Mars and Humidity
Date: Updated June 2008
What is the humidity of the planet Mars?
Humidity is the amount of water vapor in the air. This varies from
day to day and depends on the temperature: warm air can hold more
water vapor than cold air . Humidity is measured as a percentage of
the maximum amount of water that the air can hold at a given temperature.
The greater the difference between the two temperatures, the greater the
evaporation. When there is a lot of evaporation, the air is drier and the
humidity is low. The instrument used to measure humidity is called a
On Mars, the air is saturated (100% humidity) at night, but undersaturated
during the day. This is because of the huge temperature difference between
day and night.
To demonstrate this:
Take a clean, dry jar and place the lid on it.
Allow to stand 10 minutes in a shaded area and observe.
Put it in a freezer for at least an hour.
Remove and observe. (At room temperature, the air inside the jar was not
saturated, but in the cold freezer the air could not hold much water-it became
saturated-and the water condensed and formed frost.)
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Update: June 2012