Figure 8-18 Asteroids (a) Reflecting only half as much light as a charcoal briquette, Mathilde is half as dense as typical stony asteroids. Slightly larger than Ida (see Figure 8-14), irregularly shaped Mathilde measures 66 km × 48 km × 46 km, (41 mi × 30 mi × 29 mi) rotates once every 17.4 days, and sitting on Earth, it would weigh 110 trillion tons. The part of the asteroid shown is about 59 km × 47 km (37 mi × 29 mi). The large crater in shadow is about 20 km (12 mi) across. (b) The near-Earth asteroid Itokawa was visited by the Japanese space probe Hayabusa. Samples of dust particles from it are now being analyzed. Note the similar two-lobed structure of Itokawa and Toutatis (see Figure 8-13).