Temperatures on Neptune Are Mysteriously Fluctuating, And It Doesn't Make Sense

Something strange is taking place at the most distant planet in our Solar System after an unprecedented analysis of the temperature of Neptune.

Each season on Neptune lasts for over 40 Earth years because it takes about 165 Earth years to make its trek around the star.

The southern hemisphere of Neptune is in the midst of an epic four-decade-long summer, but for reasons scientists can't fully explain, the temperature hasn't been warming up.

A new study compiled 17 years of observations of Neptune's temperature instead shows the opposite happening, with readings indicating a mysterious drop of about 8 degrees C between 2003 and 2018, as evidenced by a significant decline in atmospheric radiation from 2003

Michael Roman is from NASA/JPL/Voyager-ISS.

The thermal-infrared brightness of Neptune was observed.

Michael Roman is a planetary scientist from the University ofLeicester in the UK.

Since we have been observing Neptune during its early southern summer, we expected temperatures to grow warmer.

Neptune is far away from Earth so gathering reliable atmospheric temperature data is not easy.

Since the turn of the century, it has only been possible to get such readings with newer space telescopes. The European Southern Observatory's Very Large Telescope has a VISIR that can be used to infer temperature based on the level of the light emission.

Roman and his team analyzed almost 100 thermal observations of the planet, many captured by VISIR, but also included data from NASA's Spitzer Space Telescope and numerous ground-based telescopes in Hawaii.

The results suggest that temperatures in Neptune's stratosphere cooled over the course of the study period, although a late burst in temperatures was seen.

The researchers think that changes in atmospheric chemistry may be behind Neptune's sudden temperature fluctuations.

While absorbing methane sunlight and warms the atmosphere, photochemically produced hydrocarbons, primarily ethane and acetylene, are powerful infrared emitters that serve to cool the stratosphere.

As the amount of photochemical hydrocarbons changes, the balance between this radiative heating and cooling changes.

The interplay of chemicals in atmospheric clouds could affect their temperature and it is possible that this is happening here.

The researchers say that seasonal changes are expected to occur gradually over decades.

The rapid changes observed between the years of 2020 and 2018 appear surprisingly swift for seasonal response.

Another explanation could be weather variations, which might affect atmospheric cloud composition and chemistry, as well as the effects of dark vortices seen on Neptune.

The researchers say that radiance changes brought about by the Sun's activity cycle might be triggering photochemical changes in Neptune's atmosphere, which could account for the temperature fluctuations we're seeing.

All we know for certain is that we will need a lot more research to get to the bottom of these surprising readings.

Roman says that Neptune is intriguing to many of us because we still don't know much about it.

This all points towards a more complicated picture of Neptune's atmosphere and how it changes with time.

The findings are reported in a journal.