June 10, 2015

What Are The Bright Spots On Ceres?

A guest post by Joseph Friedlander

Paul Scott Anderson of The Meridiani Journal blog has written about the bright spots on Ceres, 

at  http://themeridianijournal.com/2015/05/image-gallery-closer-view-of-ceres-bright-spots/ Anderson has published a nice crop of the area of interest "taken by the Dawn spacecraft. It was taken on May 16, 2015, with a resolution of 700 metres (2,250 feet) per pixel"

Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Cropped zoom of bright spots. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/Paul Scott Anderson

 What are we looking at here?  My own guess is basically the space equivalent of 'black smokers' under the sea-- but better termed 'white sublimers' in vacuum.  In a phrase, vapor deposit in vacuum.  What's going on? Surfaces in a space environment (solar influx and cooling in dark (thermal cycling), vacuum desiccation,  go to faded colors (solar bleaching) and dustlike breakdown of crustal materials (in part from micrometeors but from multiple causes). In a word, surfaces look like the Moon, spectacular and faded and muted at the same time.

But these white spots look fresh. Pristine surfaces often need maintenance. Therefore, they are being maintained.
  Water is known to outgas from Ceres---losing about 6 kg a second in resublimation probably from these very spots.  http://themeridianijournal.com/2014/01/water-vapour-discovered-dwarf-planet-ceres/

What we are seeing, to my view- is either vapor deposit of some fraction of the water or other ices escaping vents on the surrounding terrain, (part takes more heat and escapes, part cools and deposits as ice) or chemicals like white salts that go out of solution and deposit on the terrain, or both, possibly in layers depending on what's coming out the vents. 

That is the most likely explanation of what the bright spots on Ceres are. 

The ice could easily be very undrinkable/poison/impure by human standards, containing chlorides, sulfides, ammonia compounds, cyanides, etc. But with the right equipment it could be easily refined.

We can see here on the rough order of a hundred square kilometers of outgassed ice or salts, if 1-2 meters thick easily massing over 100 million tons.  What a resource, right there on the surface.

If you're planning a landing on Ceres and hope to refuel you could do worse than pack a lab and a mini refinery into the lander stage, and take off only with the  already fuelled ascent stage if you are disappointed in your search for water ice. (Unlikely)

But if you are not disappointed you can easily launch a laden tanker into Ceres orbit, since the escape velocity is only 510 meters a second or so.

As the Dawn probe is lowered into mapping orbit,  we will soon have even better pictures. The mass of Ceres has been measured more precisely now, to be  1.03 billion billion English tons (939 billion billion kilograms) and about a quarter of that is estimated to be water.  I would not be shocked if it was salty water which on Earth is not good news to the farmer but in space is good news for all future colonists, since water soluble chemicals are high on the wish list of wanted resources.  

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