Sorry that last post was so long, I didn't scroll down on the message I was replying to to notice that the original was so long. I would have cut out most of it had I noticed that..... Jim. Jim Scotti Lunar & Planetary Laboratory jscotti@pirl.lpl.arizona.edu University of Arizona Tucson, AZ 85721 USA http://www.lpl.arizona.edu/~jscotti/