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Dawn at Ceres Thread

Frida Space

By Frida Space
in Science & Spaceflight

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monstah

monstah

Posted
Posted
Judging from this photo posted earlier in the thread, Ceres has some color, unless it is a false color image.

http://upload.wikimedia.org/wikipedia/commons/f/fc/Ceres_optimized.jpg

Most times when "false color" is mentioned in astrophotography, it's not the same kind as when you process a B&W picture with a color gradient (think heat cameras, where blue is colder and red is warmer - in truth, it is a single infrared color, colorized so brighter is red and darker is blue).

Rather, it usually means "some true color your eye can't perceive", as in pictures taken in two different infrared frequencies, one assigned red and the other green in post-production.

So, I'd say those Ceres pics do show actual color variation on the surface, even if it looks grey to our squisky fleshy eyes.

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Newt

Newt

Posted
Posted (edited)

opnav3_700.jpg

Another New Image

Seeing crater peaks is neat. It starts to give a better scale to the place, to me anyway.

@Aethon: I may be able to do something to get that effect in Blender. I will post if it goes well....

EDIT:

The main issue is alignment... the colour view shows about nothing that can be matched up to Dawn's view. This makes it difficult to match the images and to make a decent animation.

I may beable to find a grid that will help, though.

Edited by Newt
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Streetwind

Streetwind

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The leading hypothesis is that the white spot(s) are some very young impact craters. Ceres is expected to have a giant ice shell, but a covering of dust and dirt. When an impact occurs, the dust is blasted away and the crater reveals the high-albedo ice underneath for a couple thousand years until dust covers it up again.

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monstah

monstah

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http://www.universetoday.com/118795/an-even-closer-view-of-ceres-shows-multiple-white-spots-now/

Multiple spots!

Multiple spots!

- - - Updated - - -

The leading hypothesis is that the white spot(s) are some very young impact craters. Ceres is expected to have a giant ice shell, but a covering of dust and dirt. When an impact occurs, the dust is blasted away and the crater reveals the high-albedo ice underneath for a couple thousand years until dust covers it up again.

I'm also reminded of the depressions on Chucky-Gerry, which are not formed from impacts but from ice sublimating beneath dust, and the dust then settling down smoothly. On the comet, the process is kinda gentle and the "craters" are dusty and smooth-rimmed, but if something similar happens on DresCeres, exposing some bedrock of some kind...

Now... where's my Ship of Imagination?

- - - Updated - - -

Holy crap check that pretty central-peaked crater which crosses the terminator near the south pole in the beginning of the GIF loop!

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Robotengineer

Robotengineer

Posted
Posted
The leading hypothesis is that the white spot(s) are some very young impact craters. Ceres is expected to have a giant ice shell, but a covering of dust and dirt. When an impact occurs, the dust is blasted away and the crater reveals the high-albedo ice underneath for a couple thousand years until dust covers it up again.

Most likely explanation, also the most boring one. Still hoping it's a monolith.

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-Velocity-

-Velocity-

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Posted
What is the current primary theory about the white spot?

I do wonder, what is its albedo? Ceres is much dimmer than Vesta in the sky, so that probably means it has a much lower albedo, since it is about the same distance as Vesta AND angularly larger. So how white is the spot? I've been kinda assuming it's some patch of ice, but if it's simply, like a 40% albedo feature on the surface of an object that has an average albedo of like 10%, maybe it's not ice. Ice I think generally has an albedo of what, 90%+?

Well, we won't have long to wait, at least! Maybe we should start a betting pool! Hmm... you know what I'm HOPING- because it would be fascinating- is that it's ices from some kind of eruptive feature (geyser or cryovolcano) that have settled back down to/flowed on to the surface to make a white coating.

Maybe it's a recent impact crater that punched through into an icy mantle?

Could it be ice that just happened to settle into a crater? If so, its latitude is awfully low for that, you'd expect that more by the poles- I think that surface ice would slowly sublimate at Ceres' distance,or no? I don't know much about sublimation.

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Tommygun

Tommygun

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I used "newish" as we don't know how recent they are. I think I recall last year that they thought that Ceres was outgassing something, so things are going on.

I wonder if the dust from a small impact could look like outgassing.

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Camacha

Camacha

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Posted
I used "newish" as we don't know how recent they are. I think I recall last year that they thought that Ceres was outgassing something, so things are going on.

I wonder if the dust from a small impact could look like outgassing.

It would be pretty neat if Ceres turns out to be active in one or more ways.

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Newt

Newt

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I do wonder, what is its albedo? Ceres is much dimmer than Vesta in the sky, so that probably means it has a much lower albedo, since it is about the same distance as Vesta AND angularly larger. So how white is the spot? I've been kinda assuming it's some patch of ice, but if it's simply, like a 40% albedo feature on the surface of an object that has an average albedo of like 10%, maybe it's not ice. Ice I think generally has an albedo of what, 90%+?

Ceres Albedo: 0.09± 0.0033

Vesta Albedo: 0.423

I got the white spot as c3 and the other areas as 98 using GIMP, but that does not say an exact albedo. Albedo, of course, is not to easy to measure, as not everything reflects light the same. If you take a mirror, and hold it in the sun, you will not necessarily see it getting brighter, because of the nature of the light's reflection, not because the mirror absorbs the light. The same sort of things happen with dust and rocks, though to different degrees and in different ways.

As for ice, it depends a lot, but generally in the range of .3 to .9, depending on cleanliness, thickness, surface roughness et cetera. It would stand out on either of these objects, but I am not sure how long it would last exposed, due to sublimation. If it is bright because of ice, therefore, it should probably be new.

But remember, ice is not the only thing that looks bright and sits underground; fresh lunar craters generally have bright rays, not because of ice but because the regolith darkens in exposed environment of the surface. This could be what we see on Ceres, too.

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-Velocity-

-Velocity-

Posted
Posted
in case you missed it

The spots are areas of slightly increased reflectiveness, representing barely a 9% higher albedo than the surrounding surface.

source: http://io9.com/could-this-be-the-answer-to-ceress-mysterious-white-spo-1680926247

Ouch. Only 9% higher? So it's not very white at all, just lighter in color than the dark rocks/dust around it.

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  • 2 weeks later...
-Velocity-

-Velocity-

Posted
Posted

Thanks for the heads-up! I just checked yesterday on Dawn's NASA site, I figured new images HAD to be coming soon.

I'm still baffled why the camera on Dawn has only a 20 mm aperture. It's only a few times sharper than the human eye. Surely, with all the money they spent, they could have put a camera with a bigger lens on the spacecraft. Anybody know why they chose such a small lens?

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