getting to know vesta

www.psrd.hawaii.edu/Nov07/HEDs-Vesta.html

Getting to Know VestaGetting to Know Vesta

• Based on its spectral similarities to HED achondrite meteorites, Vesta’s surface is expected to be a mixture of three rock types: diogenites, basaltic eucrites, and cumulate eucrites.



• The Gamma Ray and Neutron Detector (GRaND), on Dawn, will measure elemental compositions of Vesta’s surface.

• Usui and McSween developed a way to evaluate the proportion of different HED rock types represented in the GRaND spectral data.

• Their HED-based mixing model uses molar ratios of Mg, Fe, Al, and Si (see plot), which show the compositional differences between the HED rock types.

Plot of (Mg+Fe)/Si abbreviated as [M/Si]mol versus Al/Si abbreviated as [Al/Si]mol



• The plot of concentrations of oxides of Si, Fe, Ti, Mg, Al, Ca, Cr, Mn, Na, and K measured in HED meteorites versus their concentrations calculated from the mixing model by Usui and McSween shows excellent agreement.

• A logarithmic scale is used to easily show all the elements on one diagram (K is lowest and Si is highest).



• Usui and McSween’s HED-based mixing model can: – accurately estimate the

abundances of major elements measured by GRaND

– predict abundances of minor elements (Na, Cr, and Mn) not analyzed by the instrument.

• Shows the value of an

integrated approach using:– laboratory data on HED

meteorites (Cosmochemistry)– remote sensing data from a

spacecraft orbiting Vesta (Missions)

Neutron Activation Analysis

getting to know vesta

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