How does the atmospheric UVB attenuation of terrestrial planets compare? On Earth, UVB (280nm - 315nm or 320nm depending on the source) undergoes extensive attenuation through the atmosphere, when observed at the planet's surface, as illustrated below:

Image source
This is primarily due to the ozone layer, a feature unique to Earth amongst the terrestrial planets (Venus, Earth and Mars).
Given the different atmospheric chemistries and differences in distances from the Sun of Venus and Mars, what UVB attenuation has been observed or simulated for Venus and Mars?
Additionally, what UVB attenuation has been observed (or simulated in this case) on Titan?
Any peer reviewed resources would be appreciated here.
 A: In the chapter The Ultraviolet Radiation Environment of Earth
and Mars: Past and Present, the author describes that, despite being closer to the UV source (the sun), Venus's atmosphere is

so dense
  that no UV-C or UV-B radiation reaches the surface of the planet and only very small
  amounts of UV-A penetrate. 

As for Mars, the very thin $CO_2$ atmosphere allows UVA, UVB and UVC to reach the surface, albeit at a reduced flux given Mars' distance from the sun.  However, slight fluctuations exist (from the article):

Mars does not have a significant ozone column,
  although some ozone build-up occurs over the poles in spring and winter. These
  levels, although about two orders of magnitude lower than typical terrestrial column
  abundances, can reduce UV-C flux reaching the ground.

One of the main reason for UVB penetration to the surface on Mars (and on Venus had it not had a dense atmosphere) is that both planets have predominantly $CO_2$ atmsopheres.  $CO_2$ absorbs in the infrared, as can be seen in the following diagram:
 
Image source
