Info on the "Venus Express" is at the ESA Site;
http://sci.esa.int/science-e/www/are...cfm?fareaid=64
This site is very useful regarding our knowledge about the planet Venus.
According to the Nature abstract (
Nature,
456, pg.620-623 (4 December 2008) written by Titov, D.A. of the ESA ("
Atmospheric structure and dynamics as the cause of ultraviolet markings in the clouds of Venus"
http://sci.esa.int/science-e/www/obj...objectid=43850), the ;
"
...visible cloud top is located at a remarkably constant altitude of 72±1 km" and that "
The cloud top descends to 64 km"
This suggest differences in brightness of the cloud patterns and observed heights are probably the cause of these brightness differences rather than any geological feature well below!
