Close-Up Flyover Of The Mysterious Bright Spots On Ceres

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How could the bright spots be caused by reflected sunlight if they keep emitting light when viewed from completely different angles?

Also, do salt planes or snowy/icy areas on Earth or other known heavenly bodies appear this bright when viewed from space?

originally posted by: ForestDweller
Also, do salt planes or snowy/icy areas on Earth or other known heavenly bodies appear this bright when viewed from space?

The exposure levels so far have been set very high to be able to see the rest of the surface of Ceres. Ceres is very dark (about the color of coal), so the exposures need to be high. However, that means that the bright spots would be overexposed in those images (higher than the image sensors can handle).

Eventually, I suspect once they do a complete map of the entire surface at the Survey Orbit altitude (Dawn will reach that Survey orbit on June 6), they will reduce the exposure levels to better resolve the spots -- even though the rest of Ceres may be too dark at those lower exposure levels.

a reply to: Soylent Green Is People

So are you suggesting that these spots are not emitting or reflecting light at all, but are just less dark spots compared to the background, seeming to emit light because of overexposure? If this is the case then NASA would obviously know what is causing the mystery, and it is not a mystery at all.

originally posted by: ForestDweller
a reply to: Soylent Green Is People

So are you suggesting that these spots are not emitting or reflecting light at all, but are just less dark spots compared to the background, seeming to emit light because of overexposure? If this is the case then NASA would obviously know what is causing the mystery, and it is not a mystery at all.

Or, they know what the lights are, and easing everyone into a new paradigm about the nature of, well, they haven't eased that out yet.

originally posted by: ForestDweller
a reply to: Soylent Green Is People

So are you suggesting that these spots are not emitting or reflecting light at all, but are just less dark spots compared to the background, seeming to emit light because of overexposure? If this is the case then NASA would obviously know what is causing the mystery, and it is not a mystery at all.

I'm suggesting that they are reflecting light, and much of that reflected light is bright enough to be overexposed due to the high exposure settings.

There may in fact be variation in the reflection's brightness at different sun angles, but if all of that variable reflection is higher than the image sensors can handle, then we would not see those variations.

a reply to: Soylent Green Is People

I'm suggesting that they are reflecting light, and much of that reflected light is bright enough to be overexposed due to the high exposure settings.

Can you explain how this relates to my post that you responded to originally?

There may in fact be variation in the reflection's brightness at different sun angles, but if all of that variable reflection is higher than the image sensors can handle, then we would not see those variations.

Like I said before, how is it possible that these spots keep reflecting sunlight when the viewing angle changes by an estimated 140 degrees judging from the image posted in the OP? Or is the satelite moving completely in sync with Ceres' movement relative to the sun?

a reply to: ForestDweller

Say you represent the brightness of Ceres with numerical values ranging from 0-1000. 0 is the darkest point and 1000 is the brightest.

In any one image, the camera can only capture a range of brightness, say from 0-500. Say the bright spots range in brightness from 800-900. All those points will show up as pure white, because they exceed the maximum brightness the camera can register in an exposure set to capture values from 0-500. The bright spots do change in brightness depending on the angle to the sun. But if the dimmest they get is greater than 500, they're still going to show up as pure white in an image set for an exposure of 0-500.

What they need to do, and I'm sure they will do at some point, is take an image with the exposure set to 500-1000. Most of the surface of Ceres, which has a brightness value less than 500 will appear black in such images, but they will be able to show detail in the bright areas.

originally posted by: ForestDweller
Like I said before, how is it possible that these spots keep reflecting sunlight when the viewing angle changes by an estimated 140 degrees judging from the image posted in the OP? Or is the satelite moving completely in sync with Ceres' movement relative to the sun?

If it was something like a salt or some other kind of crystal, they wouldn't all necessarily line up flat with the surface, and some of the crystal facets would continue to reflect as the light angle changed.

a reply to: nataylor

If the seemingly light emitting or reflecting spots appear to be doing so because of overexposure, don't you think that someone at NASA would have made a statement about it, clearing up the mystery?

a reply to: Blue Shift

Nonsense, as you can see in the image the spots don't change in shape when viewed from the different angles which they sure would if it was different facets reflecting light when viewed from different angles.

a reply to: ForestDweller

The mystery isn't that the spots are overexposed. The mystery is why they are so much more reflective than most of Ceres' surface.

a reply to: nataylor

The mystery isn't that the spots are overexposed. The mystery is why they are so much more reflective than most of Ceres' surface.

Well it seems that some posters here are trying to explain away the fact that they seem to be emitting light by saying it is because of overexposure.

Since they can't be reflecting sunlight constantly from completely different angles it seems they are actually emitting light, not reflecting sunlight.

a reply to: ForestDweller

I just explained how it's possible they can instead change in brightness as the sun angle changes without the photos registering that change.

Scientists aren't mystified by that.

a reply to: nataylor

I just explained how it's possible they can instead change in brightness as the sun angle changes without the photos registering that change.

You seem to be missing the fact that the viewing angle changes drastically too. You do understand that light is reflected at a set angle in relation to the angle of the light source? Meaning that if the viewing angle changes you would not see any reflection.

The only way this reflection story would work is if the viewing angle is changing completely in sync with the sun angle.

Is it?

a reply to: ForestDweller

You'd only not see a reflection if the area was a perfectly flat plane, like a mirror. The surface is irregular, like dirt or rock, so it produces a diffuse reflection.

a reply to: nataylor

Like I said before, the shapes don't change even though the viewing angle changes drastically. If it were differently angled parts of the formation reflecting sunlight we would see the formation change in shape as the viewing angle changes but it doesn't.

It is emitting its own light.

a reply to: ForestDweller

Do you see the rest of the of Ceres change shape? It's producing the same kind of diffuse reflections.

originally posted by: ForestDweller
Nonsense, as you can see in the image the spots don't change in shape when viewed from the different angles which they sure would if it was different facets reflecting light when viewed from different angles.

It's not just one big crystal, but a huge field of tiny crystals. It creates a retroreflection from different angles, just like how 3M Scotchlite works.

"Nonsense" me, will you?