NASAsay Hubble Space Telescope gives astronomers a look at changes in Saturn‘s expansive and turbulent atmosphere as the summer of the northern hemisphere passes over the planet and falls as evidenced by this series of images taken in 2018, 2019 and 2020 (left to right).
“These small year-on-year changes in Saturn’s color bands are fascinating,” said Amy Simon, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “As Saturn moves toward the fall in the northern hemisphere, we see the polar and equatorial regions change, but we also see the atmosphere change on much shorter time scales.” Simon is lead author of a paper on these observations published on 11 March 2021 in Planetary Science Journal.
“What we found was a slight change from year to year in color, possibly cloud height and winds. It’s not surprising that the changes are not large, because we are only looking at a small fraction of a Saturn year. , “Simon added. “We expect big changes on a seasonal time scale, so it shows the progress towards the next season.”
Hubble Space Telescope images of Saturn taken in 2018, 2019 and 2020 as the summer’s northern hemisphere summer is about to fall. Credit: NASA / ESA / STScI / A. Simon / R. Roth
The Hubble data show that the equator became 5 to 10 percent brighter from 2018 to 2020 and that the winds changed slightly. In 2018, winds measured near the equator were about 1,000 miles per hour (about 1,600 kilometers per hour), higher than those measured by NASA. Cassini spacecraft during 2004-2009, when they were about 800 miles per hour (about 1,300 kilometers per hour). In 2019 and 2020, they slowed down to the Cassini speed. Saturn’s winds also vary with altitude, so the change in measured velocities could possibly mean that the clouds in 2018 were about 60 kilometers deeper than those measured during the Cassini mission. Further observations are needed to determine what is happening.
Saturn is the sixth planet from our sun and orbits at a distance of about 1.4 billion kilometers from the sun. It takes about 29 Earths to orbit the Sun, making each season on Saturn more than seven Earth years. The earth is tilted toward the sun, which changes the amount of sunlight each hemisphere receives as our planet moves in its orbit. This variation in solar energy is the cause of our seasonal changes. Saturn is also tilted, so as the seasons change in that distant world, the change in sunlight can cause some of the observed atmospheric changes.
As Jupiter, the largest planet in the solar system, Saturn is a ‘gas giant’ consisting mostly of hydrogen and helium, although deep in a rocky core. Enormous storms, some nearly as large as the earth, occasionally break deep out of the atmosphere. Since many of the planets discovered around other stars are also gas giants, astronomers are eager to learn more about how gas giant atmospheres work.
Saturn is the second largest planet in the solar system, more than 9 times wider than Earth, with more than 50 moons and a spectacular ring system made mainly of water ice. It seems that two of these moons, Titan and Enceladus, have oceans beneath their icy crusts that can sustain life. Titan, Saturn’s largest moon, is the only moon in our solar system with a thick atmosphere, including clouds that allow liquid methane and other hydrocarbons to rain on the surface and form rivers, lakes and seas. This mixture of chemicals is thought to be similar to that on Earth billions of years ago when life first came into being. NASA’s Dragonfly mission will fly over the surface of Titan and hit various locations, searching for the ancient building blocks of life.
Reference: “Midsummer Atmospheric Changes in Saturn’s Northern Hemisphere from the Hubble OPAL Program” by Amy A. Simon, Ricardo Hueso, Agustín Sánchez-Lavega, and Michael H. Wong, March 11, 2021, Planetary Science Journal.
DOI: 10.3847 / PSJ / abe40f
The Saturn observations are part of Hubble’s Outer Planets Atmospheres Legacy (OPAL) program. “With the OPAL program, we can observe each year with Hubble each of the outer planets, enabling new discoveries and seeing how each planet changes over time,” said Simon, chief researcher for OPAL.
The Hubble Space Telescope is a project of international collaboration between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, controls the telescope. The Space Telescope Science Institute (STScI) in Baltimore is conducting scientific operations of Hubble. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, DC