Tests performed in a simulated cloud chamber here on Earth have revealed that Martian clouds may contain less water than previously estimated. Like some clouds above Earth, the Martian clouds being studied are also made of water ice. These clouds form at very low temperatures, sometimes below -100°C (-212°F). Scientists found that it was much more difficult for clouds to form at these temperatures, much harder than initially thought. In this laboratory simulation, the particles composing the clouds were quite large and quickly fell out of the atmosphere, resulting in less cloud mass and a drier atmosphere. It was previously thought that Martian clouds would form at 100% humidity, but this study shows that the air must be more supersaturated with water for clouds to form. This experiment provides insight into the climate of Mars and the operation of the Martian water cycle. It is know that the amount of water in the Martian atmosphere varies greatly over space and time. The amount of water that is transferred from the North Pole to the South Pole largely depends on atmospheric clouds.