Meridiani Planum 004        2.076°S, 5.512°W

Mars

Find: 18 Nov 2008

Classification: Stony-iron

History: A small rock informally named Santorini (henceforth Meridiani Planum 004) was discovered ~800 m south of Victoria crater, along the Mars Exploration Rover Opportunity’s traverse from Victoria crater to Endeavour crater.

Physical characteristics: The angular, cobble-sized rock was investigated between sols 1713 and 1749. The cobble has a massive lithology, with angles and facets at both the cm-scale and in MI images (Weitz et al., 2010). Portions of its surface appear lustrous in MI images. Numerous pits with angular edges are also visible, typically 300-400 um in diameter. Dimensions: approx. 8 × 6 cm.

Geochemistry: The iron-bearing mineralogy determined with the rover’s Mössbauer spectrometer is dominated by ferrous iron in olivine and pyroxene, with smaller amounts in troilite; minor ferric iron is likely a result of alteration on Mars (Fleischer et al., 2010b; Schröder et al., 2010). The chemical composition of Meridiani Planum 004 is rich in Ni, Mg, and Cr and poor in Al, K, and Ti compared to other material on the plains of Meridiani Planum and excavated by craters in the area.

Classification: Meridiani Planum 004 has similar Mg/Si, Ca/Si and Al/Si ratios to HED meteorites, but is enriched in S/Si, Fe/Si and Ni and depleted in O (Fleischer et al., 2010b; Schröder et al., 2010). The HED-like silicate composition with additional metal and sulfide composition links Meridiani Planum 004 with the HED or potentially the mesosiderite group. Meridiani Planum 004 is likely paired with Meridiani Planum 002, 003, and 005.