Could Earth and the Moon be the same size?

Many questions on this site hypothesize about two planets in close orbit of each other, each developing their own civilizations. How feasible is that?

Some 4.5 billion years ago Theia, a planetary object of uncertain size, collided with the young Earth and ejected a significant quantity of the two bodies crusts into space, forming a new object, the moon (if you don't believe this theory, then assume it is true for this question). Is it possible that the same collision, if it had happened at a different speed or impact angle, could have created two planets of approximately equal size orbiting the sun together?

Constraints on the final system:

• Given that the combined mass of the Earth and the Moon is about $6\times10^{24}$ kg, each of the two objects should be about $3\times10^{24}$ kg

• The planets must orbit the sun as a single system, orbiting each other.

• The planets must stay in an orbit approximately the same distance from the sun as Earth is now.

• The planets must maintain the same characteristics that allowed life to arise on Earth: nitrogen atmosphere, plenty of water for oceans, active magnetic field and plate tectonics, etc.

posted over 6 years ago

kingledion‭

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