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Name: Pat
Status: educator
Age: 50s
Location: N/A
Country: N/A
Date: Updated June 2008


Question:
What is the humidity of the planet Mars?


Replies:
Taken from:

http://quest.nasa.gov/aero/planetary/mars.html

http://pdf.aiaa.org/preview/CDReadyMIAF04_1072/PVIAC-04-Q.P.06.pdf

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 psychrometer.

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.)

Thanks Kelsey



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