(The Moon is currently about 384,000 km or 60 Earth radii away from Earth, which is about fifteen times further away than it was when it first formed.) The Moon probably couldn't have formed closer than 3 Earth radii because tidal forces from the Earth would just pull it apart again, and it is unlikely that the impact could have ejected material ...
About 78% of Earthâs atmosphere is made up of nitrogen. Credit: NASA We might commonly think of Earth as having an oxygen-dominated atmosphere, but in reality the molecule makes up only a fifth of our air.
Mars also has an atmosphere that is primarily carbon-dioxide, but on Mars, the atmosphere is extremely thin, and prone to high winds. The giant outer planets Jupiter, Saturn, Uranus, and Neptune have extremely thick atmospheres of hydrogen, helium, methane, and ammonia. Titan, the moon of Saturn also has a methane-ammonia atmosphere. For reference, Titan has roughly the mass as the planet Mercury (which doesn't have an atmosphere at all).