NASA Dawn, What will it discover about Ceres?

originally posted by: raikata
When are new pictures supposed to be released?

Once it fully achieves orbital insertion, images will come on a regular basis.

However, due to the failure of two reaction wheels, Dawn will not be able to take pictures at all times during its approach. Camera observations require turning the spacecraft, which (without the reaction wheels) is achieved through firing the attitude control thrusters (which are different thrusters than the ion engines) which uses up the hydrazine fuel used for the attitude control thrusters. Mission planners don't want to waste the hydrazine fuel. Therefore, only a few approach images were scheduled -- January 13 and 25, February 3, 12, 19, and 25, March 1, and April 10 and 15. The gap in March and early April is when Ceres appears too close to the sun from Dawn '​s vantage point to take pictures safely.

However, once orbital insertion is complete and Dawn is close enough, the camera will be pointed at Ceres, and Dawn will begin taking the full gamut of pictures -- but that may not begin until April.

Dawn is scheduled to investigate Ceres for more than one year, and it will gradually go into progressively lower orbits over that year. It will first enter polar orbit around Ceres at an initial altitude of 13,500 km (8390 miles) so the cameras and instruments could get a first full look at the dwarf planet. They will then reduce the orbital altitude to 4,430 km (2750 miles). In August 2015, it will again reduce its altitude to 1,480 km (920 miles), where it will begin a two-month phase known as the high-altitude mapping orbit. In November 2015, it will reach its closest encounter with Ceres at a distance of about 375 km (230 miles).

So the pictures will get progressively better over the next several months, with the most detailed images coming after November.

Thank you both for the detailed answers!

A new series of animated images of Ceres has just been released. Only about 44% of the planet are illuminated, but the pictures are spread out in time. We can observed all. or most of Ceres surface as it rotates before Dawn's camera. The brightest of the bright spots is very prominent in several of the images. It presents a squarish appearance, and remains visible, even after the rotation of Ceres has carried it onto the unlit portion of the planet. The rim and floor of the crater are dark, but the bright spot within it can still be seen. A neat trick to reflect light when there is apparently none to reflect! Link to article and animated images, below:
dawn.jpl.nasa.gov...

originally posted by: Ross 54
...The rim and floor of the crater are dark, but the bright spot within it can still be seen. A neat trick to reflect light when there is apparently none to reflect! Link to article and animated images, below:
dawn.jpl.nasa.gov...

It could be the output of a cryo-volcano (or similar plume of material) that is higher than the floor of the crater -- possible slightly higher than the rim -- which would pu the top of it still in the Sun as the crater floor is in darkness.

In this first image, we see the two spots and the crater floor fully lit:




In this next image, as the crater and two bright spots turn toward the terminator line, we see the crater floor and smaller of the two spots dim a bit -- possibly because the smaller spot is a plume that is not as high in altitude as the larger spot.




In this third image, we see the crater almost at the terminator line. The creater floor is completely in shadow, and smaller spot is barely visible, but the lager spot is still visible -- as is the crater rim on the right hand side. The larger spot may be most visible because it could be that it is a plume that is still high enough to be in sunlight, maybe just at or above the rim of the crater. The right hand side of the crater rim is still in sunlight, too. The smaller spot may be a plume that is just barely still lit by the sun.

I agree that something above the elevation of the crater rim could appear as the bright spot does. If this is a vapor plume from simple ice sublimation, or cryovolcanism it seems remarkably dense, compact, and reflective.
No vertical component is discernible when the bright spot is seen at an angle that might allow this. There is no sign of a plume spreading from its source and gradually diffusing, even with the resolution at 3.7 kilometers.

At the NASA press conference on Monday, they seriously doubted that a cryovolcano was the cause of the bright spot. A mound that it would be expected to leave behind was missing, when they carefully looked for one. Even a crack, they said, out of which it might erupt was not found. Exposed ice seems to be the preferred explanation for the bright spot, at the moment.

If we have to rely on the thin, wispy sublimation of exposed ice, of the sort that has been observed on Ceres in the past, instead of an ice volcano, the question arrises-- how does such a phenomenon create a dense, highly reflective, and compact bright spot on Ceres, something that NASA's experts admit is unique in all the solar system?

originally posted by: Ross 54
At the NASA press conference on Monday, they seriously doubted that a cryovolcano was the cause of the bright spot. A mound that it would be expected to leave behind was missing, when they carefully looked for one. Even a crack, they said, out of which it might erupt was not found. Exposed ice seems to be the preferred explanation for the bright spot, at the moment.

If we have to rely on the thin, wispy sublimation of exposed ice, of the sort that has been observed on Ceres in the past, instead of an ice volcano, the question arrises-- how does such a phenomenon create a dense, highly reflective, and compact bright spot on Ceres, something that NASA's experts admit is unique in all the solar system?

Imagine for a moment that at the core of Ceres there are radioactive elements such as thorium, uranium, etc in a large concentrations. It might be possible that a deep liquid water layer could exist. Now imagine that an impact (which created the crater the bright spots are seen in) broke the crust of Ceres to the point that there is a fissure going down to that deep liquid water layer. Being that this liquid water is highly salty its freezing point would be lower.

Now imagine that over time it freezes on the surface inside this crater, and a little more is added in a steady, constant trickle. In Ceres's low gravity, over the course of millions of years a giant ice tower could be jutting up from the surface and catching the light above the rim of the crater.

That's my theory anyway.

originally posted by: Ross 54
At the NASA press conference on Monday, they seriously doubted that a cryovolcano was the cause of the bright spot...

...If we have to rely on the thin, wispy sublimation of exposed ice, of the sort that has been observed on Ceres in the past, instead of an ice volcano, the question arrises-- how does such a phenomenon create a dense, highly reflective, and compact bright spot on Ceres, something that NASA's experts admit is unique in all the solar system?

A cryo-volcano was only an example. As I mentioned it could be a plume of material created by something -- but not necessarily a cryo-volcano. I said:

"It could be the output of a cryo-volcano (or similar plume of material) that is higher than the floor of the crater"


It wouldn't be the first time a NASA probe has found something unique that was never found before. Prior to Voyager, who could have imaged that Saturn's rings were not homogenous clouds of stuff, but rather were made up of intricate thin bands? NASA never imaged that Jupiter's moon Io would have sulfur volcanoes until Voyager spotted them. They didn't consider the idea that Enceladus would have ice geysers reaching miles into space until Cassini got close enough to gather data.

As someone else mentioned above, let's wait until Dawn actually begins investigating Ceres and begins to gather good data on Ceres before we say that the bright spots "can't be _______ (whatever)". The past has shown us that there are many unique things in nature going on in the solar system that we never considered until we actually got close enough to investigate.

Nature is full of surprises -- i.e., possibilities and explanations we never considered. That's what makes these missions to new places (such as Ceres) so interesting. It's way to early to say what the bright spots "can't be"; let's gather data about Ceres first.

Giant ice towers. That's an intriguing and visually striking idea. When they looked for the elevated terrain, expected of a cryovolcano, wouldn't such a tower have made itself noticeable?
I looked at the bright spot in the latest images, when it was near the terminator. No vertical component appeared. It looked like a flat spot of light, that seemed subject to gradual geometric foreshortening, as it was viewed at a more and more oblique angle.

It was NASA 's experts who indicated that, based on the evidence, a cryovolcano was now considered very unlikely at the location of the bright spot. They don't seem to be concerned that they are being premature in this judgement.

Ceres will, no doubt, present a number of surprises.
It was under observation for quite some time with the Herschel Space Telescope. They detected plumes of water vapor, presumably from subliming surface ice. There are no reports, of which I am aware, that these plumes ever produced anything like the appearance of the now-famous 'bright spot'.

originally posted by: Ross 54
Giant ice towers. That's an intriguing and visually striking idea. When they looked for the elevated terrain, expected of a cryovolcano, wouldn't such a tower have made itself noticeable?

Probably but it would depend on how wide the base of it was, sun angle/angle of approach, etc. A cryovolcano would be expected to have a wider base than an ice tower. We'll know soon enough what it is.

originally posted by: Ross 54
...There are no reports, of which I am aware, that these plumes ever produced anything like the appearance of the now-famous 'bright spot'.

As I said, you (nor anyone else) are currently aware of any potential processes on Ceres that could create a plume of some sort of material, but that doesn't mean there is no such process. It just means there is no known explanation at this time, based on the very limited information we have on Ceres.

It doesn't even have to be a plume, but whatever the explanation (e.g., exposed bright material on a crater's central uplift peak or whatever), it may be something that changes our understanding of the compositions and/or geological processes of large asteroids (or dwarf planets, in this case).

I'm going to remain open-minded until we learn more about Ceres. Our expectations of what "should be the case" have been wrong before, so I'm not ruling anything out. Heck -- I'm not even ruling out that it could be alien!...but I'm not expecting it, either. The natural explanations can be weird enough!

That's why this mission is so scientifically exciting.

a reply to: ukmicky1980

(Looking down at my feet, slowly pushing dust and stones with my left foot, with a somber look on my face)

I have been working with a theory that is not well known, and completely rejected by main stream academia. I hesitate to share it because there are unseen and unknowable ramifications concerning it. And there appears to be a major tug of war going on about the validity of this theory. Even the public disclosure of this theory could start a chain of events that can not be completely foretold. But on the other hand, the truth will set us free.

No doubt there are many members here who are aware of the theory and agree silently for one reason or another. And others who honestly have no clue. Why is Ceres so important to send a space craft to inspect it? What would we hope to discover about this heavenly body?

Well, to answer those questions one must have a very good working knowledge of not only ancient life here, but the not so public information from those times. And what we are left with, is a ancient failure to communicate.

The reasons for that failure are lost to time, or, intentional, one can only speculate. We all are aware of warfare claimed in scriptures and ancient writings, there is little doubt to this. We find on the surface of this planet the debris of ancient societies that demonstrated a technology far greater that we would expect to find from "Cave men". Some estimates of these civilizations go from a mere 4 or 6 thousand years to a unbelievable 200 million. The major problem in accepting these timelines is if they were that advanced that long ago, where are they today?

Planet Earth has suffered through many of what we call natural disasters, meteorites, floods, earthquakes, and maybe even more that are unknowable. Mankind has had beginning after beginning as witnessed by what we find in the dirt. And as such, how does mankind re-establish itself time after time. Each time starting a new with any knowledge they may have possessed from before the calamity. WE have learned about the great mankind DNA bottleneck where the population went from millions down to a mere 10s of thousands. The human race seems to be like a virus that is able to repopulate itself with magic, a magic that was not afforded the Dinosaurs.

Where does man flee to when the sky falls with mud rock boulders, and yes, water? Yes, some might head for the hills, while the more influential have built bunker complexes in the earth. And when we go back into history what is really different?

There are ancient scriptures that continually used the word "IN" as in the earth. Academia insists they meant to use the word "ON". Rewriting history seems to be a pass-time for certain groups of intellectuals. What do the ancient Greeks have to say about the subject?

Word Origin C17: from Latin geōdēs a precious stone, from Greek: earthlike; see geo-, -ode 1

dictionary.reference.com...

Why ON Earth would the ancient Greeks call a hollow rock, Earth-like??? In the scriptures we find passages that state at least one, some say "mythical", entity that traveled to the interior of the planet many times.

King James Bible And the LORD said unto Satan, Whence comest thou? Then Satan answered the LORD, and said, From going to and fro in the earth, and from walking up and down in it

.
biblehub.com...

More recently you have a well known figure by the name of Admiral Byrd who states he has gone to this magical land to come back with a warning. He isnt the only one. There is a book by the name of "The Smoky God" that is said to be non fictional which goes into some detail about this "Argartha" "Shambolia", "Garden of Paradise". And in this book it describes a "central Sun" within. It is a object of Worship to the inhabitence, hence the name "Smoky God". Or, to be more precise, Sun Worshipers. Do we on the outer surface have in our history any Sun Worship???

So what we are left with, is a hollow planet, that is quite inhabitable, with a central point called a "Central Sun". I myself would call this object, phenomenon, a "Planet Seed". At any rate, Ceres.

Ceres orbits the Sun exactly where it is theorized a planet should be. Is Ceres this missing planet that failed to mature into a full size planet? Or, might it be that all planets are hollow, and posses a Planet Seed, Central Sun. With Ceres, being in the middle of a "Asteroid" belt, might it have been a full size planet at one time, and the asteroid field, actually be the bits and pieces of that planet. The debrief of a planet that planet earth has traversed though a few times in the past, to actually have that debris, water, pile up on our earth, to wipe out mankind and dinosaurs, and to have mankind repopulated from with IN For those who might doubt this, look up "Tiamat", it is the name the ancients called the planet that surrounded Ceres.

What would one expect to see in Ceres? Well, if this calamity of Tiamat happened millions of years ago, one might find a glowing orb, covered with millions of years worth of dust, and unrecognizable as a central sun, planet seed. Unless, that is, a meteorite just happened to blow a bit of dust off it, so that its truth can shine forth.

Of course the Academia will fight tooth and nail to preserve the "Old Ways", and political power structure. They are quick to discredit, but very very slow to debate the facts.

Well, that's the theory. Self emanating lights on Ceres? Really........

a reply to: All Seeing Eye

Our view of the bright spot on Ceres has extended from 2004 to the present. The changes in that view in the past 10 years are rather interesting, and revealing.
In 2004 the Hubble Space Telescope showed us a large bright area on Ceres, with an apparent diameter of about one-fifth that of Ceres. That amounts to about 120 Miles.
The reflective brightness ( albedo) of the spot was said to be about 12 percent, as opposed to Ceres as a whole at about 9 percent. The bright spot was not resolved, and quite blurry. It's true size and brightness were subject to correction, once the Dawn space probe got close enough, in the last couple of months, to give us better pictures.

At present, we have images of the bright spot with an apparent diameter of about 8 miles, and great brilliance.

Baring any complicating factors, the true brightness of the bright spot should increase as its apparent size is reduced, because a smaller area must be brighter, in order to emit a given amount of light.
The current apparent diameter of the bright spot is about 1/16 of the size indicated by the Hubble photographs. Since brightness depends on the area of the source, which is the diameter multiplied by itself , the current albedo of the bright spot can apparently be inferred to be about 2700 percent. Anything above 100 percent is not merely a reflector, but a source of light.

The bright spots maintaining luminosity, even as they rotate into the Sun's shadow is so interesting. We have still yet to see if Ceres, imaged in the shadow area, will show these spots still illuminated, and if so, it certainly makes and breaks many of the theories about their origin. For now, we can only speculate that they are of very high altitude above the crater rims, or could indeed be an ejected column of water vapor and other minerals. Great science is about to come out of this irregardless, and I cannot wait to see what is discovered.

Some misunderstanding seems to have crept in. Here are some improved figures, relating to Ceres-- In 2003-2004, the Hubble Space Telescope reportedly found the bright spot to be 9 percent brighter than Ceres, as a whole. Given Ceres reflective brightnss (albedo) of 9.0 percent, that of the bright spot would have worked out to about 9.8.
The apparent size of the bright spot reportedly varied, depending on the photographic filter used by Hubble. 85 miles seems a good, conservative figure for its diameter, under these circumstances. Ten years on, Dawn's best images make the bright spot appear around 8 miles in diameter.
By this we can find that the apparent area of the bright spot has been reduced by about 113 times, by improved but not yet complete optical resolution. Barring complicating factors, this means it should also be ~ 113 times brighter than was inferred from the Hubble data. This figure come out at roughly 1000 % albedo. As before, anything above 100 percent albedo indicates not a reflective object, but one that is a source of light, on its own account.

a reply to: Ross 54

So, why exactly did Hubble see the spot as being 85 miles in diameter rather than 8?

The reason I ask is because if the size determination was wrong for whatever reason, then maybe their value of the albedo at that time of 9% brighter than the average brightness Ceres was also wrong for whatever reason, which would invalidate the methodology used for your calculation of being 113 times brighter. It could even be that the feature was larger back then, also invalidating the methodology used for your calculation. I'm not saying it was larger back then. I'm saying we just don't yet have enough data to be making these calculations.

It seems to me that if they want to determine the bright feature's albedo, they would do so by actually measuring it, not by using the method you used...

...what I mean is, it should not determined by measuring the size and brightness as seen 12 years ago, then recalculate the albedo based on the size of the features seen today (8 miles wide), but ALSO using the original albedo from 12 years ago when it looked 85 miles wide. It seems illogical to mix the data sets by using the old albedo measurement, but also using the newest size measurement.

That method just seems like a round-about method that is rife with potential inaccuracies, rather than the much more simple method of just measuring the albedo right now, ignoring the Hubble observations from 12 years ago to discern albedo today.


I guess the bottom line of my concerns over that methodology is this:
I'm not an imaging expert, but is it really valid to say "Hubble saw it in 2003 as as 85 miles wide and 9% brighter than the rest of Ceres, ergo if we know now it is only 8 miles wide (113 times smaller), then that means it is also 113 times brighter than 9% brighter". I don't know enough about space object imaging to know if the calculations really work that way. Might there be other variables in play between the Hubble observations and these Dawn observations that doesn't allow us to make such apples-to-apples comparison of the data sets?

The context for albedo is the surface composition that the Sunlight is shining on, and the amount of Sunlight that is reaching it. Ceres is covered by a dark ash overlaying ice, as science thinks. The calculations would have to determine what percentage of light is being reflected by the bright spots only, and knowing the composition of those spots to determine if they are returning more light than they would be reflecting. Right now, we have not seen an image in pure shadow, but if we do, then there would be no question that they are more than reflective objects.

the bright spots look like solar panels.