Hyperion; Destroyed Moon? (APOD 27 Jan 2007)

[iamlucky13]

I think yer right there BMA.

And it is not shadows causing the black on the bottoms, that is for sure.

Norval

Indeed. I was mostly paying attention to the apparent angles of the craters when I posted that image, but as I took another look, the dark bottoms are very striking.

It appears the mosaic has been contrast-enhanced to de-emphasize shadows and emphasize the darkness of the low-lying areas.

[BMAONE23]

If it were a captured comet, it might be possible that the dark material is true "Black Ice".

[aichip]

Quite a while back we did this discussion on Hyperion and I put a couple of ideas out that to me, seem more likely than ever.

I get the impression looking at these craters (and the closeup shots) that the material is mostly ice with some other materials (perhaps methane and ammonia, easily outgassed). The darker material is possibly carbon or some other organic material, perhaps tholin.

Heat from the Sun causes the dark material to vaporize the surrounding material, causing the craters to deepen. As the material vaporizes, the darker matter (which is probably dusty or like soil) settles into the bottom, further enhancing the cone shape through further heating.

The rounded look would be because the thinnest portions would sublimate or evaporate more readily, by absorbing heat more easily. The craters all point to the center of mass, regardless of the oblong shape of the moon. This is the source of the spongelike appearance.

So some darker soil-like or dust like material is absorbing solar heat, vaporizing the material, forming cone-like craters, which point to the core of the moon. As gas evolves, the dust blows outward, only to settle back in sloping craters that continue to shape themselves.

Comments?

[FieryIce]

Fascinating Aichip. If this were true then with even the popping of a bubble of material on Hyperion the particles would achieve escape velocity from its miniscule gravity and we would see a halo of particles around and from Hyperion. Wouldn’t you think? Comments?

[aichip]

Actually, since we observe that the materal from the craters has in fact been removed, and that the dark material is still in the bottoms, we can more or less dismiss that idea. Remember that we have two gravity wells to take into account- one is that of Hyperion itself, and the other is of Saturn.

Material that might escape from Hyperion will end up in an orbit that is nearly identical to that of the moon, and will eventually fall back to its surface. That, in my opinion, is one of the mechanisms that helps preserve Titan's atmosphere as well.

We see a torus of material that falls within each moon's orbit, and that can also be seen for Io as well- a torus of sulfur and sodium that constantly escapes and then is recaptured by the moon.

But I would not expect to see any bubbles at all. For that, we would need liquid material.

[craterchains]

It would seem highly dubious at best that the sun could provide enough heat to cause these craters in Hyperion's current orbit.

Norval

[bystander]

It would seem highly dubious at best that the sun could provide enough heat to cause these craters in Hyperion's current orbit.

Could gravitational stress from Saturn provide enough heat for outgassing?

[aichip]

While Hyperion is almost as close to Saturn as Titan is (1.48 million km vs. 1.22 million km), it is very small as therefore experiences far less tidal force. Titan is about 5,000 times as massive as Hyperion and presents a much larger and much more extended body to be flexed. Hyperion is much more rigid due to its smaller size.

Notice that methane from Titan might be stripped of hydrogen by solar ultraviolet over time and make its way to Hyperion as carbon dust. This would explain the dark material in the crater floors. The carbon would be like a nanophase powder and extremely fine. So Titan's gas torus could be supplying the material that helps to create the pits and craters there.

It is true that very little heating occurs on Hyperion, but consider that what is present is sufficient to drive the weather on Saturn and on Titan. Heat is relative in this context, since there is definitely erosion and weathering on Titan, and if there were no heat present we would see a solidified atmosphere, not a rich system of clouds, lake beds, and river channels. That little bit of heat over geological periods of time could be more than sufficient to drive the outgassing from dark pits lined with carbon dust.

At a distance of about 9.5 AU, Saturn receives only 1.1% of the sunlight we do on Earth, meaning that the energy density of sunlight would be on average about 15 watts per square meter. As cold as it is, this would be enough to heat carbon black to the point where even water ice would sublimate away beneath it. Mathematically, it works.

[craterchains]

Taking into concideration the sublimation of water ice on Mars, you may want to redo the math for such a process on Hyperion.

Norval

[aichip]

Why? Hyperion is in vacuum, Mars is not. Mars' atmosphere stays near 100% relative humidity almost all the time. Big difference.

[starnut]

Nah, you are all wrong. It is what is left of a nest of giant paper wasps, the pesky kind that you find under the eaves or porch of your house. Someone on Saturn knocked it off with a baseball bat (see the indentation that looks like a crater) and sent it into space.

[aichip]

Let's look at the way the dark material is located in the bottoms of the craters. Two forces get it there, and they're simple ones.

Anyone who has handled dry ice knows what happens when a room temperature metal implement is placed on it- rapid sublimation and production of gas beneath the implement. The result is that the surface of the dry ice becomes literally frictionless. Released gas causes two phenomena of note. First, the friction of the surface becomes literally nonexistent. Second, the gas causes the implement to "sing" as it vibrates rapidly on the dry ice.

Any material that sublimates will exhibit this phenomenon if the rate of sublimation is great when compared to the forces present, such as gravitation. The weight of the implement is what forces it against the dry ice (or other sublimant). The exhausting gas works against it and creates the singing noise.

On Hyperion, the gravitational field is exceptionally weak; about what you would find on an asteroid. As a result, sublimation will create enough "thrust" under the dark grains of material to lift them off the surface a few microns, just enough to remove their friction. This means that the weak gravity will be enough to pull them "downhill" into the craters where they will settle.

So a combination of sublimation gas from ice or other volatiles, and the gravity field of Hyperion, will result in the dark material slipping down into the bottoms of the craters. This also keeps it from piling up, since the grains cannot easily move over other grains that are in crater bottoms. They do not outgas, and therefore do not provide the frictionless surface that the sublimant will.

[craterchains]

Aichip

Yer so full of , , information.

Care to post the known surface temperatures of Hyperion?

Norval

[aichip]

Hyperion appears to have a surface temperature of about 90K or roughly -300 below F. Water ice stops sublimating away usually right at 166K or lower, and the energy of sunlight on the dust particles would only have to raise it 76K or a little more to make sublimation start under the dark particles.

[craterchains]

Well, it was an idea about sublimation, just not a working one under these conditions. But, it was an possibility, although not very probable.

Norval

[aichip]

Why would this not be a "working idea"? We have dark material that strongly absorbs light, we have material that can sublimate, we have all craters aimed at the center of mass...

Note that Hyperion, unlike other Saturnian moons, does not keep one face to the planet all the time. It is influenced by the gravity field of Titan and so it rotates in a resonant manner. Sunlight strikes all its surface over time. I would be very interested in why you think this is not a valid idea. And try to express it in numbers if you can. Thanks.

[craterchains]

Your numbers worked for me.

It is a possibility, just not very probable I would say.

I think there are much more probable forces that did the "damage".

Norval

[aichip]

Odd that you should refer to craters as "damage" when they appear to be a natural part of nearly any body. Could you be more specific about your idea of cause? References would be good.

[craterchains]

, , , all you have to do is to click on my APOD Bio link below.

Nuff said.

Norval

[aichip]

Okay, so I see a little about your beliefs, but I see nothing very clear about why you think of craters as damage rather than a natural part of what we see. We have observed impacts in the past, we have laboratory equipment that duplicates the processes involved in crater formation, and we can see (in craters here on Earth) the remains of bodies that have caused them, such as the Sudbury impact and the nickle mines that are in the remains of an ancient asteroid there.

So, just to be specific, what has this to do with Hyperion, or any other moon for that matter? Keep in mind that so far, we can at least see material that will absorb sunlight and promote sublimation, and that the unusual shapes of the craters there are rather unlike the craters on the Moon, Earth, Mars, or other bodies. What sort of parallel or connection do you believe exists?

[craterchains]

What part of;

", , , all you have to do is to click on my APOD Bio link below.

Nuff said.

Norval"

, , didn't you understand?

Norval

[aichip]

I read your bio, I saw a summary of your beliefs, and I do not see anything that even remotely touches on craters on Hyperion. You need to be very clear about your theory. Say something definite and understandable. I do not know you, and I have no experience with your opinions.

My summary is simple- the material Hyperion is made of can sublimate away, and the presence of dark material, possibly carbon or some other substance, is absorbing sunlight and causing sublimation. The weak gravitational field and the sublimation outgassing can explain the presence and appearance of the craters.

The ball is in your court.