Dawn dead in Ceres orbit, ran out of fuel Oct 2018

[Janus]

The elevation map above inspired me.

First, here it is converted into a 3-D relief map:

And here I used it to create a rotating model of Ceres:

 

[OmCheeto]

The elevation map above inspired me.

First, here it is converted into a 3-D relief map:

And here I used it to create a rotating model of Ceres:

Sometimes, I get the feeling that NASA is stealing ideas from this thread...

Just released:

Fly Over Dwarf Planet Ceres
NASA Jet Propulsion Laboratory​

Published on Jun 8, 2015
A new video animation of dwarf planet Ceres, based on images taken by NASA's Dawn spacecraft , provides dramatic flyover views of this heavily cratered, mysterious world. The images come from Dawn's first mapping orbit at Ceres, at an altitude of 8,400 mile (13,600 kilometers), as well as navigational images taken from 3,200 miles (5,100 kilometers) away. The images provided information for a three-dimensional terrain model. The vertical dimension has been exaggerated by a factor of two, and a star field has been added in the background.
Category Science & Technology
License Standard YouTube License

 

[OmCheeto]

NASA's Dawn Mission ‏@NASA_Dawn 27 minutes ago
(2/2) A: Just started taking images in my new orbit. The team will share a new view of the bright spots soon. Stay tuned!

Yay!

hmmm... Actually, I'm more interested in the washed out slightly brighter than average spots now.

Argh...

 

[marcus]

The Fly-over digital animation YouTube is beautiful! "We used a three-dimensional terrain model that we had produced based on the images acquired so far," said Dawn team member Ralf Jaumann of the German Aerospace Center (DLR), in Berlin. "They will become increasingly detailed as the mission progresses -- with each additional orbit bringing us closer to the surface."

It looks just like cinematography, as if photographed. Was constructedl using 80 overlapping photos taken at 13500 and 5100 km.
having photos overlap, and digitized allows one to build a 3D digital model of the planet surface. (like stereo, basically using trig)
then from the digital model of the terrain they were able to reconstruct an image of the rotating landscape that looks completely natural.

Interestingly, they exaggerated the vertical scale by a factor of 2 so ridges twice as high, craters twice as deep. So you get a more vivid sense of the terrain.
Thanks for the link, OM!

 

[Janus]

Here I combined the relief map with the rotating globe to high light the elevation differences. it goes from blue-green for the lowest elevations to orange fro the highest elevations. I also shifted the lighting so more of the globe is lit, but you still get the shadow effect at the terminator.

 

[OmCheeto]

I'm afraid that I don't have the patience to be a scientist...

Another person on Facebook; "When will the first natural color photo of Ceres release?"

Me; "Ceres is about as colorful as Earth's moon."

 

[marcus]

You point out the need for patience, OM. For me this applies to the the infrared spectra. Because they should reveal things about the chemical composition.

I am not so impatient to see more detailed beautiful pictures of what the surface looks like to the human eye.
The human eye is a fairly limited instrument. I'm impatient to see reports interpreting the IR instrument readings. What IR wavelengths stand out? What elements and compounds do they signify?

The planetary imagery is not causing me so much suspense (though it will eventually yield answers about geological history.) What I'm wondering about are things like "how good are Dawn's instruments?" "how close does the probe have to get, to be able to tell anything?"
"how long do we have to wait before we hear some readings of the spectra? the really close orbit is not until December!"

And Marc Rayman, whether inadvertently or not, created more impatience by mentioning the IR instrument readings in the recent status report:
==quote http://dawn.jpl.nasa.gov/mission/status.html ==

June 8, 2015 - Dawn Conducts First Observations in New Science Phase

Dawn photographed Ceres and measured its spectrum in infrared and visible wavelengths as it orbited over the illuminated side on June 5 and 6. All measurements were completed as planned. When its orbit took to the night side again, the spacecraft pointed its main antenna to Earth and transmitted its findings.

Later this morning it will travel back to the day side and begin its second set of observations.
==endquote==

 

[OmCheeto]

You point out the need for patience, OM. For me this applies to the the infrared spectra. Because they should reveal things about the chemical composition.

I'm in no hurry. I keep thinking about how you've followed the mission from before it even lifted off, an tell myself to shut up.

I am not so impatient to see more detailed beautiful pictures of what the surface looks like to the human eye.
The human eye is a fairly limited instrument.

In some ways. In other ways, it is really incredible. From the "Why are there no stars?" question, it struck me as peculiar, that we can look up at the sky, and see the moon and stars, and the moon isn't super-saturated. Why is that? Drakkith and mfb posted some answers in a "Photons striking a camera sensor?" thread, but I couldn't figure out the answer.

I'm impatient to see reports interpreting the IR instrument readings. What IR wavelengths stand out? What elements and compounds do they signify?

The planetary imagery is not causing me so much suspense (though it will eventually yield answers about geological history.) What I'm wondering about are things like "how good are Dawn's instruments?" "how close does the probe have to get, to be able to tell anything?"
"how long do we have to wait before we hear some readings of the spectra? the really close orbit is not until December!"

And Marc Rayman, whether inadvertently or not, created more impatience by mentioning the IR instrument readings in the recent status report:
==quote http://dawn.jpl.nasa.gov/mission/status.html ==

June 8, 2015 - Dawn Conducts First Observations in New Science Phase

Dawn photographed Ceres and measured its spectrum in infrared and visible wavelengths as it orbited over the illuminated side on June 5 and 6. All measurements were completed as planned. When its orbit took to the night side again, the spacecraft pointed its main antenna to Earth and transmitted its findings.

Later this morning it will travel back to the day side and begin its second set of observations.
==endquote==

I don't know when it was, that I first thought; "Wouldn't it be cool if we could see the entire E-M spectrum!".
Of course, technology is doing that for us.

ps. There was another post today. I wonder if it is Dr. Rayman directing this ever increasing; "Let's put new posts in as many different places as possible, as Om is getting bored, and obviously likes a challenge".

Bright Spots Shine in Newest Dawn Ceres Images
June 10, 2015
...
The region with the brightest spots is in a crater about 55 miles (90 kilometers) across. The spots consist of many individual bright points of differing sizes, with a central cluster. So far, scientists have found no obvious explanation for their observed locations or brightness levels.

"The bright spots in this configuration make Ceres unique from anything we've seen before in the solar system. The science team is working to understand their source. Reflection from ice is the leading candidate in my mind, but the team continues to consider alternate possibilities, such as salt. With closer views from the new orbit and multiple view angles, we soon will be better able to determine the nature of this enigmatic phenomenon," said Chris Russell, principal investigator for the Dawn mission based at the University of California, Los Angeles.
...

 

[mfb]

In some ways. In other ways, it is really incredible. From the "Why are there no stars?" question, it struck me as peculiar, that we can look up at the sky, and see the moon and stars, and the moon isn't super-saturated. Why is that? Drakkith and mfb posted some answers in a "Photons striking a camera sensor?" thread, but I couldn't figure out the answer.

The reaction of human eyes is also highly nonlinear. A camera needs tricks like multiple images with different exposure times to get the same range.

 

[marcus]

Om thanks for spotting that. The picture of the bright spots is considerably sharper and shows more detail than I had see before. I can understand Chris Russell guessing that the spots are reflection from ice.

Bright Spots Shine in Newest Dawn Ceres Images
June 10, 2015
...
The region with the brightest spots is in a crater about 55 miles (90 kilometers) across. The spots consist of many individual bright points of differing sizes, with a central cluster. So far, scientists have found no obvious explanation for their observed locations or brightness levels.

"The bright spots in this configuration make Ceres unique from anything we've seen before in the solar system. The science team is working to understand their source. Reflection from ice is the leading candidate in my mind, but the team continues to consider alternate possibilities, such as salt. With closer views from the new orbit and multiple view angles, we soon will be better able to determine the nature of this enigmatic phenomenon," said Chris Russell, principal investigator for the Dawn mission based at the University of California, Los Angeles.
...

http://dawn.jpl.nasa.gov/news/news-detail.html?id=4619

If the spots are small ice-fields somehow pushed up from within then that seems even more interesting than that they might be dry salt flats. There are a remarkable number of them in just that one crater.
I see about 8 small separate speckles besides the two larger splotches.

 

[OmCheeto]

Om thanks for spotting that. The picture of the bright spots is considerably sharper and shows more detail than I had see before. I can understand Chris Russell guessing that the spots are reflection from ice.
http://dawn.jpl.nasa.gov/news/news-detail.html?id=4619

If the spots are small ice-fields somehow pushed up from within then that seems even more interesting than that they might be dry salt flats. There are a remarkable number of them in just that one crater.
I see about 8 small separate speckles besides the two larger splotches.

I'm now leaning towards salt flats...

...

Ok. I don't really care which it is. This is just freakin' fun!

 

[OmCheeto]

A few new images were posted yesterday:

Ceres' Southern Hemisphere in Survey

A large crater in the southern hemisphere of dwarf planet Ceres is seen in this image taken by NASA's Dawn spacecraft on June 6, 2015. This image shows many different surface structures associated with impacts.
This is among the first snapshots from Dawn's second mapping orbit, which is 2,700 miles (4,400 kilometers) in altitude. The resolution is 1,400 feet (410 meters) per pixel.
​

Ceres' Northern Hemisphere in Survey

...image taken by NASA's Dawn spacecraft on June 6, 2015​

VIR Image of Ceres, May 2015

Images from Dawn's visible and infrared mapping spectrometer (VIR) show a portion of Ceres' cratered northern hemisphere, taken on May 16, 2015. From top to bottom, the views include a black-and-white image, a true-color view and a temperature image. The true-color view contains reddish dots that are image artifacts, which are not part of Ceres' surface.
These images were taken at a distance of 4,500 miles (7,300 kilometers) from Ceres. They have a resolution of 1.1 miles (1.8 kilometers) per pixel.
The temperature image is derived from data in the infrared light range. The lightest areas are the hottest and the darkest are the coolest.​

 

[Dotini]

A few new images were posted yesterday:

Ceres' Southern Hemisphere in Survey

By casual inspection, the northern hemisphere seems to differ markedly from the southern hemisphere. I believe Mars and Vesta share this characteristic.

 

[mfb]

Craters all the way down.

The illumination seems to be different for the two images, so I would be careful with comparisons.

 

[OmCheeto]

The two upper pictures I posted this morning were from an altitude of 4400 km.
The other day I determined that the framing cameras wouldn't have full Ceres filling images until it was down to 3400 km.
Did I screw up my maths again, or are these cropped pictures? [I screwed up the maths]

[edit: corrected!]

Field of vision     5.5°    vertical & horizontal (θ)
1/2 Field of vision 0.048 radians
distance            6800    km
1/2 field            327    km   tan(θ) * distance
full field           653    km
1/2 diagonal         462    km   √ (2 * half field^2)
full diagonal        924    km
polar diameter       891    km   96% of full diagonal
equatorial diam      963    km   104% of full diagonal

hmmm...

6/6/2015 images
0.410    km/pixel
1024     pixels h&v
419.84   km h&v captured
927      km (Ceres average diameter)

It would appear that my previous calculations were off.
I will stop any further attempts at doing math.

I came up with 0.413 km/pixel for an altitude of 4400 km, so I'm sticking with my new numbers.

 

[OmCheeto]

More confusion. Dr. Rayman responded to my last email that I sent him:

June 4, 2015
Hi Marc,
...
As I suspected, everyone [here at PF] looked at the elliptical orbital graph you sent last time, and said it was “obvious”. I was of course, totally confused, as always.

[Om]

ps. I’ve started another argument, on Twitter this time……..

Peter Fries ‏@Peter_Fries Jun 2
@NASA_Dawn @b0yle Does Dawn have the capability to send back 'natural color' images?

NASA's Dawn Mission ‏@NASA_Dawn Jun 2
@Peter_Fries @b0yle yes, I can take data with which to make color images, but the team has not yet released any yet

OmCheeto 17 minutes ago
@NASA_Dawn @Peter_Fries @ridingrobots @b0yle I'm confused. http://blogs.egu.eu/geolog/2015/04/15/findings-from-nasas-dawn-mission-shed-new-light-on-ceres/ …​

June 12, 2015
Hi [Om],

I didn’t mean to confuse you with my plot. Never hesitate to let me know if I send you something unclear or unhelpful.

The image you refer to in your Twitter exchange is not natural color but rather false color. Dawn not only has the capability to take natural color images, but we released them for Vesta. So far, the only one we have released for Ceres is here but both the science camera and the visible mapping spectrometer can do this. It’s a surprisingly difficult process, however. Human vision is complex, and making natural color images is a little tricky. Still, we surely will release more.

Marc

I have just informed Marc that it is fortunate for him, that I am surrounded by the smartest people in the universe, here at PF.
I also asked for clarification on his response:

When you say the image is “false color”, do you mean the colors aren’t real, or are they real, but just over-saturated?

 

[OmCheeto]

For the record, I warned him, to not continue, to correspond with me...

Hi [Om],

On Dawn (and in general) false color does not mean oversaturated. Rather, certain wavelengths in the original data are assigned different (you could even say false) wavelengths in the picture. As an example, you might have data on a scene in near ultraviolet, red, and infrared. We can’t even see the first and last of those, so it would look black to us. But we can synthesize an image in which we assign the near ultraviolet data to, say, blue. That’s false, and in fact the real scene might look different in blue light, because the materials reflecting the light have different optical properties in blue light from ultraviolet light. Similarly, the other wavelengths may be given different colors. That’s OK. We label it as false color and never pretend it is anything else. We might assign the actual red wavelengths to green and the infrared wavelengths to red. So, now we have views in blue, green, and red, and we can construct a picture from that. It’s colorful, but it’s false color.

Some observations may be conducted at wavelengths that have special meaning. In astronomy, for example, one might measure the wavelength at which certain interesting atomic species emit radiation. It might be near the visible or it might even be far away. It could be gamma ray, X-ray, UV, IR, microwave, etc. Measure several of those, put them together with false color, and it’s a convenient method to see where the action is that you’re interested in.

It can be more complicated. Sometimes the false colors don’t correspond to any wavelength range in the original scene. The choice of the colors is usually meant to help our eyes pick our salient features. In some cases, it is more powerful to assign ratios of colors in the original data to individual colors in the final image. (Ratios of reflectivity at different wavelengths can be very diagnostic of certain mineral types.) So, for example, you might take the ratio of infrared to green and assign that to blue. If the ratio is high (much more IR than green light reflected from the object), it would be bright blue. If the ratio is low, it would be dark blue.

In all these cases, it is the underlying quantitative data that tell the real story, but the false color images help guide us to the interesting places. As visual creatures, such imagery can be very useful.

I hope that’s helpful.

If I had more time, I might enjoy the physics forum. I have wide ranging interests. All my degrees are in physics, and I greatly enjoy cosmology, astrophysics, particle physics, laser and atomic physics, relativity, and more. Working on a planetary mission is great fun, but my principal scientific interests lie elsewhere. Alas, Dawn keeps me much too busy to follow any popular discussions, much as I enjoy communicating with the public and sharing interesting ideas.

Marc

I don't know about you all, but I have the best pen pal in the world.

 

[OmCheeto]

But then, I yelled at him;

in the future, instead of using the term; “enhanced colour view”, could you say; “trans-human compressed electromagnetic spectrum view”.​

I have no idea why he continues to correspond...

 

[OmCheeto]

The reaction of human eyes is also highly nonlinear. A camera needs tricks like multiple images with different exposure times to get the same range.

After 7 days of study, I think I've figured it out. At the most basic of levels, of course.
I had to re-read Dr. Rayman's last email at least 5 times before I could understand what he was trying to get across.
Unfortunately, I responded after reading it only once.
But fortunately, after re-reading my response, it appears that I did not let on that I didn't really fully understand what he was saying.

I also re-read Drakkith's response in the CCD thread, and your reference. After accumulating much needed missing data, those responses too made sense.

As Mr. Spock would say; "Fascinating..."

 

[OmCheeto]

No, please don't do it! Not the obelisk!

Still no obelisks. But they did find a pyramid.

NASA's Dawn Mission ‏@NASA_Dawn 11 hours ago
A "pyramid"-like feature stands out in today's #Ceres image http://go.nasa.gov/1GP9ogi​

I'm guessing this is what they are talking about.

It looks more like a "limpet" snail to me. hmmm... They can call it Mt. O'Limet.
In a later tweet, they claim it is 5km (3 miles) high.

Is this our first mountain?Interesting "fracture" structure in the bottom left hand:

 

[johnnymorales]

That pyramid looks just like a cinder cone or stratovolcano on Earth. Though on Ceres is could very well be a cryovolcanic cinder cone.


Here is a photo of Mt. Mayon on Earth it's close to a perfect match when you take into account the likely effects of much lower gravity on Ceres.

https://en.wikipedia.org/wiki/File:Mt.Mayon_tam3rd.jpg


It's pretty surprising they'd call it a pyramid.

It's egging on the people who live and breath conspiracies as an explanation for all that they see.

It's also pretty surprising that in place of valid scientific speculation they let loose with a nonsense comparison.

Pyramids are not cones. So why inspired them to make such a brain dead comparison.

All and all par for the course regarding the Ceres team. They apparently lack the media savvy of the New Horizons team.

You can bet anything that looks vaguely volcanic or tectonic on Pluto will be declared as such immediately with validation to come later.

The fact that the Ceres team simply refuses to engage in the type of scientific speculation that makes space exploration so exciting for the public is extremely disappointing.

Suggesting the obvious in a news release would dramatically increase the public's interest and support of this mission.

The fact that it is much larger than any Earthly cinder cone can easily be explained by Ceres having just a tiny fraction of Earth's gravity. With such low gravity a cinder cone could grow to immense heights on Ceres.

 

[OmCheeto]

Ceres in the news:

Dawn over Ceres, a mission of humankind (PBS News Hour)

I'm not sure if I missed it, or forgot it, but the first image is not familiar:

THE DWARF PLANET — This image, taken by NASA's Dawn spacecraft , shows dwarf planet Ceres from an altitude of 2,700 miles (4,400 kilometers). The image, with a resolution of 1,400 feet (410 meters) per pixel, was taken on June 6, 2015. Image by NASA/JPL-Caltech/UCLA/MPS/DLR/IDA​

Here's the video imbedded in the write-up:

Dawn mission director describes the dwarf planet Ceres
​

[edit]

By casual inspection, the northern hemisphere seems to differ markedly from the southern hemisphere. I believe Mars and Vesta share this characteristic.

From the above article, it appears you are correct:

"The southern hemisphere is less densely cratered than the northern."
​

I think that's weird.

 

[Dotini]

"The southern hemisphere is less densely cratered than the northern."
​

I think that's weird.

Weird things are fun, and mean there's more to learn.

 

[OmCheeto]

Weird things are fun, and mean there's more to learn.

I can think of no mechanism inside our solar system which would cause such a thing.
So yesterday I spent about 3 hours researching the origins of asteroids.
I found tons of conflicting information.

One person here at PF said they were formed by vacuum welding. (Sounds funny to me, and no reference was listed.) [ref] Actually, it sounded like everyone was guessing in that thread. And given the level of knowledge at PF, my guess is, that know one knows.

One website article said they were formed during the big bang. (I sense that this is totally wrong. Most references list only Hydrogen and Helium production during that period) [ref]

So I researched a bit more about novas and supernovas, wondering if anyone knew if their heavy end stage nucleosynthesized elements, nickel and iron, were distributed atomically, or in big molten blobs. I found no answer. But looking at the Crab Nebula, it looks filamentized, so I thought there might be some merit to the idea.

Anyways, my theory was, that a local star, somewhere between 1 and 4 billion years ago. in the general direction of Polaris, might have gone nova, showering us with asteroids.
I was going to do the math, on the probability, given the rate of stellar explosions, local star density, and the age of our galaxy, but I was hoping that someone knew the answers to these things, off the top of their head. I hate doing needless maths. If no one knows, I will, obligingly, do the maths.

ps. Wouldn't it be fun, if the Dawn mission, gave us the answer.

 

[marcus]

Hi Om, I've never been too good at telling when my leg was being pulled but I think if an math explanation needs to be given it would be to explain why Jupiter's gravity would interfere with all that belt of rock coalescing into a planet.

I think at one time the band of near-circular orbits at 1 AU (plus or minus) where the Earth is now probably looked like Asteroid Belt only if anything much much thicker.

But the junk and rubble around 1 AU was able to start gathering and coalescing and snowballing together into one big heap called the Earth. Once one significantly bigger lump collects then it gradually pulls the rest in. But when our planet was forming it did not have the disruptive presence nearby of a planet like Jupiter to deal with.

The interesting question, for someone who wants to get into the math detail of orbital mechanics, would be to explain exactly how the proximity of Jupiter would disrupt the coalescence.

Jupiter could also have ejected asteroid matter from the belt. Pull chunks of it out of circular into eccentric orbits and then give them a gravity slingshot boost altogether out of there. That could be part of the reason there is not all that much mass in the Belt. Ceres alone represents 1/3 of the mass of the Belt. 3 x Ceres mass is really not what we expect for a usual planet.

 

[OmCheeto]

Hi Marcus,

I think I'd better slow down and start from scratch, and explain what I was looking for.
By reading Dotini and mfb's posts in sequence, I misinterpreted what Dotini had actually said.

By casual inspection, the northern hemisphere seems to differ markedly from the southern hemisphere. I believe Mars and Vesta share this characteristic.

Craters all the way down.

The illumination seems to be different for the two images, so I would be careful with comparisons.

All Dotini had said was, that they were different. I unfortunately added the two comments together and came up with; "Ceres is more heavily cratered in the north, which is true of Mars and Vesta", which is obviously not true. Unfortunately, I didn't figure that out until just now. So the original question, isn't even valid.

But I think a valid question still exists; "Why is Ceres more heavily cratered in the northern hemisphere?"

I've just spent about 6 hours trying to put the pieces together, but I think it's all just a bunch of very bad science on my part.

But all is not lost. I think I ran across the answer to your following question:

The interesting question, for someone who wants to get into the math detail of orbital mechanics, would be to explain exactly how the proximity of Jupiter would disrupt the coalescence.

Kirkwood gaps
A Kirkwood gap is a gap or dip in the distribution of the semi-major axes (or equivalently of the orbital periods) of the orbits of main-belt asteroids. They correspond to the locations of orbital resonances with Jupiter.

 

[OmCheeto]

An underexposed image of the bright spots published today:

image taken: June 15, 2015
altitude: 2,700 miles (4,400 kilometers).
resolution: 1,400 feet (410 meters) per pixel.
​

This is a heavily magnified shot from the TIFF image at JPL.

​

Well, ok. I can't see anything either. But at least they're reading my mind now.

 

[marcus]

the new Dawn Journal is out!
http://dawnblog.jpl.nasa.gov/2015/06/29/dawn-journal-june-29/

 

[marcus]

The 8th and last observation cycle in survey orbit should be completed today. So we can expect descent to the third mapping orbit (which used to be called "HAMO") to start soon.
I say that because status update http://dawn.jpl.nasa.gov/mission/status.html said the last cycle started 27 June, and a cycle lasts 3.1 days (half the time on the dayside, observing, and the rest of the time on the nightside, transmitting).

We should be seeing Dawn talking with DSN, either transmitting the data from the last cycle or getting programmed for the descent, which will take about 5 weeks if I remember right. I just checked and Canberra #45 is receiving data (it is 2AM there).
My guess is Dawn will turn on the ion thruster sometime (pacific) tomorrow, 1 July, if not earlier.

The simulated view http://neo.jpl.nasa.gov/orbits/fullview2.jpg shows the craft crossing over the N pole to the dayside. I'll bring that timetable forward, since we've turned a page. What I'm reading into it is that descent to the next orbit starts tomorrow and will take until the first week of August.

Orbit    dates      altitude(km)  pixelsize(m) res/HST  period  soccerball at
RC3    April 23–May 9    (13,500)    (1,300)    24     15 days    (3.0 meters)
Survey    June 6-30      (4,400)      (410)     72     3.1 days    (1.0 meters)
HAMO    Aug 4–Oct 15     (1,450)      (140)     215    19 hours    (33 cm)
LAMO Dec 8–end of mission  (375)      (35)      850    5.5 hours    (8.5 cm)

EDIT: Rayman's "Mission update" for 30 June includes this:
==excerpt==
...
Tonight Dawn will power on its ion propulsion system to begin a spiral descent to the third mapping orbit. It will take about five weeks to complete the maneuvering to an altitude of about 900 miles (less than 1,500 kilometers).
==endquote==
So if that went as planned propulsion is now on. I see from DSN that Dawn is not engaged in communication so I conclude the descent is in progress.
http://dawn.jpl.nasa.gov/mission/status.html

 

[OmCheeto]

Ha ha! The "bright spots" have their own wiki page:

Bright spots on Ceres

as does the mountain:

Pyramid-shaped mountain on Ceres

I discovered these this morning, when I was trying to verify a few posts on Facebook this morning; "These bright features have an albedo of about 40% (4 times brighter than the rest of Ceres's surface).^[3]"

Reference [3] is the 90 minute lecture that Dr. Rayman gave back in April.
Having already watched it, I was listening to it, while surfing this morning. I obviously missed it.

I guess it doesn't really matter what the actual albedo is, as ice/snow has a "proclaimed" variability of from 30 to 85%. [per wiki, and therefore, unreliable ]

 

[rootone]

The mountain:
"Although origin hypotheses for the mountain include volcanism, impacts, and plate tectonics, clear evidence backing any of these is currently lacking."

My bet is on it being a central 'rebound' mountain of the kind often associated with large impacts.
If this impact was very ancient, other more recent and smaller impacts could have eliminated other evidence of it - such as a discernable crater rim.

Plate tectonics and volcanism seem to me less likely on a body the size of Ceres, and if either were the case it's hard reconcile with there being just the one isolated mountain, as tectonics usually produce ranges of mountains, and volcanism usually produces several volcanos within in a well defined area..

 

[OmCheeto]

The mountain:
"Although origin hypotheses for the mountain include volcanism, impacts, and plate tectonics, clear evidence backing any of these is currently lacking."

My bet is on it being a central 'rebound' mountain of the kind often associated with large impacts.
If this impact was very ancient, other more recent and smaller impacts could have eliminated other evidence of it - such as a discernable crater rim.

Plate tectonics and volcanism seem to me less likely on a body the size of Ceres, and if either were the case it's hard reconcile with there being just the one isolated mountain, as tectonics usually produce ranges of mountains, and volcanism usually produces several volcanos within in a well defined area..

Someone, some time back, described low gravity, extra-terrestrial objects, as, "rubble piles".

It may just be a big pile of rubble.

 

[OCR]

[per wiki, and therefore, unreliable ]

Ohhhhh, my !

 

[marcus]

The 8th and last observation cycle in survey orbit should be completed today. So we can expect descent to the third mapping orbit (which used to be called "HAMO") to start soon.

Orbit    dates      altitude(km)  pixelsize(m) res/HST  period  soccerball at
RC3    April 23–May 9    (13,500)    (1,300)    24     15 days    (3.0 meters)
Survey    June 6-30      (4,400)      (410)     72     3.1 days    (1.0 meters)
HAMO    Aug 4–Oct 15     (1,450)      (140)     215    19 hours    (33 cm)
LAMO Dec 8–end of mission  (375)      (35)      850    5.5 hours    (8.5 cm)

EDIT: Rayman's "Mission update" for 30 June includes this:
==excerpt==
...
Tonight Dawn will power on its ion propulsion system to begin a spiral descent to the third mapping orbit. It will take about five weeks to complete the maneuvering to an altitude of about 900 miles (less than 1,500 kilometers).
==endquote==
So if that went as planned propulsion is now on. I see from DSN that Dawn is not engaged in communication so I conclude the descent is in progress.
http://dawn.jpl.nasa.gov/mission/status.html

It turns out that did NOT go as planned. The craft did briefly turn on ion propulsion to start the descent, but detected something was wrong and shut down the thruster, putting itself in safe mode to allow the engineers to check things out. Rayman's status update of 6 July:
http://dawn.jpl.nasa.gov/mission/status_2015.html
==quote==

2015

July 6, 2015 - Dawn Holding in Second Mapping Orbit

NASA's Dawn spacecraft is healthy and stable, after experiencing an anomaly in the system that controls its orientation. It is still in its second mapping orbit 2,700 miles (4,400 kilometers) above dwarf planet Ceres.

On June 30, shortly after turning on its ion engine to begin the gradual spiral down to the next mapping orbit, its protective software detected the anomaly. Dawn responded as designed by stopping all activities (including thrusting), reconfiguring its systems to safe mode and transmitting a radio signal to request further instructions. On July 1 and 2, engineers made configuration changes needed to return the spacecraft to its normal operating mode. The spacecraft is out of safe mode, using the main antenna to communicate with Earth.

Dawn will remain at its current orbital altitude until the operations team has completed an analysis of what occurred and has updated the flight plan.

Because of the versatility of Dawn's ion propulsion system and the flexibility of the mission's plan for exploring Ceres, there is no special "window" for starting or completing the spiral to the third mapping orbit. The plans for the third and fourth mapping orbits can be shifted to new dates without significant changes in objectives or productivity.
==endquote==

 

[OmCheeto]

...
The plans for the third and fourth mapping orbits can be shifted to new dates without significant changes in objectives or productivity.
...

As I've suspected, all along, the project is in good hands.