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

From: Dolores Hill <dhill_at_meteoritecentral.com>
Date: Fri, 11 Sep 2015 17:13:05 -0700
Message-ID: <55F36E11.3040105_at_lpl.arizona.edu>

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 ?m

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:
> 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

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
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
Received on Fri 11 Sep 2015 08:13:05 PM PDT

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