Such colossal impacts would not just gouge out a crater-they would break any monolithic body into pieces. Most of them have one or more extraordinarily large craters, some of which are wider than the mean radius of the whole body.
Those imaged at high-resolution show evidence for copious regolith despite the weak gravity. Most asteroids larger than a kilometer are now believed to be composites of smaller pieces.
But observations and computer modeling are proving otherwise. Aggregate small bodies were not thought to exist, because the slightest sustained relative motion would cause them to separate. Originally, scientists predicted small asteroids to be hard and rocky, as any loose surface material (called regolith) generated by impacts was expected to escape their weak gravity. Choose the option that best answers the question.
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