Answer: amount of precipitation, average temperature
The last equation you have written out would be the correct single replacement reaction.
Without its atmosphere, Earth would be
bombarded by meteorites, similar to mars, relatively lifeless. Without the atmosphere objects can just enter the atmosphere and cause serious harm to us, but with the atmosphere it basically reduces damage and shrinks it to size. Without the atmosphere earth would be like mars since it doesn't have a atmosphere. Without the atmosphere earth would be relatively lifeless since without air, us humans cant breathe so we will not survive.
E ground pushes you forward. But that interaction is friction. Reduce friction and it doesn't matter how strong your legs are, the surface is incapable of pushing you accordingly. The coefficient of static friction is very low so it is easy to slide your foot rather than push.