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Marc Rayman

Dawn Journal: Mapping Ceres

Posted by Marc Rayman

22-08-2015 13:05 CDT

Topics: pretty pictures, mission status, asteroids, Dawn, asteroid 1 Ceres

Dear Unhesidawntingly Enthusiastic Readers,

An ambitious explorer from Earth is gaining the best views ever of dwarf planet Ceres. More than two centuries after its discovery, this erstwhile planet is now being mapped in great detail by Dawn.

Ceres' conical mountain

NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / LPI

Ceres' conical mountain
This is a very brief clip from an animation of Ceres based on Dawn’s observations through the second mapping orbit. The entire animation (along with a recording of your correspondent’s informal commentary) is here. This excerpt shows the conical mountain, and you can see more about it in pictures below. The complete animation also shows the bright spots and a 3-D view of the dwarf planet.

The spacecraft is engaged in some of the most intensive observations of its entire mission at Ceres, using its camera and other sensors to scrutinize the alien world with unprecedented clarity and completeness. At an average altitude of 915 miles (1,470 kilometers) and traveling at 400 mph (645 kilometers per hour), Dawn completes an orbit every 19 hours. The pioneer will be here for more than two months before descending to its final orbit.

The complex spiral maneuver down from the second mapping orbit at 2,700 miles (4,400 kilometers) went so well that Dawn arrived in this third mapping orbit on Aug. 13, which was slightly ahead of schedule. (Frequent progress of its descent, and reports on the ongoing work in the new orbit, are available here and on Twitter @NASA_Dawn.) It began this third mapping phase on schedule at 9:53:40 p.m. PDT on Aug. 17.

Map of Ceres

NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

Map of Ceres
This map of Ceres shows the feature names approved by the International Astronomical Union as of August 14, 2015. We described the naming convention in December, and the most up-to-date list of names is here. (Click on the image for an enlarged view or go here for a similar version with other details.)

We had a detailed preview of the plans last year when Dawn was more than six thousand times farther from Ceres than it is today. (For reasons almost as old as Ceres itself, this phase is also known as the high altitude mapping orbit, or HAMO, although we have seen that it is the second lowest of the four mapping orbits.) Now let’s review what will happen, including a change mission planners have made since then.

The precious pictures and other data have just begun to arrive on Earth, and it is too soon to say anything about the latest findings, but stand by for stunning new discoveries. Actually, you could get pictures about as good as Dawn’s are now with a telescope 217 times the diameter of Hubble Space Telescope. An alternative is to build your own interplanetary spaceship, travel through the depths of space to the only dwarf planet in the inner solar system, and look out the window. Or go to the Ceres image gallery.

Dawn has already gained fabulous perspectives on this mysterious world from its first and second mapping orbits. Now at one third the altitude of the mapping campaign that completed in June, its view is three times as sharp. (Exploring the cosmos is so cool!) That also means each picture takes in a correspondingly smaller area, so more pictures are needed now to cover the entire vast and varied landscape. At this height, Dawn’s camera sees a square about 88 miles (140 kilometers) on a side, less than one percent of the more than one million square miles (nearly 2.8 million square kilometers). The orbital parameters were chosen carefully so that as Ceres rotates on its axis every nine hours (one Cerean day), Dawn will be able to photograph nearly all of the surface in a dozen orbital loops.

Bright spots in Occator Crater, Ceres

NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

Bright spots in Occator Crater, Ceres
The famous bright spots (or famously bright spots) in Occator crater, as viewed in the second mapping orbit. What will these mesmerizing features reveal with pictures three times sharper? We will know soon! And pictures from Dawn’s closest mapping orbit will display almost 12 times as much detail as seen here. Full image and caption.

When Dawn explored the giant protoplanet Vesta from comparable orbits (HAMO1 in 2011 and HAMO2 in 2012), it pointed its scientific instruments at the illuminated ground whenever it was on the dayside. Every time its orbit took it over the nightside, it turned to point its main antenna at Earth to radio its findings to NASA’s Deep Space Network. As we explained last year, however, that is not the plan at Ceres, because of the failure of two of the ship’s reaction wheels. (By electrically changing the speed at which these gyroscope-like devices rotate, Dawn can turn or stabilize itself in the zero-gravity conditions of spaceflight.)

We discussed in January that the flight team has excogitated innovative methods to accomplish and even exceed the original mission objectives regardless of the condition of the wheels, even the two operable ones (which will not be used until the final mapping orbit). Dawn no longer relies on reaction wheels, although when it left Earth in 2007, they were deemed indispensable. The spacecraft’s resilience (which is a direct result of the team’s resourcefulness) is remarkable!

One of the many ingredients in the recipe for turning the potentially devastating loss of the wheels into a solid plan for success has been to rotate the spacecraft less frequently. Therefore, sometimes Dawn will wait patiently for half an orbit (almost 9.5 hours) as it flies above ground cloaked in the deep darkness of night, its instruments pointed at terrain they cannot detect. Other times, it will keep its antenna fixed on Earth without even glancing at the sunlit scenery below, because it can capture the views on other revolutions. This strategy conserves hydrazine, the conventional rocket propellant used by the small jets of the reaction control system in the absence of the wheels. It takes more time, but because Dawn is in orbit, time is not such a limited resource. It will take 12 passages over the illuminated hemisphere, each lasting nearly 9.5 hours, to bring the entirety of the landscape within view of its camera, but we will need a total of 14 full revolutions, or 11 days (29 Cerean days, for those of you using that calendar), to acquire and transmit all the data. The Dawn team calls this 11-day period “11 days,” or sometimes a “cycle.”

In quite a change from the days that there simply didn’t seem to be enough hydrazine onboard to accomplish all of the mission’s ambitious objectives, engineers and the spacecraft itself have collaborated to be so efficient with the precious molecules that they now have some to spare. Therefore, mission planners have recently decided to spend a few more in this mapping orbit. They have added extra turns to allow the robot to communicate with Earth during more of the transits over the nightside than they had previously budgeted. This means Dawn can send the contents of its computer memory to Earth more often and therefore have space to collect and store even more data than originally planned. An 11-day mapping cycle is going to be marvelously productive.

Conical mountain on Ceres

NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

Conical mountain on Ceres
The conical mountain visible in the animation above is on the left of this photograph from the second mapping orbit. The mountain’s distinctive bright side is facing right. We presented two other perspectives of it in June. Scientists have recently refined their calculation of its height, now estimating that it towers an impressive four miles (six kilometers) above the surrounding terrain. In the third mapping orbit, Dawn will provide clearer views and a more accurate measurement of its elevation. The image below shows the mountain from still another perspective. Full image and caption.

But Dawn has goals still more ambitious than taking pictures and recording infrared and visible spectra of the lands passing underneath it. It will conduct six complete mapping cycles, each one looking at a slightly different angle. This will effectively yield stereo views, which when combined will make those flat images pop into full three dimensionality.

In its first mapping cycle, which is taking place now, the explorer aims its instruments straight down. For the second, it will keep the camera pointed a little bit back and to the left, making another full map but with a different perspective. For the third, it will look a little back and to the right. The fourth map will be viewing the scenery ahead and to the left. The fifth map will be of the terrain immediately ahead, and the sixth will be farther back than the third but not as far to the right.

In addition to the stereo pictures and the many spectra (which reveal the nature of the minerals as well as the surface temperature), Dawn will use the color filters in its camera to record the sights in visible and infrared wavelengths.

As always, mission planners schedule more observations than are needed, recognizing that glitches can occur on a complex and challenging expedition in the forbidding depths of space. So even if some data are not collected, the goals can still be accomplished.

The probe also will continue to acquire spectra both of neutrons and of gamma rays. It is unlikely to detect more than a whisper of neutrons from Ceres at this height, but the radiation coming from elsewhere in space now will serve as a useful calibration when it measures stronger nuclear emanations from one quarter the altitude starting in December, allowing scientists to inventory Ceres’ atomic constituents.

Precise measurements of Dawn’s radio signal will reveal more details of the dwarf planet’s gravitational field and hence the distribution of mass within. When the spacecraft is not aiming its main antenna at Earth, it will broadcast through one of its three auxiliary antennas, and the Deep Space Network will be listening (almost) continuously throughout the 84 orbits.

Conical mountain on Ceres

NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

Conical mountain on Ceres
The same conical mountain pictured above can be seen on the left of this photograph. Some of the bright material outside Haulani crater is visible near the limb on the right edge. Full image and caption.

As at Vesta, Dawn’s polar orbits are oriented so that the craft always keeps the sun in view, never entering Ceres’ shadow, even when it is nighttime on the ground below. But its course will take the robot out of sight from Earth occasionally, and the behemoth of rock and ice will block the radio signal. Of course, Dawn is quite accustomed to operating in radio silence. It follows timed instructions (called sequences) that cover a full mapping cycle, so it does not require constant contact. And in budgeting how much data Dawn can collect and transmit, mission planners have accounted for the amount of time Ceres will eclipse its view of Earth.

Thanks to the uniquely efficient and exceptionally gentle thrust of the ion engines, as well as the flexibility inherent in being in orbit, Dawn operations generally can be more leisurely than those with conventional chemical propulsion or missions that only fly past their targets rather than stay for as long as needed. In that spirit, controllers had allowed the time in the spacecraft’s main computer to drift off, as there was no need to keep it particularly accurate. But recently the clock was off by so much that they decided to correct it, so before the mapping began, they adjusted it by a whopping 0.983 seconds, eliminating a large (but still tolerable) offset.

Many residents of Earth’s northern hemisphere are completing their leisurely summer vacations. As we saw in February, Dawn has measured the orientation of Ceres’ spin axis and found that it is tipped about four degrees (compared with Earth’s axial tilt of 23 degrees). The sun then never moves very far from the dwarf planet’s equator, so seasonal variations are mild. Nevertheless, northern hemisphere summer (southern hemisphere winter) began on Ceres on July 24. Because Ceres takes longer to revolve around the sun than Earth, seasons last much longer. The next equinox won’t occur until Nov. 13, 2016, so there is still plenty of time to plan a summer vacation.

Meanwhile, Dawn is working tirelessly to reveal the nature of this complex, intriguing world. Now seeing the exotic sights with a shaper focus than ever, the probe’s meticulous mapping will provide a wealth of new data that scientists will turn into knowledge. And everyone who has ever seen the night sky beckon, everyone who has heard the universe’s irresistible invitation, and everyone who has felt the overpowering drive for a bold journey far from Earth shares in the experience of this remarkable interplanetary adventure.

Dawn is 905 miles (1,456 kilometers) from Ceres. It is also 2.06 AU (191 million miles, or 308 million kilometers) from Earth, or 775 times as far as the moon and 2.03 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 34 minutes to make the round trip.

Dr. Marc D. Rayman
5:00 p.m. PDT August 21, 2015

 
See other posts from August 2015

 

Or read more blog entries about: pretty pictures, mission status, asteroids, Dawn, asteroid 1 Ceres

Comments:

Trekker: 08/23/2015 12:16 CDT

Can you outline how the composition of the famous white spots will be determined? Will it be through spectrographic analysis, or some other method?

seyss: 08/23/2015 05:17 CDT

Hi Marc, your blog is amazing. I'm an Electrical Engineer and it really fascinates me how knowledgeable you are about science, orbital mechanics and other space areas. As a KSP player (game) I use Hohmann Transfers to get to other planets in the Solar System, so an Orbital Insertion burn is always required. With Dawn I see there is no such thing. Can you explain in more detail how Dawn achieved orbit with Ceres? Best regards.

Marc Rayman: 08/23/2015 07:25 CDT

Trekker: I expect several methods to be applied to determine their nature. The principal one will be infrared spectroscopy. The visible spectra will help as well. (Neither the neutron spectra nor gamma ray spectra are likely to bear on this.) Color images from the camera will yield much less spectral information but will contribute better spatial resolution than the spectrometers. Other methods will include measurements of how the brightness depends on both the angle of the incident sunlight and the angle from the spots to Dawn. (I have a few more details on this in my comments at http://dawnblog.jpl.nasa.gov/2015/03/06/dawn-journal-march-6/#comment-9019) Finally, geological context will play an important role in understanding these features. I have always preferred to call them bright spots. "White" is a description of the spectrum. Most of the pictures show only the relative brightness, but not the intensity at different wavelengths.

Marc Rayman: 08/23/2015 07:35 CDT

Hi seyss. I appreciate your nice comment. Dawn's method of entering orbit (and escaping) is very different indeed from what we normally think of from other planetary missions. There isn't room here to describe it, but I'll mention that it doesn't have anything to do with Vesta or Ceres. It is thanks to the unique characteristics of the ion propulsion system. I have written about it in many Dawn Journals. Two good ones to start with for some insight into how this works are January 2014 (search for Rendawnvous ) and March 6, 2015 (search for unprecedawnted).

Paul McCarthy: 08/23/2015 10:49 CDT

Hi Marc, "Neither the neutron spectra nor gamma ray spectra are likely to bear on this." Are you making some assumptions about the likely composition of the bright material in saying this ie: excluding certain apparent possibilities? Otherwise, why is it likely that these spectra won't help with identification under all possible scenarios?

sangos: 08/24/2015 02:47 CDT

Apologies but i would be lying if i did not admit that all i care about this mission right now is simple - what are those frikkin lights all about? :-) We also need to figure out better reaction wheel tech. Its a bummer when oh we cannot do any more earth like planets coz kepler's lost its marbles and there is no way we can replace the flat tyre...sorry for the scot part!

ScienceNotFiction: 08/24/2015 04:28 CDT

POSSIBLE EXPLANATION OF HOW BULGES FORM INSIDE SOME CRATERS ON CERES During the Semi Muddy Crust Period, an icy and porous asteroid would penetrate the muddy surface and leaving behind a sunken mud pool. This icy asteroid would sink toward the core until the force of buoyancy made it float back up. The surface to core ocean temperature during this crusting period may be in between 100C to 1900C (aided by Calcium Chloride effect). Much of the icy asteroid would have melted and left only the light porous material. The volume loss of an icy asteroid would go as high as 70% to 80%. These re-surfacing asteroids would bumped up in the form bulges near the center of the mud pool in which they had first created. Why are the bulges always near the center of the crater? During this period, there were no gas layer existed on Ceres because light gases would have bubbled away from the muddy surface into space. The muddy crust was sit right on the liquid ocean. The internal liquid pressure kept this layer afloat as the surface became hardened. The icy asteroids dropping vertically over the surface would penetrate into the ocean and then resurfaced vertically toward the point of impact. This repeating process helped Ceres to build up its H2O reserve over time in its early years.

ScienceNotFiction: 08/24/2015 04:35 CDT

Here are possible phases of Ceres surface formation (Only actual crust samples can help us determine the time duration of each period): 1. Molten protoplanet encased in a body of greenish ocean layer. (it would look like a greenish fluorescent sphere from space) 2. Early Muddy Crust Period - patches of grayish material layer began to cover the entire planet. 3. Semi Muddy Crust Period - the surface crust layer thickened and hardened, but the underneath layer remained moist and soft. 4. Late Muddy Crust Period - the surface was cooled and hardened, a sandwiched gas layer began to form inside, creating an internal atmosphere. 5. Early Stalactite Period - stalactites were formed everywhere and primitive microbes were also evolved. 6. Recurring Stalactite Period - heavy stalactites would fall from various scenarios and the geological self-repairing process would replace the exposed spots with new stalactites underneath.

ScienceNotFiction: 08/24/2015 05:12 CDT

HOW TO EXAMINE THE AGE OF EACH CRATER ON CERES: Based on each crust formation periods, we can formulate a visual guide to group the various craters by their ages. 1. Crater sizes are the indication of the initial impact size of the asteroids. 2. The sharpness of the crater rim and the depth of the impact basin determine the time when the impact had occurred. 3. Craters formed during Semi Muddy Crust Period will appear very shallow and blurry on the rim. 4. Uneven crater bottom (bulges) indicates that an resurfacing event has taken place after impact. 5. Skid marks or light trenches indicate near horizontal impact, tangent to the surface. 6. Ice only asteroid impact at Late Muddy Crust Period may leave a crater with irregular scattering. It may have failed to penetrate the surface. It creates a clear depression on the surface and dents the underneath stalactite layer, thus exposing or generating holes on the surface near the impact point.

Trekker: 08/24/2015 11:42 CDT

Thanks for the informative reply, Mark. How soon into the HAMO will Dawn be able to undertake these measurements of the ‘bright’ spots? And yes, I understand your frustration at hearing them called ‘white’ spots. It’s just that their brightness in the early photos took us all by surprise, with the intensity of their apparent whiteness. I imagine though, that you find it even more frustrating to hear people calling them ‘lights’, and getting angry and abusive, and launching into NASA conspiracy theories, when asked to be patient, that nothing is being hidden and being told they’re not ‘lights’.

Marc Rayman: 08/24/2015 01:33 CDT

Paul: My thought about the nuclear spectra is independent of the potential composition. Rather, it is simply that even at Dawn's lowest altitude, the spatial resolution of both kinds of spectra will be not be sufficient to resolve such a small area. I expect the contributions to the spectral measurements from the bright spots to represent such a tiny fraction that they will not be detected. Trekker: Dawn made some of the pertinent measurements in its previous phases and has already begun making more in this orbit. The full set, however, including the highest spatial resolution, will not be completed until the spacecraft is in its lowest orbit around the end of the year. (Whether all measurements will be needed to reach a conclusion about the composition of the bright spots is not yet clear.)

ScienceNotFiction: 08/24/2015 11:02 CDT

Dr. Rayman, From your blog, we can see everyone wants to know more about the Occator "Bright Spots" and wishes DAWN can yield more scientific data from its instruments. Perhaps your teams have planned out how DAWN will orbit around Ceres after December. Anyway, I would like to propose a suggestion for your team to consider. Could it be possible to align DAWN's LAMO orbit to pass right over the Occator light spots (especially directly over the largest light hole) at a fixed cycle for an extended period (at least 1 year). This way DAWN can take pictures of this light hole at an exact location repeatedly and we can compare the photos for any subtle changes in appearance. One year time is really too short for observing stalactite formation, but we may be able to observe the icy cap (white heads) formation. In addition, we can observe the changes of the interior "bright" ocean, especially any contrasting shadows on the liquid surface (or waves). We may be able to capture floating debris on the liquid surface inside the light hole. We may even be able to detect the vertical distance change between DAWN and the ocean surface ! With strong light coming out of the bright spots, Dawn's spectral data may be inaccurate. We may never be able to determine the light conductivity index of the mantle liquid without an actual sample of that stuff. But nonetheless, we can observe the variance of spectral intensity to determine whether Ceres' core reaction has an observable fluctuation pattern in relationship to its orbit and surrounding gravitational pulls. This may help us confirm that the core shifts and the Mg reaction is non uniform on the core sphere. Also, we can visually comparing the change of gas cloud volume above the holes.

ScienceNotFiction: 08/25/2015 03:49 CDT

Dr. Rayman, DAWN is now much closer to the surface CERES, would it be possible to release more photos of the night side, especially focusing on those bright/white spots areas. Will there be weak illumination of these light spots in total darkness ? NASA/JPL did not release too many dark side photos so far.

Marc Rayman: 08/25/2015 10:51 CDT

ScienceNotFiction: Thank you for your continuing interest! Yes, we have devised very detailed plans for our final orbit, which we will reach in December. I believe we will acquire a great deal of extremely valuable data. We will observe Occator multiple times, but it will not be on a "fixed cycle." Ceres rotates in 9.1 hours, and Dawn will be in a polar orbit with a period of about 5.5 hours. Ceres has a very large area, and we do not want to neglect the many, many other interesting sights (including bright material elsewhere, which you can see in many released images). The bright spots are visible only by reflected light. Dawn no longer takes photos on the nightside of Ceres, as doing so is not in the best scientific interests of exploring this dwarf planet. The last time we took photos of the nightside of Ceres was in the first mapping orbit, as I explained in May (search for Emboldawned). We now are focusing our efforts on acquiring other data.

ScienceNotFiction: 08/25/2015 08:18 CDT

Dr. Rayman: Thank you for your reply. The reason that I suggest more night side photos is that I had seen several so-called bright spots looked very different from others. There are two types which will prevent DAWN to see them from high altitude (HAMO). Even at 450mi, DAWN's orbit may not be able to pick them up. One type of tiny opening appears as a tiny hole opening up non-vertically (like the eye of a cameleon facing other angle). The other type of openings (such as the narrow crescent bright trench) is below a trench or basin. If DAWN's orbit does not fly directly over it, we will never see anything. If you examine the recent HAMO photos, you will see a short distance of light streaking out from the spot facing an angle (not toward the sky). It will take some luck for DAWN to capture images of these types of bright spots under total darkness. Keep in mind that these tiny openings were nearly sealed by the stalactites growing underneath. Unlike the other reflective bright spots, these spots are much weaker in light intensity. Just to think for a moment, if we can see light coming from the Occator spots, why can't light coming out from other tiny spots. You should really consider taking a full set of dark side photo at LAMO as final mapping reference. There may just be big surprises waiting for us to discover. This discovery will go to your team's credit anyway. It will provide solid evidence for a bright ocean underneath Ceres.

ScienceNotFiction: 08/26/2015 09:48 CDT

Dr. Rayman, With all due respect, I have picked out the following three photos that your team should focus on taking a night side shot during LAMO. These are PIA19596, 19622, 19593. These photos have shown several spots on cracked surfaces with irregular edges same as the Occator bright spots. There are also several super thin crust area showing tiny dots of light and less opaque surface showing the illumination of light underneath (Jade Rock Lantern Effect). The last photo of the crescent bright trench bottom is definitely not reflective material. Solar light would not be able to reach the bottom of a trench unless sun light is shining on top of it near noon time. If DAWN can retake these spot positions under total darkness at LAMO, we will know for sure that these are not light reflections. I know NASA/JPL research team already rejected the idea of H2O icy reflection on all spots. If we can see faint light on close up photos of these interesting areas, we will form a basic understanding of how Ceres is formed.

ScienceNotFiction: 08/26/2015 10:07 CDT

Dr. Rayman, In addition, I have spotted a faint dot of light on the famous dark side photo PIA19579 of Occator Spots. Zoom in the photo on the Occator spots and move down southward toward the edge of the planet, you should see a very faint light dot on the surface.

ScienceNotFiction: 08/27/2015 03:00 CDT

Amazing Recovery of Occator Spots In just 3 months, the Occator spots shown in the night photo of PIA19630 were much smaller in their sizes. A transparent sheet of thin ice cap may have completely covered the openings of the pair columns (dumbbell) and the surrounding tiny dots. The pair columns are now separated by a thickened solid bridge. The resealing process continues inside the spots. The large spots now look much smoother on their edges. Two pairs of distinctively curved stalactites are reaching down and connected at the tips. This confirms that splash stalactites do grow underneath the crust. Seems the mantle sea continues to supply sufficent material for the stalactites to grow. This dense liquid may have been thickened so much over a billion years and the liquid temperature may be much higher. I would bet that the bright liquid surface is quite near the basin, perhaps a gas layer of only 10m to 20m deep. \ The latest 3D video confirms that the largest spot is in fact an opening and not light reflection of white material. Imagine one day we can drop a probe through this opening and explore the vast hidden sea of Ceres. Planetary Society should work with Hollywood to make an exciting Sci-Fi movie based on Ceres (A manned exploratory mission). The proceed can fund all kinds of solarsail projects in the coming years.

ScienceNotFiction: 08/27/2015 11:05 CDT

On the latest photo PIA19635, one can clearly see a cracked open light spot near the rim on a small crater positioned on the right from the center of the picture. There are a few other tiny dots of light on the photo as well. The fact is clear, tiny cracks near the rims of many impact craters occurred naturally. Under infrared imaging, we saw high contrast of warm temperature on many of these rims. This coincides with the stalactite theory that icy asteroid impacts may dent on the surface cracking near the upper portion of the impact rim. The ice will sublimate into space and sometimes leaving rocky remnants in the middle of its crater. The pillars of splash stalactite underneath sometimes be crushed and fallen leaving behind tiny exposure of light. I can infer to another fact that the calcium rich stalactite ceiling can reflect light in many directions. We can see the resealing material on the wall of spot#5 is very whitish indeed on the latest photo PIA19630. The liquid mantle should also be whitish which can conduct intense light from the core. This high density liquid has been thickened due to the continuous evaporation of water vapors. With a lack of fresh icy asteroids impacting Ceres, the internal ocean temperature will rise rapidly as it no longer can cool off by the mantle circulation because of shrinking water volume. The core chemical reaction will stop in the future because the lack of reactants, and Ceres will be cooled off just like those frozen moons of Saturn (I.e. Dione, Tethys, Rhea etc.).

ScienceNotFiction: 08/28/2015 12:44 CDT

Furthermore on Photo PIA19630, I am now 100% convinced that there are shadowy objects floating on the bright mantle sea. By comparing the previous Occator photos, we know for sure that these floating objects moves are not stationery.They vary in sizes and shapes. You could see them from the dumbbell holes too, Are they floating debris? Floating organisms ? Ocean wave shadows ? This is the most exciting discovery of the century, my salute to the entire team of DAWN. This mission has brought us several steps closer to the truth of how planets and moons formed in our solar system.

ScienceNotFiction: 08/29/2015 11:06 CDT

WHAT IS THE WHITE MATERIAL ON MANY CRATERS AND MOUNTAINS? Given the assumptions that the surface of Ceres has rich deposit of Magnesium Silicates (Talc) and clay, the heat generated by a high speed asteroid (rocky) impacting the surface may convert Ceres' suface soil into steatite ceramic streaks. Such reaction takes less than 1600C to achieve. The liquified crystal will sinter into smooth traces of white streaks. In some cases, the impurites of Mg silicates (with calcium) may make the resulted surface whitishly glossy and smooth with high reflectance of light. The formation of white streaks on the Pyramid may have occurred during its initial impact on the surface. The top soil at impact point was fused on to the conical surface. As it plunged into the mantle, the dense liquid and floating sepiolite precipitants lifted its low density section above a soft mud plain. This explains why the Pyramid has a shiny streaky surface. The conical tip had penetrated the surface at an agle other than vertically. This also explains why white streaks formed on the walls of many craters. A recent asteroid impact on our Moon during 2013 had left a bright white spot. Perhaps there are still many Mg silicate asteroids flying in our solar system. If we can see whitish streaks on a meteor, this may be an indication that its Mg-silicate rich surface was heated at least once during planetary flybys.

PhillipWynn: 08/30/2015 01:53 CDT

Could the Ceres mountain be ejecta excavated by a shallow angle impact that created the crater at the mountain's base?

ScienceNotFiction: 08/30/2015 07:40 CDT

PhillipWynn: If you take a closer look at the newest closeup of the Pyramid, the mountain top was attached with a layer of dark rocky material. Perhaps this material was deposited and dried when the asteroid was bumping up the mud plain from below. The smooth mountain side would slide much of the wet mud down to the foot during this period. The surface temperature of Ceres at that period would be well above zero degree. The impact crater right next to the Pyramid was probably done at a much later period. Sharp rim and deep basin indicated that it should have formed at Late Muddy Crust Period when this mud plain region has already thickened and hardened.

Marc Rayman: 08/30/2015 09:09 CDT

PhillipWynn: That's an intriguing idea, but the geology just doesn't add up. The cone is too well defined, with boundaries that are too sharp, for it to have been excavated by an impact. Impact ejecta have very different shapes and distributions. Also I should mention that the dwarf planet's gravity is large enough that impacts will never be slow, even at shallow angles.

Jonathan Chone: 08/31/2015 08:01 CDT

Hi Dr. Marc, as you mentioned, "Dawn will use the color filters in its camera to record the sights in visible and infrared wavelengths." That means in this mapping orbit, we'll get global maps of Ceres in true color and infrared light range? If this is the case, will you release this maps?

jumpjack: 09/03/2015 02:54 CDT

Is it available any site showing coverage of currently available images, like MRO and LRO sites?

jumpjack: 09/03/2015 02:55 CDT

The animation is cute... but it causes headache! A "ping-pong" version would be much better!

ScienceNotFiction: 09/05/2015 02:31 CDT

THEORATICAL STUDY OF CERES MANTLE LIQUID: Calcium Chloride (CaCl2) Based on my proposed composition of the mantle liquid (mainly consisted of CaCl2, H2O, and Magnesium silicates), I am now focusing on the inorganic chemical interaction between the liquid mantle and the stalactite crust. Indeed, a very intriguing relationship exists among these chemical ingredients that will perpetuate the current state of Ceres. Several intermediary chemical reactions as well as complex chemical decompositions are taking place inside Ceres in order to maintain the equilibrium. Among many chemicals, CaCl2 plays a major role in the entire chemical system of Ceres. It has a pivotal role in the well being of Ceres. It is our answers to the many mysteries of Ceres observed from DAWN. Let's look at the unique properties of CaCl2-Water system: CaCl2 can absorb a lot of water molecules to form various type of hydrates - 6xH20, 4xH20, 2xH20. Each hydrates achieves their equilibrium within the system at various temperatures under different concentration levels. At 31% CaCl2 by mass concentration, the solution will freeze at -52C under 1 atm (eutectic point). If we increase the concentration to 51% or more by mass at temperature higher than 25C, several CaCl2 hydrates will begin to precipitate and leaving fewer hydrates as water molecules will be freed and evaporated from the CaCl2 hydrates forming anhydrous CaCl2 solid. Increasing the temperature and concentration, fewer hydrates (including CaCl2-6xH2O, CaCl2-4xH20 and CaCl2-2xH2O) will remain in liquid state. The viscosity of CaCl2 solution increases rapidly at high concentration under lower temperature. If water has 0.6 centipoise, CaCl2 solution can go beyond 12 centipoises at 50% concentration and >50C. That is 20 times more viscous that H2O. But interesting enough, the viscosity level drops to 4 centipoises when the by-mass-concentration is nearing 100%...continues

ScienceNotFiction: 09/05/2015 02:33 CDT

Another interesting aspect of CaCl2 solution is its surface tension. At 50% concentration and 50C, the surface tension is around 98 dynes/cm (normal water at 50C is around 67 dynes/cm). The surface tension increases as surrounding temperature drops in any fixed concentration level. So the surface of Ceres mantle sea is thick with high surface tension. The specific heat of CaCl2 at 50C with 50% concentration under 1 atm is around 0.53 cal/gC. This means it takes less energy to raise the temperature of a CaCl2 solution. Vapour pressure of CaCl2 solution at 50% concentration at 50C would be 24mm Hg. In another word, in between 95% to 100% humidity, solid calcium chloride will begin to liquefy. Since calcium chloride is both hygroscopic and deliquescent, anhyrous CaCl2 solid will absorb moisture from the air until it dissolves, and the solution will continue to absorb moisture until an equilibrium is reached between the vapor pressure of the solution and that of the air. Based on the above data, we can see why the mantle ocean of Ceres has a high viscosity and how it regulates the humidity and atmospheric pressure of the gas gap layer under equilibrium condition (where there are no large punctures on the stalactite sphere). Any drop in the internal atmospheric pressure, a new equilibrium will need to be established. If we are to decend deeper toward the core layer, viscosity will decrease which in turn increase the liquid circulation of the mantle, so the viscous upper layer of the ocean will quickly absorb much of the internal heat and trnasfer the heat toward the ocean surface in the form of H2O evaporation. The H2O will eventually be absorbed by the anhydrous CaCl2 and revert to liquid again. Heat will be released and absorbed by the stalactite crust toward the surface of Ceres...continues

ScienceNotFiction: 09/05/2015 02:34 CDT

I would speculate that there exists a liquid-gas reaction layer between the mantle and the core where many exothermic chemical reactions continue. The high density and high liquid pressure of the mantle ocean help to contain the ongoing reactions and provide a natural cooling mechanism. Fortunately, the light conductive nature of CaCl2 has given us a good glimpse of the core through the Occator spots.

Marc Rayman: 09/08/2015 07:35 CDT

Jonathan: Dawn's camera, as on many other planetary missions, takes pictures in specific wavelength ranges in visible and infrared, and those images can indeed be used to construct approximate true color. We are not only acquiring such data in this mapping orbit, but we did so in the two previous mapping orbits (and at Vesta as well). The need for accuracy and scientific review of the data sometimes slow the release of some products, but all of Dawn's data are released to the public after the science team has performed the necessary analysis and interpretation for scientific publication. jumpjack: I believe vestatrek.jpl.nasa.gov may be what you are interested in. We do not yet have an equivalent site for Ceres, but we will.

ScienceNotFiction: 09/11/2015 02:32 CDT

Theoratical Analysis of Cerean Mantle: Calcium Sulfate CaSO4, Calcium Carbonate CaCO3 & Sepiolite Mg4Si6O15(OH)2·6H2O In order to speculate the makeups of the stalactite ceiling, we should examine the origin of three basic materials - gypsum, CaCO3, and sepiolite. Gypsum (CaSO4 hydrates) is one of the main ingredient of light weight asteroids. When such asteroids impacted the early Cerean ocean, portion of the CaSO4 will react with NaCl-H2O(sea water) to form CaCl2 as well as sodium sulfate hydrates (or Mirabilite). Mirabilite melts at 33C and its hydrate has a density of 1.464g/cm3 which means it may float on the surface of the mantle eventually (Cerean ocean has an estimated density of >1.5g/cm3 could have been lower in the beginning). Since the mantle sea is in constant contact with the thin crusts, there would be selenite crystals formed underneath the surface of Ceres. As the gas gap layer expands, the high internal humidity (95-100%) and warm temperature (40-50C) may support the growth of long gypsum crystals. Moreover, gypsum flowers may formed on the sides of the stalactite columns. Gypsum flower is the growth of mineral deposit in curved-shape similar to a flower pedal. Calcium carbonate (Limestone) is another predominant substance in the Cerean core. It reacts with H2O and CO2 to form calcium bicarbonate vice versa. As the mantle liquid splashes onto the ceiling plus water vapour carrying some molecules due to low gravity , stalactites will continue to form everywhere on the ceiling. As for sepiolite, the process is much more complex. Sepiolite will form from alkaline solution of Mg silicates (Talc), MgCl2 (sea water) and sodium hydroxide NaOH with hydrothermal treatment at 150C-200C. The build up of sepiolite on the ceiling will further strengthen the Cerean crust. This clay mineral act as moisture absorbent. With a high enough concentration, sepiolite rich solution can turn into gels at room temperature.

Jonathan Chone: 09/11/2015 10:05 CDT

Thanks for your explanation Dr. Marc. Can't wait to see global true color of Ceres, the true color images that Dawn released previously shows that the color of the northern hemisphere and Haulani Crater are very different, so I'm very curious about what colors will we see at other region on Ceres? This maybe caused by different chemical composition on different region?

Phillip Wynn: 09/11/2015 02:47 CDT

Boy, the latest image of the bright spot in Occator crater really, really looks like it's dead center in the crater. And give the ubiquity of the light material such as on the conical mountain, doesn't it look like the impact accessed underlying material? My question is, isn't it the case that over a sufficiently long period of time, solar radiation will "discolor" anything "white"? Does that not mean either that the crater is relatively young, or that Ceres is within relatively "recent" times still "active"?

ScienceNotFiction: 09/11/2015 09:08 CDT

Lo and Behold: Light Holes Are Fast Disappearing! The latest photo PIA19889 has confirmed that the geological resealing process is still functioning inside Ceres. Since Hubbles' first spotting of water vapour plume from the hole in Jan 2014, Ceres took roughly 20 months to seal the openings. The dumbbell hole on the right had been sealed completely. The surrounding tiny round dots are no longer in oval shapes and rapidly closing up. As for the main light hole, we can see the rim wall now being saturated with a thick coat of material and left with a small opening toward the bright mantle sea. It is obvious that the resealing process has sped up during July-August. Perhaps Earth's gravity has influenced the ocean tidal cycle which raises the liquid surface near the Occator crater region. When the mantle liquid exposed to the cold temperature of the exposed crater, it coagulated almost instantaneously. If you closely examine the photo, you will see a lot of stalactite columns extending toward the center, like a rocky tunnel extending into the deep. The surfaces of these stalactite columns have a lower reflectance in comparison to the intense light from the center. With this latest photo, we can now solve many mysteries of the exterior surface of Ceres. It also confirms that a self-repairing mechanism continues at work inside Ceres. Using orbital simulation, we can even predict how the tidal height changes inside the Cerean ocean in accordance to its relative distances with surrounding planets. Once the light holes are sealed, DAWN will no longer be able to peek at the mantle ocean from above. Until the next asteroid penetration or giant stalactite fallen event, we won't see another hole on the Cerean surface again !

ScienceNotFiction: 09/13/2015 11:36 CDT

Are giant lianas growing inside Ceres ? No kidding ! After examining every bit of the recent close-up photos of Ceres, I would speculate the likelihood of large lianas growing on the higher region of the stalactite ceiling. With high humidity, high concentration of CO2 gas and constant light, the stalactite ceiling provides the ideal environment for the growth of tropical lianas. Their vines can grow as thick as tree trunks, stretching a vast area as well as building bridges from column to column. They live a long time just like trees on Earth. They can provide another layer of strength for the Cerean crust to withstand minor impact events. With clearer photos coming in during December, we may be better able to speculate their existence on Ceres. We should never be surprised to find life dwelling inside Ceres. Ceres is just as unique as our mother Earth. Plant evolution on a miniature planet is certainly a fascinating subject.

ScienceNotFiction: 09/14/2015 07:30 CDT

Framing Camera Defect Seen on all Recent Photos ! A small triangular dark spot (looks like a triangular hole on the surface crust) appears on each and every recent photos. It is positioned about an inch (72 dpi screen resolution) to the left from the center.

ScienceNotFiction: 09/14/2015 07:32 CDT

It may be the shadow of DAWN !!!

ScienceNotFiction: 09/15/2015 01:35 CDT

Theoratical Analysis of Cerean Mantle : Calcium Silicate Ca2SiO4 & Sodium Silicate Na2SiO3 (waterglass) Calcium Silicate is another by-product coming from the core reaction layer. It has a very low density 0.29g/cm3 and high water absorption property. This fireproofing material is used in high temperature insulation application. When chemically reacts with carbonate or calcium hydroxide, the calcium silicate hydrate can seal pores. Sodium silicate is another by-product from the core reaction. When heated with acid, it can form clear silica gel. When mixing with magnesium silicate, a thick paste will form. Its flocculant property will coalgulate colloidal particles in a solution. Although sodium silicate has a high density of 2.4g/cm3, but because it can coalgulate with lighter particles in the mantle, it will float to the mantle surface and adhere to the stalactite ceiling sealing up tiny pores and holes.

ScienceNotFiction: 09/16/2015 01:15 CDT

Framing Camera Defect First appeared on PIA19630 !!! I have gone back to all photos released by JPL and confirmed that prior to PIA19630, the triangular black dot did not appear then. Since its position is fixed with exact darkness intensity, it must be a cluster of sensor pixels got hit by powerful high energy particles. It should not hamper the mission, we just need to omit this tiny black hole when looking for other tiny black holes (straw stalactite depression) on Ceres.

ScienceNotFiction: 09/18/2015 02:11 CDT

The Depth Estimates of Cerean Mantle and the Core It is nearly impossible to estimate the true depth of the Cerean mantle without data on the light conductivity property of the liquid. Without knowing the exact composition of the mantle, we will never know the truth. Based on scientists' estimates that the Cerean ocean volume is approximately equalled to 1/4 of Earth's ocean. I've attempted to find out a reasonable range of ocean depths. I use 1.31 billion km3 as the Earth Ocean Volume. By subtracting the combined depth of the crust and the gas layer, I use 468.5km as the radius in all of my calculations (It is the sphere radius of core plus mantle). At 170km depth, I have worked out the liquid pressure at such depth based on 1.55g/cm3 liquid density at 0.27 gravity. The result is a shocking pressure of 6882 atm. But water vapor (super saturated steam) cannot escape at such pressure. This means one thing only, the reactions that could generate escaping H2O vapour would take place at about 504 atm (max pressure of saturated steam at 431C) depth or else H2O steam is permanently trapped at lower depth. 1/4 Earth's ocean volume, core's radius=291km, mantle depth= 170km, seafloor pressure = 6882 atm. 1/5 E.O.V., C.R.=343km, M.D.= 125km, SF.P.= 5060 atm. 1/8 E.O.V., C.R.=399km, M.D.=70km, SF.P. = 2834 atm. 1/10 E.O.V., C.R.=415km, M.D.=54km, SF.P.=2186 atm. 1/12 E.O.V., C.R.=425km, M.D.=44km, SF.P.=1761 atm. 1/15 E.O.V..C.R.=434km, M.D.=35km, SF.P.=1397 atm. 1/20 E.O.V. C.R.=443km, M.D.=26km, SF.P.=1052 atm. ...continues

ScienceNotFiction: 09/18/2015 02:16 CDT

A mantle depth range of between 26km to 44km sounds more reasonable for the current state of Ceres. I assume 50% attenuation loss of a 80km length fiber optic cable. Another word, I assume the mantle light intensity inside Occator spot is only 50% of the light generated by Mg core reaction. During the protoplanet formation period, much of the salt water had reacted with the core forming solid precipitates. Some H2O vapour would escaped to space before the exo-crust was fully formed. The core had grown in size over billions of years. At the Mg reaction layer, Mg will burn in CO2, H2O, and oxygen, giving off intense white light (and strong UV). Mg also reacts with strong acid (HCl) at higher level to form more salts. There would be several other silicate forming layers at various temperature-depth with reactants of similar density. H and CO2 gases and H2O vapor will eventually escape to the ocean surface. I would speculate a phenomenon of common occurrence on the mantle surface- Gas Bubble Burst (GBB). It is similar to gas bursts from lava craters in Earth.

ScienceNotFiction: 09/18/2015 03:14 CDT

With all indications, Ceres' Mg core reaction is based on thermo plasma chemical process at an equilibrium state. The inner core is made up of mineral and salt at temperature much lower than the Mg reaction layer (plasma layer operated in 1950C-1100C range). The liquid mantle acts as a flexible insulator/containment shield on the plasma system. Secondary reaction layers exists at several temperate-depth range including 800C-700C, 500C-400C, 300C-200C. Without an observable magnetic field, Ceres' plasma layer would remain stable, unless it is disturbed by the magnetic field from nearby planet during its solar orbit.

ScienceNotFiction: 09/18/2015 04:06 CDT

On several September closeup photos, there are unusual surface patterns near the rim of several large craters. These craters have similar appearance as the Occator which means they must be formed at the same period. Instead of seeing branching creeks running down a slope, I actually see extrusions of these branches. Portions of the branches are overhanging above the ground. There are tiny gaps/cavities in between branches. Because of the high viscosity nature of the mantle fluid which would prevent multi-branching flow on slopes, my only plausible explanation is that these are branching trunks of giant lianas. My speculation is that the formation of craters may have compressed the crust and exposed the giant vines which had grown (may still be growing) near the stalactite ceiling for many years ago. Over thousands of years, these liana vines were buried by layers of mantle deposit on the ceiling. Large crater impact events have uncovered these fossilized lianas by chance. There are also color variations on these "wooden vines." Perhaps the plant evolution within Ceres have ended in the past due to unfavorable chemical and temperature changes in the mantle ocean. If we are searching for life on Ceres, these fossilized lianas will serve as evidence.

SceinceNotFiction: 09/20/2015 04:07 CDT

Ceres' Secrets are from its Mg Plasma Core Layer Based on the Mg reaction core theory, scientists should be able to answer three more mysteries of Ceres: Does Ceres have a magnetic field? Without a magnetometer, DAWN cannot provide us a decisive answer. However, the ionized Mg-plasma layer would generate a small stable magnetic field. This plasma sphere will interact with its neighboring layers of charged material to generate rotation. Because the plasma layer is shielded by alternating layers of electrically conductive salt solutions as well as a charged H gas layer, the Cerean magnetic field would be nearly concealed. You will need a magnetometer to detect such field near the surface of Ceres. Why Ceres has such short period of rotation? This is a direct result of the plasma-core rotation mechanism. The high speed core rotation makes Ceres to rotate in the same direction. This would mean the core rotates much faster than 9.074 hours. The gas gap layer actually drags down the speed a little. What else can we observe from Ceres? I think that frequent electrostatic lightnings may occur inside the liquid mantle as well as in between the mantle surface and the stalactite ceiling. The high intensity light from the core will prevent us from observing such lightning. If oxygen ions exist on regions of the stalactite sphere, then localized rain may also occur. The haze observed above the light holes may be cloud of water vapor formed by electrostatic lightning. As for the mantle, we may observe intense light flashes/bursts on the surface of the ocean. Again, the intense background light (and UV) from the deep will interfere our observation of such effect. Harvesting electricity from Ceres would be as simple as sticking electrodes into the viscous liquid or just use solar panels facing the mantle ocean. If an outpost can be secure at the stalactite ceiling underneath the crust, the threat of solar and cosmic radiation would be minimized.

ScienceNotFiction: 09/24/2015 07:35 CDT

Ceres May Have Multiple Plasma Layers within the Core In the beginning, the light weight core with Mg rich molten minerals reacts with large body of salt water coming from space. The build up of a dense Mg plasma cloud at 3100C would gradually expand over time, ionizing its neighboring layers. The salt-saturated mantle at different depth would generate precipitants and soft minerals at different temperatures. The intense UV light will decompose chemical compounds such as HCl into their ionic components and help to form more salts. The lighter stuffs will float toward the surface forming early crust while the heavier ones such as Mg silicates will fall back toward the plasma layer and get ionized again. A growing layer of molten MgO starts to form around the dense plasma cloud (at 2850C) where ionization/recombining of Mg ions and O electrons occurs. Electrical resistance increases as the outer MgO layer cools away from the plasma. As the density of the ocean increases, more light weight particles would float toward the ocean surface. They coagulate to form a variety of stalactites and chemically bonded materials. New Mg silicate asteroids would continue to bring in additional silicates to fuel the build up of MgO layer over the plasma core. At 3.58g/cm3 density, the molten MgO plus crystallized MgO with depth of 200km will exert a pressure of near 20000atm or more (2GPa) on the plasma. Under such extreme pressure and the electrical shielding effect of MgO layers, the core would condense into an impermeable plasma (solid plasma). The outer plasma shells maintains the core rotation and shields it with with double layers and electric-field screening. The thickened cooler layer of MgO (1600-1100C) above the plasma sphere becomes a dielectric insulator on the core. The highly conductive upper ocean mantle would provide further shielding on the magnetic field generated by the plasma core under equilibrium condition.......

ScienceNotFiction: 09/24/2015 07:51 CDT

...As the surface crust develops over time, the formation of a gas layer saturated with H, O, CO2 from multiple reactions within the system will separate the mantle from the crust. Electrostatic lightning will generate H2O vapor that is readily absorbed by many moisture-absorbing salts such as CaCl2. Excess H2O vapor will form clouds near the ceiling under specific atmospheric pressure, thus forming a habitable zone. Photosynthetic species such as plant begin to develop during this period. As layers of mantle materials piling up on to the stalactite ceiling, many plant species were extinct with the exception of giant lianas. They can flourish on the stalactite ceiling with high humidity, CO2 and light. As the crust thickens, fewer asteroids can penetrate the surface into the mantle, the plasma core expansion process becomes stable in an equilibrium state. Only external magnetic field can disrupt the system and generate plasma wave that can influence the thermal circulation of the mantle in which super tidal surge with touch the crust ceiling. Once the crust is penetrated, pressurized H2O vapor will eject from the opening (plume) until the internal atmospheric pressure become stable again. This process repeats for millions of years on Ceres. Function as a heat insulator, from time to time the Cerean crust layer will accumulate enough electrostatic charges to interact with solar wind in forming discharging events near the polar regions. This may induce electrostatic zapping on the soft dusty surface of Ceres leaving tiny chained-craters.

Dan: 10/12/2015 11:41 CDT

Hello Marc Just wondering if the map above is the first map of Ceres created?

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