QUESTION:
We all would like to know, when you talk about wind on Mars, exactly what is
blowing?

ANSWER from Jim Murphy on July 12, 1997:
When the wind blows on Mars, it is the "air" on Mars moving about, just as
it is the air moving about here on Earth which we call wind.  While the air
on Earth is made up of oxygen (which we breathe), nitrogen (which plants use
to grow), and other gases, the "air" on Mars is made up primarily of carbon
dioxide gas.  When there are differences in the atmospheric pressure
(really, just the number of gas molecules above you to the top of the
atmosphere) between two places, the air tries to flow from the high pressure
area to the low pressure area.  It is this air flow which is the wind.  Now,
since the atmospheric pressure on Mars is much, much less than it is here on
Earth (about 100 times less, in fact), we would feel the wind much less if
we were on Mars than we would for the same wind speed here on Earth.

We are measuring the wind on Mars right now with instruments on the Mars
Pathfinder lander.  We are doing a good job determining which direction the
wind is blowing, but we are still studying our data to determine how fast it
is blowing.  Stay tuned to the web pages, and as soon as we get the wind
speeds determined, we will put them out.