Based on its spectral similarities to HED achondrite meteorites, Vesta

1
Getting to Know Vesta

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

2
Getting to Know Vesta

• The Gamma Ray and Neutron Detector (GRaND), on
  Dawn, will measure elemental compositions of
  Vestas 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 (MgFe)/Si abbreviated as M/Simol
versus Al/Si abbreviated as Al/Simol
3
Getting to Know Vesta

• 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).

4
Getting to Know Vesta

• Usui and McSweens 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