The difference in surface conditions of the first four terrestrial planets can be explained almost solely by their atmospheres rather than their proximity to the Sun. Mercury has very little atmosphere to where it does not really play a factor in this, but the stark differences between Venus, Earth and Mars can be explained through the greenhouse effect in each of their atmospheres. The composition of Venus’s atmosphere is almost entirely carbon dioxide, which it has a lot of, making its atmosphere around 100 times greater than Earth’s atmosphere. The greenhouse effect on Venus is therefore greater, which is why the average surface temperature across the entire planet is around 850 degrees Fahrenheit, which is much higher than Earth’s even though the difference in distances from the planet to the Sun is not as great as the difference of the surface temperatures. Earth’s atmosphere is composed of primarily oxygen and nitrogen, which means the greenhouse effect on Earth is not nearly as great as it is on Venus. This causes the average temperature on Earth to be 60 degrees Fahrenheit across the entire planet. Mars’s atmosphere, which is composed primarily of carbon dioxide, but is around 100 times more diffuse than the Earth’s atmosphere makes the average temperature across the planet negative 60 degrees Fahrenheit and the greenhouse effect on it much less than that on Earth and especially Venus. For a more in depth explanation of this topic, watch this video.