ~6800 km (= Earth’s core) Same surface area of all Earth’s continents Deserts, ice caps, canyons, giant volcanoes Upper hemisphere may be giant impact basin

18. Mars

19. Asteroid Belt Small bodies: asteroids/minor planets >50% mass: Ceres, Vesta, Pallas, Hygiea Protoplanets that orbited too fast to acrete Mainly loosely-bound piles of rubble

20. Asteroid Belt

21. Jupiter Largest body after the Sun (D: ~143,000 km) Primarily H, He, with putative rocky core High-energy storms in its atmosphere At least 63 moons

22. Jupiter

23. Saturn Second-largest planet, diameter ~121,000 km Prominent set of rings 53 officially-named moons Hosts largest moon in the system, Titan

24. Saturn

25. Uranus Larger of the two “ice giants”, D ~51,000 km Gas atmosphere + contains H 2 0, NH 3, CH 4 Axis of rotation inclined almost 90

26. Neptune Second “ice giant”, D ~49,000 km Same composition as Uranus (H 2 0, NH 3, CH 4 ) Tenuous ring system, 13 known moons

27. Dwarf Planets Currently 5: Ceres, Pluto, Haumea, Makemake, Eris Most occur beyond Neptune (except Ceres) Best known is Pluto (former planet)

28. Trans-Neptunian Objects (TNOs) Composed of 3 regions: Kuiper Belt, scattered disk, and Oort Cloud

29. Trans-Neptunian Objects (TNOs) Composed of 3 regions: Kuiper Belt, scattered disk, and Oort Cloud