Saturn's Hyperion: A Moon with Odd Craters (2009 Jan 18)

[aristarchusinexile]

Neufer, how canst thou knoweth so mucheth of so many different thingseth!?

Being old with internet access helps a lot.

But simply knowing does not not always equate with understanding.

It must be the internet access .. you have far too much energy to be old.

[Alex]

RE: NASA APOD image of January 18, 2009 - Saturn's Hyperion: 'A Moon with Odd Craters' may be a spent comet. My conjecture is that Hyperion is the remnant of a comet captured by Saturn. The capture drew Hyperion into an orbit near Titan. Hyperion resembles a burnt-out clinker. The 'craters' of Hyperion suggest ebullient outgassing. Unlike typical impact craters, those on Hyperion are conical and exhibit a clear funnel-like shape. There's also evidence of a smaller compact spherical core deep inside Hyperion (just possibly an optical illusion). If there were two such denser cores, arranged like dumbbells, they could account for Hyperion's erratic rotation. Its very low density supports the notion that Hyperion is riddled with caverns and also my conjecture that it originally housed volatile matter that was heated and expelled during it's tenure as a sun-circling comet. In my Google search, I've not yet found a similar official explanation for Hyperion. I'm glad to see that APOD Forum participant Orin Stepanek on Sunday, January 18, 2009, and ‘Ruidh’ on Monday, October 03, 2005, agree with my theory: Orin wrote, “I think what were seeing is a captured comet.” Ruidh wrote, “It looks like a spent comet nucleus that was captured by Saturn.” A number of previous Forum participants dating back to 2005 agree with the ‘spent comet’ idea. It looks like NASA has an excellent spent comet specimen to examine in detail. The appearance of Hyperion can probably be duplicated in a laboratory to verify the spent comet clinker conjecture. Alex Vary

[neufer]

RE: NASA APOD image of January 18, 2009 - Saturn's Hyperion: 'A Moon with Odd Craters' may be a spent comet. My conjecture is that Hyperion is the remnant of a comet captured by Saturn. The capture drew Hyperion into an orbit near Titan. Hyperion resembles a burnt-out clinker. The 'craters' of Hyperion suggest ebullient outgassing. Unlike typical impact craters, those on Hyperion are conical and exhibit a clear funnel-like shape. There's also evidence of a smaller compact spherical core deep inside Hyperion (just possibly an optical illusion). If there were two such denser cores, arranged like dumbbells, they could account for Hyperion's erratic rotation. Its very low density supports the notion that Hyperion is riddled with caverns and also my conjecture that it originally housed volatile matter that was heated and expelled during it's tenure as a sun-circling comet. In my Google search, I've not yet found a similar official explanation for Hyperion. I'm glad to see that APOD Forum participant Orin Stepanek on Sunday, January 18, 2009, and ‘Ruidh’ on Monday, October 03, 2005, agree with my theory: Orin wrote, “I think what were seeing is a captured comet.” Ruidh wrote, “It looks like a spent comet nucleus that was captured by Saturn.” A number of previous Forum participants dating back to 2005 agree with the ‘spent comet’ idea. It looks like NASA has an excellent spent comet specimen to examine in detail. The appearance of Hyperion can probably be duplicated in a laboratory to verify the spent comet clinker conjecture. Alex Vary

Two problems with Hyperion = captured cometary nuclei:

• 1) No known cometary nuclei looks like Hyperion.
  2) Cometary nuclei (~ 10 km) are normally much smaller than Hyperion (360×280×225 km).

More likely Hyperion was a CENTAUR like 2060 Chiron:
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<<2060 Chiron (Greek: Χείρων) is a planetoid in the outer Solar System. Discovered in 1977 by Charles T. Kowal (precovery images have been found as far back as 1895), it was the first known member of a new class of objects now known as centaurs, with an orbit between those of Saturn & Uranus. Although it was initially classified as an asteroid, it was later found to exhibit behaviour typical of a comet. Today it is classified as both, and accordingly it is also known by the cometary designation 95P/Chiron.

Data from the Spitzer Space Telescope in 2007 suggests that Chiron is 233 ± 14 km in diameter.

In February 1988, at 12 AU from the Sun, Chiron brightened by 75 percent. This is behaviour typical of comets but not asteroids. Further observations in April 1989 showed that Chiron had developed a cometary coma, and a tail was detected in 1993.

Chiron is officially designated as both a comet and an asteroid, an indication of the sometimes fuzzy dividing line between the two classes of object. The term proto-comet has also been used. Being at least 130 km in diameter, it is unusually large for a comet nucleus. Chiron differs from other comets in that water is not a major component of its coma, because it is too far from the sun for water to sublimate.

Chiron's orbit was found to be highly eccentric (0.37), with perihelion just inside the orbit of Saturn and aphelion just outside the perihelion of Uranus. According to the program Solex, Chiron's closest approach to Saturn in modern times was in May 720, at just under 30 Gm. During this passage Saturn's gravity caused Chiron's semi-major axis to decrease from 14.4AU to 13.7AU. Centaurs are not in stable orbits and over millions of years will eventually be removed by gravitational perturbation by the giant planets, moving to different orbits or leaving the solar system altogether. Chiron is probably a refugee from the Kuiper belt.>>

• Hyperion: Titan associated with the sun
  Phoebe: Titan associated with the moon

Explanation: <<Was Saturn's moon Phoebe once a comet? Images from the robotic Cassini spacecraft taken two years ago when entering the neighborhood of Saturn indicate that Phoebe may have originated in the outer Solar System. Phoebe's irregular surface, retrograde orbit, unusually dark surface, assortment of large and small craters, and low average density appear consistent with the hypothesis that Phoebe was once part of the Kuiper belt of icy comets beyond Neptune before being captured by Saturn. The image was taken from around 30,000 kilometers out from this 200-kilometer diameter moon.>>

http://antwrp.gsfc.nasa.gov/apod/ap040710.html
http://antwrp.gsfc.nasa.gov/apod/ap001103.html
http://en.wikipedia.org/wiki/Phoebe_(moon)

<<Cassini-Huygens indicates that Phoebe's craters show a considerable variation in brightness, which indicate the presence of large quantities of ice below a relatively thin blanket of dark surface deposits some 300 to 500 metres (980 to 1,600 feet) thick. In addition, quantities of carbon dioxide have been detected on the surface, a finding which has never been replicated on an asteroid. It is estimated that Phoebe is about 50% rock, as opposed to the 35% or so that typifies Saturn's inner moons. For these reasons, scientists are coming to believe that Phoebe is in fact a captured Centaur (planetoid)>>

[Alex]

Re: Saturn's Hyperion: A Spent Comet?

Postby neufer on Wed Apr 29, 2009 2:41 pm
Two problems with Hyperion = captured cometary nuclei:
1) No known cometary nuclei looks like Hyperion.
2) Cometary nuclei (~ 10 km) are normally much smaller than Hyperion (360×280×225 km).

Response by Alex on Sunday May 3, 2009 10:45 pm
1) No spent comet nuclei have been cataloged to claim Hyperion is atypical.
2) EKO's (Edgeworth-Kuiper Belt objects) and Centaur comet sizes range to 200 km.

Reference: Comet Size Distributions and Distant Activity, Meech, Karen J.; Hainaut, Olivier R.; Marsden, Brian G., Minor Bodies in the Outer Solar System: Proceedings of the ESO Workshop Held at Garching, Germany, 2-5 November 1998, ESO ASTROPHYSICS SYMPOSIA. ISBN 3-540-41152-6. Edited by A. Fitzsimmons, D. Jewitt, and R.M. West. Springer-Verlag, 2000, p. 75

[neufer]

Re: Saturn's Hyperion: A Spent Comet?

Postby neufer on Wed Apr 29, 2009 2:41 pm
Two problems with Hyperion = captured cometary nuclei:
1) No known cometary nuclei looks like Hyperion.
2) Cometary nuclei (~ 10 km) are normally much smaller than Hyperion (360×280×225 km).

Response by Alex on Sunday May 3, 2009 10:45 pm
1) No spent comet nuclei have been cataloged to claim Hyperion is atypical.
2) EKO's (Edgeworth-Kuiper Belt objects) and Centaur comet sizes range to 200 km.

Well, I thought I WAS arguing that Phoebe & Hyperion were captured Centaurs;
however, I don't consider Centaurs to be "comets" in the normal sense.

What exactly do you mean by "Spent Comet" ... an old non-functioning comet
that has trekked off to the cometary graveyard around Saturn to die?

[Chris Peterson]

What exactly do you mean by "Spent Comet" ... an old non-functioning comet
that has trekked off to the cometary graveyard around Saturn to die?

I agree with you that this moon is far too large to be considered a "comet" by the usual definitions. That doesn't mean it can't be a captured body from the outer system, of course.

There are "spent comets", and they are physically difficult to distinguish from asteroids. A "spent comet" is one which has traveled enough times through the inner system to lose all its volatile material (ices). Clearly, Hyperion does not meet this description. If it is going to be discussed as a captured icy body that has, in its history, made one or more trips near the Sun, some term other than "spent" should be adopted.

[Alex]

What exactly do you mean by "Spent Comet" ...

Chris Peterson relplied:

There are "spent comets", and they are physically difficult to distinguish from asteroids. A "spent comet" is one which has traveled enough times through the inner system to lose all its volatile material (ices). Clearly, Hyperion does not meet this description. If it is going to be discussed as a captured icy body that has, in its history, made one or more trips near the Sun, some term other than "spent" should be adopted.

The term that came to mind when I first studied the Hyperion image is 'clinker' as in mass of vitrified material ejected from a volcano or fused non-combustible matter left over from burnt coal (such as I emptied from my dad's furnace back in the 1940's). Of course, the concept may just be a clinker as in a wrong note in a musical performance.

Alex