NASA’s Hubble Space Telescope is giving astronomers a view of changes in Saturn’s vast and turbulent atmosphere as the planet’s northern hemisphere summer transitions to fall as shown in this series of images taken in 2018, 2019, and 2020 (left to right).
“These small year-to-year changes in Saturn’s color bands are fascinating,” said Amy Simon, planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “As Saturn moves towards fall in its northern hemisphere, we see the polar and equatorial regions changing, but we are also seeing that the atmosphere varies on much shorter timescales.” Simon is lead author of a paper on these observations published March 11 in Planetary Science Journal.
“What we found was a slight change from year-to-year in color, possibly cloud height, and winds – not surprising that the changes aren’t huge, as we’re only looking at a small fraction of a Saturn year,” added Simon. “We expect big changes on a seasonal timescale, so this is showing the progression towards the next season.”
The Hubble data show that from 2018 to 2020 the equator got 5 to 10 percent brighter, and the winds changed slightly. In 2018, winds measured near the equator were about 1,000 miles per hour (roughly 1,600 kilometers per hour), higher than those measured by NASA’s Cassini spacecraft during 2004-2009, when they were about 800 miles per hour (roughly 1,300 kilometers per hour).
In 2019 and 2020 they decreased back to the Cassini speeds. Saturn’s winds also vary with altitude, so the change in measured speeds could possibly mean the clouds in 2018 were around 37 miles (about 60 kilometers) deeper than those measured during the Cassini mission. Further observations are needed to tell which is happening.
Saturn is the sixth planet from our Sun and orbits at a distance of about 886 million miles (1.4 billion kilometers) from the Sun. It takes around 29 Earth years to orbit the Sun, making each season on Saturn more than seven Earth years long. Earth is tilted with respect to the Sun, which alters the amount of sunlight each hemisphere receives as our planet moves in its orbit.
Source/Further Reading: Nasa Goddard