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$\begin{figure} \par\includegraphics[width=8.5cm]{5850fig1.eps} \end{figure}$ Figure 1: Photometrically normalized brightness variation across the apparent disk of Mercury for April 14, 2003. The map has N up and is labelled by western longitude and latitude at 20 $^\circ$ grid spacing. The sub-observer point is marked "SO''. This hemisphere of Mercury, unimaged by Mariner 10, is dominated by the following optically bright albedo features (also labelled in Fig. 4A), identified as in Warell & Limaye (2001) and from which the base map is taken: SVST ID #52 at (242 $^\circ$ W, +10 $^\circ$ ), #53 (244 $^\circ$ W, -8 $^\circ$ ), #54 (245 $^\circ$ W, -24 $^\circ$ ), #55 (254 $^\circ$ W, +24 $^\circ$ ), and #56 (265 $^\circ$ W, +16 $^\circ$ ). The classical dark feature Solitudo Criophori ("SC'') is located on the terminator at (260 $^\circ$ W, -1 $^\circ$ ). Other local dark features are "A'' (245 $^\circ$ W, -50 $^\circ$ ), "B'' (262 $^\circ$ W, -25 $^\circ$ ) and "C'' (225 $^\circ$ W, 0 $^\circ$ ).
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In the text

$\begin{figure} \par\includegraphics[width=6cm]{5850fig2.eps} \end{figure}$ Figure 2: The distributions of the 750 nm albedo versus 415 nm/750 nm reflectance ratio of Mercury ( bottom) and the global Moon ( top). The scatterplot for Mercury (filled dots) is the observed distribution for the longitude range 210 $^\circ$ W-270 $^\circ$ W, the shaded ellipse represents the derived true extent of the distribution, and the crosses depict the result of Blewett et al. (2005) from Mariner 10 data for longitudes 10 $^\circ$ W-70 $^\circ$ W. Errorbars for the observed Mercury data are shown in the lower right corner. The lunar scatterplot (circles) is derived from Clementine images of the whole lunar surface between latitudes -70 $^\circ$ and +70 $^\circ$ . The region enclosed by a dark grey line defines the simulated distribution of the global Moon under Mercury observation conditions (to be compared with the region of filled dots for Mercury), while the smaller light grey line shows the corresponding envelope for the lunar farside. The cross mark to the lower left of the lunar distribution is located at the point (0.00, 0.42) used by Lucey and coworkers as the origin in the derivation of the Ti-sensitive parameter $\theta _{\rm Ti}$ (Lucey et al. 2000a). The cross mark at the lower left of the mercurian distribution at coordinates (0.00, 0.29) is the corresponding origin used here for calculating the Ti-sensitive and the iron-maturity sensitive parameters for Mercury.
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In the text

$\begin{figure} \par\includegraphics[width=6cm]{5850fig3.eps} \end{figure}$ Figure 3: The distributions of the 750 nm albedo versus 950 nm/750 nm reflectance ratio of Mercury ( top) and the global Moon ( bottom). The scatterplot for Mercury (filled dots) is the observed distribution for the longitude range 210 $^\circ$ W-270 $^\circ$ W. The lunar scatterplot (circles) is derived from Clementine images of the whole lunar surface between latitudes -70 $^\circ$ and +70 $^\circ$ . The region enclosed by a dark grey line defines the simulated distribution of the global Moon under Mercury observation conditions, while the smaller light grey line shows the corresponding envelope for the lunar farside. The cross mark to the upper left of the lunar distribution is located at the point (0.08, 1.19) used by Lucey and coworkers as the origin in the derivation of the Fe-sensitive parameter $\theta _{\rm Fe}$ (Lucey et al. 2000a) and the optical maturity parameter OMAT (Lucey et al. 2000b). The cross mark at the upper left of the mercurian distribution at coordinates (0.06, 1.37) is the corresponding origin used here for calculating the Fe-sensitive and optical maturity sensitive parameters for Mercury. Errorbars for Mercury are similar to those of Fig. 2.
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In the text

$\begin{figure} \par\includegraphics[width=17.2cm]{5850fig4.eps} \end{figure}$ Figure 4: Reduced UVVIS images of Mercury. Panel A shows the 750 nm albedo image with feature identifications and a coordinate grid with N at top and grid lines every 20 $^\circ$ ; the terminator longitude is 271 $^\circ$ W, limb longitude 186 $^\circ$ W. Optically bright features are labelled in white according to identifications in Warell & Limaye (2001), while dark features are color coded in black (refer to caption of Fig. 1 for identifications of the labelled features). The mid-disk pixel scale is 140 km. Panel B redisplays the 750 nm albedo image (range of disk-pixel values 0.17-0.22) and panel C the 415/750 nm ratio (range 0.37-0.44) which forms the basis for the derivation of the spectral parameters in the following two panels. Panel D displays the iron-plus-maturity parameter FeOMAT (brighter features are more immature and/or have lower abundances of iron; pixel range 0.17-0.30), and panel D the Ti-sensitive parameter $\theta _{\rm Ti}$ (bright features have higher opaque mineral abundance; pixel range 0.48-0.65).
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In the text

$\begin{figure} \par\noindent\includegraphics[width=8.5cm]{5850fig5.eps} \end{figure}$ Figure 5: Reduced VISNIR images of Mercury. Panel A displays the 950/750 nm ratio (range 1.21-1.40) which forms the basis for the derivation of the spectral parameters in the following two panels. Panel B shows the Fe-sensitive parameter $\theta _{\rm Fe}$ (brighter indicates a higher iron abundance; pixel range 0.0-0.84), and panel C the optical maturity-sensitive OMAT parameter (bright features have a lower degree of optical maturity; pixel range 0.08-0.20).
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In the text