How do we figure out what the atmosphere of a planet is made of? Use spacecraft data to figure out what the atmospheres of Venus, Earth, and Mars are made of, and what other factors go into why the planets have vastly different climates. This is part of the Laboratory for Atmospheric and Space Physics' (LASP) Project SPECTRA! suite of activities that uses concepts of light and the electromagnetic spectrum to explore our Solar System. Funded by NASA's MAVEN Mission to Mars.