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Air tends to flow from areas of high pressure to areas of low pressure. This movement occurs in an attempt to equalize pressure differences in the atmosphere.
Air travels from high to low pressure in the atmosphere during flight through the process of air movement known as wind. Wind is created by the pressure differences between high and low pressure systems, causing air to move from areas of high pressure to areas of low pressure. This movement of air helps to balance out the pressure differences in the atmosphere.
Mars has an atmosphere with low air pressure which is mostly carbon dioxide.
Rain most often occurs with low pressure.
Mars
The pressure in the mesosphere is very low, around 0.1 millibars at the bottom of the mesosphere and decreasing even further with altitude. This low pressure is due to the thinning of the atmosphere at higher altitudes in the Earth's atmosphere.
Pressure differences in Earth's atmosphere create areas of high and low pressure. Air flows from high pressure to low pressure, creating wind. The greater the pressure difference between two areas, the stronger the resulting winds will be.
A fluid will move from high pressure to low pressure.
Low pressure and high pressure are not absolute. You find those pressures at any place. http://en.wikipedia.org/wiki/Atmospheric_pressure
Mercury has almost no atmosphere so that could be the answer. The otherpossible answeris Mars, which certainly does have a (thin)atmosphere.
Hurricanes form around areas of low pressure. As warm air rises in the atmosphere, it creates an area of low pressure at the surface, which can develop into a hurricane under the right conditions.
A low pressure system I believe.