1. Wayne G. Roberge & Raymond L. Menzel NY Center for Astrobiology (NYCA) Rensselaer Polytechnic Institute Electrodynamic Heating in Protoplanetary Disks

2. Motivation Chondritic meteorites deliver amino acids to Earth. Chondrites are fragments of C-type asteroids. Were prebiotics synthesized on C asteroids? They were warm and wet! But why? What heated asteroids and how prevalent is this process in protoplanetary disks?

3. Asteroid Composition Types Image: NASA/Hubble Space Science Institute (STScI). W.B. McKinnon, Nature, 340, 343 (1989) Igneous (SME) - melting; partially or completely exposed metallic cores. Metamorphic (CBGF) - aqueous alteration at 25-150 o C; hydrated minerals. Primitive (PD) – no heating; primitive solar system materials (?).

4. Radioactive Heating of Asteroids Urey 1955 26 Al 26 Mg + energy Half life t 1/2 = 0.7 Myr 26 Mg in meteorite Allende implies live 26 Al was present. 26 Al/ 27 Al = 6 x 10 -5 in Allende, enough to melt asteroids. But how did 26 Al arrive at the party live? Unknown but 26 Al DID get here! Why did heating decrease with heliocentric distance? Only ~10 -3 -10 -2 of Sun-like stars receive live SLR (Ouellette et al. 2010).

5. “Induction” Heating of Asteroids Sonnet et al. 1970 Sonnet et al: Electric field E’ in asteroid frame. Currents in plasma (yellow) flow from + to -. Currents inside asteroid (green) close circuit. Heating rate : P = J E =  E 2 ~ 10 -8 W/kg. Plasma Frame: E=0, B=B 0 Body frame: E’= -v 0 /c x B 0 asteroid Ionized T Tauri Wind v 0 =400 km/s E’

6. Induction Heating Reexamined What’s wrong with E’=-v 0 /c x B? V 0 here!

7. Our Calculation

8. Electric Field at Asteroid Surface In weakly inonized disks  << 1 and E ~ E H ~ v 0 B 0 /c!!!

9. Conclusions Classical induction heating invalid. Found new “electrodynamic” mechanism. Operates in weakly ionized disks! Also operates in ionized disks. At least as efficient as induction heating.