Epimetheus (APOD 11 Feb 2008)

craterchains · Post by **craterchains** » Mon Feb 11, 2008 5:17 am

Now this is interesting, most all craters shown seem to be round. No near misses with no gravity to attract them straight in, hmmmmmm.

Go figure, , ,

emc · Post by **emc** » Mon Feb 11, 2008 12:46 pm

Could Epimetheus be a "chunk" from a much larger source?

http://apod.nasa.gov/apod/ap080211.html

Dean Sloan · Post by **Dean Sloan** » Mon Feb 11, 2008 1:58 pm

I think it most likely came from the same place that the 2 moons of Mars came from, and that is the planet that exploded and created the asteroid belt.

zbvhs · Post by **zbvhs** » Mon Feb 11, 2008 2:42 pm

Note the large crater at the top of the side facing us: Material seems to be "falling down" and collecting on the "bottom" wall of the crater. Why do you suppose that is? Gravity gradient?

neufer · Post by **neufer** » Mon Feb 11, 2008 5:28 pm

zbvhs wrote:Note the large crater at the top of the side facing us: Material seems to be "falling down" and collecting on the "bottom" wall of the crater. Why do you suppose that is? Gravity gradient?

The lighter albedo seems to be solid rock while the darker albedo seems to be dust or loose material that has found it's way somehow to the lower spots on Epimetheus.
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A good rule of thumb is that both gravity & escape velocity
generally scale directly with the satellite diameter:

Earth's moon diameter = 3500 km
moon gravity = 1/6 (earth's)
moon escape velocity = 2400 m/sec

Epimetheus diameter = 115 km __________ [ = 3500/30 km ]
Epimetheus gravity = 1/180 (earth's)___ [ = (1/6)/30]
Epimetheus escape velocity = 80 m/sec ______ [ = 2400/30 m/sec]

A major league pitcher would weigh 1 pound
and be able to throw a baseball into Saturn orbit
[; albeit that the ball would eventually land
back on Epimetheus (or it's brother Janus)
due to intersecting orbits].
-----------------------------------------------
http://en.wikipedia.org/wiki/Epimetheus_%28mythology%29

<<In Greek mythology, Epimetheus (Greek: Ἐπιμηθεύς) ("hindsight", literally "hind-thought") was the brother of Prometheus ("foresight", literally "fore-thought"), a pair of Titans who "acted as representatives of mankind" . They were the inseparable sons of Iapetus, who in other contexts was the father of Atlas. While Prometheus is characterized as ingenious and clever, Epimetheus is depicted as foolish.

According to Plato's use of the old myth in his Protagoras, where he puts it in the mouth of the old philosopher, the twin Titans were entrusted with distributing the traits among the newly-created animals; Epimetheus was responsible for giving a positive trait to every animal, but when it was time to give man a positive trait, lacking foresight he found that there was nothing left. His brother Prometheus then stole fire from Zeus and gave it to man, and was punished for his impiety by being strapped to a mountain top and visited by an eagle who ate his liver every day. Since Prometheus was a Titan and therefore practically immortal, his liver grew back every day, so the eagle had to come back, keeping Prometheus in constant pain. As further punishment, Zeus created Pandora, the first woman, for Epimetheus, knowing that he would fall in love with her despite the warnings of his brother, the embodiment of foresight, who told him never to accept a gift from the Olympian gods, with whom the primordial Titans, sprung from Mother Earth, were ever at odds.

According to Hesiod Epimetheus and Pandora were married. Pandora had been given a covered pithos, or storage jar, by Hermes and was instructed never to open it. However, Hermes also gave her curiosity, so she opened it anyway, releasing all the misfortunes of mankind. She shut it in time to keep one thing in reserve: hope. Thus mankind always has hope in times of evil. The daughter of Epimetheus and Pandora was Pyrrha, who married Deucalion and was one of the two who survived the deluge.>>

-----------------------------------------------

salientNZ · Post by **salientNZ** » Mon Feb 11, 2008 8:01 pm

[quote="zbvhs"]Note the large crater at the top of the side facing us: Material seems to be "falling down" and collecting on the "bottom" wall of the crater. Why do you suppose that is? Gravity gradient?[/quote]

Which way does it spin, and at what rate ?

neufer · Post by **neufer** » Mon Feb 11, 2008 10:15 pm

Note that the neighboring Saturn moons of Janus/Epimetheus
also breakdown into two distinct pairs of moons but in
~2:1 resonance periods rather than 1:1:

Mimas Ecc: 0.0202 per: 0.9424218 days
Tethys Ecc: 0.0001 per: 1.887802 days

Enceladus Ecc: 0.0047 per: 1.370218 days
Dione Ecc: 0.0022 per: 2.736915 days

While it may help two comparable moons to be in such near resonance
smaller moons definitely do NOT like to be in such near resonance
with larger moon neighbors.

Hence the Janus/Epimetheus pair (period = 0.6945 days) straddles
the "Kirkwood gap" resonances of its larger neighboring pairs with:

1) slightly too long a period for a 2:1 resonance with Enceladus/Dione
2 x 0.6945 days = 1.389 > 1.370218 days

2) slightly too short a period for a 4:3 resonance with Mimas/Tethys
4/3 x 0.6945 days = 0.926 < 0.9424218 days

-------------------------------------

(From Wikipedia)

<<Kirkwood gaps are gaps or dips in the distribution of main belt asteroids with semi-major axis (or equivalently their orbital period), as seen in the histogram below. They correspond to the location of orbital resonances with Jupiter:

* 1.9 AU (9:2 resonance)
* 2.06 AU (4:1 resonance)
* 2.25 AU (7:2 resonance)
* 2.33 AU (10:3 resonance)
* 2.5 AU (3:1 resonance)
* 2.71 AU (8:3 resonance)
* 2.82 AU (5:2 resonance)
* 2.95 AU (7:3 resonance)
* 3.03 AU (9:4 resonance)
* 3.075 AU (11:5 resonance)
* 3.27 AU (2:1 resonance)
* 3.47 AU (11:6 resonance)
* 3.7 AU (5:3 resonance)>>

craterchains · Post by **craterchains** » Mon Feb 11, 2008 10:16 pm

Which way does it spin, and at what rate ?

, , , or in other words, simply stated;
It is like our moon, it does not rotate to an observer on Saturn.

craterchains · Post by **craterchains** » Wed Feb 13, 2008 1:18 am

Imagine what it may have looked like before all this destruction we see? If now only 115 km would it have been larger at one time? Say about 150km ? It is thought that the big red circle is a crater and that the smaller circle represents the rebound center peaks from the blast. Now why is this tiny moon in such a perfect orbit with only 0.0098 oval shape to it's orbit? And it just so happens that Janus (0.0068), as noted by Art, is also in an incredible orbit that defies all odds. It "just happened" that these little moons ended up in such remarkably accurate orbits that they pass each other by just 60 km? After such blasts to such a small surface they should be flying all over our solar system. Go figure.

astrolabe · Post by **astrolabe** » Wed Feb 13, 2008 2:48 am

Boy, hard to believe that eons ago a coupla asteroids out of a million falling solward didn't get captured. This forum is amazing and my first one ever! Keep the great ideas afloat.

craterchains · Post by **craterchains** » Wed Feb 13, 2008 5:09 pm

Look at the eccentricity of the orbit of the Space Station, , , , , , ,

auroradude · Post by **auroradude** » Wed Feb 13, 2008 6:06 pm

Crater Chains wrote:

It is thought that the big red circle is a crater and that the smaller circle represents the rebound center peaks from the blast.

Since this is such a small body, instead of a "rebound center peak" which would imply something "liquid", could this central peak actually be caused by material from the impacting body? (It would be much like part of a snowball sticking to the side of a building while the rest blasts out radially.)

This perhaps could imply a "slow" impact as anything faster from something this size might have totally destroyed the moon.

FieryIce · Post by **FieryIce** » Sat Feb 16, 2008 4:00 pm

You are using those silly words like “snowball sticking to the side of a building” and “falling solward” when you’re overlooking the fascinating.
What are the odds of such a unique co-orbit?

Gravity Simulator, Janus and Epimetheus
Gravity Simulator link thanks to neufer.

Doum · Post by **Doum** » Sun Feb 17, 2008 6:01 pm

(emc write:Could Epimetheus be a "chunk" from a much larger source?)

Interresting. A good idea to explore.
Can they have been one bigger asteroid that have been hit with the right amoubt of force to split them apart just enough. A slow impact. May be it can explain all those moonlet in there. They seem to be made of the same composition (icy). Just curious to know. If anyone know some facts about it, please tell. Just curious. TY.

neufer · Post by **neufer** » Mon Feb 18, 2008 3:23 pm

Doum wrote:(emc write:Could Epimetheus be a "chunk" from a much larger source?)

Interesting. A good idea to explore.
Can they have been one bigger asteroid that have been hit with the right amount of force to split them apart just enough. A slow impact. May be it can explain all those moonlet in there. They seem to be made of the same composition (icy). Just curious to know. If anyone know some facts about it, please tell. Just curious. TY.

A slow impact? The momentum of, at least, a 4km comet would have been needed to separate Janus from Epimetheus in the strong gravitational well of Saturn.

Consider the neighboring "The death star" moon Mimas:
http://antwrp.gsfc.nasa.gov/apod/ap050308.html

Mimas has 4 to 5 times the linear dimensions of Epimetheus & Janus and yet was nearly split asunder itself by a (130km/15 ~) 9 kilometer comet/asteroid.

Janus/Epimetheus might have been formed during this event or Janus/Epimetheus might have resulted from a somewhat similar event at a different time in which a smaller ~140km moon WAS broken in two by a somewhat smaller (~4.5km) comet/asteroid.

FieryIce · Post by **FieryIce** » Mon Feb 18, 2008 4:04 pm

PIA09813: Epimetheus Revealed PIA07761: Cosmic Blasting Zone

Hyperion has an unusually low density and high porosity whereas Epimetheus has been described as having possibly more of a bedrock layer. I wouldn’t conclude that all those moonlets seem to be made of the same composition. But I would examine the presumed large crater with a rebound center peaks, it’s interesting to note how the size of these presumed craters match the impacted body.

neufer · Post by **neufer** » Mon Feb 18, 2008 5:35 pm

FieryIce wrote:
PIA09813: Epimetheus Revealed PIA07761: Cosmic Blasting Zone

Hyperion has an unusually low density and high porosity whereas Epimetheus has been described as having possibly more of a bedrock layer. I wouldn’t conclude that all those moonlets seem to be made of the same composition. But I would examine the presumed large crater with a rebound center peaks, it’s interesting to note how the size of these presumed craters match the impacted body.

Or, at least, match what's left of the impacted body.

Certainly an enormous shock wave went through each impacted body
and quite likely tore a large chunk off the back of it.

Epimetheus's chunk is probably Janus;

Hyperion's (250km?) chunk may have formed "Xanadu" on nearby Titan:

http://antwrp.gsfc.nasa.gov/apod/ap041028.html
http://en.wikipedia.org/wiki/Xanadu_%28Titan%29

<<Xanadu is a highly reflective area on the leading hemisphere of Saturn's moon Titan. Its name comes from Xanadu, the legendary palace described in Samuel Taylor Coleridge's poem Kubla Khan. The feature was first identified in 1994 by astronomers using the Hubble Space Telescope at infrared wavelengths, and has recently been imaged in more detail by the Cassini space probe. Xanadu is about the size of Australia. Preliminary observations indicate that Xanadu is a plateau-like region of highly reflective water ice, contrasting somewhat with the darker lower regions. These in turn seem to contrast quite sharply with the very dark maria, which were once believed to be seas of liquid hydrocarbons, but are now thought to be plains.

Recent images by Cassini during encounters in October and December 2004 reveal complex albedo patterns in the western portion of Xanadu. While scientists are still debating the significance and cause of the albedo patterns, one likely culprit is tectonism. Evidence for this exists in a pattern of criss-crossing dark lineaments near the western side of Xanadu. Scientists are also investigating the boundary between Xanadu and Shangri-la, a dark region to the west. The shape of the boundary suggests that the dark material embays the bright terrain. Radar images taken by Cassini have revealed dunes, hills, rivers and valleys present on Xanadu. The features are likely carved in ice, rather than solid ground, by liquid methane or ethane.>>

In Xanadu did Kubla Khan
A stately pleasure-dome decree :
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless CH4/C2H6 sea.

http://antwrp.gsfc.nasa.gov/apod/ap070530.html

<<What is this vast dark region on Titan? Quite possible a sea of liquid hydrocarbons. The region was imaged earlier this month when the robotic Cassini spacecraft swooped past Saturn's cloudy moon and illuminated part of it with radar. The dark region in the above image reflected little radar, an effect expected were the dark surface relatively flat, as expected for a liquid. Other indications that the vast dark area is liquid include the coastline-like topology of the brighter regions, which appear to include islands, inlets, and tributary channels. The uninterrupted smoothness of much of the dark sea may indicate that the sea runs deep, with speculation holding a depth estimate of tens of meters. A hydrocarbon sea on Titan holds particular interest for exobiologists as it might be a place where life could develop.>>

FieryIce · Post by **FieryIce** » Tue Feb 19, 2008 1:56 pm

Epimetheus's chunk is probably Janus;

Hyperion's (250km?) chunk may have formed "Xanadu" on nearby Titan:

That is a stretch.

neufer · Post by **neufer** » Tue Feb 19, 2008 2:59 pm

FieryIce wrote:
Epimetheus's chunk is probably Janus;

Hyperion's (250km?) chunk may have formed "Xanadu" on nearby Titan:
That is a stretch.

Titan's escape velocity is only 2.64 km/s so Hyperion's (250km?) chunk would have crashed at a pretty low velocity;
perhaps even slow enough to generate a continent rather than a crater.
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Drizzly Mornings On Xanadu -- Saturn's Moon Titan
http://www.sciencedaily.com/releases/20 ... 142631.htm

<<New near-infrared images from Hawaii's W. M. Keck Observatory and Chile's Very Large Telescope show for the first time a nearly global cloud cover at high elevations and, dreary as it may seem, a widespread and persistent morning drizzle of methane over the western foothills of Titan's major continent, Xanadu.

In most of the Keck and VLT images, liquid methane clouds and drizzle appear at the morning edge of Titan, the arc of the moon that has just rotated into the light of the sun.

"Titan's topography could be causing this drizzle," said Imke de Pater, UC Berkeley professor of astronomy. "The rain could be caused by processes similar to those on Earth: Moisture laden clouds pushed upslope by winds condense to form a coastal rain."

Lead author Mate Adamkovics, a UC Berkeley research astronomer, noted that only areas near Xanadu exhibited morning drizzle, and not always in the same spot. Depending on conditions, the drizzle could hit the ground or turn into a ground mist. The drizzle or mist seems to dissipate after about 10:30 a.m. local time, which, because Titan takes 16 Earth days to rotate once, is about three Earth days after sunrise.

"Maybe only Xanadu has misty mornings," he said.>>

FieryIce · Post by **FieryIce** » Tue Feb 19, 2008 3:38 pm

Until those anal science teams with thousands of images start releasing those images rather than just four out of twelve hundred then it can all just be considered supposition.

craterchains · Post by **craterchains** » Sat Feb 23, 2008 8:38 am

While, as Art said, "Hyperion's (250km?) chunk may have formed "Xanadu" on nearby Titan: " , and, "Epimetheus's chunk is probably Janus; " may sound possible, it is highly unlikely. Trajectories and orbits would not have permitted it. 8)

FieryIce says it is a "stretch", but I say it is just about the purest form of BS I have yet to hear. Or, as she calls it "supposition".

Looks down upon g-banjo's post and FOCLMFAO
Reading your thirteen posts thus far on this forum indeed proves your point of,

Most people who browse this forum have a genuine interest in what is going on out there and find your ignorant, self important garbage annoying and embarrassing.

, , , that is against yourself.

g-banjo · Post by **g-banjo** » Sat Feb 23, 2008 9:33 am

Fieryice and craterchains, if indeed you are two different people, it would be far better for you to just email each other your nonsense rather than post it here. Most people who browse this forum have a genuine interest in what is going on out there and find your ignorant, self important garbage annoying and embarrassing.

FieryIce · Post by **FieryIce** » Sat Feb 23, 2008 2:02 pm

I have only two words that apply to this forum.
Broken Arrow

neufer · Post by **neufer** » Sat Feb 23, 2008 2:31 pm

craterchains wrote:While, as Art said, "Hyperion's (250km?) chunk may have formed "Xanadu" on nearby Titan: " , and, "Epimetheus's chunk is probably Janus; " may sound possible, it is highly unlikely. Trajectories and orbits would not have permitted it. 8)

FieryIce says it is a "stretch", but I say it is just about the purest form of BS I have yet to hear.

It was an hypothesis based primarily upon your own idea that Epimetheus & Hyperion show clear evidence of moon sized impact craters.

Indeed, if the back half of the moons broke off from the impact it would have generated a return (rarefaction) shock wave that might have broken down the central crater peaks as observed on Epimetheus & Hyperion (but not on the intact Mimas).

Why would "trajectories and orbits not have permitted it"?

And what is your own scenario of the aftermath of such violent impacts?

craterchains · Post by **craterchains** » Sat Feb 23, 2008 3:53 pm

neufer wrote;

It was an hypothesis based primarily upon your own idea that Epimetheus & Hyperion show clear evidence of moon sized impact craters.

Indeed, if the back half of the moons broke off from the impact it would have generated a return (rarefaction) shock wave that might have broken down the central crater peaks as observed on Epimetheus & Hyperion (but not on the intact Mimas).

Why would "trajectories and orbits not have permitted it"?

And what is your own scenario of the aftermath of such violent impacts?

Art, you are sadly mistaken in ever assuming that I subscribe to the theory that these craters are caused by asteroids, comets, or even so called moons colliding with other so called moons. FieryIce and I, along with many others, have changed our minds about accepting such a "pat answer theory" of these craters forming by so called impactors years ago.

This is the scenario I subscribe to, and I quote from a previous post.

But speaking of theories, I find the audacity of some posters that ridiculously and ignorantly challenge some theories to be of great interest to FieryIce, myself, and many others. Why would such ones post in such a fashion? What is it they want to keep people from thinking about? Is it their fear of truth and reasonable questioning that provokes such blatant lies about evidence provided that causes them to deny such proof?

The research done concerning the theory that Concise and Systematic Crater Chains are positive evidence of alien interaction in our solar system in the past couple centuries was closed a few years ago. The losers of said War in the Heavens having been cast out of heaven and thrown down to the earth would of course have an attitude about that. Just think of the psychological blow that would have been for an intergalactic movement against it's government and the creation of the human race to have been beaten then tossed down here amongst mankind of whom they were so jealous of. Like on broken knee caps, they would deny their fall from such technological advancement and way of life, deny everything and crawl on to their soon final defeat here on earth. Sucks to be "them". Note some of the posters attitudes, quite fascinating.

Great story, you should read the bible with out the religion.

Have a nice day. Broken Arrow

Starship Asterisk*

Epimetheus (APOD 11 Feb 2008)

Epimetheus (APOD 11 Feb 2008)

How did Epimetheus form?

"Kirkwood gap" resonances