It is negligible.
The atmospheric density on Mercury has not been directly measured, and may not be for many years. The thin collection of ionized gases on Mercury has an estimated surface pressure only ten-quadrillionths that of Earth (about 10-14 bar or 10-9 Pa).
If you're referring to atmospheric pressure, then it's zero.Mercury has no atmosphere.
A mercury barometer measures atmospheric pressure, which is the weight of the air pressing down on Earth's surface. It works by using a column of mercury in a sealed tube to balance the pressure of the air outside. When the air pressure increases, the mercury in the tube rises, and when the air pressure decreases, the mercury falls.
When air pressure increases, the mercury in a barometer rises.
mercury
About equal to 30 inches of Mercury.
A mercury barometer is a 1 meter long glass tube with the top sealed and turned upside down in a bath of mercury the pressure on the surface of the bath of mercury lifts the level of the mercury in the tube dependent on atmospheric pressure.
Planet Mercury's Surface pressure is almost none existent. This is due to its low gravity and extremely thin atmosphere that has been blasted away by solar winds.
Mercury has a very high surface tension and does not easily wet most other surfaces. For a given amount of mercury, a sphere has the smallest possible ratio of surface area to volume and is therefor the lowest energy shape for the mercury.
A low pressure system contains near surface winds.
A column of air exerts atmospheric pressure on the air or surface below it. This pressure is caused by the weight of the air above pushing down on the lower air or surface.