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What Has the Cassini-Huygens Spacecraft Discovered About Saturn's Atmosphere?

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

Read on to learn about what the Cassini-Huygens spacecraft has discovered about Saturn's atmosphere.

Read on to learn about what the Cassini-Huygens spacecraft has discovered about Saturn's atmosphere.

The Cassini-Huygens revealed much about the Saturn system, including the rings, moons, and planetary information. It is the details of the atmosphere that we shall discuss here, revealing new details that until then had remained hidden deep in the heart of Saturn.

Surprising Radiation

In December 2004, it was reported that a ring of radiation between Saturn's clouds and its inner rings was found. This was unexpected because radiation is absorbed by matter, so it is a mystery how it could have gotten there unscathed.

Don Mitchell of John Hopkins University theorizes that positively charged particles such as protons and helium ions in the outer belt (themselves captured from cosmic sources) merged with electrons (negative particles) from the cold gas around Saturn. This creates neutral atoms that can move around in the magnetic field freely. Eventually, they lose their hold on electrons and will become positive again, potentially in that inner zone. Some could crash into Saturn, changing its temperature and potentially its chemistry.

Later evidence from the end of Cassini's mission not only confirmed this but surprisingly found that the D ring had two moonlets (D73 and D68) that moved in this zone and effectively trapped protons that formed in this process due to different densities at play (Webb 13, Lewis).

The discoloration in the upper hemisphere is in fact...a thunderstorm!

The discoloration in the upper hemisphere is in fact...a thunderstorm!

Thunderstorms

Anthony Delgenio, an atmospheric scientist at NASA's Goddard Institute for Space Studies, discovered through Cassini that Saturn has thunderstorms like those on Earth. That is, they, too, emit electrostatic discharges. Unlike Earth, the storms are 30 miles deep into the atmosphere (3 times deeper than on Earth). Cassini also measured the wind speeds at the equator, which clocked in at 230-450 mph, a decrease from Voyager 1's measurement of 1000 mph. Anthony is unsure why this change occurred (Nething 12).

Another parallel to Earth weather was observed when Cassini spotted a storm at the south pole of Saturn. It was 5000 miles wide with wind speeds of 350 miles per hour! It was similar in appearance to hurricanes on Earth, but a big difference was the lack of water. Therefore, because water mechanics govern Earth's hurricanes, Saturn's storm must result from some other mechanism. Also, the storm hovers above the pole and rotates, not moving otherwise (Stone 12).

Now, with a finding like that, it may come as a surprise that Saturn's awesome storms, which seem to cycle every 30 years, don't get much attention. But they certainly should. Cassini's data seems to point to an interesting mechanism, which is as follows: First, a minor storm passes by and removes water from the upper atmosphere as precipitation. On Saturn, this takes the form of hydrogen and helium, and the precipitation falls between cloud layers. This caused a transference of heat, leading to a decrease in temperature. After a few decades, enough cold air is built up to hit a lower layer and cause convection, thus a storm (Haynes, Nething 12, JPL).

Energy

Saturn has another difference from Earth besides these thunderstorm patterns. Scientists found that the energy output from Saturn differs in each hemisphere, with the southern portion radiating about 17% more than the northern. The CIRS instrument detected this result, and scientists think several factors play into this.

One is cloud cover, which has fluctuated greatly from 2005 to 2009, the window of this energy change. It does match with the changes in the seasons as well. But when compared to Voyager 1 data from 1980-81, the energy change was far greater than then, possibly hinting at a positional variance or even a solar radiance change on Saturn's cloud cover (Goddard Space Flight Center).

False color image of Saturn's north pole from 2013.

False color image of Saturn's north pole from 2013.

The Hexagon

But I would be remiss if I didn't mention the north pole of Saturn, which has, of all things, a hexagonal pattern at it. Yes, that picture is real, and since its discovery by Voyager in 1981, its been a real humdinger. Cassini data only made it even cooler, for the hexagon may act like a tower by channeling energy from below the surface to the top via storms and vortexes that were spotted forming. As to how the hexagon formed in the first place or how it remains so stable over time remains a mystery (Gohd).

Works Cited

Goddard Space Flight Center. "Cassini Reveals Saturn is on a Cosmic Dimmer Switch." Astronomy.com. Kalmbach Publishing Co., 11 Nov. 2010. Web. 24 Jun. 2017.

Gohd, Chelsea. "Saturn's hexagon could be an enormous tower." astronomy.com. Kalmbach Publishing Co., 05 Sept. 2018. Web. 16 Nov. 2018.

Haynes, Korey. "Saturnian Storms Explained." Astronomy Aug. 2015: 12. Print.

JPL. "NASA-funded study explains Saturn's epic tantrums." Astronomy.com. Kalmbach Publishing Co., 14 Apr. 2015. Web. 27 Aug. 2018.

Lewis, Ben. "Cassini data reveals Saturn's layer of imprisoned protons." cosmosmagazine.com. Cosmos. Web. 19 Nov. 2018.

Nething, Jessa Forte. “Cassini Watch: Stormy Saturn.” Discover Feb. 2005: 12. Print.

Stone, Alex. "Cosmic Katrina." Discover Feb. 2007: 12. Print.

Webb, Sarah. "Cassini Watch: Saturn’s Invisible Belt” Discover Dec. 2004: 13. Print.

© 2022 Leonard Kelley