Mars orbits farther from the sun than does Earth, and therefore receives smaller doses of solar radiant energy than our planet. As a result, Mars is colder than Earth. But Mars is much colder, because it contains a very thin atmosphere of low-concentration greenhouse gases. Mars's atmospheric pressure (and hence gas concentration) is less than 1% of Earth's, and is mostly CO2. Most ice on Mars is 'dry ice' or frozen carbon dioxide. Because greenhouse gas molecules are in short supply on Mars, the planet's arctic regions are very cold - about minus180 degrees F (-120 deg.C).
Venus, orbiting between Earth and Mercury, receives more solar radiation than Earth. However, the primary reason Venus is such a hot planet - about 900 degrees F - is the greenhouse effect. Atmospheric pressures and gas concentrations on Venus are 90 to 100 times greater than on our home planet - trapping much more heat than the earth does. The 'air' on Venus consists of mostly CO2, with layers of thick 'clouds' made up of sulfuric acid. ***