Atmosphere of Pluto
The atmosphere of Pluto is the layer of gasses that surround the dwarf planet Pluto. It consists mainly of nitrogen (N2), with minor amounts of methane (CH4) and carbon monoxide (CO), all of which are vaporized from surface ices on Pluto's surface. It contains layered haze, probably consisting of heavier compounds which form from these gases due to high-energy radiation. The atmosphere of Pluto is notable for its strong and not completely understood seasonal changes caused by peculiarities of the orbital and axial rotation of Pluto.
Departure shot of Pluto by New Horizons, showing Pluto's atmosphere backlit by the Sun. The blue color is close to what a human eye would have seen, and is caused by layers of haze in the atmosphere | |
| General information | |
|---|---|
| Height | ~1 700 km (exobase) |
| Average surface pressure | ~1.0 Pa (9.87×10−6 atm) (2015) ~0.91 Pa (8.98×10−6 atm) (2020) |
| Composition | |
| Nitrogen (N 2) | >99% |
| Methane (CH 4) | 0.25% |
| Carbon monoxide (CO) | ~0.0515% |
| Acetylene (C 2H 2) | 0.0003% |
| Ethylene (C 2H 4) | 0.0001% |
| Hydrogen cyanide (HCN) | 10-5-10-6% |
The surface pressure of the atmosphere of Pluto, measured by New Horizons in 2015, is about 1 Pa (10 μbar), roughly 1/100,000 of Earth's atmospheric pressure. The temperature on the surface is 40 to 60 K (−230 to −210 °C), but it quickly grows with altitude due to methane-generated greenhouse effect. Near the altitude of 30 km it reaches 110 K (−163 °C), and then slowly decreases.
Pluto is the only trans-Neptunian object with a known atmosphere. Its closest analog is the atmosphere of Triton, although in some aspects it resembles even the atmosphere of Mars.
The atmosphere of Pluto has been studied since the 1980s by way of earth-based observation of occultations of stars by Pluto and spectroscopy. In 2015, it was studied from a close distance by the spacecraft New Horizons.