Mars Exploration Rover Landing Sites Research Articles

Contrasting styles of water–rock interaction at the Mars Exploration Rover landing sites

The nature of ancient hydrological systems on Mars has been the subject of ongoing controversy, driven largely by a disconnect between observational evidence for flowing water on the Martian surface at multiple scales and the incompatibility of such observations with theoretical models that predict a cold early Martian environment in which liquid water is unstable. Here we present geochemical data from the Mars Exploration Rovers to evaluate the hydrological conditions under which weathering rinds, soils, and sedimentary rocks were formed. Our analysis indicates that the chemistry of rinds and soils document a water-limited hydrologic environment where small quantities of S-bearing fluids enter the system, interact with and chemically alter rock and soil, and precipitate secondary mineral phases at the site of alteration with little to no physical separation of primary and secondary mineral phases. In contrast, results show that the sedimentary rocks of the Burns Formation at Meridiani Planum have a chemical composition well-described as a mixture between siliciclastic sediment and sulfate-bearing salts derived from the evaporation of groundwater. We hypothesize that the former may be derived from the recently investigated Shoemaker Formation, a sequence of impact breccias that underlie the Burns Formation. This result has important implications for the style of chemical weathering and hydrology recorded by these sedimentary materials, revealing long-range transport of ions in solution in an open hydrological system that is consistent only with subsurface or overland flow of liquid water.

A Comparative Analysis of Evaporate Sediments on Earth and Mars: Implications for the Climate Change on Mars

Abstract:The knowledge of Martian salts has gone through substantial changes during the past decades. In the 70th of last century, Viking landers have noticed the existence of salts on Mars. Several salt species have been suggested from then on, such as sulfates and chlorides. However, their origin was a mystery due to the lack of observations. The recent explorations and related studies at the beginning of this century revealed that the crustal composition of Mars is similar to that of Earth, and it was hypothesized that almost one third of Martian surface was covered by oceans and lakes in the early stage of Mars. The huge water bodies may have dissolved a large quantity of ions from Martian primary rocks during the whole Noachian and Hesperian epoch. After the enormous drought event happened during the late Hesperian and the early Amazonian, these dissolved ions have formed huge salts deposits and most of them were preserved on Mars until today. To date, carbonates, sulfates, chlorides have all been detected by orbital remote sensing and by landers and rovers. However, the salt mineral assemblages on Mars seems to have some differences from those on Earth, e.g., rich in sulfates and lack of massive carbonates. To explain this difference, we propose that most of the surface carbonates precipitated from the ancient oceans may have been dissolved by the later ubiquitous acidic fluids originated from the global volcanism in the Hesperian era, and formed the enormous sulfate deposits as detected, and this hypothesis seems to be supported by the evidence that most of the sulfate deposits distribute around the Tharsis volcanic province while the survived carbonates located far from it. This process can release most of the carbon on Mars to the atmosphere in the form of CO2 and then be erased by the late heavy bombardments, which might have profound influence on the climate change happened in the Hesperian age. The positive correlation between the GRS results of the potassium distributions and the distribution of chlorides on Mars, together with the high Br concentration measured from the evaporate sediments at two Mars exploration rover landing sites, indicate that the brines in the regions where the chlorides deposited may have reached the stage for potassium salts deposition, thus we propose for the first time that potassium salts deposits might be prevalent in these regions.

Soil mineralogy at the Mars Exploration Rover landing sites: An assessment of the competing roles of physical sorting and chemical weathering

Soils in Gusev Crater and Meridiani Planum derive primarily from a surface dominated by basalt. The modal mineralogy of primary (igneous) and secondary (alteration) phases in the soils is estimated using Mössbauer, MiniTES, and APXS spectra. Primary minerals include plagioclase, pyroxene, and olivine with less common apatite, magnetite, and chromite. Secondary phases are dominated by sulfates, and include nanophase oxides, chlorides, hematite, and are assumed to include amorphous silica and phyllosilicates. Most soil chemical compositions overlap with basalts indicating that despite the presence of a secondary component in the soils, they have not been significantly chemically weathered. We modeled the significance of olivine dissolution by acid‐S by iteratively removing the molar FeOT + MgO component (olivine proxy) from the mean bulk compositions of the Gusev rock classes Adirondack, Algonquin, and Irvine until none remained. Regardless of modeling conditions, acid‐S alteration cannot account for many soils in Gusev Crater that are either depleted or enriched in molar FeOT + MgO, although it is a process capable of explaining some soil compositions. Based on a rock and mineral mixing model, supports our hypothesis for soil formation that consists of surface comminution by impact gardening, followed by compositional modification by hydrodynamic sorting and admixing of secondary components, including phyllosilicates and sulfates. Such a physical process can produce the range of molar FeOT + MgO in soils by concentrating or depleting specific minerals. For example, dust and fine sands are enriched in molar FeOT + MgO relative to coarse sand, which suggests accumulation of more mafic phases in finer grain fractions.

Implementation of Martian virtual reality environment using very high-resolution stereo topographic data

Topography over terrestrial or other planetary surfaces is an important base data for virtual reality construction. In particular, with inaccessible topography such as the Martian surface, virtual reality provides great value not only for public interaction but also for scientific research. For the latter application, since field surveys are essential for the geological and geomorphological researches, the virtual reality environment created based on verified topographic products provides an alternative solution for planetary research.The performance of virtual reality implementation over a planetary surface can be assessed by two major factors: (1) The geodetically controlled base topographic products, such as DTM and ortho-image, and (2) Technological integration of topographic products into virtual reality software and hardware. For the first aspect, the multi-resolution stereo analysis approach has already provided a solid basis so that specific topographic data sets over testing areas were generated by the hierarchical processor. To address the second problem, a parallel processor with multiple screen display combining 3D display software was employed in this research.As demonstrated in this paper, the constructed Martian virtual environment showed highly detailed features over the Athabasca Valles (one of former potential Mars Exploration Rover landing sites) and Eberswalde crater (one of the main original landing candidates for the NASA’s rover mission scheduled to launch in late 2011). The employment of such virtual reality environments is expected to be a powerful simulator after integrating a 3D Martian model, engineering and environment constraints for Martian geological and geomorphic researches including landing site selection and rover navigation.

Extraterrestrial Mössbauer spectroscopy: more than 3 years of Mars exploration and developments for future missions

After almost 4 years of operating on the surface of Mars, Mossbauer spectroscopy has become a mature technique for robotic planetary exploration. The combination of quantitative information about the distribution of Fe among its oxidation and coordination states, identification of Fe-bearing phases, and relative distribution of Fe among those phases provides valuable contributions to the search for past water activity, the assessment of past environmental conditions, and the suitability for life of the two NASA Mars Exploration Rover landing sites. Experience from the Mars Exploration Rover Mission highlights needs for improvement of the instruments for future missions such as the Russian Phobos-Grunt and the European ExoMars rover.

Erosion rates at the Mars Exploration Rover landing sites and long‐term climate change on Mars

Erosion rates derived from the Gusev cratered plains and the erosion of weak sulfates by saltating sand at Meridiani Planum are so slow that they argue that the present dry and desiccating environment has persisted since the Early Hesperian. In contrast, sedimentary rocks at Meridiani formed in the presence of groundwater and occasional surface water, and many Columbia Hills rocks at Gusev underwent aqueous alteration during the Late Noachian, approximately coeval with a wide variety of geomorphic indicators that indicate a wetter and likely warmer environment. Two‐toned rocks, elevated ventifacts, and perched and undercut rocks indicate localized deflation of the Gusev plains and deposition of an equivalent amount of sediment into craters to form hollows, suggesting average erosion rates of ∼0.03 nm/yr. Erosion of Hesperian craters, modification of Late Amazonian craters, and the concentration of hematite concretions in the soils of Meridiani yield slightly higher average erosion rates of 1–10 nm/yr in the Amazonian. These erosion rates are 2–5 orders of magnitude lower than the slowest continental denudation rates on Earth, indicating that liquid water was not an active erosional agent. Erosion rates for Meridiani just before deposition of the sulfate‐rich sediments and other eroded Noachian areas are comparable with slow denudation rates on Earth that are dominated by liquid water. Available data suggest the climate change at the landing sites from wet and likely warm to dry and desiccating occurred sometime between the Late Noachian and the beginning of the Late Hesperian (3.7–3.5 Ga).

Mars Soil Mechanical Properties and Suitability of Mars Soil Simulants

Determination of Mars soil mechanical properties will improve future lander mission success and provide narrower constraints for geomorphological modeling. A soil mechanics investigation was conducted wherein soil mechanical properties were determined by computer reconstruction of mass wasting features observed in photographs of Mars Exploration Rover landing sites and analysis of natural slope stability. Mars soil mechanical properties were compared with thermal inertia measurements and a correlation is presented. Tests with rovers and equipment for Mars surface exploration and various past laboratory experiments have incorporated a number of different Mars soil simulants. Standard laboratory measurements were conducted to characterize the shear strength, grain size distribution, and densities of various Mars soil simulants. From these measurements, the ability of a given simulant to appropriately represent the mechanical properties of in situ Mars soils was judged. Specific simulants are recommended for certain regions of Mars.

Physical properties of the Mars Exploration Rover landing sites as inferred from Mini‐TES–derived thermal inertia

The Miniature Thermal Emission Spectrometer (Mini‐TES) on board the two Mars Exploration Rovers provides the first opportunity to observe thermal properties from the Martian surface, relate these properties to orbital data, and perform soil conductivity experiments under Martian conditions. The thermal inertias of soils, bedforms, and rock at each landing site were derived to quantify the physical properties of these features and understand geologic processes occurring at these localities. The thermal inertia for the Gusev plains rock target Bonneville Beacon (∼1200 J m−2 K−1 s−1/2) is consistent with a dense, basaltic rock, but the rocks at the Columbia Hills have a lower thermal inertia (∼620 J m−2 K−1 s−1/2), suggesting that they have a volcaniclasic origin. Bedforms on the floors of craters at both landing sites have thermal inertias of 200 J m−2 K−1 s−1/2, consistent with a particle diameter of ∼160 μm. This diameter is comparable to the most easily moved grain size in the current atmosphere on Mars, suggesting that these bedforms may have formed under current atmospheric conditions. Along the Meridiani plains, the thermal inertia is lower than that derived from TES and Thermal Emission Imaging System (THEMIS) orbital data. This discrepancy is not well understood. Mini‐TES–derived thermal inertias at Gusev along a ∼2.5 km traverse follow trends in thermal inertia measured from orbit with TES and THEMIS. However, along the traverse, there are variability and mixing of particle sizes that are not resolved in the orbital thermal inertia data due to meter‐scale processes that are not identifiable at larger scales.

Surface and near-surface atmospheric temperatures for the Mars Exploration Rover landing sites

Downward-looking spectra of the martian surface from the Miniature Thermal Emission spectrometer (Mini-TES), onboard each of the two Mars Exploration Rovers, are modeled in order to retrieve surface and near-surface atmospheric temperatures. By fitting the observed radiance in the vicinity of the 15-μm CO 2 absorption feature, the surface temperature and the near-surface atmospheric temperature, approximately 1.1 m above the surface, are determined. The temperatures from the first 180 sols (martian days) of each surface mission are used to characterize the diurnal dependence of temperatures. The near-surface atmospheric temperatures are consistently 20 K cooler than the surface temperatures in the warmest part of each sol, which is 1300–1400 LTST (local true solar time) depending on the location. Seasonal cooling trends are seen in the data by displaying the temperatures as a function of sol. Long ground stares, 8.5 min in duration, show as much as 8 K fluctuation in the near-surface atmospheric temperatures during the early afternoon hours when the near-surface atmosphere is unstable.

Assessment of Mars Exploration Rover landing site predictions

Comprehensive analyses of remote sensing data during the three-year effort to select the Mars Exploration Rover landing sites at Gusev crater and at Meridiani Planum correctly predicted the atmospheric density profile during entry and descent and the safe and trafficable surfaces explored by the two rovers. The Gusev crater site was correctly predicted to be a low-relief surface that was less rocky than the Viking landing sites but comparably dusty. A dark, low-albedo, flat plain composed of basaltic sand and haematite with very few rocks was expected and found at Meridiani Planum. These results argue that future efforts to select safe landing sites based on existing and acquired remote sensing data will be successful. In contrast, geological interpretations of the sites based on remote sensing data were less certain and less successful, which emphasizes the inherent ambiguities in understanding surface geology from remotely sensed data and the uncertainty in predicting exactly what materials will be available for study at a landing site.

Selection of the Mars Exploration Rover landing sites

The selection of Meridiani Planum and Gusev crater as the Mars Exploration Rover landing sites took over 2 years, involved broad participation of the science community via four open workshops, and narrowed an initial ∼155 potential sites (80–300 × 30 km) to four finalists based on science and safety. Engineering constraints important to the selection included (1) latitude (10°N–15°S) for maximum solar power, (2) elevation (less than −1.3 km) for sufficient atmosphere to slow the lander, (3) low horizontal winds, shear, and turbulence in the last few kilometers to minimize horizontal velocity, (4) low 10‐m‐scale slopes to reduce airbag spin‐up and bounce, (5) moderate rock abundance to reduce abrasion or strokeout of the airbags, and (6) a radar‐reflective, load‐bearing, and trafficable surface safe for landing and roving that is not dominated by fine‐grained dust. The evaluation of sites utilized existing as well as targeted orbital information acquired from the Mars Global Surveyor and Mars Odyssey. Three of the final four landing sites show strong evidence for surface processes involving water and appear capable of addressing the science objectives of the missions, which are to determine the aqueous, climatic, and geologic history of sites on Mars where conditions may have been favorable to the preservation of evidence of possible prebiotic or biotic processes. The evaluation of science criteria placed Meridiani and Gusev as the highest‐priority sites. The evaluation of the three most critical safety criteria (10‐m‐scale slopes, rocks, and winds) and landing simulation results indicated that Meridiani and Elysium Planitia are the safest sites, followed by Gusev and Isidis Planitia.

Mars Exploration Rover Athena Panoramic Camera (Pancam) investigation

The Panoramic Camera (Pancam) investigation is part of the Athena science payload launched to Mars in 2003 on NASA's twin Mars Exploration Rover (MER) missions. The scientific goals of the Pancam investigation are to assess the high‐resolution morphology, topography, and geologic context of each MER landing site, to obtain color images to constrain the mineralogic, photometric, and physical properties of surface materials, and to determine dust and aerosol opacity and physical properties from direct imaging of the Sun and sky. Pancam also provides mission support measurements for the rovers, including Sun‐finding for rover navigation, hazard identification and digital terrain modeling to help guide long‐term rover traverse decisions, high‐resolution imaging to help guide the selection of in situ sampling targets, and acquisition of education and public outreach products. The Pancam optical, mechanical, and electronics design were optimized to achieve these science and mission support goals. Pancam is a multispectral, stereoscopic, panoramic imaging system consisting of two digital cameras mounted on a mast 1.5 m above the Martian surface. The mast allows Pancam to image the full 360° in azimuth and ±90° in elevation. Each Pancam camera utilizes a 1024 × 1024 active imaging area frame transfer CCD detector array. The Pancam optics have an effective focal length of 43 mm and a focal ratio of f/20, yielding an instantaneous field of view of 0.27 mrad/pixel and a field of view of 16° × 16°. Each rover's two Pancam “eyes” are separated by 30 cm and have a 1° toe‐in to provide adequate stereo parallax. Each eye also includes a small eight position filter wheel to allow surface mineralogic studies, multispectral sky imaging, and direct Sun imaging in the 400–1100 nm wavelength region. Pancam was designed and calibrated to operate within specifications on Mars at temperatures from −55° to +5°C. An onboard calibration target and fiducial marks provide the capability to validate the radiometric and geometric calibration on Mars.

Geology of the MER 2003 “Elysium” candidate landing site in southeastern Utopia Planitia, Mars

The NASA Mars Exploration Rover (MER) Project has been considering a landing‐site ellipse designated EP78B2 in southeastern Utopia Planitia, southwest of Elysium Mons. The site appears to be relatively safe for a MER landing site because of its predicted low wind velocities in mesoscale atmospheric circulation models and its low surface roughness at various scales as indicated by topographic and imaging data sets. Previously, the site's surface rocks have been interpreted to be marine sediments or lava flows. In addition, we suggest that Late Noachian to Early Hesperian collapse and mass wasting of Noachian highland rocks contributed to the deposition of detritus in the area of the ellipse. Furthermore, we document partial Late Hesperian to Early Amazonian resurfacing of the ellipse by flows and vents that may be of mud or silicate volcanic origin. A rover investigation of the Utopia landing site using the MER Athena instrument package might address some fundamental aspects of Martian geologic evolution, such as climate change, hydrologic evolution, and magmatic and tectonic history.

Meteorology of proposed Mars Exploration Rover landing sites

A descriptive study of the near‐surface meteorology at three of the potential Mars Exploration Rover (MER) landing sites (Terra Meridiani, Gusev Crater, and Melas Chasma) is presented using global and mesoscale models. The mesoscale model provides a detailed picture of meteorology on scales down to a few kilometers but is not well constrained by observations away from the Viking and Pathfinder landing sites. As such, care must be taken in the interpretation of the results, with there being high confidence that the types of circulations predicted will indeed occur and somewhat less in the quantitative precision of the predictions and the local‐time phasing of predicted circulations. All three landing sites are in the tropics and are affected by Hadley circulation, by diurnal variations due to the global thermal tide, and by planetary scale topography (in these particular cases from Tharsis, Elysium, and the global topographic dichotomy boundary). Terra Meridiani is least affected by large variations in local topography. Mean winds at Terra Meridiani during MER landing would be less than 10 m/s with little vertical shear. However, these low wind speeds result from strong mixing in the early afternoon convective boundary layer, which creates its own hazard in the horizontal variation of vertical winds of up to 8 m/s (both upward and downward). In Gusev Crater the topography of Ma'adim Vallis and the crater rim generates strong diurnally reversing channeling of wind in Ma'adim Vallis and diurnally reversing radial flow in the crater associated with thermal slope winds on the crater rim. The overturning circulation in Gusev Crater slightly suppresses the daytime convective boundary layer. Melas Chasma in Valles Marineris provides an example of strong topographic forcing of near‐surface circulation. Of particular interest is the channeling of regional scale wind toward the center of the Tharsis plateau during the evening. This results in a surface level jet along the canyon of over 25 m/s. Drainage of air from the plateau and into the canyon produces vertical winds down the canyon walls in the evening of over 5 m/s. In contrast, during the early afternoon (MER landing time), horizontal winds at the proposed MER landing site are relatively calm, with little mean shear with height. This results from the proposed site being in a region of local divergence and the action of daytime convection. The nature of flow in Melas Chasma results in an interesting dual maximum in boundary convection and depth, with the usual daytime afternoon free convective maximum being joined by a mechanically forced nighttime boundary layer of almost 2 km depth.

Near‐surface temperatures at proposed Mars Exploration Rover landing sites

Minimum nighttime temperatures at the Mars Exploration Rover (MER) landing sites may limit power available for science activities and thus mission lifetime. Here, 1 m air temperatures at the end of the nominal 90 sol primary mission are derived for the four primary and three previously considered MER landing sites based on Mars Global Surveyor Thermal Emission Spectrometer thermal inertia and albedo, estimated opacity, and predictions of air temperatures from a one‐dimensional atmospheric model. Taking these results and mapping them onto the probability density distribution of the landing ellipses shows that of the air temperatures of the primary sites, Sinus Meridiani (“Hematite”) is the coldest, with an 8% chance of encountering minimum nighttime temperatures below the 176 K value considered a practical limit for operations. Elysium and Gusev are at 7% and 3%, respectively, whereas Isidis has no computed temperatures below 191 K. For the Hematite site, preliminary observations and interpretations are also made using high‐resolution Odyssey Thermal Imaging System predawn images.

Mars: Aeolian features and wind predictions at the Terra Meridiani and Isidis Planitia potential Mars Exploration Rover landing sites

Orientations of 11,497 aeolian (wind related) features at the potential Mars Exploration Rover (MER) landing site in Isidis Planitia reflect formative winds from the northwest and are consistent with strong morning winds predicted by a regional‐scale atmospheric model for Mars. Orientations of 3296 aeolian features mapped at the Terra Meridiani potential MER site suggest multidirectional wind patterns. The results for the Terra Meridiani site are consistent with gentle winds which change direction as a function of Martian season (predicted by a general circulation model) and erratic winds that occur diurnally (predicted by a regional‐scale atmospheric model). Results for both sites give confidence that the predictions from the atmospheric models are basically correct when time of day and local topography are taken into account.

Paleolakes and impact basins in southern Arabia Terra, including Meridiani Planum: Implications for the formation of hematite deposits on Mars

The hematite deposit in Meridiani Planum was selected for a Mars Exploration Rover (MER) landing site because water could be involved in the formation of hematite, and water is a key ingredient in the search for life. Our discovery of a chain of paleolake basins and channels along the southern margin of the hematite deposits in Meridiani Planum with the presence of the strongest hematite signature adjacent to a paleolake basin, supports the possible role of water in the formation of the hematite and the deposition of other layered materials in the region. The hematite may have formed by direct precipitation from lake water, as coatings precipitated from groundwater, or by oxidation of preexisting iron oxide minerals. The paleolake basins were fed by an extensive channel system, originating from an area larger than Texas and located south of the Schiaparelli impact basin. On the basis of stratigraphic relationships, the formation of channels in the region occurred over much of Mars' history, from before the layered materials in Meridiani Planum were deposited until recently. The location of the paleolake basins and channels is connected with the impact cratering history of the region. The earliest structure identified in this study is an ancient circular multiringed basin (800–1600 km diameter) that underlies the entire Meridiani Planum region. The MER landing site is located on the buried northern rim of a later 150 km diameter crater. This crater is partially filled with layered deposits that contained a paleolake in its southern portion.