The NASA Goddard science education page answer to Reading about Mars, I noticed that it has .03% of water vapor in it's atmosphere, and my question was if it has water vapor why doesn't it have precipitation? says
Mars does have precipitation.
[...]However, this precipitation most likely takes the form of frost, rather than rain or snow. The ground is likely to be colder than the air (especially on cold clear nights), and so air hitting the ground cools and the water freezes to the ground as frost. Viking II (a Mars lander in the 1970's) saw frost on the ground some mornings.
A part of the polar ice caps of Mars is made of precipitated water ice (the rest is made of carbon dioxide as 'dry ice').
However another educational page Precipitation (Weather) says:
Precipitation in meteorology refers to all forms of liquid or solid water particles that form in the atmosphere and then fall to the earth's surface. Types of precipitation include hail, sleet, snow, rain, and drizzle. Frost and dew are not classified as precipitation because they form directly on solid surfaces.
Mars has polar ice caps and a 25.19° inclination similar to that of Earth's. We see the polar caps shrink and grow regularly with the seasons each year.
- Can we say that the changes in the polar ice caps is due to "frost"?
- Can we say that the changes in the polar ice caps is due to "precipitation"?
- Is there really precipitation on Mars? Does frost count?