英语听力精选进阶版 13277（在线收听）

Earth may once have had two moons

Vocabulary

struck by

hit by

smash

violent collision

debris

rubble

paper

scientific essay

stuck

fixed

gravitational tug of war

pull in opposite directions by the force of gravity

sibling

brother or sister

slow paced

moving at low speed

far side

face of the Moon that can't be seen from the Earth

craters

big holes on the surface