Neptune’s balmy south pole
By Ron Cowen
The first temperature map of Neptune’s lower atmosphere shows that the planet’s south pole is about 10°C warmer than any other place on the planet. The average temperature of the atmosphere’s lower depths is –200°C. The south pole is warm enough for gaseous methane to rise into the upper atmosphere, says study coauthor Glenn Orton of NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
The escaping methane could explain a long-standing puzzle—the presence of methane in Neptune’s stratosphere.
Neptune’s tilt means that its south pole is heated by continuous sunlight. That’s been the case for the past 40 years of Neptune’s 165-year orbit around the sun. Eighty years from now, when it’s summer at the north pole, methane may escape from that region instead, says Orton.
Large temperature differences between the south pole and adjacent regions may stir up gases and generate 2,000-kilometer-per-hour winds, the strongest planetary winds in the solar system.
The study, which used the European Southern Observatory’s Very Large Telescope in Paranal, Chile, appears in the Sept. 18 Astronomy & Astrophysics.
