Do all planets have an ozone layer?

Over billions of years the oxygen has used up all the elements it can react with and then accumulated and allowed the ozone layer to form. So the existence of oxygen and ozone in a planetary atmosphere is evidence of plant life and most probably animal life as well. read more

As Vishwad Desai writes, if there is sufficient oxygen and UV light one can drive the production of ozone on other planets. Thus, there is a thin ozone layer on Venus and also Mars, but due to the lack of oxygen, there is insufficient ozone to screen out all solar UV near 250 nm as happens on earth. read more

All three planets have an ozone layer. "This ozone detection tells us a lot about the circulation and the chemistry of Venus' atmosphere" says Håkan Svedhem, ESA Project Scientist for the Venus Express mission. read more