One of the best things about science it is that it develops itself over time. Data collected decades ago is still valid and helps scientists spot trends that might otherwise get lost in the flood of new data they’re trying to collect. And sometimes, that data contains something interesting. Such is the case when a group of scientists took a look at infrared data from Neptune’s atmosphere and found not one, but two strange changes.
To put the changes into context, it would be helpful to understand Neptune’s “weather.” The planet has an axial tilt, which means it also has seasons. Since scientists began collecting valid data in 2003, it has gone through about half a summer in the southern hemisphere, which, like Neptune’s other seasons, each lasts 40 Earth years.
With that perspective, scientists didn’t expect to see much change in the temperature of Neptune’s atmosphere even over a 20-year observation period, but they did. They saw an overall global cooling of around 8 ? through the planet’s stratosphere between 2003 and 2018. Even more shocking, they saw an 11? temperature rise at the south pole for just two years between 2018 and 2020. These results were published in April in the Planetary Science Journal.
Credit: Michael Roman/NASA/ESA/STSci/MH Wong/LA Sromovsky/PM Fry
Observations of the planet’s stratosphere were completed with a wide variety of infrared telescopes for nearly 20 years. All of that data showed the same cooling trend during the initial data period, which confounded scientists who expected to see general warming due to the onset of summer, which was expected to have higher temperatures than spring.
Furthermore, the two-year jump in temperatures at the south pole was faster than the researchers expected. These observations were collected with just two telescopes, Gemini North in 2019 and Subaru in 2020, but both confirmed the same dramatic change. That big jump in just 5% of a season is a surprising jump and could signal ever-widening changes to come later in the season.
These two trends are obviously contradictory, and scientists are still trying to make sense of them. His best theory at the moment is that seasonal changes throughout the austral summer could affect the planet’s atmospheric chemistry, which would also affect how it cools or warms. Additionally, it could be affected by the 11-year solar cycle or random weather patterns on the planet itself for which we don’t yet have good models.
Another great thing about science is that while there are always old data sets to review, there are also new ones to get excited about. Researchers are very excited about what James Webb’s Mid-Range Infrared Instrument (MIRI) will be able to show them about Neptune’s atmospheric composition. That telescope continues to progress through its shipboard stages, and one of the authors of the current paper, Leigh Fletcher of the University of Leicester, has allocated some time to it as part of the European Research Council’s GIANTCLIMES grant. The new patterns that MIRI reveals have yet to be determined, but they are sure to be interesting.
Learn more:
University of Leicester- Neptune is colder than we thought: study reveals unexpected changes in atmospheric temperatures
Roman et al. – Subseasonal variation in Neptune’s mid-infrared emission
UT – What is the surface temperature of Neptune?
UT – Neptune’s south pole is the hottest place on the planet
Main Image:
Graph of changes in Neptune’s atmospheric temperature.
Crédito: Michael Roman/NASA/JPL/Voyager-ISS/Justin Cowart