How can we still not have Answers for Ceres Lights?

originally posted by: Ross 54

originally posted by: cmdrkeenkid
a reply to: weirdguy

The albedo, or ability to reflect light, of Ceres is about 9%. This means that of all the light that teaches Ceres only 9% is reflected back. This is pretty low, due to the dark soil and dust that compromises most of the surface. So when you have an area of a significantly higher albedo in these dark areas, the contrast makes it go all wonky and creates the bright spots we're seeing in the photographs.

For comparisons: The albedo of ice is around 35%, while snow can reach up to the mid-80s% if it's really fresh. I don't know what salt is offhand, but 20-40% comes to mind got some reason.

So it could be salt, at least until salt is officially ruled out.

The figure I found for fresh salt was a maximum of about 0.4 albedo (40 percent reflectivity). The current figure given for the bright spots is ~ 50 percent. I'm seriously inclined to doubt it's salt. So is NASA, I expect. Still, they're being careful and thorough; checking the most likely things first.

It might be some other light colored minerals, plowed up by asteroid impacts, but NASA has already noted that the distribution of the spots isn't like that of normal cratering.
Maybe some gas trapped below the surface, blowing up surface dust. Not at all likely, especially on this large scale, and on a continuing basis, but it can't be entirely ruled out yet.
Cryovolcanoes, or geysers--probably not, they should have been able to detect the water vapor, but didn't. Besides that, Ceres isn't tidally squeezed, as Enceladus is by nearby Saturn. Where's the heat to drive them?

Chris Russel recently said, in response to the Haze release, that the team mostly thinks what they've found is not ice and probably a salt or something else. Another thing I noted was its presence might not be tied to the crater and that perhaps is something "active". Take from that what you will--and I might possibly have stated something wrongly.

BUT regarding the bolded statement above, the linkg below. Note it's an old link and it's about cryvolcanoes--which have been all but eliminated as a possible explanation for the 5th spot. HOWEVER, it does give some details about what might be expected if there were a cryvolcano on Ceres...
www.newscientist.com - Bright spots on Ceres could be water volcanoes...

Another explanation is cryovolcanism, in which ice and water are forced out of the surface by processes similar to those that drive magma volcanoes on Earth. But according to a second model presented at the LPSC by David O’Brien of the Planetary Science Institute in Tucson, Arizona, Ceres doesn’t have enough muscle to drive these eruptions.

Water down deep

The idea is that Ceres has a subsurface ocean covered by an icy shell. As the bottom of the shell freezes, it expands, putting pressure on the ocean and the shell itself. In order to create a cryovolcano, says O’Brien, the water pressure needs to build up enough to launch up through the shell before the ice cracks and relieves the pressure.

We don’t know exactly how deep the ice is on Ceres, so O’Brien tried a range of plausible depths. None produced the conditions for spewing cryovolcanoes – the ice always cracked before enough pressure built up. The best case scenario was water reaching about 90 per cent of the way to the surface.

Intriguingly, that means water could potentially reach the surface from a deep crater, where there was less ice to get through – perhaps even from a crater like the one where Dawn saw the bright spot. That doesn’t mean there is a cryovolcano producing a massive plume, but it could be just enough to replenish the ice on the surface, countering the instability that Titus discovered.

a reply to: 3danimator2014

Well, I suppose there is right now. Figuratively, anyway.

a reply to: Ross 54

I was able to find a good amount of information that points to the albedo of the bright spots being closer to 40%, however it's in the Wikipedia article and other forums/discussion boards. All of which seem to refer a speech by Marc Rayman, the Mission Director and Chief Engineer for Dawn, from April of this year. I was hoping to find a transcript for the video to save time, but no dice. However, I did post the video below.

These bright features have an albedo of about 40%...

Bright Spots on Ceres

The source for that is: Rayman, Marc (8 April 2015). Now Appearing At a Dwarf Planet Near You: NASA's Dawn Mission to the Asteroid Belt (Speech). Silicon Valley Astronomy Lectures. Foothill College, Los Altos, CA.

You can watch the video here:


Now Appearing At a Dwarf Planet Near You: NASA's Dawn Mission to the Asteroid Belt (If YouTube embed doesn't work.)

Another thing I kept seeing referenced to was an interview given by Chris Russell, a professor of geophysics and space physics at UCLA, in March of this year.

In this case, the feature is very reflective... Now, we don't know what size it is, so we can't tell if the albedo is 40 percent, 60 percent, 80 percent or 100 percent, but it's probably in that range someplace.

Studying Dwarf Planet Ceres: Q&A with Dawn Scientist Chris Russell

The more recent (July 23rd) article, linked below, quotes Chris Russell as saying that the albedo of the Occator crater spots is now thought to be 50 percent. This article was apparently written before the results essentially ruling out ice were available.
A cryovolcano or geyser large to make a haze over half a crater 60 miles in diameter should have produced enough water on the surface to have been detected. There has been no detection reported of water in any form in Occator crater.
www.universetoday.com...