Question: how are today’s atmospheres of venus and mars similar how are they different?
Answer: Mars has weak magnetic field, has a very thin atmosphere composed of CO2, is geologically dead, has lots of craters, no plate tectonics. How are today's atmospheres of Venus and Mars similar? ... They are both composed of 95-96% CO2, with most of the rest being N2. Venus' atmosphere has 10^4 X the pressure on the surface.