D. Rodionov

Jarosite and Hematite at Meridiani Planum from Opportunity's Mossbauer Spectrometer

Mössbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions.

Mössbauer mineralogy of rock, soil, and dust at Meridiani Planum, Mars: Opportunity's journey across sulfate-rich outcrop, basaltic sand and dust, and hematite lag deposits

Additonal co-authors: P Gutlich, E Kankeleit, T McCoy, DW Mittlefehldt, F Renz, ME Schmidt, B Zubkov, SW Squyres, RE Arvidson

Overview of the Spirit Mars Exploration Rover Mission to Gusev Crater: Landing site to Backstay Rock in the Columbia Hills

Spirit landed on the floor of Gusev Crater and conducted initial operations on soil-covered, rock-strewn cratered plains underlain by olivine-bearing basalts. Plains surface rocks are covered by wind-blown dust and show evidence for surface enrichment of soluble species as vein and void-filling materials and coatings. The surface enrichment is the result of a minor amount of transport and deposition by aqueous processes. Layered granular deposits were discovered in the Columbia Hills, with outcrops that tend to dip conformably with the topography. The granular rocks are interpreted to be volcanic ash and/or impact ejecta deposits that have been modified by aqueous fluids during and/or after emplacement. Soils consist of basaltic deposits that are weakly cohesive, relatively poorly sorted, and covered by a veneer of wind-blown dust. The soils have been homogenized by wind transport over at least the several kilometer length scale traversed by the rover. Mobilization of soluble species has occurred within at least two soil deposits examined. The presence of monolayers of coarse sand on wind-blown bedforms, together with even spacing of granule-sized surface clasts, suggests that some of the soil surfaces encountered by Spirit have not been modified by wind for some time. On the other hand, dust deposits on the surface and rover deck have changed during the course of the mission. Detection of dust devils, monitoring of the dust opacity and lower boundary layer, and coordinated experiments with orbiters provided new insights into atmosphere-surface dynamics.

Soils of Eagle Crater and Meridiani Planum at the Opportunity Rover Landing Site

The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.

Indication of drier periods on Mars from the chemistry and mineralogy of atmospheric dust

The ubiquitous atmospheric dust on Mars is well mixed by periodic global dust storms, and such dust carries information about the environment in which it once formed and hence about the history of water on Mars. The Mars Exploration Rovers have permanent magnets to collect atmospheric dust for investigation by instruments on the rovers. Here we report results from Mössbauer spectroscopy and X-ray fluorescence of dust particles captured from the martian atmosphere by the magnets. The dust on the magnets contains magnetite and olivine; this indicates a basaltic origin of the dust and shows that magnetite, not maghemite, is the mineral mainly responsible for the magnetic properties of the dust. Furthermore, the dust on the magnets contains some ferric oxides, probably including nanocrystalline phases, so some alteration or oxidation of the basaltic dust seems to have occurred. The presence of olivine indicates that liquid water did not play a dominant role in the processes that formed the atmospheric dust.

The Miniaturized Mössbauer Spectrometer MIMOS II for Extraterrestrial and Outdoor Terrestrial Applications: A Status Report

In May and July 2003 both the European space agency ESA and the American space agency NASA will launch space missions to Mars. The ESA lander Beagle 2 and the two NASAMars-Exploration-Rovers (MER) will explore the Martian surface with a set of sophisticated instruments. Part of the payload will be our miniaturized Mossbauer spectrometer MIMOS II. It operates in backscattering geometry and meets the requirements for space application of low mass (⩽500 g), small volume (coke can size), and low power consumption (⩽3 W). Main goals are the determination of the oxidation state of iron and the iron mineralogy on the surface. This information will contribute to a much deeper understanding of the evolution of the planet Mars, its surface and atmosphere, and the history of water. The MIMOS II flight units for MER were delivered in April 2002 to the NASA Jet Propulsion Laboratories (JPL), California, for integration to the Rovers. After some more testing of the complete Rover system the spacecraft will be shipped to the Kennedy Space Center early February 2003. The first launch will be in May 2003 and the second launch in late June on early July 2003. The flight unit for the ESA Mars-Express Beagle lander was delivered to ESA by the end of May 2002 for integration to the lander in late November/early December 2002. The launch is scheduled for June 2003 from Baikonur, Kazakhstan. The instrument MIMOS II is also under consideration for an ESA space mission to Mercury in 2009, and it is part of the ESA exobiology multi-user facility to be launched as part of one of the next lander Mars missions after 2005.

Field-portable Mössbauer spectroscopy on Earth, the Moon, Mars, and beyond

ABSTRACT Iron occurs naturally as Fe2+, Fe3+, and, to a lesser extent, as Fe0. Many fundamental (bio)geochemical processes are based on redox cycling between these oxidation states. Mössbauer spectroscopy provides quantitative information about the distribution of Fe among its oxidation states, identification of Fe-bearing phases, and relative distribution of Fe among those phases. Portable, miniaturised Mössbauer spectrometers were developed for NASAs Mars Exploration Rovers (in operation since 2004) and provide a means for non-destructive, in-situ field investigations. On Mars, these instruments provided evidence for aqueous activity with implications for habitability, were applied in geological mapping of the landing sites, and helped to identify meteorites, for example. On Earth, they were used in field studies of green rust, the identification of air pollution sources, or the study of archaeological artefacts. Their application to in-situ resource utilisation (ISRU) on the Moon has been demonstrated in a recent NASA field test of hardware for oxygen production. A new detector system in an advanced version of these instruments is based on Si Drift Detectors and permits the simultaneous acquisition of X-ray fluorescence spectra to determine elemental compositions.

Robotic Exploration of Planetary Surfaces – Rover Technologies Developed for Space Exploration

Mobility is a key feature for any science mission and for space exploration in general. Missions with mobile systems provide a much wider spectrum of outcomes by employing a higher number of samples within an increased area of exploration. The additional degree of freedom of a rover in comparison to a lander or even a robotic arm allows the mission to be flexibly adapted to the landing site as it is encountered.

Surface and bulk crystallization of Fe61Co21Nb3B15 alloy

Surface and bulk crystallization of Fe61Co21Nb3B15 alloy has been studied. Crystallization (surface and bulk) of specimens starts after annealing at 400°C. Differences in crystalline fraction, order in crystalline phase and environment around Featom are observed at the surface and in the bulk. Crystalline component appearance (both at the surface and in the bulk) after annealing at 480°C is attributed to Fe3Co.