1. How do “Habitable” Planets Form? Sean Raymond University of Washington Collaborators: Tom Quinn (Washington) Jonathan Lunine (Arizona)

2. Habitable Zone: temperature for liquid water HZ is function of: planet’s atmosphere, type & age of star

3. Habitable Planets NEED WATER!

4. The Paradox of Habitable Planet Formation Liquid water: T > 273 K To form, need icy material: T < 170 K →icyrocky← ”snow line”

5. Liquid water: T > 273 K To form, need icy material: T < 170 K Local building blocks of habitable planets are dry! →icyrocky← ”snow line” The Paradox of Habitable Planet Formation

6. So where did Earth get its water? Late Veneer: Earth formed dry, accreted water from bombardment of comets, or …    Comets    Asteroid Belt

7. So where did Earth get its water? Late Veneer: Earth formed dry, accreted water from bombardment of comets, or …  Some of Earth’s “building blocks” came from past snow line, in outer Asteroid Belt: Earth did not form entirely from local material    Comets    Asteroid Belt

8. To guide the Habitable Planet Search (TPF, Darwin), we need to know: 1.Are habitable planets common? 2.Can we predict the nature of extrasolar terrestrial planets from knowledge of: a)Giant planet mass? b)Giant planet orbital parameters (a, e, i)? c)Metallicity of host star?

9. Overview of Terrestrial Planet Formation 1.Condensation of grains from Solar Nebula 2.Planetesimal Formation 3.Oligarchic Growth: Formation of Protoplanets (aka “Planetary Embryos”) 4.Late-stage Accretion

10. Simulation Parameters a JUP = Giant planet’s orbital radius e JUP = Giant planet’s orbital eccentricity M JUP = Giant planet’s mass t JUP = Giant planet’s time of formation Surface density  stellar metallicity Position of snow line

11. Snapshots in time from 1 simulation Eccentricity Semimajor Axis

12. Radial Migration of Protoplanets

13. Simulation Results 1.Stochastic Process 2.All systems form 1-4 planets inside 2 AU, from 0.23 to 3.85 Earth masses 3.Water content: dry to 300+ oceans (Earth has 1-10 oceans)

14. Trends 1.Higher e JUP  drier terrestrial planets 2.Higher M JUP  fewer, more massive terrestrial planets 3.Higher surface density  fewer, more massive terrestrial planets

15. Effects of e JUP

16. Habitability In most cases, planet forms in 0.8-1.5 AU In ~1/4 of cases, between 0.9-1.1 AU Range from dry planets to “water worlds” with 30 times as much water as Earth

17. 43 planets between 0.8-1.5 AU

18. 11 planets between 0.9-1.1 AU (1) (2) (3)(4)

19. What might planets around other stars look like? (1) a JUP = 4 AU Images from NASA (4) Solar System (2) M JUP = 10 M EARTH (3) M JUP = 1/3

20. Conclusions 1.Most of Earth’s water was accreted during formation from bodies past snow line 2.Terrestrial planets have a large range in mass and water content 3.Habitable planets common in the galaxy

21. Conclusions Cont’d 4.Terrestrial planets are affected by giant planets! Can predict the nature & habitability of extrasolar terrestrial planets - Useful for TPF, Darwin 5.Future: develop a code to increase number of particles by a factor of 10

22. 2004 Icarus paper, ”Making other Earths...” http://www.astro.washington.edu/raymond Papers by John Chambers Talk to me! Additional Information

23. Additional Slides

24. What is a “habitable” planet? Habitable Zone == Temperature for liquid water on surface –~0.8 to 1.5 AU for Sun, Earth-like atmosphere –varies with type of star, atmosphere of planet Habitable Planet: Need water!

25. Initial Conditions Assume oligarchic growth to 3:1 resonance with Jupiter Surface density jumps at snow line Dry inside 2 AU, 5% water past 2.5 AU, 0.1% water in between Form “super embryos” if Jupiter is at 7 AU

26. Simulation Parameters a JUP = 4, 5.2, 7 AU e JUP = 0, 0.1, 0.2 M JUP = 10 M EARTH, 1/3, 1, 3 x real value t JUP = 0 or 10 Myr Surface density at 1 AU: 8-10 g/cm 2 Surface density past the snow line

27. Simulations Collisions preserve mass Integrate for 200 Myr with serial code called Mercury (Chambers) –6 day timestep –currently limited to ~200 bodies –1 simulation takes 2-6 weeks on a PC

28. Data from our Solar System Raymond, Quinn & Lunine 2003

29. Oligarchic Growth: “growth by the few” Protoplanets grow faster closer to the Sun! Take approx. 10 Myr to form at 2.5 AU Mass, distribution depend on surface density Kokubo & Ida 2002

31. Distributions of Terrestrial Planets