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

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Fri, 11 Sep 2015 18:13:53 -0700
Message-ID: <97b1ff421f7690c632dcb2959d5f7a9c.squirrel_at_webmail.lpl.arizona.edu>

Hello from the VATT (cloudy, unfortunately). The problem with mineral
identification is that the spectrometer is not able to do very high
surface resolution spectra. I think this is related to the loss of one or
two of the reaction wheels, so they are limited to more global spectra and
thus mineral ID. Someone please correct me if this is wrong.

Larry Lebofsky

> 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
> 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
>
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Received on Fri 11 Sep 2015 09:13:53 PM PDT