One of Neptune's moons has warmed up suddenly over the past nine years, possibly because a rare southern summer has heated the polar caps, turning frozen nitrogen into gas, scientists report in today's Nature. The Space Telescope Science Institute said that the temperature on the moon Triton had risen from -392 degrees Fahrenheit to -389 degrees since the spacecraft Voyager visited in 1989.
The increase may seem small, but the warming is making Triton's thin atmosphere noticeably denser as the frozen nitrogen on the surface turns to gas. Triton is approaching an extreme southern summer, a season that occurs every few hundred years. During this special time, the moon's southern hemisphere receives more direct sunlight, which heats the polar icecaps.
Compiled by Times medical writer Thomas H. Maugh II