[meteorite-list] Ceres' Bright Spots Seen in Striking New Detail

[Dolores Hill]

Hello fellow meteorite (and asteroid) aficionados,

Yes. There is a mapping spectrometer in the visual and infrared on board 
the Dawn spacecraft:
> VIR, the hyperspectral imaging
> spectrometer onboard Dawn, with a spectral range
> 0.25-5.1 μm
http://www.hou.usra.edu/meetings/lpsc2015/pdf/1365.pdf


Don't worry; we all want to know about those mysterious bright spots on 
Ceres. Yesterday I heard a talk by Matthew Izawa (U. of Winnipeg) on 
this very topic. From the Planetary Sciences Institute website: 
http://www.psi.edu/
>
>   Composition of Ceres’ Bright Spots
>
> Wednesday, September 9, 2015
> Matthew
> Izawa
>
> Abstract:  The dwarf planet Ceres, located at a mean solar distance of 
> ~2.8 Astronomical Units, is the largest (diameter ~950 km) object in 
> the main asteroid belt between Mars and Jupiter. Several evolution 
> models suggest a differentiated body with potential geologic activity. 
> One of the objectives of the Dawn mission during the Ceres encounter 
> is to search for signs of past or present geological activity, 
> including processes that might be linked to observations of transient 
> water vapour events. One of the most striking features of Ceres’ 
> surface are localized bright areas, which are commonly associated with 
> impact craters. Of particular interest is a bright pit on the floor of 
> a 90.5 km diameter crater named Occator that shows signs of activity 
> in the form of water ice sublimation. I will present evidence that the 
> Ceres bright spots are hydrated salt deposits, using a combination of 
> Dawn Framing Camera (FC) multispectral observations, laboratory 
> spectroscopy, and geochemical data from carbonaceous chondrite 
> leaching experiments. Based on previous spectroscopic mineral 
> identifications, a range of candidate high albedo materials were 
> investigated including ice, Mg-carbonates, brucite, saponite and 
> ammonium saponite, (Mg,Na) sulphate salts, and (Mg,Na) halide salts. 
> Of these, the best matches are to mixtures of hydrated Mg sulfates 
> along with dark ‘average Ceres material’, which may be broadly 
> analogous to aqueously altered carbonaceous chondrite. The bright 
> spots may be forming as a result of sublimation of water from brines 
> exposed near the surface, leaving behind a chemical lag deposit of 
> former solutes, which are predicted on experimental and theoretical 
> grounds to be dominated by MgSO_4 hydrates.
>

Best regards,
Dolores Hill
UA-Lunar and Planetary Laboratory
https://www.lpl.arizona.edu/
http://www.asteroidmission.org/

On 9/11/2015 12:00 PM, Greg B. via Meteorite-list wrote:
> There is now a very close up high resolution of the bright spots in 
> one of the craters. Why are we still
> in the dark as to the composition of the bright material?  Does NASA 
> have a spectrometer on the craft. If so why can't they determine what 
> the white substance is composed of. If they do not have a spectrometer 
> on the craft.
> ..what were they thinking!!
> Greg B.
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-- 
Dolores H. Hill
Sr. Research Specialist
Lunar & Planetary Laboratory
Kuiper Space Sciences Bldg. #92
The University of Arizona
1629 E. University Blvd.
Tucson, AZ 85721
http://www.lpl.arizona.edu/

OSIRIS-REx Asteroid Sample Return Mission Communication & Public Engagement Team
Lead OSIRIS-REx Ambassadors program
Co-lead OSIRIS-REx Target Asteroids! citizen science program
Co-coordinator Target NEOs! observing program of the Astronomical League

http://osiris-rex.lpl.arizona.edu/
http://osiris-rex.lpl.arizona.edu/?q=target_asteroids
http://www.astroleague.org/files/u3/NEO_HomePage.pdf