Calculated lifetimes for silicates (green), graphite (black) and THEMIS a-C (blue). The thicker the line the bigger the grains: 0.4, 0.7, 1.5, 10, 30, 100 nm and the thickest for 1cm radius particles. The solid vertical lines represent the “classical” sublimation temperatures of the three dust materials. The red dashed line is the apparent “model required” temperatureof 1700 K. Refer to Kobayashi et al. (2009) to see the calculation of the lifetimes.