This greenish mist gets its color through Spitzer's color-coding abilities. The fog is comprised of polycyclic aromatic hydrocarbons (PAHs) which NASA says are "found right here on Earth in sooty vehicle exhaust and on charred grills." Spitzer allows the human eye to see PAHs glow via infrared light. This image was compiled after Spitzer's helium ran out, marking the beginning of its "warm" mission. You can follow Spitzer’s path here.