New Study Finds Unexpected Temperature Changes on Neptune

The average global temperature on Neptune unexpectedly fluctuated during a recent 17-year period, according to a new study published by the American Astronomical Society in The Planetary Science Journal.

Researchers, including scientists from NASA, analyzed ground-based images of Neptune taken in the mid-infrared range between 2003 and 2020. The images reveal Neptune’s stratosphere appears to have cooled between 2003 and 2009, followed by a dramatic warming of the south pole between 2018 and 2020. Conversely, upper-tropospheric temperatures didn’t vary much except for the south pole, which appeared warmest between 2003 and 2006.

Scientists had expected seasons would change slowly on Neptune because it takes the planet so long to orbit the Sun – 165 years.

Neptune is the most distant planet in our solar system – the eighth major planet outward from the Sun. Dark, cold, and whipped by supersonic winds, the ice giant is more than 30 times as far from the Sun as Earth. Neptune does not have a solid surface. Its atmosphere is made mostly of hydrogen, helium, and methane, and extends to great depths, gradually merging into water and other melted ices enclosing a solid core with about the same mass as Earth.

Neptune is our solar system's windiest world. These winds drive clouds of frozen methane across the planet at speeds of more than 1,200 miles per hour (2,000 kilometers per hour). Even Earth's most powerful winds hit only about 250 miles per hour (400 kilometers per hour).