“When you see Saturn floating in the eyepiece of your telescope, you feel a cosmic connection –as if you uncovered mystery in the cosmos,” says Carolyn Porco, who led the science-imaging team for NASA’s Cassini spacecraft mission, which in its final year provided intricate detail on the workings of Saturn’s complex rings showing that they may not have been there during the reign of Earth’s dinosaurs, and may be a fairly recent development in our solar system.
Now, a new Hubble image of Saturn shown below was taken on July 4, 2020, during summer in the giant ringed planets’ northern hemisphere, when the “opulent giant world” was 839 million miles from Earth. Hubble’s sharp view, reports NASA’s Goddard Space Flight Center “resolves the finely etched concentric ring structure –composed of pieces of ice, with sizes ranging from tiny grains to giant boulders–and perhaps solves one of our solar system’s biggest mysteries of how and when the rings formed. Two of Saturn’s icy moons, Mimas at right, and Enceladus at bottom. (NASA, ESA, A. Simon -Goddard Space Flight Center, M.H. Wong, University of California, Berkeley), and the OPAL Team)
Conventional wisdom, reports Goddard, “is that they are as old as the planet, over 4 billion years. But because the rings are so bright – like freshly fallen snow – a competing theory is that they may have formed during the age of the dinosaurs. Many astronomers agree that there is no satisfactory theory that explains how rings could have formed within just the past few hundred million years.”
“However, NASA’s Cassini spacecraft measurements of tiny grains raining into Saturn’s atmosphere suggest the rings can only last for 300 million more years, which is one of the arguments for a young age of the ring system,” said team member Michael Wong of the University of California, Berkeley.
The Hubble image revealed a number of small atmospheric storms, transient features that appear to come and go with each yearly observation. The banding in the northern hemisphere remains pronounced as seen in Hubble’s 2019 observations, with several bands slightly changing color from year to year. The ringed planet’s atmosphere is mostly hydrogen and helium with traces of ammonia, methane, water vapor, and hydrocarbons that give it a yellowish-brown color.
Hubble photographed a slight reddish haze over the northern hemisphere in this color composite. This may be due to heating from increased sunlight, which could either change the atmospheric circulation or perhaps remove ices from aerosols in the atmosphere. Another theory is that the increased sunlight in the summer months is changing the amounts of photochemical haze produced.
“It’s amazing that even over a few years, we’re seeing seasonal changes on Saturn,” said lead investigator Amy Simon. Conversely, the just-now-visible south pole has a blue hue, reflecting changes in Saturn’s winter hemisphere.
This image is taken as part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar system’s gas giant planets. In Saturn’s case, astronomers continue tracking shifting weather patterns and storms.
The Daily Galaxy, Sam Cabot, via Goddard Space Flight Center
Image top of page shows Cassini’s before its mission ended in the spacecraft’s fiery death-plunge into Saturn in 2017.