Dawn at Ceres Thread

[oversoul]

I can't wait until we get some LAMO pics back and they point some of their tools at those bright spots...I am still guessing water ice.

[-ctn-]

My guess is water ice too. Maybe a part of the mantle peeking through the deepest part of the crater?

[oversoul]

I was thinking maybe it is in the right zone that the daytime sunlight doesn't vaporize it so it remains as surface ice.

If so, time to build a base there. O_O (Reading too much "The Expanse" recently)

http://dawn.jpl.nasa.gov/feature_stories/NASA_Spacecraft_Nears_Historic_Dwarf_Planet_Arrival.asp

Edited March 6, 2015 by oversoul

[smjjames]

I was thinking maybe it is in the right zone that the daytime sunlight doesn't vaporize it so it remains as surface ice.

If so, time to build a base there. O_O (Reading too much "The Expanse" recently)

http://dawn.jpl.nasa.gov/feature_stories/NASA_Spacecraft_Nears_Historic_Dwarf_Planet_Arrival.asp

That depends on which side of the 'snowline' Ceres is on.

[-Velocity-]

My guess is water ice too. Maybe a part of the mantle peeking through the deepest part of the crater?

No, it actually looks like these features are at high altitudes, as they are in light when most of rest of the crater floor is in shadow.

[smjjames]

If it were high altitude, wouldnt we see shadows cast by them? Plus higher altitude doesn't neccesarily mean brighter.

[-Velocity-]

If it were high altitude, wouldnt we see shadows cast by them? Plus higher altitude doesn't neccesarily mean brighter.

I didn't say brighter, I said they remain in sunlight when the rest of the crater is in shadow. Have you not seen this picture yet?

See how the spots remain illuminated by the Sun when the rest of the crater is mostly in shadow? That is an obvious indication that the spots can't be in a deep depression, and they really are probably on the top of a hill or mountain. The brightest spot is even right where you'd expect the central peak of a crater to be.

Edited March 6, 2015 by |Velocity|

[peadar1987]

Central rebound peak of an impact crater that broke through a rocky crust and into an icy mantle? Does that make sense from a planetary formation point of view?

[vger]

Broadcast from earlier of Dawn arriving at Cares

http://live.slooh.com/stadium/live/dawn-to-arrive-for-ceres

(kept reading that guy's name as Bob Kerman )

Edited March 6, 2015 by vger

[lajoswinkler]

I was thinking maybe it is in the right zone that the daytime sunlight doesn't vaporize it so it remains as surface ice.

You're trying to explain something that you postulated. Not scientific at all.

The thing is bathed in sunlight for half a day. Water ice is unstable this close to the Sun.

[smjjames]

You're trying to explain something that you postulated. Not scientific at all.

The thing is bathed in sunlight for half a day. Water ice is unstable this close to the Sun.

Ah, it's on the wrong side of the 'snow' or 'ice' line then.

And yeah, I thought to myself 'wouldn't it make more sense to be at the poles if it was water ice?'

[vger]

Ah, it's on the wrong side of the 'snow' or 'ice' line then.

And yeah, I thought to myself 'wouldn't it make more sense to be at the poles if it was water ice?'

Doesn't mean it can't be ice. One of the more popular hypotheses is that there is ice beneath the surface. A meteor impacted deeply enough to expose that ice. And while the ice IS sublimating, the crater is recent enough that all the ice hasn't been lost yet.

[Rakaydos]

Especially if Ceres is right on the frost line, so while the ice is subimating, it's doing so at a, uh.... glacial pace.

[Darnok]

Nobody thinks it can be liquid water? o_O

[stupid_chris]

Nobody thinks it can be liquid water? o_O

No, that makes no sense, liquid water would require a substantial atmosphere.

[Darnok]

No, that makes no sense, liquid water would require a substantial atmosphere.

I read Ceres have some atmosphere (http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29#Atmosphere), not substantial, but always something

and maybe heat from planet core or from gravitational tides, so temperature could be above 0ºC from time to time.

[Frozen_Heart]

I read Ceres have some atmosphere (http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29#Atmosphere), not substantial, but always something

and maybe heat from planet core or from gravitational tides, so temperature could be above 0ºC from time to time.

Still not even remotely close enough to get liquid water. And even if Ceres was warm that wouldn't help either. At those pressures water goes from a solid to a gas without an intermediate state.

[lajoswinkler]

Ah, it's on the wrong side of the 'snow' or 'ice' line then.

And yeah, I thought to myself 'wouldn't it make more sense to be at the poles if it was water ice?'

Ceres definitively has water ice, that is not even in question. The shallowest dust, with the thickest ice layer (available for radar) should be in the polar craters. Just like our Moon does, as well as Mercury.

However this crater we're discussing, and few others with higher albedos, can't be water ice unless like less than a year ago an armada of meteoroids struck the surface. That would be too convenient, wouldn't it?

Doesn't mean it can't be ice. One of the more popular hypotheses is that there is ice beneath the surface. A meteor impacted deeply enough to expose that ice. And while the ice IS sublimating, the crater is recent enough that all the ice hasn't been lost yet.

What are the chances that this happened right before Dawn came? Ceres has surface old as the Solar system and I frankly don't believe that all of the sudden, right before humans start to investigate it, meteoroids expose the ice. It is possible, but highly unlikely with emphasis on highly.

Especially if Ceres is right on the frost line, so while the ice is subimating, it's doing so at a, uh.... glacial pace.

No, Ceres is deep inside the frost line. It's at roughly 2.77 AU, and the line is at 5 AU. Water ice on Ceres' surface would last for a very short amount of time. I'd say even a month would be an overestimation.

Nobody thinks it can be liquid water? o_O

Liquid water is an unstable phase in vacuum. Any liquid that evaporates needs to have pressure applied to it in order to stay liquid at a given temperature. Check this diagram.

I read Ceres have some atmosphere (http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29#Atmosphere), not substantial, but always something

and maybe heat from planet core or from gravitational tides, so temperature could be above 0ºC from time to time.

Ceres doesn't have an atmosphere, it has outgassing which doesn't (as far as we know it) form any layers. It just vents into space because barely anything holds it and the heat from the Sun is too high. Any pressure on the surface is ephemeral and for all intents and purposes infinitesimally small.

Its core can not possibly be molten. Ceres is a dead body in terms of lava flows and tectonics. It is way too small.

Gravitational tides from the Sun are negligible.

[vger]

What are the chances that this happened right before Dawn came? Ceres has surface old as the Solar system and I frankly don't believe that all of the sudden, right before humans start to investigate it, meteoroids expose the ice. It is possible, but highly unlikely with emphasis on highly.

Million dollar question?

It's been stated that Ceres is venting material, and that's been known even before the "white dots" became known. And if it's been doing this for billions of years then it's been on one heck of weight-loss program.

And what if the subsurface "ocean" wasn't a huge singular item, but divided into smaller regions like lakes? Then an impact would expose just one of the 'pockets.'

Besides, depending on how deep the ice is, just ANY meteorite might not be able to reach it.

[PakledHostage]

What are the chances that this happened right before Dawn came? Ceres has surface old as the Solar system and I frankly don't believe that all of the sudden, right before humans start to investigate it, meteoroids expose the ice. It is possible, but highly unlikely with emphasis on highly.

One of my coworkers has read too much science fiction... He's hoping it is a bracewell probe. It would explain so much, he says.

[Scotius]

Beacon left by an alien expedition to our Solar system? Like that diamond pyramid on the Moon in a story by Arthur Clarke? It would make a certain sense to place such thing in a place that budding space civilisation will not miss - but a place that is not so easy to reach either, so said civilisation would have to progress a bit beyond basic chemical propulsion. It would be so cool to find such artifact...

Privately, i think it might be a splotch of salts left behind by a outgassing event. Water evaporated long ago of course.

[vger]

Beacon left by an alien expedition to our Solar system? Like that diamond pyramid on the Moon in a story by Arthur Clarke?

*snerk*

[Camacha]

Before landing? If you are going to be misinformed, you should not be that blatant about it

[lajoswinkler]

Venting gaseous water doesn't mean there's neccessarily a hole through which it wents it. I'd expect the whole surface to vent it, like a giant comet. Rate of venting would not be near comets' venting, though. It's just traces.

[jfull]

Its aliens, I can tell from the pixels and from seeing a few monoliths in my time