Peter Denham Lanagan

Rootless cones on Mars indicating the presence of shallow equatorial ground ice in recent times

High resolution Mars Orbiter Camera (MOC) images have revealed the existence of clusters of small cones in the Cerberus plains, Marte Valles, and Amazonis Planitia, Mars. These cones are similar in both morphology and planar dimensions to the larger of Icelandic rootless cones, which form due to explosive interactions between surficial lavas and near-surface groundwater. Impact crater size-frequency relationships indicate that surfaces upon which the cones sit are no older than 10 Ma. If martian cones form in the same manner as terrestrial rootless cones, then equatorial ground ice or ground water must have been present near the surface in geologically recent times.

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

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 geologists hand lens, the MI is mounted on Opportunitys 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 Opportunitys traverse between Endurance and Erebus craters.