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A 'recent' (~2002) paper on the topic indicated that impact craters on low density/porous objects more likely result in indentations rather than 'normal' cratering events ( ie via ejecta), the object being hit absorbing the impact. The large 'frontal crater' may not actually be a crater.
I'm reading a draft paper on a bifurcated asteroid which indicates that YORP can spin an elongated asteroid up and down, throwing a moon by rotational fission on spin up BUT that it is also possible that the system can be unstable and combined with YORP the spun off moon can reconnect to the parent. YORP can spin it up throw it off again. Note that each of these events can take several My, but given the age of the solar system, these events can occur a number of times. The bifurcated target we are looking at comprises a spherical component on the end of a prolate spheroid component with some 'overlap' at the transition. If the 2 components were simply gravitationally bound then the new fission event would leave some of the overlapping material attached to both components, giving the impression of a large crater with a very large central dome. In this case the dome was the original surface of the spherical component!
Cheers
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