Triton orbits Neptune, the eighth planet from the Sun, some 2.7 billion miles from Earth—at the cold outer fringe of the Solar System’s major planet zone. Surface temperatures hover near absolute zero, so low that common compounds we know as gases on Earth freeze into ices. Triton’s atmosphere, which is 70,000 times less dense than Earth’s, is composed of nitrogen, methane and carbon monoxide.
Source:
https://phys.org/news/2019-07-unprecedented-discovery-unique-infrared-signature.html