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

[marcus]

Mission director Marc Rayman posted a status update today:
==quote==
September 8, 2015 - Third Mapping Cycle Commences Tonight

Dawn is completing transmission to Earth of the pictures and spectra it acquired during its second mapping cycle while orbiting Ceres at an altitude of 915 miles (1,470 kilometers).

The robotic explorer will begin its third mapping cycle at 12:12 a.m. PDT on Sept. 9. During each of its 12 flights over the dayside of Ceres, it will point its camera and spectrometers behind and to its right, providing a third perspective on the landscape for use in developing topographic maps.
==endquote==
You will recall that there are to be 6 mapping cycles. Each cycle involves 12 of the 19 hour orbits, 12 passes over the day side. Each cycle covers the entire surface of Ceres.

On the first cycle the camera was pointed straight down, on the second (just finishing) it was a little back and to the left. On the third it will point a little back and to the right.

For me, the real meat of the mission starts in mid December--three months from now, when Dawn, using gamma and neutron spectroscopy, will actually SMELL which chemical elements make up the surface rubble (to a depth of about one meter) and it will be able to GAUGE the amount of WATER in the surface material by the extent to which the neutrons being emitted have been slowed down ("thermalized") by repeated collisions with hydrogen nuclei.

I'll bring forward the schedule to have it handy:

Orbit    dates      altitude(km)  pixelsize(m) res/HST  period  soccerball at
RC3    April 23–May 9    (13,600)    (1,300)    24     15 days    (3.0 meters)
Survey    June 6-30      (4,400)      (410)     73     3.1 days    (1.0 meters)
HAMO    Aug 17–Oct 23    (1,470)      (140)     217    19 hours    (33 cm)
LAMO Dec 15–end of mission (375)      (35)      850    5.5 hours    (8.5 cm)

 

[marcus]

Again, since we've turned a page, I'll bring forward two diagrams key to understanding the type of information Dawn may be acquiring in the "LAMO" (low altitude mapping orbit) starting in mid December.

 

[marcus]

What Dawn is doing now, in HAMO, is taking the data needed to construct a TOPOGRAPHICAL map---precisely determining the heights of all the mountains, ridges, ice-mounds, etc. Om has suggested that some of the bumps warts pockmarks and pimples on Ceres could have formed by pressure raised by ice bodies like the PINGOS that form in arctic regions on Earth---but higher due to the low (1/30) gravity.

It's clear that constructing a topographical map is interesting, in part because it will enable a quantitative understanding of the geological processes at work on Ceres. E.g. how did that 5 km high mountain that Rayman refers to as "Mt Lonely" get that high. BTW it has streaks of what looks like ice running down one side. So there are puzzles which point to questions about the internal structure of the planet.

For an overview of what's going on (and incidentally a nice animation of Mt. Lonely seen from many angles) check out Rayman's August journal:
http://dawnblog.jpl.nasa.gov/2015/08/21/dawn-journal-august-21/

 

[OmCheeto]

No pictures of the bright spots from HAMO orbit so far :(.

New pictures were posted about an hour ago.
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19889
I don't see any squares.
Though William Shatner just tweeted that they've found barbells next to a toaster on Mars.
https://twitter.com/WilliamShatner/status/641629127649288192/photo/1

There is also a topographical map of Occator crater, with and without animation.
http://www.jpl.nasa.gov/spaceimages/details.php?id=pia19891
with color coded elevation

​

http://www.jpl.nasa.gov/spaceimages/details.php?id=pia19890
black and white

It looks as though my earlier observation about the central peak being higher than the crater wall was was completely wrong.

 

[marcus]

Om thanks for the alert! In that release you linked to there was this nice still:
http://photojournal.jpl.nasa.gov/tiff/PIA19889.tif
I tried to insert it as an image here but got a red-X. However I think it will show up if you click "reply"
http://photojournal.jpl.nasa.gov/tiff/PIA19889.tif
The Occator crater with those bright spots, now at much higher resolution.

 

[OmCheeto]

...
Can you understand their description of pingo formation?

Did you edit in this question? I don't remember seeing it before.
Anyways, they use a lot of pingo lingo, which I do not understand:
"thermokarst lake"

Googling "thermokarst" did not help things at all.
It only leads to "karst", which is another jumble of fairly non-descriptive babble.

wiki; "Karst topography is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes, dolines, and caves."
...
"Morphology
The karstification of a landscape may result in a variety of large- or small-scale features both on the surface and beneath. On exposed surfaces, small features may include flutes, runnels, clints and grikes, collectively called karren or lapiez."​

Where are our exo-geologists when you need them?

 

[marcus]

Where are our exo-geologists when you need them?

They are hiding in their karsts.

 

[OmCheeto]

Never known to be patient enough to wait on NASA, Emily Lakdawalla put together some 3D images, and posted them today.

Dawn Ceres image bonanza: Grab your 3D glasses!
Posted By Emily Lakdawalla
2015/09/10 01:04 UTC

Most fascinating for me is the Haulani crater, situated very near both the equator and prime meridian.
Here's a heavily zoomed in image I captured:

Haulani crater, Ceres
​

You of course need red-green 3D glasses to see why this is so interesting.
The crater rim reminds me of a melting snow and dirt mixture pile.

Melting dirt and snow pile, Earth
​

Ha ha! I grabbed this image, as it was the best melting snow and dirt pile I could find on the internet.
I clicked on the link to the page it is on, and the title of the page is Postcards from Pluto.
The author: My name is Amanda Zangari, and I’m a postdoc working on NASA’s New Horizons mission to Pluto and the Kuiper Belt.

What are the odds?
Anyways, she says some interesting things on her page.
I think I'll send her a thank you card for her dirty snow pile pic.

 

[Zeno Ether]

I have compared the previous image with the new and there is something odd. The two bright lights on the right side of the crater are missing. Here is the comparison.

 

[Zeno Ether]

Here is a closeup with the profile of the missing spots.

 

[Zeno Ether]

And here is a closeup of the largest spot. It seems organic to me. If you look carefully you can see cylindrical

structures, blobs, corrugated tubes, tentacles and a central bulge.

 

[OmCheeto]

I have compared the previous image with the new and there is something odd. The two bright lights on the right side of the crater are missing. Here is the comparison.View attachment 88495

As was posted; "This view is a composite of two images of Occator: one using a short exposure that captures the detail in the bright spots, and one where the background surface is captured at normal exposure".

In the olden days of chemical photography, this technique was known as, um...
I'm old, and can't remember the name.
It involved wiggling a dark circular piece of paper, on the end of a stick, over the photographic paper, where the photographer knew the image was over-exposed.

The first word to come to mind is "vignette".
But, on further examination, it appears the proper term is expanded to two: Dodging and Burning.

 

[mfb]

The previous images were overexposed, so many pixels were pure white without contrast. The new ones have a better dynamic range.
Still surprising that the areas are close to the surrounding terrain in the new images. If the area is really that dynamic, we'll see more changes soon.

 

[Dotini]

If the area is really that dynamic, we'll see more changes soon.

Are we looking at dynamic changes? Perhaps we are dealing with plumes?

 

[mfb]

Are we looking at dynamic changes?

I don't know. Would be amazing.

I'm sure the NASA scientists have or are working on some simulation transforming the new better picture to the conditions of the old picture to see if they are compatible.

 

[Zeno Ether]

The previous images were overexposed, so many pixels were pure white without contrast. The new ones have a better dynamic range.
Still surprising that the areas are close to the surrounding terrain in the new images. If the area is really that dynamic, we'll see more changes soon.

I don't agree. The two big bright spots on the right have completely vanished in the surrounding terrain, whereas the other dimmer spots are still there in the new processed image. I think maybe NASA has (inadvertently?) erased the spots during post-processing.

 

[Zeno Ether]

I have another question for you. If the light we see were sunlight reflected by the surface of this "material", there should be some direction, where the surface should be visible without receiving the reflected light, according to the laws of optics. So, there should be the possibility for Dawn to capture an image of the spots without the reflection. If this is not possible then maybe 1) the reflection is diffuse (in all directions) or 2) the material itself is emitting light.

 

[OmCheeto]

... 2) the material itself is emitting light.

hmmm...

That would be interesting. I've been saying for some time that exo-planetary-physics is a bit odd.
But nothing I've ever learned/observed in a half a century tells me that your idea is worth even pondering. Sorry!

ps. I've sent an email to someone who might have access to the original two images. Crossing my fingers.

 

[mfb]

I don't agree. The two big bright spots on the right have completely vanished in the surrounding terrain, whereas the other dimmer spots are still there in the new processed image.

Let the brightness of the environment be 1, the two "vanishing" spots 2 and the other spots 10, in arbitrary units.

Make a picture where 2 is the maximum => vanishing spots are there and look the same as the other spots
Make a picture where 10 is the maximum => vanishing spots look a bit brighter than the surrounding area, but you see a huge difference to the other spots.

I have another question for you. If the light we see were sunlight reflected by the surface of this "material", there should be some direction, where the surface should be visible without receiving the reflected light, according to the laws of optics. So, there should be the possibility for Dawn to capture an image of the spots without the reflection. If this is not possible then maybe 1) the reflection is diffuse (in all directions) or 2) the material itself is emitting light.

The spots are not visible on the night side.
The reflection is quite diffuse, we have pictures of the spots from many different angles without obvious differences. There might be some peak brightness in some direction, but most angles get similar light.

 

[marcus]

Mission director Marc Rayman posted a brief status update today:
==quote==
September 11, 2015 - Dawn Continuing to Map Ceres

Dawn is making good progress on photographing Ceres for its third map. It is also acquiring a wealth of spectra at infrared and visible wavelengths. Today the explorer is making its fourth passage over the lit hemisphere.
==endquote==
http://dawn.jpl.nasa.gov/mission/status.html
http://dawn.jpl.nasa.gov/multimedia/images/index.html?view=list_view&start=0

 

[OmCheeto]

...
ps. I've sent an email to someone who might have access to the original two images. Crossing my fingers.

Mission success!

2015.09.11 07:15 pm PST
Hi [Om],
I have wondered if you were still following the mission, although I confess to being too busy ever to visit the forum. I'm glad to know your managing to keep busy.

I do have all the Dawn images, but what has been approved for public release is currently available for distribution. Ultimately, of course, all of Dawn's data from all investigations will be released, as it was for Vesta. As we see Occator in each mapping cycle (remember, in this third mapping orbit, we map Ceres six times, or once every 11 days), we will see Occator six times. I imagine that even before the first analysis of the images is complete, our daily release will include some more views which will include raw images. I do recommend some images for the approval process, and based on your message, I will suggest the original images (or something equivalent).

In the meantime, if there's a specific question about the images, let me know.

Thank you for continuing to follow the mission!

Marc

 

[Zeno Ether]

The more I look at the images of the large spot, the more I have the impression of looking at some sort of lattice with nodes and webs and rays irradiating from a central point.

 

[marcus]

Om, I'm so glad you are keeping in touch with Marc Rayman. If you ever have a good opportunity, would you consider asking him about any IR and visible spectroscopic results about the surface chemistry? We are getting all these pictures, in fine detail and from different angles. So topographical info is obviously building up rapidly.
But he mentions the spectroscopy going on at the same time. Can they tell anything about the chemistry from the wavelengths emitted by the surface?

Rahman posted another status update today. A bit of trouble with the main camera (!) that seems to have been resolved.
==quote==
September 14, 2015 - Third Mapping Cycle More Than Half Complete

On Sept. 13, during the seventh transit over the dayside of Ceres in the third mapping cycle, the computer in the camera detected an unexpected condition in the camera and turned off. Engineers observed the situation not long afterwards when Dawn was over the night side of Ceres. In preparation for the next dayside observations, they returned the camera to its normal configuration and confirmed it is healthy.

Today Dawn will observe terrain in the illuminated hemisphere of Ceres for the eighth time. The spacecraft revolves around the dwarf planet every 19 hours, so the twelfth and final dayside pass for this cycle will conclude on Sept. 18.
==endquote==

Third mapping cycle, out of 6 to be completed at this altitude, is in progress. Each cycle takes 12 passes over the dayside. And then a couple of orbits devoted to transmitting images and spectroscopic data. So the work at this altitude will be roughly half completed by 18 September.
In October she fires up her ion thruster again and starts the the most difficult descent spiral of the entire mission.
I'll bring forward the schedule to have it handy:

Orbit    dates      altitude(km)  pixelsize(m) res/HST  period  soccerball at
RC3    April 23–May 9    (13,600)    (1,300)    24     15 days    (3.0 meters)
Survey    June 6-30      (4,400)      (410)     73     3.1 days    (1.0 meters)
HAMO    Aug 17–Oct 23    (1,470)      (140)     217    19 hours    (33 cm)
LAMO Dec 15–end of mission (375)      (35)      850    5.5 hours    (8.5 cm)

 

[OmCheeto]

Om, I'm so glad you are keeping in touch with Marc Rayman. If you ever have a good opportunity, would you consider asking him about any IR and visible spectroscopic results about the surface chemistry? We are getting all these pictures, in fine detail and from different angles. So topographical info is obviously building up rapidly.
But he mentions the spectroscopy going on at the same time. Can they tell anything about the chemistry from the wavelengths emitted by the surface?
...

Will do. I have too many questions myself. I saw something about "terraced craters" on Mars the other day, and it reminded me of Ceres: ...Scientists discover strange terraced crater...

Bright Spots Aren't the Only Mysteries on Dwarf Planet Ceres

By Marc Rayman
JUNE 29, 2015
...
Several craters here have central peaks. The largest also has a ridge at the center. Note other intriguing geological structures, including the terraced walls of that crater and the contrast between the smooth area in the top half of the picture and the more rugged terrain at the bottom.
...

Anyone else have a question? As I recall, I took a survey last time, picked my favorite question, but he answered them all!

I'm most interested in his thoughts on the "Pingo" mountain theory. My first thoughts were that this was some type of photo processing anomaly.

 

[marcus]

It would be great if Rayman would comment on any of these questions! I share your curiosity about "pingo" mountain-building on Ceres.
I guess the technical term for mountain-building is orogenesis. Oro- a greek root for mountain is not to be confused with "oreo".

I don't completely understand the pingo ice-pimple process. I think it has to do with the the tendency of water to join with other water when it freezes, rather than freezing in a mix with interspersed grains of mineral. Ice likes to bond with other ice, and that can actually create upthrust pressure and a swollen hump.

I would imagine (Rayman may wish to correct this) that the same process that can raise a 70 meter ice-bump on Earth could raise a bump 30 times higher (>2000 meter or 2 km) on Ceres with its 1/30 strength gravity.

 

[OmCheeto]

It would be great if Rayman would comment on any of these questions! I share your curiosity about "pingo" mountain-building on Ceres.
I guess the technical term for mountain-building is orogenesis. Oro- a greek root for mountain is not to be confused with "oreo".

I don't completely understand the pingo ice-pimple process. I think it has to do with the the tendency of water to join with other water when it freezes, rather than freezing in a mix with interspersed grains of mineral. Ice likes to bond with other ice, and that can actually create upthrust pressure and a swollen hump.

I would imagine (Rayman may wish to correct this) that the same process that can raise a 70 meter ice-bump on Earth could raise a bump 30 times higher (>2000 meter or 2 km) on Ceres with its 1/30 strength gravity.

I think I mentioned that the image at first reminded me of "frost heaving". I've seen it before around my house in the winter.
I'd never heard of a "pingo" until I researched "frost heaving".

As far as I understand the pingo process, water collects unevenly, and forms something called an "ice lens". I don't think this type phenomenon would be logical on Ceres, so I'm more inclined towards my original "seed" theory. And, as mfb suggested, I've decided that the adjacent crater, is probably not the motive force, but merely coincidental.

I'll wait until tomorrow to send your question to Marc, as I'll add any additional questions on as a "post script", and hopefully, he'll answer them all.

 

[marcus]

OK well my pet question is can he tell us anything about the surface composition of Ceres that has been learned from the IR and visible spectra Dawn has taken so far?

And my pingo conjecture which I hope you try out on him is the same processes could be at work, although perhaps more rarely on Ceres, and could create a comparable pressure, so that a Ceres pingo could be on the order of 30 times higher than an Earth pingo.

 

[OmCheeto]

OK well my pet question is can he tell us anything about the surface composition of Ceres that has been learned from the IR and visible spectra Dawn has taken so far?

And my pingo conjecture which I hope you try out on him is the same processes could be at work, although perhaps more rarely on Ceres, and could create a comparable pressure, so that a Ceres pingo could be on the order of 30 times higher than an Earth pingo.

Mission [finally ] accomplished.

ps. I sent him a couple of post script message/questions also.
Did Christopher Russell really do an interview with Linda Moulton Howe?
Are you excited about seeing "The Martian"?

 

[Dotini]

Did Christopher Russell really do an interview with Linda Moulton Howe?

Apparently yes, and the louche lady of mysteries asked some good questions and received some intriguing answers.

 

[marcus]

Here's text of the interview:
https://www.earthfiles.com/news.php?ID=2349&category=Science

He says the VIR (visual and infrared spectrometer) has not reported any surface ice, in particular at the bright spots. So that suggests they might be salt residue left where salty water dried or salty ice sublimated.

Moulton Howe writes the "earth files" blog , I won't say more about her. She interviewed Chris Russell principal investigator for the Dawn mission (their top planetary scientist).
Dotini is right that it was a good interview!

 

[OmCheeto]

Here's text of the interview:
https://www.earthfiles.com/news.php?ID=2349&category=Science

He says the VIR (visual and infrared spectrometer) has not reported any surface ice, in particular at the bright spots. So that suggests they might be salt residue left where salty water dried or salty ice sublimated.

Moulton Howe writes the "earth files" blog , I won't say more about her. She interviewed Chris Russell principal investigator for the Dawn mission (their top planetary scientist).
Dotini is right that it was a good interview!

When I first saw the interview, it looked very interesting. But then I googled Linda's name, and decided I would get an insta-ban should I even mention her name!

I'm guessing that that Chris did this, as intra-solar system science is turning out to be even more outlandish than aliens.

Pluto looks to me, more Earth-like, than any other planet in the system. Very weird.

However, on Pluto, the “snow” is the carbon monoxide, methane and nitrogen, while the “dirt” is water ice.

Water ice is dirt? Ultra weird!

 

[marcus]

Rayman posted a status update:
=quote=
September 21, 2015 - Dawn Conducting Fourth Mapping Cycle

Dawn began its fourth mapping cycle on Sept. 19 at 10:13 p.m. PDT. The probe has now completed two of the 12 revolutions needed to photograph the dwarf planet's entire surface.

For this mapping cycle, the spacecraft points its camera and spectrometers at the scenery ahead and to the left as it orbits at an altitude of 915 miles (1,470 kilometers). Together with the pictures from the other mapping cycles, the different views will allow scientists to develop topographical maps. The visible and infrared mapping spectrometers, which observe a smaller area than the camera, are continuing to study previously unobserved regions with each new mapping cycle.
=endquote=

As I said earlier, I gather from remarks by the principal investigator Chris Russell that the spectrometers have not detected ice on the surface---meaning that the "bright spots" are more likely to be salt residue from ice or water that has evaporated.

Ice would not last long in the vacuum, on surface. However SOME of the bright spots could be fresh ice. Some process (e.g. impact) could cause melting in the subsurface ice layer and cause small amounts of water to seep up to the surface, where it would freeze and exist for a while as ice. It would eventually sublimate leaving whatever salt residue. But there might be some ice fields currently for the spectrometer to detect.

Dawn will make 6 complete coverages ("mapping cycles) at altitude 1450 km, and it's already into the fourth. Seems likely that it would have detected ice if there was any on the surface.

Gamma and neutron spectroscopy at 375 km altitude (beginning December) will be able to sense water below the surface.
View attachment 88403View attachment 88402

 

[OmCheeto]

Mission [finally ] accomplished.

ps. I sent him a couple of post script message/questions also.
Did Christopher Russell really do an interview with Linda Moulton Howe?
Are you excited about seeing "The Martian"?

And... Success!

I've inserted a comment where his response may seem out of the blue.

2015.09.22.1255 PDT
Hi [Om],

{me; I understand that there is currently a “gag order” on some of the information regarding Ceres due to an upcoming article in the “Nature” journal, so no need to apologize if you can’t expand...}​

You kindly acknowledged the embargo on results, but still I'm sorry I can't give you more informative answers.

Yes, the spectroscopy provides insight into the composition of the surface, and information on that will be released when the science team, peer-reviewed journal, and media relations office collectively are ready to do so. The issue date for the journal has not been decided yet. Feel free to check back with me, but it can take a while for the papers to make their way through the review process. I don't believe I can say anything about the nature of the papers.

The visible and IR spectroscopy show chemical composition. Molecules and compounds tend to have spectral signatures in those wavelength ranges. Elemental composition, however, is different. The atomic constituents are determined from the two nuclear spectroscopic techniques. Neutron and gamma ray spectra reveal what kinds of atoms are there. We will not have those results until Dawn is in its lowest orbit. I have written about this before, including on August 31, 2014.

Even well before Dawn arrived at Ceres, there was much speculation within the science team about the possibility of pingos there. Indeed, the team has expertise in such structures, and some of the geologists studied them specifically for that reason. For the mountain to be a pingo, it would have to be a uniquely large one. In addition, it is not yet certain that the conditions for forming a giant pingo really can occur on Ceres. So, it's a very intriguing idea, and for now remains an open question.

I've been interviewed by Linda Mouton Howe too. I like your description of her, and I'm going to pass that along to some people here whom I've told about some of the questions she asked me. The interview is real, but I'm not sure what exactly you have in mind. In such a long running interview, some comments may come out a bit confusing.

I greatly enjoyed the novel The Martian, and yes, I'm very much looking forward to the movie. (Bland as it may make me sound, however, I prefer science to science fiction.) I had an opportunity to see an advanced screening but had to decline because I had a conflict. Are you looking forward to it?

Regards,

Marc

 

[marcus]

==mission director's update==
September 25, 2015 - Dawn Conducting Fourth Mapping Cycle

Dawn has completed more than half of its fourth mapping cycle, acquiring more stereo pictures as well as spectra in infrared and visible wavelengths. Today the ship will make its eighth transit over the hemisphere of Ceres lit by the sun.
==endquote==

 

[marcus]

Dawn Journal 27 September
http://dawnblog.jpl.nasa.gov/2015/09/27/dawn-journal-september-27-2/

 

[marcus]

==quote mission update==
September 28, 2015 - Fourth Mapping Cycle Nearly Complete

This afternoon Dawn will begin the 12th and final observation session in its fourth mapping cycle. Upon completing this last flight over the illuminated hemisphere, the spacecraft will point its main antenna at Earth for two days to transmit the many pictures and spectra it has acquired.

On Sep. 27, Dawn celebrated its eighth anniversary of being in space. This month's Dawn Journal looks at the spaceship's progress on its interplanetary travels.
==endquote==

 

[OmCheeto]

Twitter is atwitter about the cornucopia of images just released:

Parent article: Dawn Team Shares New Maps and Insights about Ceres

Sub articles:

Topographic View of Ceres Mountain
Occator Topography
Hints at Ceres' Composition from Color
Topographic Ceres Map with Feature Names II​

A tad confusing, as they color code the images differently.

 

[OmCheeto]

I'm starting to understand why no one wants to make a guess about what's going on with the "Lonely Mountain".
From the false color image(left), there's really nothing outstanding about it.
It's just a mountain, with freaky streaks.

double hmmmm...

My extraction from the two big images.
​

It took me forever to find the left image, as they didn't provide lat/long marks on the parent image. (location: 11°S 316°E)

 

[Dotini]

Amazing images and a surprise observation.

http://scitechdaily.com/dawn- spacecraft -reveals-new-maps-and-insights-about-ceres/

This view, made using images taken by NASA’s Dawn spacecraft , is a color-coded topographic map of Occator crater on Ceres. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDAA surprising bonus observation came from Dawn’s gamma ray and neutron spectrometer. The instrument detected three bursts of energetic electrons that may result from the interaction between Ceres and radiation from the sun. The observation isn’t yet fully understood, but may be important in forming a complete picture of Ceres. “This is a very unexpected observation for which we are now testing hypotheses,” Russell said.

This color-coded map from NASA’s Dawn mission shows the highs and lows of topography on the surface of dwarf planet Ceres. It is labeled with names of features approved by the International Astronomical Union. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

 

[marcus]

Nice finds, Dotini!
I have links to some papers presented at the Ceres session of a European space conference last week, in Nantes, France. But nothing as striking as what you just posted. For completeness, here they are.
Ceres session, a few of the many papers, presented at the Nantes conference:
http://meetingorganizer.copernicus.org/epsc2015/sessionprogramme

http://meetingorganizer.copernicus.org/EPSC2015/EPSC2015-400.pdf
Impact Craters on Ceres: Evidence for Water-Ice Mantle?

http://meetingorganizer.copernicus.org/EPSC2015/EPSC2015-490-1.pdf
Ceres: ice stability and water emission

http://meetingorganizer.copernicus.org/EPSC2015/EPSC2015-525.pdf
Color variations on Ceres derived by Dawn/VIR: Implications for the surface composition

 

[marcus]

==Rayman's latest update==

October 1, 2015 - Dawn Begins Fifth Mapping Cycle

After sending the last of its data from the fourth mapping cycle to Earth, Dawn started its fifth mapping cycle on Sep. 30 at 11:40 p.m. PDT. During this 11-day period, the tireless explorer will aim its sensors toward the terrain immediately ahead as it orbits the alien world at an altitude of 915 miles (1,470 kilometers). This new angle will provide scientists with another stereo view to use in developing 3-D perspectives.

This morning Dawn completed the first transit in this cycle over the side of Ceres facing the sun. The dwarf planet turns on its axis in nine hours, and the spacecraft revolves around it in 19 hours, spending half that time over the sunlit landscape and half over the ground hidden in the dark of night. With 12 orbital loops, Dawn's camera can see all of the terrain.
==endquote==

 

[marcus]

Dawn's six mapping cycles in HAMO are nearing completion
==Rayman, 5 October update==

October 5, 2015 - Fifth Mapping Cycle Half Complete

Dawn conducted its sixth observing session in mapping cycle #5 today, spending more than nine hours photographing Ceres and collecting more spectra.

Since entering orbit in March, Dawn has completed more than 100 revolutions around the dwarf planet, with 62 of those occurring since the start of this third mapping phase on Aug. 17.
==endquote==

Orbit    dates      altitude(km)  pixelsize(m) res/HST  period  soccerball at
RC3    April 23–May 9    (13,600)    (1,300)    24     15 days    (3.0 meters)
Survey    June 6-30      (4,400)      (410)     73     3.1 days    (1.0 meters)
HAMO    Aug 17–Oct 23    (1,470)      (140)     217    19 hours    (33 cm)
LAMO Dec 15–end of mission (375)      (35)      850    5.5 hours    (8.5 cm)

For me personally, the real meat of the results will only start coming in December when the probe finally gets down to 375 km altitude and can make effective use of gamma and neutron spectrometers for tasting the chemistry of Ceres' surface layer to a depth of about one meter.

The final descent, from altitude 1470 km to 375 km, will be long and arduous, because so much more gravitational potential energy is involved, closer into the planetto. You can see it will take nearly 8 weeks of work with the solar-powered ion engine to get down to LAMO.

 

[OmCheeto]

...
For me personally, the real meat of the results will only start coming in December when the probe finally gets down to 375 km altitude and can make effective use of gamma and neutron spectrometers for tasting Ceres' surface chemistry down to a depth of about one meter.
...

Me too! I've been going over the posts and references [see below] since August, trying to figure out how the neutron detectors can differentiate between fast and slow ones, but it all looks like black magic to me.

I also checked out a couple of other references:
Dawn’s GRaND to reveal the complex geochemistry of Vesta [lpi.usra.edu] (Where I learned that Vesta is covered in "Howardite")
Scintillation counter, Neutron detector efficiency [wiki] (Told me absolutely nothing. My apologies if you clicked on the link.)
PDS: The Planetary Data System, GAMMA-RAY AND NEUTRON DETECTOR [nasa] (Where I learned that "GRaND is mounted on the +Z deck of the spacecraft ". Woo Hoo!)

I used to be a nuclear trained technician in the USN, where they made us study neutron detector theory. But after 35 years, it's all a bit fuzzy now.

ps. I surfed through at least 15 other websites, and didn't learn very much, other than rocks from Vesta are named after someone named Howard: Howardite
I thought that was very funny.
Sorry.Previously referenced references:
[1] Gamma Ray and Neutron Spectrometer (GRNS) [messenger-education.org]
[2] Planetary gamma-ray spectrometers [wiki]
[3] DAWN JOURNAL | OCTOBER 29, 2006, re: GRaND [jpl]

 

[OmCheeto]

Just in case anyone interested in the mission missed the announcement:

Get your popcorn ready!

(About 90 minutes from now, for those of you not on the west coast of the USA)

 

[marcus]

A lecture by Carol Raymond, deputy principal investigator. Starts at 7 PM pacific at this website:
http://www.ustream.tv/nasajpl2

Here's a bit about the lecture:
http://www.jpl.nasa.gov/events/lectures_archive.php?year=2015&month=10

I gather that Dr. Raymond will be giving it twice each time at 7 PM pacific, on Thursday 8 Oct and Friday 9 Oct.

 

[OmCheeto]

A lecture by Carol Raymond, deputy principal investigator. Starts at 7 PM pacific at this website:
http://www.ustream.tv/nasajpl2

Here's a bit about the lecture:
http://www.jpl.nasa.gov/events/lectures_archive.php?year=2015&month=10

I gather that Dr. Raymond will be giving it twice each time at 7 PM pacific, on Thursday 8 Oct and Friday 9 Oct.

Did you watch it?
Was I mistaken, or did she not say they didn't know what the bright spots were?

I watched a video yesterday that kind of contradicted that:

European Planetary Science Congress
27 Sept - 02 Oct 2015
2015 EPSC Opening Ceremony: C. Russell


Regarding the "bright spots" in Occator Crater:
@ t = 15:30
"Eventually, we found the albedo, and that ruled out ice.
So we believe this is a huge salt deposit.
It tells me, that this is an active surface".
​

Not that it makes much of a difference to me.

But, hmmm...
Ah ha!

Never mind.

 

[marcus]

I watched some of Dr. Raymond's talk---it was for wide audience. Thanks for the link to Chris Russell's more informative EPSC opening talk, more for professional audience. I heard the same remark you did---not ice but rather salt. The fraction in the icy mantle is now estimated at 20%, it seems. He said the surface is clay-ey rather than regolith. If I understood correctly the current best guess model is a small core which may have metal surrounded by a thick layer of "hydrated minerals" then a layer of ice (thinner than that shown in earlier guesses but still some 50-100 km thick) and then a dry clay-like surface.

 

[OmCheeto]

I watched some of Dr. Raymond's talk---it was for wide audience. Thanks for the link to Chris Russell's more informative EPSC opening talk, more for professional audience. I heard the same remark you did---not ice but rather salt. The fraction in the icy mantle is now estimated at 20%, it seems. He said the surface is clay-ey rather than regolith. If I understood correctly the current best guess model is a small core which may have metal surrounded by a thick layer of "hydrated minerals" then a layer of ice (thinner than that shown in earlier guesses but still some 50-100 km thick) and then a dry clay-like surface.

My "Ah ha!" comment was based on my perception that JPL may be playing the media, to gather attention.

Faux Headline:

Top scientists fighting at JPL!
JPL's Dawn PI says it's salt, while the deputy PI says they don't know.
Intra-stellar smackdown at 7​

They did refer to Ahuna Mons as a "pyramid".

 

[newjerseyrunner]

I have a question, why can't a spectral analysis tell us what the bright spot's made out of?

 

[mfb]

It will, but Dawn has to go to the lower orbit to do sensitive spectroscopy.