Mercury resolved spectroscopy from NTT

Mercury has been observed in June 2006 with the SofI instrument at NTT. Resolved spectroscopy was performed in the 0.94 – 2.5 μ m range. The observations were acquired close to a favorable quadrature with maximum elongation, and span mostly the southern hemisphere in the 235–315°E longitude area. trast to recent observations from IRTF, the present study does not indicate any pyroxene absorption in the near-infrared range, neither in the 2 μ m region nor at 1 μ m . Detailed spectral analysis allows to derive an upper limit of 1.5% type-A pyroxene (hedenbergite) or 1.1% enstatite (assuming minimum lunar iron content) in the regions observed, at the 700 km scale. Assuming lunar-like maturity effects on band depth, this corresponds to an upper limit of 0.15 and 0.6 wt.% FeO content in silicates, an order of magnitude less than previous estimates.