Planetary Science Seminar

Planetesimals are primordial bodies in the solar nebula. Measurements of meteorites and thermal modelling of parent body of meteorites could constrain formation time and size of planetesimals. I will talk about the thermal evolution of planetesimals, especially on a parent body of asteroid Itokawa (Wakita et al. 2014). Studies from dust particles returned from Itokawa (Nakamura et al. 2011; Yurimoto et al. 2011) indicate the parent body experienced at the peak temperature of 800 degree Celsius (but less than 1000) and kept > 700 degree Celsius at 7.6 Myr after Ca-Al rich inclusions (formed 4567 Myr ago). We modelled the the parent body of Itokawa as an instantaneously-accreted spherically symmetric one and heated by the decay energy of short-lived radionuclide (aluminum-26). Our results showed that the parent bodies of Itokawa would have been larger than 20 km in radius at least and accreted at a period between 1.9 and 2.2 Myr after CAIs, in order to satisfy evidences from Itokawa dust particles. These values of Itokawa parent asteroids would be the size and accretion time of planetesimals in the asteroid belt.