the composition of the moon is suspiciously like that of earth's upper mantle if it had formed at the same time the earth did ('sister'), it would have had to be as massive as earth is!
(earth; is; ) (it; had formed; T:at the same time) (the earth; did; sister; T:the same time) (it; to be; as massive as earth is)
earth it the earth it
is had formed did to be
T:at the same time
sister T:the same time
as massive as earth is