Dawn at Ceres Thread

[vger]

Maybe an out gas occurred? And it's settling down now...

Any links to the hypothesis about out-gassing? It was mentioned once before, but it's hard to imagine something that size having anything left to "vent" that could be detectable. Unless there's some very complex (not sure what else to refer to it as besides a) honeycomb-like structure? Small, Independent gas pockets everywhere that only get released when there's an impact?

[Bill Phil]

Any links to the hypothesis about out-gassing? It was mentioned once before, but it's hard to imagine something that size having anything left to "vent" that could be detectable. Unless there's some very complex (not sure what else to refer to it as besides a) honeycomb-like structure? Small, Independent gas pockets everywhere that only get released when there's an impact?

I have no idea. It could be that there was a massive outgassing some time ago. It could be settling down now. that's something I thought about, and I don't know if it's true. Considering my luck, it's not.

[Tommygun]

Any links to the hypothesis about out-gassing? It was mentioned once before, but it's hard to imagine something that size having anything left to "vent" that could be detectable. Unless there's some very complex (not sure what else to refer to it as besides a) honeycomb-like structure? Small, Independent gas pockets everywhere that only get released when there's an impact?

Are you looking for something like this?

http://www.universetoday.com/108415/herschel-discovers-water-vapor-spewing-from-ceres/

http://www.nature.com/nature/journal/v505/n7484/abs/nature12918.html

[Frozen_Heart]

The scientists are suggesting it was caused by volcanoes. I'd assume long dead ones due to the planets small size.

[FishInferno]

I'm telling you, its an alien settlement. Mark my words:P

[Cydonian Monk]

It's just Motel 6. They left the light on.

(Seriously kinda weird though.)

[Cirocco]

The scientists are suggesting it was caused by volcanoes. I'd assume long dead ones due to the planets small size.

cryovolcanoes, not "regular" magma volcanoes. From what I read, Chris Russel (one of the Dawn mission scientists) said that "normal" magma volcanoes are pretty much out of the question because if that were the case, the light would be different (brighter). Ice volcanoes or cryovolcanoes are quite plausible though. Other theories incluse ice patches or salt patches

[vger]

Are you looking for something like this?

http://www.universetoday.com/108415/herschel-discovers-water-vapor-spewing-from-ceres/

http://www.nature.com/nature/journal/v505/n7484/abs/nature12918.html

Informative, thanks.

[-Velocity-]

cryovolcanoes, not "regular" magma volcanoes. From what I read, Chris Russel (one of the Dawn mission scientists) said that "normal" magma volcanoes are pretty much out of the question because if that were the case, the light would be different (brighter).

Not only are volcanoes erupting silicates impossible on such a small body (with no tidal heating either!), the lava would not in fact be "brighter". It would be dark. I know that's what an article probably said, but it's wrong. Popular science articles are often full of errors. Silicate lava is dark, in general. I guess pumice is kinda white... but again, that kind of heat on Ceres is impossible.

The extreme reflectivity of these spots really points to ice, I think. These are far more reflective than previously estimated at 40%. These spots are probably going to end up being like 90% reflective or more. Who knows, maybe salt like they say is a possibility, but we don't have any examples of reflective salt patches in the solar system, outside maybe Earth (and those are probably not reflective enough), but we have tons and tons of examples of highly reflective ice all over the solar system. So it's almost certainly gonna be ice. Hopefully cryovolcanoes!

Edited February 26, 2015 by |Velocity|

[lajoswinkler]

Remember that those "very bright" spots are actually rather dull looking. This is not a true representation of what we see with out eyes.

I just hope we'll get true color images and not just near infrared. It would be a terrible shame if the probe wasn't capable of that.

[vger]

The extreme reflectivity of these spots really points to ice, I think. These are far more reflective than previously estimated at 40%. These spots are probably going to end up being like 90% reflective or more. Who knows, maybe salt like they say is a possibility, but we don't have any examples of reflective salt patches in the solar system, outside maybe Earth (and those are probably not reflective enough), but we have tons and tons of examples of highly reflective ice all over the solar system. So it's almost certainly gonna be ice. Hopefully cryovolcanoes!

Another reason I was asking about the possibility of venting before is, Ceres is supposedly around 5 billion years old. If this kind of 'venting' has been happening the whole time, then how much mass would it have had a couple billion years ago?

All of this is making me think about the old hypothesis that the asteroid belt is the remains of a primordial planet that fell apart.

Edited February 27, 2015 by vger

[Kryten]

That there is at least some outgassing of water at Ceres is an observation, not a hypothesis.

[vger]

That there is at least some outgassing of water at Ceres is an observation, not a hypothesis.

Ehh, I didn't say it was.

[Cirocco]

Not only are volcanoes erupting silicates impossible on such a small body (with no tidal heating either!), the lava would not in fact be "brighter". It would be dark. I know that's what an article probably said, but it's wrong. Popular science articles are often full of errors. Silicate lava is dark, in general. I guess pumice is kinda white... but again, that kind of heat on Ceres is impossible.

Silicate lava is dark when oozing across the earth surface and viewed in the visible spectrum, but on an infrared or near-infrared picture (and I believe that those pictures are near-IR?) it would be extremely bright due to the intense heat. Mind you I absolutely agree that magma volcanoes on Ceres are pretty much impossible due to the lack of any real heat source.

My money is also on ice, possible cryovolcanoes, but I'm actually secretly hoping that it's something else entirely that no-one even thought of and would be totally surprising. Probably not gonna happen, but one can hope

this post, as all my other posts comes with the caveat that I'm no astronomer so I could be totally wrong

[Streetwind]

I too am hoping for something extraordinary - if only because it will motivate more space exploration across the globe

Dawn is now merely one week away from capturing into orbit (expected to happen next Friday IIRC), so the resolution of images taken isn't going to increase that quickly anymore from now on. After capture, the ion drive is going to take weeks to execute noticable orbit changes. But I'm convinced that they'll make every attempt to suss out what those spots are as soon as possible. I mean hey, imagine you were a scientist on the team - with photos like these after waiting all these years, I'm not sure I'd be able to sleep at night

[lajoswinkler]

Silicate lava is dark when oozing across the earth surface and viewed in the visible spectrum, but on an infrared or near-infrared picture (and I believe that those pictures are near-IR?) it would be extremely bright due to the intense heat. Mind you I absolutely agree that magma volcanoes on Ceres are pretty much impossible due to the lack of any real heat source.

My money is also on ice, possible cryovolcanoes, but I'm actually secretly hoping that it's something else entirely that no-one even thought of and would be totally surprising. Probably not gonna happen, but one can hope

this post, as all my other posts comes with the caveat that I'm no astronomer so I could be totally wrong

Near infrared has almost nothing to do with the body's heat (at least at expected temperatures and not things like lava). Consider it to be red so deep we can't see it. The heat rays have larger wavelengths. Also we're talking about reflected spectrum. Ceres' emission spectrum is in weak radiowaves like any other cold lump of rock.

This material is not white, just like 67P Churyumov-Gerasimenko is not light ash gray and I wish that NASA actually explained those things in image captions instead of creating disinformation.

Therefore, we're not seeing fresh ice, but gray material excavated by the impact. Take a look at this lunar example.

What about the other spot?

Compare with this lunar crater.

Material can slide away and reveal lighter surface, especially when there are ices locked and now dislodged and disrupted, which sublimate and leave unstable terrain.

For this to be very rich in ice it would have to be VERY fresh crater. Ice would sublimate away quickly because it's not in a permanent shadow.

Edited February 27, 2015 by lajoswinkler

[Cirocco]

yup, did some research, near-IR actually is quite far away from the heat radiation spectrum and the heat of a surface wouldn't change much about its near IR emissions, my bad.

That being said I got not a singular bloody clue what the two white spots would be. Might be what Lajos suggested, but the two dots seem to be kinda big for that?

Again though, I'm a total n00b when it comes to astronomy, I'm just a passionate amateur Can't wait until Dawn enters orbit and we get some closer and more high-resolution images.

[lajoswinkler]

There are some materials which look pitch black to us, and are highly reflective (and show up as white on b/w representations) in near infrared. Some plastics around the house are like that. My backpack, for example, which is made out of some polymer. Some types of plants have striking differences in those two spectra, too.

That said, it is possible that there are rocks which display high absorption in visible and high reflectivity in near infrared, but we don't know what kind of Ceres image we're looking at. Blame NASA for causing confusion...

[-Velocity-]

Near infrared has almost nothing to do with the body's heat (at least at expected temperatures and not things like lava). Consider it to be red so deep we can't see it. The heat rays have larger wavelengths. Also we're talking about reflected spectrum. Ceres' emission spectrum is in weak radiowaves like any other cold lump of rock.

This material is not white, just like 67P Churyumov-Gerasimenko is not light ash gray and I wish that NASA actually explained those things in image captions instead of creating disinformation.

Therefore, we're not seeing fresh ice, but gray material excavated by the impact. Take a look at this lunar example.

http://lroc.sese.asu.edu/news/uploads/M108971316L_thumba.png

What about the other spot?

Compare with this lunar crater.

http://lroc.sese.asu.edu/news/uploads/LROCiotw/M1145254989RL_thumb.png

Material can slide away and reveal lighter surface, especially when there are ices locked and now dislodged and disrupted, which sublimate and leave unstable terrain.

For this to be very rich in ice it would have to be VERY fresh crater. Ice would sublimate away quickly because it's not in a permanent shadow.

Ceres is close enough for ice to sublimate that quickly? Quickly enough that even a cryovolcano could not keep it around? I doubt it.

Also, I did not realize these were near-IR images. Are you sure they are not visible light? They were taken with the framing camera, but I'm not sure which filter. But as they are still approaching, why shouldn't we assume they were taken with the clear filter? It's a little too early to start looking at specific wavelengths, is it not?

Also, I really doubt these are grey spots. They're saying that they're still not resolving these spots fully. Much earlier, when the spots spanned much less than one pixel, they had estimated an albedo of 40%. The spots spanned so little angular area they didn't even yet realize that there were two of them. And still, the estimated albedo was 40%! That number was clearly wrong, as the light was being spread over a large area during the earlier estimates.. They even said the spots are still not fully resolved, even now. So the albedo is very high. This appears to be some kind of white material. The scientists even are speculating ice, salt, something white.

[Aethon]

Not only are volcanoes erupting silicates impossible on such a small body (with no tidal heating either!), the lava would not in fact be "brighter". It would be dark. I know that's what an article probably said, but it's wrong. Popular science articles are often full of errors. Silicate lava is dark, in general. I guess pumice is kinda white... but again, that kind of heat on Ceres is impossible.

A slice of the eucrite achondrite meteorite NWA 3147. Most eucrites are derived from lava flows on Vesta and are rich in light toned minerals.

[-Velocity-]

http://i2.wp.com/www.universetoday.com/wp-content/uploads/2015/02/Eucrite-NWA3147_8_8g.jpg?zoom=1.5&resize=580%2C372

A slice of the eucrite achondrite meteorite NWA 3147. Most eucrites are derived from lava flows on Vesta and are rich in light toned minerals.

I'm pretty sure the albedo is much too high for that to be the culprit. I could be wrong, which is why I'm only pretty sure. But look to see if they've released an updated albedo estimate somewhere. It's not going to be only 40% anymore.

[lajoswinkler]

Ceres is close enough for ice to sublimate that quickly? Quickly enough that even a cryovolcano could not keep it around? I doubt it.

Also, I did not realize these were near-IR images. Are you sure they are not visible light? They were taken with the framing camera, but I'm not sure which filter. But as they are still approaching, why shouldn't we assume they were taken with the clear filter? It's a little too early to start looking at specific wavelengths, is it not?

Also, I really doubt these are grey spots. They're saying that they're still not resolving these spots fully. Much earlier, when the spots spanned much less than one pixel, they had estimated an albedo of 40%. The spots spanned so little angular area they didn't even yet realize that there were two of them. And still, the estimated albedo was 40%! That number was clearly wrong, as the light was being spread over a large area during the earlier estimates.. They even said the spots are still not fully resolved, even now. So the albedo is very high. This appears to be some kind of white material. The scientists even are speculating ice, salt, something white.

If you're comparing this to martian polar caps, remember that that's dry ice under carbon dioxide atmosphere and that there's a cycle going on of continuous sublimation and deposition. It's a system in balance, for most intents and purposes.

Ceres doesn't have an atmosphere as a stable stratified system. Ice is under practical vacuum. That's an opened system. Particles escape.

Take a look at this diagram.

At almost zero pascals, solid-gas equilibrium exists at let's say -60 °C. However even at lower temperatures ice sublimes just like liquid water evaporates below 100 °C.

I've found out that current measurements from Earth indicate the maximum temperature on Ceres surface to be -38 °C. That's way more than you need for ice to go away in vacuum in a relatively short amount of time.

Check this out.

http://www.ifa.hawaii.edu/~meech/a740/2006/spring/papers/PPV2006.pdf

Ceres is at a distance of roughly 2.8 AU and below 5 AU there can't be indefinitively stable vacuum exposed ice.

This is why these bright spots could be ice only if they were made very recently (like, within a few years or less) which is an extremely low probability event, or - more reflective rock. I go with rock.

No, I don't know if this is a NIR image. Maybe it is not.

Thing is, if we took that material into our hands and looked at it at normal white light on a white surface, it would be gray. Not white. Ceres is a very dark body so these spots are overexposed.

Edited February 28, 2015 by lajoswinkler

[Newt]

I just thought of the crater Messier on the Moon, possibly the pair of spots is a fresh double crater?

Edited March 2, 2015 by Newt
I said 'double' too many times

[Aethon]

Dawn arrives at Ceres this week.

http://www.nasa.gov/press/2015/march/nasa-spacecraft-nears-historic-dwarf-planet-arrival/index.html#.VPS2VfnF-Yd

It looks like whatever the super bright spot is, it stands up pretty high. It appears to be in the light well past sunset.

Edited March 3, 2015 by Aethon

[lajoswinkler]

Amazing. I didn't assume it will be this tall.

Now we know what it is.

Edited March 3, 2015 by lajoswinkler