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Saturn’s Rings Alter Its Ionosphere

From Jake Parks | December 15, 2017 10:34 am

This image shows Cassini’s past two orbital stages. Even the ring-grazing orbits are shown in grey (far left), although the Grand Finale orbits — during which Cassini’s accumulated unprecedented measurements of Saturn’s ionosphere — are shown in blue. The orange line shows Cassini’s final plunge into Saturn on September 15, 2017. (Credit: NASA/JPL-Caltech)

In April of the past year, NASA divides the Cassini spacecraft to an orbit that took it by a narrow gap between Saturn’s innermost ring (the D-ring) and the petrol giant itself.

Over the upcoming few months, Cassini skimmed the upper atmosphere of the ringed planet nearly twice. During 11 of these orbits, Cassini’s Radio and Plasma Wave Science (RPWS) instrument took unprecedented measurements of Saturn’s ionosphere — a casing of charged particles that surrounds the entire world and protects it from incoming solar radiation and cosmic rays.

In a study published yesterday in the journal Science, investigators using Cassini’s RPWS information showed that Saturn has a cold, streamlined and lively ionosphere with a density that may vary just up to a factor of 100. What’s more, the researchers discovered that Saturn’s opaque and enormous rings throw ionosphere-altering shadows across the planet, and they might even create “ring rainfall.”

When Cassini traveled throughout the corners of Saturn’s biggest and brightest rings (the A and B rings), it measured a drastic drop in the amount of ionized plasma gift, meaning the ionosphere got weaker as it had been shaded. Though interesting, this isn’t entirely surprising. Ionospheres are produced when ultraviolet light in the Sun strips charged particles from atoms from the planet’s upper atmosphere; so it makes sense that Saturn’s ionosphere is weaker when the rings block incoming sunlight.

On the other hand, the team discovered that even when the planet’s rings veiled Saturn’s ionosphere, there was still measurable activity in the plasma screen. This indicates that sunlight isn’t the only thing that influences Saturn’s ionosphere. Though researchers are not sure what causes the phenomenon they theorize that Saturn’s innermost D-ring might be generating “ring rain” — in which billed water particles embedded within Saturn’s rings migrate to the ionosphere, maintaining the plasma mildly active.

“It’s as though the little ice cubes from the D-ring suck electrons from the ionosphere,” explained Jan-Erik Wahlund at a news release. “As a result of the coupling, electrical flows of gas to and out of the rings along the magnetic field of Saturn cause the best variations in density.”

Since the investigators’ findings were based on just half of the information Cassini accumulated during its grand finale, it’s safe to say there’s a lot more left to detect.

“Consider this a prelude of things to come from Cassini,” explained Hunter Waite, directory of planetary mass spectrometry at South West Research Institute, at a press release. “Saturn’s ionosphere is far more complicated than anyone could imagine.”

CATEGORIZED UNDER: Space & Physics, top posts

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