Saturn is famous for its rings, which can be easily seen with a regular telescope. Now, the scientist has used her observations collected over 40 years to discover that the planet’s iconic rings may not be as calm as they seem, suggesting that the relationship between the planet and its iconic rings revealed unprecedented interactions between
Scientists collated observational records of Saturn and discovered that Saturn’s vast ring system heats its upper atmosphere. This is a phenomenon that has never been seen anywhere else in the solar system.
To arrive at this conclusion, it was necessary to piece together observations of ultraviolet (UV) light from four NASA planetary missions. This included data from the Voyager 1 and His 2 probes, which flew by Saturn in the 1980s and measured UV excess, then considered noise. It also included data from the Cassini mission, which arrived at Saturn in 2004 and collected UV data over several years. Additional data came from the International Ultraviolet Spacecraft, launched in 1978, and the Hubble Space Telescope.
From measurements provided by the Cassini spacecraft, scientists already knew that particles in Saturn’s rings were slowly falling toward the planet. The question was how it affected the level of atomic hydrogen. Atomic hydrogen appears as a single atom rather than a molecule, which makes it very reactive.
“It’s well known that rings decay slowly, but their effect on planetary hydrogen atoms is surprising,” said Lofty Ben Jaffel, lead author of the study. “From the Cassini spacecraft, we already knew about the effects of the rings. But we knew nothing about the atomic hydrogen content.”
Combining archival data using high-resolution measurements from the Hubble Space Telescope’s Imaging Spectrograph (STIS) was key to the discovery. Accurate STIS observations were used to reconcile archival data obtained by Cassini and the Voyager craft. The resulting images revealed excess ultraviolet radiation seen as spectral lines of hot hydrogen in Saturn’s atmosphere, indicative of atmospheric heating.
For scientists, the best explanation for Saturn’s atmospheric heating was a constant rain of icy particles that rain down on the planet from its rings, pulled by its gravity.
“Everything is driven by ring particles cascading into the atmosphere at specific latitudes,” said Benjafel. “They modify the upper atmosphere and change its composition.”
It is hoped that the unexpected interactions between Saturn and its rings can be used to determine whether exoplanets orbiting other stars have Saturn-like ring systems. Although they are too far away to be seen, ultraviolet spectroscopy of planets can be used to indicate their presence.
“We are just at the beginning of the ring’s characterizing effect on the planet’s upper atmosphere,” said Ben Jaffel. “Ultimately, we need a global approach that will yield true characterizations of the atmospheres of far-flung worlds. One of the goals of this research is to see how it can be applied to planets orbiting other stars is to do.”
This research Journal of Planetary Science.
Source: NASA
