Saturn’s Moon Reveals Weird Science

Ever since the Cassini–Huygens satellite mission flew past Saturn’s moon Enceladus, it has been one of the hot topics in astronomy. It has continued to reveal itself in strange and unusual ways that have provided quandaries for researchers to puzzle over.

When Enceladus was first photographed by Cassini it revealed ice geysers that were spewing matter out in to the surrounding space. It was discovered that this matter helped to make up Saturn’s E-ring. Following that, it was found that a “deflection” in the local magnetic field that is characteristic of the existence of a thin, yet significant atmosphere. Next up was the discovery that Saturn’s entire magnetic environment was being weighed down by material spewed from Enceladus.

So it is no surprise that another discovery has been revealed thanks to Enceladus.

Apparently Cassini scientists are confirming that the plasma – the gas of electrically charged particles that spews from Enceladus – which creates a donut-shaped cloud around Saturn, is being mopped up by Saturn’s A-ring.

"Saturn's A-ring and Enceladus are separated by 100,000 kilometers (62,000 miles), yet there’s a physical connection between the two," says Dr. William Farrell of NASA's Goddard Space Flight Center in Greenbelt, Md. "Prior to Cassini, it was believed that the two bodies were separate and distinct entities, but Cassini’s unique observations indicate that Enceladus is actually delivering a portion of its mass directly to the outer edge of the A-ring." Farrell is lead author of a paper on this discovery that appeared in Geophysical Research Letters January 23.

The science behind it explains that when the gas particles are expelled from within Enceladus’ interior, the gas particles subsequently become electrically charged, or ionized. Once this happens, the particles will then feel the magnetic pull of Saturn and sweep in to the space surrounding the planet, thus producing the donut-shaped cloud.

At this point they are trapped in Saturn’s magnetic field, bouncing back and forth between Saturn’s two poles. However this excitement ends if their paths carry them within range of Saturn’s A-ring, at which point they stick, and become part of the ring. "Once they get to the outer A-ring, they are stuck," says Farrell.

"This is an example of how Saturn’s rings mitigate the overall radiation environment around the planet, sponging up low- and high-energy particles," says Farrell. By contrast, Jupiter has no dense rings to soak up high-energy particles, so that planet’s extremely high radiation environment persists.

These observations made by Cassini confirm a prediction by Dr. John Richardson and Dr. Slobodan Jurac of the Massachusetts Institute of Technology. Back in the early 1990’s, the pair focused on observations taken by the Hubble Space Telescope that revealed the presence of a large body of water-related molecules in orbit around Saturn, about 240,000 km (almost 150,000 miles) from the planet. Together, the pair modeled that this water cloud could migrate inwards to the A-ring. "We relied on their predictions to help us interpret our data," said Farrell. "They predicted it, and we were seeing it."

It was only in 2005, when Cassini made her flyby, that it was discovered that Enceladus was the source of the water cloud.

But this isn’t the only recent Enceladus study to catch our attention. A team astrophysicists led by Juergen Schmidt of the University of Potsdam, near Berlin, have provided evidence that bolsters theories that water exists within Enceladus.

The so named “cryo-volcanoes” eject their matter from the south pole, right near the surface stripes – or tiger stripes – that give Enceladus’ it’s peculiar outer image. The issue that has been brewing in the scientific community is that icy particles of dust are mixed in with the eruptions, but travel far slower than the vapor.

According to Juergen’s team, this is because the water vapor and ice grains are blasted through funnels in the surface of Enceladus, but that because the ice particles are heavier, rub against the rough sides of these holes. Thus, the friction caused slows the particles down.

That’s all good and well, but the point is that this can only happen if there is liquid water exiting in equilibrium with the ice and vapor beneath the moons crust.

The team have also begun to work on just why there are these cryo-volcano eruptions down south. One theory is that the small moon – just 504 kilometres (315 miles) across – is suffering from tidal heating. Because of the gravitational pull from the giant Saturn and from nearby satellites Dione and Janus, Enceladus’ insides are squeezed and stretched, causing friction that wamrs the water within.

All in all, with more and more data to analyze from our own solar system, it’s a wonder anyone has time to look outside it.

Posted by Josh Hill.

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