Compare the atmospheres of Mars and Venus. Mars is rich in oxygen, like ours, accounting for its red surface. Like Earth, nitrogen is the chief atmospheric gas. Both are too hot for water to now exist as a liquid at the surface. Both are chiefly carbon dioxide, but at Mars it can freeze as dry ice. Both are made of hydrogen and helium, like the jovians.

Venus's atmosphere is very thick, dry and hot whereas Mars's atmosphere is very thin and cold.

Both Venus's and Mars's atmospheres are about 95 percent carbon dioxide.

The surface temperature of Venus is around 890 degrees F, the hottest average temperature in the Solar System. This is due to abundance of greenhouse gasses. The atmosphere of Venus is composed of 97% CO2, 2% N2 and less than 1% of O2, H2O and CH4 (methane). Since CO2 is a major greenhouse gas, the radiation from the Sun is trapped in the atmosphere of Venus producing an extremely high surface temperature.

Mars has an atmospheric composition of 95% CO2, 3% N2, 2% Ar and less than 1% O2. A high noble gas content implies that Mar's atmosphere was much thicker in the past (noble gases do not react with other elements and are heavy enough to stay within the gravitational field of Mars). The climate on Mars is very desert-like due to its thin atmosphere. There is too little mass in the atmosphere to hold in heat so the warmest daytime temperatures are around 50 degrees F, but the nighttime temperatures are - 170 degrees F. Other weather features are massive dust storms and occasional CO2 fog in the canyons.