Spirit Rover Research Articles

One Short Stroll for Mankind

![Figure][1] CREDIT: BBC DIMENSIONS Did you know that Neil Armstrong's and Buzz Aldrin's first walk on the moon was as short as a lap around the Statue of Liberty (above)? Or that the plucky Mars rover Spirit has wandered about as far as from Wall Street to Central Park in New York City? You

Regional and grain size influences on the geochemistry of soil at Gusev crater, Mars

Congruous with earlier work, Martian soil along the Spirit Rover's traverse at Gusev crater can be divided into three broad groups by size: fines (<150 μm), sand, and a mix of various grain sizes. The key chemical observation is greater homogeneity in fines relative to the other two, consistent with regional‐ and global‐scale sampling of chemical compositions by finer particle sizes. The mix class is generally more heterogeneous as are samples from the Columbia Hills within each class. Variation in the trace element Ni is consistent with a CI contribution not exceeding 3%, while that of Ti is compatible with Fe‐Ti oxide enrichment not exceeding 3%. Physical mixing models are poorly supported. Among many potential binary and three‐component mixing models, only two show some consistency with the soil data: typical fines with the opaline Si end‐member identified at Home Plate and typical fines with sulfates (bearing a variable mix of Ca, Fe, and Mg cations). We also infer that binary mixing transcends classes, contrasting strongly with terrestrial sediments, and that mixing trends are consistent with significant nonmixing contributions, perhaps including localized chemical alteration. The decoupling between chemistry and grain size classes also suggests that processes linking composition with grain size, such as heavy mineral sorting, may have been minimal or absent entirely. The primary exception to this is the correlation between Cl and Si, Cl‐S, and Al‐Si, which is strongest in the fines class.

Gone with the wind: Eolian erasure of the Mars Rover tracks

The wheel tracks left by the Mars Exploration Rovers Spirit and Opportunity are unique artificial markings on the surface of Mars. The tracks stretch several kilometers across diverse terrain in two widely separated regions of the planet. The initial appearance and characteristics of the tracks were well documented by the science and navigation cameras aboard the vehicles at the time the tracks were formed. Orbital observations by Mars Global Surveyor and Mars Reconnaissance Orbiter document the erasure of the tracks over a period of more than 2 Mars years. Close‐up examinations of track crossings, where the rovers encountered tracks made hundreds of Martian solar days earlier, provide insights into the mechanisms and time scales of eolian alteration on Mars. These observations suggest that fallout of atmospheric dust plays only a minor role in obscuring rover tracks over time. Instead, track erasure is dominated by sediment that is transported by surface winds. Both deposition and erosion act to erase the rover tracks. The length scales for eolian sediment transport are hundreds of meters at least, much larger than the size of the tracks. Gradual processes such as dust devils and sand saltation have minor effects that can nonetheless erase rover tracks over long time periods. However, short‐lived strong wind events associated with seasonal dust storms have much more pronounced effects, significantly altering the tracks on time scales of days. These episodic strong winds tend to occur annually during the perihelion season. The time scale for track erasure is typically only 1 Martian year.

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

This paper summarizes Spirit Rover operations in the Columbia Hills, Gusev crater, from sol 1410 (start of the third winter campaign) to sol 2169 (when extrication attempts from Troy stopped to winterize the vehicle) and provides an overview of key scientific results. The third winter campaign took advantage of parking on the northern slope of Home Plate to tilt the vehicle to track the sun and thus survive the winter season. With the onset of the spring season, Spirit began circumnavigating Home Plate on the way to volcanic constructs located to the south. Silica‐rich nodular rocks were discovered in the valley to the north of Home Plate. The inoperative right front wheel drive actuator made climbing soil‐covered slopes problematical and led to high slip conditions and extensive excavation of subsurface soils. This situation led to embedding of Spirit on the side of a shallow, 8 m wide crater in Troy, located in the valley to the west of Home Plate. Examination of the materials exposed during embedding showed that Spirit broke through a thin sulfate‐rich soil crust and became embedded in an underlying mix of sulfate and basaltic sands. The nature of the crust is consistent with dissolution and precipitation in the presence of soil water within a few centimeters of the surface. The observation that sulfate‐rich deposits in Troy and elsewhere in the Columbia Hills are just beneath the surface implies that these processes have operated on a continuing basis on Mars as landforms have been shaped by erosion and deposition.

Constraints on the geologic history of “Home Plate” materials provided by clast morphology and texture

We quantified and classified the size, shape, roundness, and texture of 333 loose surface particles (clasts) along the Spirit rover traverse from Martian solar days 750 to 1889. These data provided clues to origin, transport mechanisms, association with geologic units, and other alteration processes. Clasts average 15 mm in size and 0.73 sphericity, and display a low degree of roundness; textures include vesicular, smooth and rough flat‐faceted, and granular, platy clasts. Characteristics are comparable to those for clasts outside the “Home Plate” region. Mapped geologic units around “Home Plate” are characterized by distinctive clast morphologic parameters and only minor adjustments were made to unit boundaries and definitions mapped by others; no new units are suggested by the data. Consistent roundness values seen from unit to unit, coupled with the correlation between unit boundaries and clast characteristics in and outside “Home Plate,” indicate that no appreciable transport has occurred subsequent to fragmentation from outcrop and emplacement. Rather, clasts have been emplaced through volcanic activity and/or impact and have been subjected to weathering processes since that time. We interpret vesicular and flat‐faceted clasts (texture types 1–3) to be derived from Mitcheltree ridge basalts and the presence of these clasts to provide a general outline of the original extent of this unit. Platy, granular‐textured clasts (texture type 5) are derived from the upper Home Plate unit.

Nuclear, chemical and biological characterization of formation histories of ironstones from several sites in Southern California: Dominant role of bacterial activity

Pebble-sized sandstone concretions, cemented by iron and manganese oxides, are found in several semi-arid regions in the world. Although recognized for a long time, their formation mechanisms have not yet been constrained from scientific studies. We have made extensive studies of the chemical composition, cosmogenic 10Be and radiogenic U/Th concentrations, and biological fossils in ironstones from six sites in southern California. The ironstones exhibit appreciable enrichments of Mn, Zn, Mg, Ti, Fe, U, Th, and fossil bacteria. In addition to elemental data, we report here first observations of radionuclides, U, Th, K, and concentrations of cosmogenic 10Be which we show are an excellent indicator of precipitation amounts. Our data favor the model that the ironstones formed within sandy beach ridges during wetter climates following dry climates during which aeolian sediment was added to the beach ridges. Iron, Mn, Zn and other trace element-rich leachates from the dust layers nurtured and accelerated bacterial activity in the beach ridges down to depths of a few meters, as first suggested by Abbott (1981). Our observations of trace-element enrichments and bacterial fossils support the model proposed by Abbott and underscore the fact that the ironstones are principally a product of bacterial activity, which concentrates the leachates in a narrow layer within the beach ridges. The extreme alternating dry/wet climatic conditions which existed in the past in southern California led to the formation of ironstone concretions within the ancient beach ridges, which provided suitable host mineralogy for their formation. The time periods represented by the ironstones from the six sites presumably cover the past ∼ 1 my. The recent surface explorations on the surface of Mars by the rovers SPIRIT and OPPORTUNITY (Squyres et al., 2006), showed that similar to southern California, extreme climatic conditions existed on Mars in its early history. It therefore seems that studies of ironstones may provide useful clues to the evolution of soils on Mars in such extreme climates, and possibly even provide criteria to evaluate whether any bacterial activity was present at that time.

Identification of Carbonate-Rich Outcrops on Mars by the Spirit Rover

Decades of speculation about a warmer, wetter Mars climate in the planet's first billion years postulate a denser CO2-rich atmosphere than at present. Such an atmosphere should have led to the formation of outcrops rich in carbonate minerals, for which evidence has been sparse. Using the Mars Exploration Rover Spirit, we have now identified outcrops rich in magnesium-iron carbonate (16 to 34 weight percent) in the Columbia Hills of Gusev crater. Its composition approximates the average composition of the carbonate globules in martian meteorite ALH 84001. The Gusev carbonate probably precipitated from carbonate-bearing solutions under hydrothermal conditions at near-neutral pH in association with volcanic activity during the Noachian era.

Terrestrial Quadstatic Interferometric Radar Observations of Mars

A new technique for resolving the ambiguity inherent in delay-Doppler radar observations of Mars has been developed and implemented using a suite of data collected during 2001, 2003, and 2005 oppositions. New recording systems, processing techniques, and, most importantly, the addition of a fourth receiving telescope allow for the high-resolution mapping of Mars' radar properties. In this paper, we develop a maximum likelihood method to probabilistically estimate the contributions to the received radar signal from the ambiguous resolution cells. Our delay-Doppler interferometric radar observations are designed to map the radar properties of Mars surface while disregarding the historically typical goal of measuring topography, instead using Mars' topography as <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> knowledge. Example data from the September 27, 2003 observation over Mars' southern highlands, including Ma'adim Vallis and Gusev Crater, and the June 7, 2001 observation crossing Terra Meridiani are presented to demonstrate the effectiveness of the technique. Analysis of these observations predicted a root-mean-square (rms) roughness, or slopes, for the Mars Exploration Rover (MER) Spirit landing site of 1.80° ± 0.75°. Similarly, analysis of the Gusev Crater landing site of MER Opportunity predicted rms slopes of 1.1° ± 0.1°. Both predictions were validated by analysis of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> rover images.

Reexamining the relationship between Apollinaris Patera and the basalts of the Gusev crater plains, Mars

A possible source of the Gusev crater basalts analyzed by the Spirit rover is Apollinaris Patera. We test this hypothesis by identifying and analyzing potential lava flow paths using Thermal Emission Imaging System, Mars Orbiter Camera, High Resolution Imaging Science Experiment, and Mars Orbiter Laser Altimeter data sets together with published geologic mapping. Image interpretation reveals three possible flow paths from Apollinaris onto Gusev crater floor via a breach in Gusev's northwest rim; an unnamed crater that must have postdated any potential flow along the paths currently blocks the breach. After correcting for the unnamed crater, topographic profiles constructed along possible flow paths demonstrate that elevation along each path increases from ∼80 to 430 m. For two of the pathways, this elevation change indicates that lavas could not have traversed through them. The third profile, though, is less conclusive as the topography may reflect a broad flexural arch. However, on the basis of two of the topographic profiles together with the lack of obvious lava flow structures that indicate flow south through the breach, we propose that Apollinaris was not the direct source of the Gusev basalts. Instead, we argue that it seems more likely that the Gusev basalts were sourced from below the crater itself. The similar ages (as derived from crater counts) of Apollinaris's south flank and the Gusev plains lavas, however, suggest that the two volcanic regions may be part of a common magmatic feature.

Silica coatings in the Ka'u Desert, Hawaii, a Mars analog terrain: A micromorphological, spectral, chemical, and isotopic study

High‐silica materials have been observed on Mars, both from orbit by the CRISM spectrometer and in situ by the Spirit rover at Gusev Crater. These observations potentially imply a wet, geologically active Martian surface. To understand silica formation on Mars, it is useful to study analogous terrestrial silica deposits. We studied silica coatings that occur on the 1974 Kilauea flow in the Ka'u Desert, Hawaii. These coatings are typically composed of two layers: a ∼10 μm layer of amorphous silica, capped by a ∼1 μm layer of Fe‐Ti oxide. The oxide coating is composed of ∼100 nm spherules, suggesting formation by chemical deposition. Raman spectroscopy indicates altered silica glass as the dominant phase in the silica coating and anatase and rutile as dominant phases in the Fe‐Ti coating; jarosite also occurs within the coatings. Oxygen isotopic contents of the coatings were determined by secondary ion mass spectrometry (Cameca 7f and NanoSIMS). The measured values, δ18OFe‐Ti = 14.6 ± 2.1‰, and δ18Osilica = 12.1 ± 2.2‰ (relative to SMOW), are enriched in 18O relative to the basalt substrate. The observations presented are consistent with a residual formation mechanism for the silica coating. Acid‐sulfate solutions leached away divalent and trivalent cations, leaving a silica‐enriched layer behind. Micrometer‐scale dissolution and reprecipitation may have also occurred within the coatings. Chemical similarities between the Hawaiian samples and the high‐silica deposits at Gusev suggest that the Martian deposits are the product of extended periods of similar acid‐sulfate leaching.

Spirit Is Willing, Though Weak

At the Lunar and Planetary Science Conference, there was talk of resurrecting the Spirit rover, which has been stuck since January, or at least a realistic prospect of a return to limited mobility. NASA missions are indeed hard to kill.

Spring awakening planned for Mars rover Spirit

Spring awakening planned for Mars rover Spirit

Mars Rover Enters New Phase of Mission

The wandering days for NASA's Mars Exploration Rover Spirit appear to be over. Spirit, which has been exploring the planet on a science mission since January 2004, is embedded in sandy soil and will remain at its current location at 14.6°S, 175.5°E, at the “Home Plate” plateau within Gusev crater, through the coming Martian winter and for the rest of its days.Despite NASA's best efforts to extricate the six‐wheeled Spirit from the sulfate salt—rich soil for the past 8 months, mission scientists indicated on 26 January that they now believe the rover is stuck for good, aside from minor movements on its four remaining operational wheels and other small adjustments. For the next several weeks, NASA will continue efforts to slightly reposition the robot so that it can better catch the Sun, endure the coming Martian winter in a state of hibernation, and remain at least in infrequent communication with the science team.

A Commanding and Visualization Software Suite for Controlling the Mars Rovers and Other Planetary Robots

The Rover Sequencing and Visualization Program is a suite of tools for the commanding of planetary rovers and other robots. The overall program architecture is based on components synchronizing and messaging over an inter-process communication bus. This paper will provide a description of these components and discuss how they work together to provide several modes of information display and visualization for robotic commanding. Results from over 3000 sols of combined operations of the Mars Rovers Spirit and Opportunity will be used to illustrate features of the RSVP suite. Support for the Phoenix Mars Lander, Mars Science Lander and other lunar and planetary missions will also be discussed.

Raman spectroscopic analysis of minerals and organic molecules of relevance to astrobiology

Characteristic geological features and hydrated minerals recently found on the surface of Mars by the NASA planetary rovers Spirit and Opportunity suggest that a possible biosphere could have once existed there. Analytical instrumentation protocols for the unequivocal detection of biomarkers in suitable geological matrices are critical for future unmanned explorations, including the forthcoming ESA-ExoMars mission scheduled for 2018. Raman spectroscopy is currently a part of the Pasteur instrumentation suite of the ExoMars mission scheduled for 2018 for the remote detection of extant or extinct life signatures in the Martian surface and subsurface. Terrestrial analogues of Martian sites have been identified, and the biogeological modifications incurred as a result of extremophilic survival activity have been studied. Polyaromatic hydrocarbons (PAHs) are recognised as a class of degradation product that occur from biological processes terrestrially. In this work, various concentrations of polyaromatic hydrocarbons in matrices of gypsum, calcite and quartz have been investigated by Raman microspectrometry to determine the lowest detectable organic levels. The studies are conceived in simulation of their potential PAHs identification in geobiological conditions in Martian scenarios. Two laser source wavelengths, namely, 785 and 633 nm, were adopted to excite Raman spectra from the PAHs, which represent degraded carbons and therefore potentially provide a key bimolecular marker of ancient life.

Mars Rover Trapped in Sand, But What Can End a Mission?

The crisis with the Spirit rover, which has become mired in a dry martian version of quicksand, raises a perennial question: When, if ever, should a NASA mission in its declining years be put out of its misery?

Silica-rich deposits and hydrated minerals at Gusev Crater, Mars: Vis-NIR spectral characterization and regional mapping

The Mars Exploration Rover (MER) Spirit has discovered surprisingly high concentrations of amorphous silica in soil and nodular outcrops in the Inner Basin of the Columbia Hills. In Pancam multispectral observations, we find that an absorption feature at the longest Pancam wavelength (1009 nm) appears to be characteristic of these silica-rich materials; however, spectral analyses of amorphous silica suggest that the ∼1009 nm spectral feature is not a direct reflection of their silica-rich nature. Based on comparisons with spectral databases, we hypothesize that the presence of H 2O or OH, either free (as water ice), adsorbed or bound in a mineral structure, is responsible for the spectral feature observed by Pancam. The Gertrude Weise soil, which is nearly pure opaline silica, may have adsorbed water cold-trapped on mineral grains. The origin of the ∼1009 nm Pancam feature observed in the silica-rich nodular outcrops may result from the presence of additional hydrated minerals (specific sulfates, halides, chlorides, sodium silicates, carbonates or borates). Using the ∼1009 nm feature with other spectral parameters as a “hydration signature” we have mapped the occurrence of hydrated materials along the extent of Spirit’s traverse across the Columbia Hills from West Spur to Home Plate (sols 155–1696). We have also mapped this hydration signature across large panoramic images to understand the regional distribution of materials that are spectrally similar to the silica-rich soil and nodular outcrops. Our results suggest that hydrated materials are common in the Columbia Hills.

Temperature dependence of the hyperfine parameters of the iron bearing phases in the Mössbauer spectra collected by the Mars Exploration Rover Spirit

This contribution focuses on the Mossbauer spectra acquired by the Mars Exploration Rover Spirit which carried a MIMOS II Mossbauer spectrometer. Only those spectra which present a reasonable statistical quality were selected to for this study. Twenty five Mossbauer spectra have been considered. Common phases identified from the temperature dependent hyperfine parameters are olivine, pyroxene, hematite and magnetite. It is believed that the applied analysis method has provided accurate values for the various hyperfine data averaged over single 10 K temperature intervals in the range 210–260 K. The obtained results, to some extent forced to evolve consistently over the various ΔT intervals considered for a given soil/rock target, are in many cases different from previously published data. Possible reasons for these differences will be discussed.

Spectral, mineralogical, and geochemical variations across Home Plate, Gusev Crater, Mars indicate high and low temperature alteration

Over the last ~ 3 years in Gusev Crater, Mars, the Spirit rover observed coherent variations in color, mineralogy, and geochemistry across Home Plate, an ~ 80 m-diameter outcrop of basaltic tephra. Observations of Home Plate from orbit and from the summit of Husband Hill reveal clear differences in visible/near-infrared (VNIR) colors between its eastern and western regions that are consistent with mineralogical compositions indicated by Mössbauer spectrometer (MB) and by Miniature Thermal Emission Spectrometer (Mini-TES). Pyroxene and magnetite dominate the east side, while olivine, nanophase Fe oxide (npOx) and glass are more abundant on the western side. Alpha Particle X-Ray Spectrometer (APXS) observations reveal that eastern Home Plate has higher Si/Mg, Al, Zn, Ni, and K, while Cl and Br are higher in the west. We propose that these variations are the result of two distinct alteration regimes that may or may not be temporally related: a localized, higher temperature recrystallization and alteration of the east side of Home Plate and lower temperature alteration of the western side that produced npOx.

Quantitative compositional analysis of martian mafic regions using the MEx/OMEGA reflectance data: 2. Petrological implications

The primary objectives of this paper are to determine the modal mineralogy of selected low albedo terrains of different ages ranging from Noachian to Amazonian exposed on the surface of Mars. This analysis is conducted using the spectral modeling of the Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) reflectance data. Results from this work are consistent with the major results of previous spectroscopic studies: plagioclase (40–60% in volume) and high calcium pyroxene (20–40%, HCP) are the dominant minerals of the most regions. Low calcium pyroxene (10–15%, LCP) and minor amounts of olivine are also present. The oldest terrains are characterized by the largest amount of LCP and the lowest concentration of plagioclase. These overall compositions are consistent with two-pyroxene basalts. The particle sizes are in the range of a few hundreds of micrometers, which is in good agreement with the thermal inertia of the martian low albedo regions. In the region around the Nili Fossae, localized concentrations of olivine up to 40% with millimeter particle size similar to picritic basalts observed in situ by the Spirit rover in the Gusev crater are inferred. Chemical compositions are calculated for the first time from OMEGA spectra. They are quite consistent with Gusev rocks and shergottite compositions but they appear to be significantly SiO 2-poorer than Thermal Emission Spectrometer data. A decreasing low calcium pyroxene abundance with the decreasing age of the low albedo regions is reported. This may be indicative of decreasing degree of partial melting as thermal flux decreases with time. We propose that the ancient Noachian-aged, LCP-rich terrains could have been formed from H 2O-bearing melts. Then, dry, basaltic volcanism occurred leading to decreasing LCP abundance with time due to decreasing degree of partial melting. The olivine-bearing material modeled in Nili Fossae resembles the composition of ALH77005 and Chassigny meteorites consistent with prior studies. Implications on the formation of the basaltic Shergottites are discussed.