Ceres High Altitude Mapping Orbit (HAMO), Late summer through fall 2015 Options

[Bill Harris]

No problemo-- it's hard to tell who the players are. And on the "current best Ceres map" that area is near where the resolution goes from good to less-than-good and it's hard to tell. It may be some time before the maps get updated with all of the SO imagery.

I have most ("selected") of the SO images with added Feature and Annotation Overlays where I can outline the "slumpages and flowages" and Faculae (bright spots) and a couple of flavors of Lineations and plan to use the Survey images as an Index for the more detailed HAMO and LAMO imagery.

--Bill

[hendric]

The lighting is really screwing with my head. Does anyone else see the double crater in HAMO4 as a caldera, a la Olympus Mons? I get a feeling that there was a pyroclastic flow to the NW that etched the ground, giving it those lineations and making that area fuzzy.

[Bill Harris]

Yes, I have been thinking that many of these craters look quite un-impactlike. This takes us back to the early days of Lunar exploration where there was a vigorous debate on the Impact or Volcanic origin of craters.

And on the Second Day of HAMO...

--Bill

[dvandorn]

Bill, you posted that exactly as I was bringing the thread up to post the same thing. These craters may be impact-formed, but if so, the target material has far different properties from what we've seen on rocky worlds, and also far different from what we've seen on icy worlds farther out from the Sun. Some of these flows look more like they were blurped onto the surface, not thrown as ejecta or erupted as volcanic units. More like a they were vomited onto the surface.

I wonder how much difference it makes that Ceres is too close to the Sun for the exposed ices to completely resist sublimation, yet too far from the Sun for a world with so much water to be primarily rocky. We're in a different thermal environment for a watery world than we've seen before. Perhaps that's what is driving the strangeness we're seeing in the surface features.

-the other Doug

[JohnVV]

The lighting is really screwing with my head. Does anyone else see the double crater in HAMO4 as a caldera,

on that image ... No

normally if the shadows are UP or on the RIGHT the brain sees craters
if the shadow is DOWN or on the LEFT people see mounds

[Bill Harris]

For sure, Doug. This world is going to be driving planetologists bonkers for years to come. I was hesitant to stir the pot again and suggest impact or non-impact, but I kept wondering if this or that feature is a cradera or a calter.

I'm almost giddy awaiting higher rez images of the Occator Fluctae (to get in step with proper terminology)...

--Bill



ADDED: In reflection, one thing we have learnt with Comet 67P/C-G is that crater-like structures are not always caused by impact. These active pits or vents are sublimation-related features where the icy material in warmed, loses it's volatile "cementation" and erodes in a circular manner with increasing depth. An icy world like Ceres formed near the frost line would be much more prone to this than our Moon, which by virtue of it's formation process was devolatilized, or other small bodies, like Vesta, which are rocky.

--b

[TheAnt]

@MarsInMyLifetime: The "Little Prince's volcano." Cute name for the mountain. That's why I am advocating that this feature be named Saint-Exupéry, even though it seem less likely that it might be an actual volcano.

....
Now that I'm looking more carefully, I see relatively fewer small craters around the base to the North and East (12-4 o'clock), especially between the mountain and the crater (12-2 o'clock). There is obvious flow INTO the crater (11 o'clock). And to the Northwest and West, perhaps what looks like a splash or flow (11-9 o'clock).

What if the Northeastern half of the mountain lifted first? The ice (?) interior was exposed as the regolith sloughed off. By this interpretation, the Southwestern quarter of the mountain has uplifted more recently, carrying its cratered surface with it. The regolith has not yet sloughed away. I see no sign of debris flow (yet) there, around the base of the mountain (~9-4 o'clock)....

Yes I also noted that there's craters on part of the mountain slope, but not on the other sides, so yes also I wondered if it might one unusual pingu like iceplug that first tilted up on one side, and then on the other to give that appearance.
But since I am unable to even find a speculation why it should behave that way I left that idea rest here, until you now mentioned it.
So yes it's a possibility, but until someone can come up with a example of such a stepwise behaviour I will go with the idea that it is a single event that created the mountain and that we simply see crust material that happened to stick together in those positions.

.............The feature definitely continues to look strange. If the white material here was just slightly under a dusting of the grey material, why aren't we seeing it where this more rectangular edge is located? As I recall from the animations I did of this spot from the survey orbit images, the crater just south of of the rayed crater, is another uplifted mound with a large crater at the top. The craters with the white flecks always seem to have very sharply definitely edges and steep walls. I'll be very interested to see Spot 1.

I agree it is odd, unless the white material is salts, and the crack happened to contain a splinter of ice brought closer to the surface by the impact that sublimated afterwards. (This means that that crater could have more ice on adjacent sides that simply happened to have more ice that just got it lucky by being covered by more regolith / asteroid dust material - only said as one possible solution to what we're seeing here.)

[HSchirmer]

In reflection, one thing we have learnt with Comet 67P/C-G is that crater-like structures are not always caused by impact.
These active pits or vents are sublimation-related features where the icy material in warmed, loses it's volatile "cementation" and erodes in a circular manner with increasing depth.

Actually, the best analog for Ceres may be Mercury. Both have surface material near the melting/sublimation point.

Some of the Mercurian crater pits share features with Cere's odd craters,

http://messenger.jhuapl.edu/gallery/scienc...4M_RA_3_web.png

And consider the stunning images of Mercury's "hollows"
http://news.nationalgeographic.com/news/20...-space-science/

Then compare those to Habukaz's croped image of the crater-

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[Guest_Steve5304_*]

Maybe lonely mountain is an ice spike. We know ceres has liquid/slosh water below. An impactor.comes in and hits a spring and exposes it to the vacuum and low gravity of space and it freezes into this big ice mountain which is shaped so strange on its sides it has to be ice. I see lots of evidence of temporary flows on the surface and they are all adjancent to larger impactors.


https://en.m.wikipedia.org/wiki/Ice_spike

[Bill Harris]

One good reference to refresh the impact vs volcanic discussion is The Measure of the Moon, by Ralph B. Baldwin. This is one of the seminal works in planetology which shifted thought towards lunar impact processes on the 1960's and influenced views on other planets. Although Baldwin was an impact advocate, he does present both sides of the debate. It's just hard to find a volcanic crater advocate nowadays.

A review of the book of you have a Science Mag account:
http://www.sciencemag.org/content/140/3565/374.1.citation

No e-book available, but here is the Google Books page:
https://books.google.com/books/about/The_Me...id=LZMHAgAACAAJ

Ceres will prove to be a worthwhile world and will bring about some major changes in thought about impact processes.

--Bill

[dvandorn]

Yes -- Both Spudis and Wilhelms (two of my favorite lunar science authors) give kudos to Baldwin. And wasn't it Baldwin who, after holding stubbornly to other theories for a time, finally pronounced Barringer Crater an impact feature?

I completely agree, Baldwin is seminal for impact theory. And much of the later work, from many people including the above-mentioned, has expanded on the dynamics of ejecta formation and re-emplacement, shock effects on the impact targets, and development and emplacement of impact melt sheets on rocky bodies and also on hydrated rocky bodies like Earth and Mars. And on the propagation of energy into the impact target, something I think is key to the festures we're seeing on Ceres. I think a lot of the cryovolcanism we're seeing might be the result of impact-generated temporary heating and agitation of Ceres' icy mantle (or perhaps subsurface ocean/convecting warm ice mantle), causing sudden movement and eruption of subsurface materials.

It appears that there has also been ejecta splash resurfacing going on around the larger basin-forming impacts. And the large, extremely relaxed basins we see wouldn't just have relaxed like that immediately -- the impacts would have moved and displaced a lot of the material around and below the impact site, which would have pushed back in (and up) to raise the basin floors back up. That movement would affect the entire mantle in one way or another, and I bet it would cause cryovolcanic processes and features.

Of course, all of this assumes that Ceres has some kind of either liquid or convecting warm ice mantle, and makes some assumptions about how globally contiguous of a unit it is. I'd be interested to see if some of the first papers to come out on Ceres from the Dawn data will deal with the qualities of the mantle deduced from the imagery and the spectroscopy...

-the other Doug

[Bill Harris]

Even the crustal morphology of Ceres will prove to be engimatic.

By the Survey Orbit, Elevation maps were developed and they told a strange story. Ceres has a significant elevation relief of +/-- 7.5 Km around a zero datum. And it seems to be more relief than can be accounted for with a warm-ish icy crust without sagging down or up, back to the datum. But look at the distribution of elevations-- the highland areas are several discrete continents with the abyssal plains in between. Intuitively it would seem that the continental highlands are a low density, thick icy material floating isostatically on the higher density silicates of the upper mantle with the abyssal plains created by relict large impact craters. This is just arm-waving, and we'll learn more from upcoming gravity surveys and determination of the composition of the crust.

By terrestrial analogy, these are granitic crustal blocks bobbing about in basaltic ocean basins.

Illustrations:

A geomorphology map of Ceres showing surface features and continents and abysses:
https://univ.smugmug.com/Dawn-Mission/Ceres...geomorph-v1.jpg

Elevation map, cylindrical projection:
http://photojournal.jpl.nasa.gov/catalog/PIA19606

Elevation map, hemispherical projection:
http://photojournal.jpl.nasa.gov/catalog/PIA19607

Global animation:
http://photojournal.jpl.nasa.gov/catalog/PIA19605

Be thinking about the distribution of surface features on these two crustal provinces.

--Bill

[Bill Harris]

A montage of SO and HAMO images of "Tall Mountain"

https://univ.smugmug.com/Dawn-Mission/Ceres...n_montage.png

--Bill

[Herobrine]

The terrain next to the young crater in today's HAMO release is some of the strangest I've seen on Ceres to date. I don't really know what to make of it.

It's times like these that I wish I'd paid more attention to the moons of the gas giants so I might have something to compare it to.

From http://photojournal.jpl.nasa.gov/catalog/PIA19882

[Habukaz]

The interior of the crater looks rather interesting, too. The bright streaks running down the crater walls, and patches of smooth(er) floor terrain. Guess it's a relatively young crater.