Aegaeon & Prometheus

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The Planetary Society Blog By Emily Lakdawalla

Cassini Aegaeon and Prometheus awesomeness
Jan. 28, 2010 | 11:38 PST | 19:38 UTC

<<Yesterday, Cassini traversed the G ring, taking photos all the way. While doing so the spacecraft passed within 13,000 kilometers of Aegaeon, the tiny, recently discovered moon that is now believed to be the parent body of the G ring. (Small meteorite impacts onto Aegaeon would toss up dust particles that would escape the little moon's almost nonexistent gravity and go into their own orbits around Saturn; various sorts of drag extend the dust from Aegaeon's neighborhood all the way around the planet, but it's densest near the moon.) That distance is relatively close -- close enough for Cassini to get a very respectable 80 meters per pixel or so on the moon -- but since the moon's only roughly 500 meters across, you're only looking at 5 or 10 pixels.

Seventeen images of Aegaeon

On January 27, 2010, Cassini approached to within 13,000 kilometers of Aegaeon, the recently discovered moon that is now believed to be the parent body from which Saturn's dusty G ring is built. The 17 images in this animation have been cleaned of some of their cosmic ray hit artifacts and have been enlarged by a factor of two. Credit: NASA / JPL / SSI / animation by Emily Lakdawalla

The Prometheus images were taken from about three times the distance of the Aegaeon photos, but Prometheus is much bigger than Aegaeon (about 119 by 87 by 61 kilometers in diameter). Here are three clear-filter views.

Prometheus in color with ring rainbows

Cassini captured the four images that were combined to make this approximately natural color view of Prometheus on January 27, 2010 from fewer than 40,000 kilometers away. Credit: NASA / JPL / SSI / color composite by Emily Lakdawalla

There are some color fringes in the image where the individual color frames do not align properly. Some of this misalignment is due to Cassini's and Prometheus' relative motions and Prometheus' rotation. A separate issue causes the two rainbows crossing Prometheus' sunlit disk: these are shadows from two tendrils of the F ring, which moved across Prometheus' face in the time separating the images.>>

http://antwrp.gsfc.nasa.gov/apod/ap090427.html
http://antwrp.gsfc.nasa.gov/apod/ap951223.html

[RJN]

Good post -- I hadn't seen this. With the new board forums, this might have gone better in the "The Observation Deck: Sky Photography" forum. I am currently thinking of running a Cassini Prometheus image on Monday's APOD. I might use the image on the Cassini Image team website though: http://ciclops.org/view/6171/Prometheus ... aw_Preview

[geckzilla]

The shadow of the rings in approximate natural color is really stunning once you realize what it is. Assuming, of course, that the red tint isn't an artistic liberty on Emily's behalf. These "natural color" images are sometimes such a puzzle to understand.

[harry]

G'day

Prometheus
http://www.theoi.com/Titan/TitanPrometheus.html

PROMETHEUS was the Titan god of forethought and crafty counsel who was entrusted with the task of moulding mankind out of clay. His attempts to better the lives of his creation brought him into direct conflict with Zeus. Firstly he tricked the gods out of the best portion of the sacrificial feast, acquiring the meat for the feasting of man. Then, when Zeus withheld fire, he stole it from heaven and delivered it to mortal kind hidden inside a fennel-stalk. As punishment for these rebellious acts, Zeus ordered the creation of Pandora (the first woman) as a means to deliver misfortune into the house of man, or as a way to cheat mankind of the company of the good spirits. Prometheus meanwhile, was arrested and bound to a stake on Mount Kaukasos where an eagle was set to feed upon his ever-regenerating liver (or, some say, heart). Generations later the great hero Herakles came along and released the old Titan from his torture.

This is why he was given a small moon to play with.

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Seventeen images of Aegaeon

Credit: NASA / JPL / SSI / animation by Emily Lakdawalla

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<<Aegaeon (Αιγαίων pronounced ee-JEE-ən) is a natural satellite of Saturn. Its discovery was announced by Carolyn Porco of the Cassini Imaging Science Team on March 3, 2009. Aegaeon orbits within the bright segment of Saturn's G Ring, and is likely a major source of the ring. Debris knocked off the moon forms a bright arc near the inner edge, which in turn spreads to form the rest of the ring.

• Aegaeon orbits in a 7:6 resonance with Mimas.

The ring arcs associated with Methone, Anthe, and Pallene strongly hinted
that there must be some parent body hiding within that G ring arc.
In this diagram from Matt Hedman, you can see where the Methone
& Anthe orbits are located (orange and yellow dashed lines);
and where Mimas' orbit is located (red dashed line).

The very next faint ring closer to Saturn than Mimas is the G ring, now known to contain
its own moon, [i.e., Aegaeon]. It is named after Aegaeon, one of the hecatonchires.>>

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<<The Hecatonchires, or Hekatonkheires (Greek: Ἑκατόγχειρες), were three giants of incredible strength & ferocity. Their name derives from the Greek ἑκατόν (hekaton; "hundred") and χείρ (kheir; "hand"), "each of them having a hundred hands and fifty heads." Their names were Briareus Βριάρεως the Vigorous, a.k.a. Aigaion Αιγαίων (Latinized as Aegaeon) the "sea goat", Cottus Κόττος the Striker or the Furious, and Gyges Γύγης the Big-Limbed. If some natural phenomena are symbolized by the Hecatonchires then they may represent the gigantic forces of nature that appear in earthquakes and other convulsions or in the motion of sea waves.

Soon after they were born their father Uranus threw them into the depths of Tartarus because he saw them as hideous monsters. The Hecatonchires remained there, guarded by the dragon Campe, until Zeus rescued them. During the War of the Titans the Hecatonchires threw rocks as big as mountains, one hundred at a time, at the Titans, overwhelming them.

Achilles speaks to his mother the sea nymph Thetis of "the monster of the hundred arms whom the gods call Briareus, but mankind Aegaeon, a giant more powerful even than his father." The Olympian gods were trying to overthrow Zeus but were stopped when Thetis brought Aegaeon to his aid -"at one time he must have shared with the goddess dominion over the depths of the Aegean Sea". "He squatted by the Son of Cronos with such a show of force that the blessed gods slunk off in terror, leaving Zeus free."

Briareus is mentioned in the Divine Comedy as one of the Titans who attacked Jove on Olympus. He is in the pit of the giants in the ninth circle of hell. The giant is also mentioned in Cervantes' Don Quixote, in the famous episode of the windmills.

• 

"The wind increased, and the mill sails began to turn about; which Don Quixote espying, said,

• ‘Although thou movest more arms than the giant Briareus thou shalt stoop to me.’

And, after saying this, and commending himself most devoutly to his Lady Dulcinea, desiring her to succor him in that trance, covering himself well with his buckler, and setting his lance on his rest, he spurred on Rozinante, and encountered with the first mill that was before him, and, striking his lance into the sail, the wind swung it about with such fury, that it broke his lance into shivers, carrying him and his horse after it, and finally tumbled him a good way off from it on the field in evil plight.">>