Edward A. Guinness

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.

Nature and origin of the hematite‐bearing plains of Terra Meridiani based on analyses of orbital and Mars Exploration rover data sets

The ~5 km of traverses and observations completed by the Opportunity rover from Endurance crater to the Fruitbasket outcrop show that the Meridiani plains consist of sulfate-rich sedimentary rocks that are largely covered by poorly-sorted basaltic aeolian sands and a lag of granule-sized hematitic concretions. Orbital reflectance spectra obtained by Mars Express OMEGA over this region are dominated by pyroxene, plagioclase feldspar, crystalline hematite (i.e., concretions), and nano-phase iron oxide dust signatures, consistent with Pancam and Mini-TES observations. Mossbauer Spectrometer observations indicate more olivine than observed with the other instruments, consistent with preferential optical obscuration of olivine features in mixtures with pyroxene and dust. Orbital data covering bright plains located several kilometers to the south of the landing site expose a smaller areal abundance of hematite, more dust, and a larger areal extent of outcrop compared to plains proximal to the landing site. Low-albedo, low-thermal-inertia, windswept plains located several hundred kilometers to the south of the landing site are predicted from OMEGA data to have more hematite and fine-grained olivine grains exposed as compared to the landing site. Low calcium pyroxene dominates spectral signatures from the cratered highlands to the south of Opportunity. A regional-scale model is presented for the formation of the plains explored by Opportunity, based on a rising ground water table late in the Noachian Era that trapped and altered local materials and aeolian basaltic sands. Cessation of this aqueous process led to dominance of aeolian processes and formation of the current configuration of the plains.

Ancient Aqueous Environments at Endeavour Crater, Mars

Opportunity has investigated in detail rocks on the rim of the Noachian age Endeavour crater, where orbital spectral reflectance signatures indicate the presence of Fe+3-rich smectites. The signatures are associated with fine-grained, layered rocks containing spherules of diagenetic or impact origin. The layered rocks are overlain by breccias, and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the Endeavour impact. Compositional data for fractures in the layered rocks suggest formation of Al-rich smectites by aqueous leaching. Evidence is thus preserved for water-rock interactions before and after the impact, with aqueous environments of slightly acidic to circum-neutral pH that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate-rich rocks at Meridiani Planum.

Pancam Multispectral Imaging Results from the Opportunity Rover at Meridiani Planum

Panoramic Camera (Pancam) images from Meridiani Planum reveal a low-albedo, generally flat, and relatively rock-free surface. Within and around impact craters and fractures, laminated outcrop rocks with higher albedo are observed. Fine-grained materials include dark sand, bright ferric iron–rich dust, angular rock clasts, and millimeter-size spheroidal granules that are eroding out of the laminated rocks. Spectra of sand, clasts, and one dark plains rock are consistent with mafic silicates such as pyroxene and olivine. Spectra of both the spherules and the laminated outcrop materials indicate the presence of crystalline ferric oxides or oxyhydroxides. Atmospheric observations show a steady decline in dust opacity during the mission. Astronomical observations captured solar transits by Phobos and Deimos and time-lapse observations of sunsets.

Localization and physical property experiments conducted by Opportunity at Meridiani Planum.

The location of the Opportunity landing site was determined to better than 10-m absolute accuracy from analyses of radio tracking data. We determined Rover locations during traverses with an error as small as several centimeters using engineering telemetry and overlapping images. Topographic profiles generated from rover data show that the plains are very smooth from meter- to centimeter-length scales, consistent with analyses of orbital observations. Solar cell output decreased because of the deposition of airborne dust on the panels. The lack of dust-covered surfaces on Meridiani Planum indicates that high velocity winds must remove this material on a continuing basis. The low mechanical strength of the evaporitic rocks as determined from grinding experiments, and the abundance of coarse-grained surface particles argue for differential erosion of Meridiani Planum.

Lithologic mapping in arid regions with Landsat thematic mapper data: Meatiq dome, Egypt

Digital Landsat thematic mapper (TM) data were evaluated for lithologic mapping capabilities over the Meatiq dome area in the hyper-arid Eastern Desert of Egypt. Bi-directional spectral reflectance data (0.4–2.5 µm) for powders of the major rock types exposed in the dome and published spectral reflectance data were used as guides in selecting TM band reflectance ratios that maximize discrimination of individual rock types on the basis of their respective mineralogies. Comparison of TM data with field and petrographic observations shows (1) increasing amounts of magnetite and other opaque minerals, with low, flat spectral reflectances, decrease the ratio of TM band 5 (1.55 to 1.75) to band 1 (0.45 to 0.52 µm); (2) increasing amounts of hydroxyl-bearing minerals, with hydroxyl ion vibrational absorptions in TM band-7 wavelength region (2.08 to 2.35 µm), increase the ratio of TM band 5 to band 7; (3) increasing amounts of Fe-bearing aluminosilicates that absorb in the band-4 wavelength region (0.76 to 0.9 µm) increase the product of the following two TM ratios: band 5 to band 4 and band 3 (0.63 to 0.69 µm) to band 4; and (4) thin (≤5 µm), desert varnish that covers many outcrops modulates, but does not obscure, the spectral reflectance signatures of the Meatiq rocks. The varnish consists of amorphous to poorly crystalline dioctahedral smectite, iron oxides, and/or oxyhydroxides. Serpentinite, mafic mylonite, massive amphibolite, quartzofeldspathic mylonite, biotite schist, and quartz phyllonite were mapped on the basis of their unique values in one or more of the three ratio images, whereas coarse- and fine-grained granites, granite gneiss, and tonalite, with similar mineralogies and TM band ratios, were mapped as a group. Finer subdivisions were made where field traverses provided local verification. Results demonstrate that appropriate processing and presentation of Landsat TM data can significantly augment field observations for lithologic mapping of large areas in arid regions.

Three Mars years: Viking Lander 1 imaging observations

The Mutch Memorial Station (Viking Lander 1) on Mars acquired imaging and meteorological data over a period of 2245 martian days (3:3 martian years). This article discusses the deposition and erosion of thin deposits (ten to hundreds of micrometers) of bright red dust associated with global dust storms, and the removal of centimeter amounts of material in selected areas during a dust storm late in the third winter. Atmospheric pressure data acquired during the period of intense erosion imply that baroclinic disturbances and strong diurnal solar tidal heating combined to produce strong winds. Erosion occurred principally in areas where soil cohesion was reduced by earlier surface sampler activities. Except for redistribution of thin layers of materials, the surface appears to be remarkably stable, perhaps because of cohesion of the undisturbed surface material.

Spirit Mars Rover Mission: Overview and selected results from the northern Home Plate Winter Haven to the side of Scamander crater

Spirit Mars Rover Mission : Overview and selected results from the northern Home Plate Winter Haven to the side of Scamander crater

Accumulation of Sedimentary Debris in the South Polar Region of Mars and Implications for Climate History

Abstract Stratigraphic units of the south polar region of Mars were mapped, relative chronology determined, and detailed modeling of the observed crater populations was used to set absolute constraints on the age of emplacement of materials. Significant secular variation in the net debris accumulation rate over history is evident. An episode of enhanced crater obliteration at about 3.7 Ga ago, lasting a few hundred Ma, is inferred for south polar cratered terrains. A similar peak in low latitude obliteration rates suggests that the event may have been global in scale. Whether the debris is volcanic or aeolian in origin, the event suggests a possible enhancement in atmospheric density at the time. Modeling results imply that cratered terrains poleward of 65° south latitude have subsequently experienced steady state net accumulation of material at a rate of about 0.1 km/Ga, while equatorial cratered terrains have been retained in relatively pristine form. Fifteen craters of impact origin were discovered on the south polar layered terrain, formerly thought to be almost devoid of craters. Their presence implies that the surface is at least a few 100 Ma old, and that the net accumulation rate is no more than 10 km/Ga. If layer formation is modulated by periodic climatic effects, either the period of oscillation is a few Ma or longer, or the layer deposition mechanism ceased operating at least several 100 Ma ago.

One Mars year: viking lander imaging observations.

Throughout the complete Mars year during which they have been on the planet, the imaging systems aboard the two Viking landers have documented a variety of surface changes. Surface condensates, consisting of both solid H2O and CO2, formed at the Viking 2 lander site during the winter. Additional observations suggest that surface erosion rates due to dust redistribution may be substantially less than those predicted on the basis of pre-Viking observations. The Viking 1 lander will continue to acquire and transmit a predetermined sequence of imaging and meteorology data as long as it is operative.