Surface processes recorded by rocks and soils on Meridiani Planum, Mars: Microscopic Imager observations during Opportunity's first three extended missions

TLDR

The Microscopic Imager (MI) on Opportunity has returned higher‑resolution images than any previous Mars camera, enabling detailed petrographic and sedimentological studies of rocks and soils at Meridiani Planum. The paper overviews MI operations, data calibration, and analysis of MI data from the first 900 sols of Opportunity’s mission. The MI, mounted on Opportunity’s arm, functions like a hand lens with 0.1 mm resolution, allowing high‑resolution imaging of Martian surface materials. MI data resolved key questions about textures and features, showing eolian sediment transport as the dominant depositional mechanism for Burns formation strata, supporting liquid‑water flow interpretations for similar structures in Eagle Crater, and revealing well‑sorted spherules on ripple surfaces with a north‑south size gradient along the traverse.

Abstract

The Microscopic Imager (MI) on the Mars Exploration Rover Opportunity has returned images of Mars with higher resolution than any previous camera system, allowing detailed petrographic and sedimentological studies of the rocks and soils at the Meridiani Planum landing site. Designed to simulate a geologist's hand lens, the MI is mounted on Opportunity's instrument arm and can resolve objects 0.1 mm across or larger. This paper provides an overview of MI operations, data calibration, and analysis of MI data returned during the first 900 sols (Mars days) of the Opportunity landed mission. Analyses of Opportunity MI data have helped to resolve major questions about the origin of observed textures and features. These studies support eolian sediment transport, rather than impact surge processes, as the dominant depositional mechanism for Burns formation strata. MI stereo observations of a rock outcrop near the rim of Erebus Crater support the previous interpretation of similar sedimentary structures in Eagle Crater as being formed by surficial flow of liquid water. Well‐sorted spherules dominate ripple surfaces on the Meridiani plains, and the size of spherules between ripples decreases by about 1 mm from north to south along Opportunity's traverse between Endurance and Erebus craters.