Hi Stefan, I know Brian has made numerous kinds of spiral scripts and I found his post here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4975.5

So the method is to take any curve on a sphere like the 180 degree arc seam edge will do (duplicate it to a standalone curve by copy/paste), then run Transform > Deform > Twist picking the twist axis along the sphere's axis. The result will be a spherical spiral:



- Michael