Giant Craters on 253 Mathilde Revealing the Cohesive Porous Interior of Carbonaceous Parent Bodies

The dark carbonaceous asteroids, comprising over 75% of the main belt population (~50% by mass), are thought to contain the most primitive materials from the early solar system. However, the lack of direct interior measurements has greatly limited our understanding of the formation and evolution of this category. One such primitive asteroid, the 53-km Mathilde, characterized by its well-preserved giant craters, has remained a puzzle since the NEAR spacecraft's first glimpse in 1997. Recent missions to Ryugu and Bennu have provided valuable insights into the composition and structural properties of km-size rubble piles, which are debris aggregates of primitive asteroids, offering a unique opportunity to re-examine the interior of their parent bodies---the large primitive objects like Mathilde. Here we show that large primitive asteroids could possess a cohesive and porous interior, by reconstructing the formation of giant craters on Mathilde with hydrodynamics simulations. Most low-albedo asteroids 40--100 km diameter may possess similar interiors and similar giant craters; this will be tested by the Lucy and MBR Explorer missions. Based on these simulations, and to explain the hydration diversity and exogenic contamination observed among Ryugu and Bennu, we propose that ~85% of the small carbonaceous asteroids could have originated from the catastrophic and super-catastrophic disruptions of large primitive asteroids like Mathilde. Conversely, small basaltic asteroids are more likely to originate from less energetic events thus containing less exogenic.