Atmospheric Pressure

The atomspheric pressure to first order is a measure of the amount of mass contained in the atmosphere of a planet. The higher the pressure the larger the mass of the atmosphere. Why is this so? Well, imagine you are standing on the surface of a planet.

This weight determines the pressure you feel due to the atmosphere. On the Earth at sea level, you feel around 14.7 pounds per square inch pushing on you. On Venus, where the atmospheric pressure is 90 bars or roughly 90 times that of the Earth, you would feel a pressure of 1,300 pounds per square inch!! This is roughly the pressure you would feel if you were at a depth of around 900 meters in the ocean. This suggests that the mass of Venus's atmosphere is much greater than ours (a point which we will consider is, why is this so and where does the mass come from or, more to the point for the Earth, why is our atmospheric mass so low?).