- Saturn’s inner rings are made of water, ammonia, methane, molecular nitrogen, carbon monoxide, and carbon dioxide.
- The rings eject these chemicals into the planet’s upper atmosphere at 10 times faster speed than previously thought.
- This infalling material heats the Saturn’s atmosphere and changes its composition.
NASA’s Cassini spacecraft spent more than 13 years studying Saturn’s atmosphere and its rings which are far more complicated than previously thought. The Grand Finale phase of the mission took the Cassini through the gap between planet’s atmosphere and its innermost ring (the D-ring), providing a great opportunity to study its internal magnetic field and composition and behavior of the D-ring.
Recently, they published a paper reporting outcomes from the Grand Finale phase. In this paper, they have discussed a few major points: Saturn’s magnetic field that implies the complex internal structure of the planet, additional radiation belt inside the rings, and composition of dust particles falling from the D ring into the planet’s upper atmosphere.
They also analyzed the molecules of the infalling material and studied the planet’s atmosphere composition. The results suggest that this infalling material will change the volume of oxygen and carbon present in the atmosphere over a long timescale.
The Surprising Element
Two things that surprised the researchers are chemical complexity and quantity of matter coming off the rings. Most of the ring was thought to be made of water, some of which must be getting absorbed by Saturn’s ionosphere, but clearly, this is not the case anymore. Both the quality and quantity of ring materials are way too different than expected.
Cassini’s mass spectrometer sampled chemicals at altitudes between Saturn’s ionosphere and its inner D ring. Along with water, the ring contains ammonia, methane, molecular nitrogen, carbon monoxide, and carbon dioxide.
Saturn’s Ring | Image credit: Nasa
A vast amount of these chemicals is being flung into the Saturn’s upper atmosphere which is spinning slower than the inner D ring. These chemicals (in the form of dust and grains), including benzine, is changing the planet’s ionosphere in the equatorial area.
Scientists at the Southwest Research Institute in San Antonio reported that chemicals ejected by rings change the composition of Saturn’s equatorial ionospheric by transforming triatomic hydrogen ions and hydrogen ions into heavy molecular ions, which reduces the density of the atmosphere.
This higher-than-expected material falling into the planet’s atmosphere is enough to conclude that the lifespan of rings might be shorter than previously calculated. Records show that the D ring is ejecting these material 10 times faster than we expected, and if it’s not being replenished, it’s not going to last.
Since the atmosphere is moving at a slower speed as compared to planet’s rings, the matter does not just drop in smoothly. It enters the Saturn’s atmosphere in the same way a satellite re-enters the Earth. These dust and grains move at satellite speed, heating the ionosphere and altering its composition.
Some models predict that Jupiter had a ring, which eventually evolved into the wispy ring due to the same reasons. Rings do get drain away with time unless somehow they are receiving new matter from external sources.
How These Findings Are Useful?
The results could shed light on how our solar system and other solar systems and exoplanets work. It could eventually help us understand why and how does a planet get its own rings. How old are Saturn’s rings and what’s their lifetime? Was there a time when Saturn had no rings? How did they get there in the first place?