alleryStart learning →In the giant impact idea for the Moon's birth, how big was the body that struck Earth?
AAbout the size of Venus
BAbout the size of Ceres
CAbout the size of Pluto
DAbout the size of Mars
Answer & Solution
Correct answer: D. About the size of Mars
1. The giant impact idea needs a striker big enough to eject a Moon's worth of rock.
2. That body carried roughly one tenth of Earth's mass.
3. A body of that mass is about the size of Mars.
4. Anything as large as Venus would have shattered Earth rather than spun off a ring.
_Source: OpenStax Astronomy (CC BY 4.0), section 9.4 The Origin of the Moon_
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