About one trillion (please, don’t tell 0bama what comes after a trillion) radio meteors (those with enough energy to ionize the atmosphere) a day, with a total mass of about ten tons enter the Earth’s atmosphere daily. The mass of the individual members is roughly exponentially distributed, so very large objects are rare, but not impossible.
It’s happen before, of course. The crater is called the Pacific Ocean and the residual debris is called the Moon. No other planet in our solar system has a satellite with nearly as large a relative mass. The earth/moon system could almost be considered a double planet. I say almost, because the center of mass of the combination lies below the surface of the earth.
I'm not so sure about that. Isn't Pluto's moon (Charon) about 50% of Pluto's size?
I'd always heard that the earth collision that produced the moon is believed to have liquified the earth and the colliding body, allowing both the moon and the earth to coalesce into the round bodies we see today.
How could a liquifying event leave a crater?