alleryStart learning →Nearly every impact crater is circular rather than oval. Why does that happen?
AThe rock melts and then flows
BThe world spins under the hit
CThe impact sets off an explosion
DThe rim slumps into a ring
Answer & Solution
Correct answer: C. The impact sets off an explosion
1. An incoming body arrives at least as fast as the escape speed of the world it hits.
2. At that speed the energy of motion turns into a violent explosion on contact.
3. An explosion digs outward evenly in every direction, so the pit comes out round.
_Source: OpenStax Astronomy (CC BY 4.0), section 9.3 Impact Craters_
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