From one of the latest images from Spirit shows an asymmetric dust pattern
in the crater "Bonneville". Which way is the prevailing winds and why do
you think so. I pretty sure of the line the wind follows, but I'm not
sure of which direction...
http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20040318a/07-JG-01-pan-A074R1_br.jpg
http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20040318a/07-JG-01-pan-A074R1_br2.jpg
http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20040318a/07-JG-01-pan-A074R1.jpg
These links are for the same image, just in order of increasing size and
resolution (second is 1MB, third is 9MB)..
-Paul