Viking Research Articles

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.

Origin and evolution of a cold‐based tropical mountain glacier on Mars: The Pavonis Mons fan‐shaped deposit

Each of the large Tharsis Montes volcanoes in the equatorial region of Mars has an unusual Amazonian‐aged fan‐shaped deposit on its west‐northwestern flank. On the basis of Viking Orbiter data, the origin of these deposits has been variously ascribed to volcanic, mass‐wasting, tectonic, and glacial processes. Using new MGS and Odyssey data, combined with recent developments in the study of cold‐based glaciers, we reassess the geology and mode of origin for these deposits with particular emphasis on Pavonis Mons. The deposits share three characteristic facies, including (1) a ridged facies, consisting of tens to >100 parallel, concentric ridges around the margins of the deposits, (2) a knobby facies composed of irregular hills and hummocks, and (3) a smooth facies of broad, lobate plains that superposes all other units within the deposits. On the basis of morphology, topography, superposition relationships, and close terrestrial analogs in the Dry Valleys of Antarctica, we interpret the Pavonis fan‐shaped deposit as the depositional remains of a cold‐based glacier that formed on the northwestern flank in recent Martian history. We interpret the ridged facies as drop moraines formed around the margins of a retreating cold‐based glacier, the knobby facies as a sublimation till derived from in situ down‐wasting of cold‐based glacial ice, and the smooth facies as extant debris‐covered glacial ice. In addition to the three main facies, the fan‐shaped deposit at Pavonis Mons contains several unique features, including arcuate scarps, high‐relief flow‐like features, and radial ridges, which suggest that volcanism played a role during its formation. Using recent results from Mars general circulation model simulations, we outline a model of glacier formation involving atmospheric deposition of water ice on the northwestern flanks of the Tharsis Montes during periods of high mean obliquity. Reconstructed ice sheet profiles for each of the Tharsis Montes glaciers suggest that the ice sheets attained average thicknesses of ∼1.6–2.4 km, values that are consistent with a cold‐based glacial origin. Analysis of crater size‐frequency distributions using new data indicates that the age of the glaciation lies within the Late Amazonian (∼10–200 Ma). Thus our results suggest that multiple phases of tropical mountain glaciation occurred on Mars within the past few hundred Myr and that significant amounts of near‐surface, equatorial ice may remain within the deposit today.

The living universe: NASA and the development of astrobiology

In the opening weeks of 1998 a news article in the British journal Nature reported that NASA was about to enter biology in a big way. A virtual Astrobiology Institute was gearing up for business, and NASA administrator Dan Goldin told his external advisory council that he would like to see spending on the new institute eventually reach $100 million per year. You just wait for the screaming from the physical scientists (when that happens), Goldin was quoted as saying. Nevertheless, by the time of the second Astrobiology Science Conference in 2002, attended by seven hundred scientists from many disciplines, NASA spending on astrobiology had reached nearly half that amount and was growing at a steady pace. Under NASA leadership numerous institutions around the world applied the latest scientific techniques in the service of astrobiology's ambitious goal: the study of what NASA's 1996 Strategic Plan termed the living universe. This goal embraced nothing less than an understanding of the origin, history, and distribution of life in the universe, including Earth. Astrobiology, conceived as a broad interdisciplinary research program, held the prospect of being the science for the twenty-first century which would unlock the secrets to some of the great questions of humanity. It is no surprise that these age-old questions should continue into the twenty-first century. But that the effort should be spearheaded by NASA was not at all obvious to those - inside and outside the agency - who thought NASA's mission was human spaceflight, rather than science, especially biological science. NASA had, in fact, been involved for four decades in a field that embraced many of the same questions but which had stagnated after the 1976 Viking missions to Mars. In this volume we tell the colorful story of the rise of the discipline of exobiology, how and why it morphed into astrobiology at the end of the twentieth century, and why NASA was the engine for both the discipline's founding and for its transformation.

Meteorological results from the Global Mars Multiscale Model at the Viking 1 lander site

The present study is a comparison of the local meteorological conditions (pressure, temperature and wind) simulated by the Global Mars Multiscale Model and observed by the Viking lander 1. The model uses a global variable resolution grid with a uniform increased resolution of 20 km in a limited area of 1000 × 1200 km 2 centred at the Viking 1 landing site. Local conditions are examined for summer and winter seasons. The model gives an overall satisfactory agreement with the data and the different regimes in the two seasons are relatively well depicted. An attempt is made to understand the origin of the regular daily wind rotation in the summer and the semi-diurnal surface pressure oscillation in the winter.

Utility of Viking Orbiter Images and Products for Mars Mapping

This paper reports on mapping procedures developed by the U.S. Geological Survey that use Viking Orbiter imagery and Mars Orbiter Laser Altimeter (MOLA) derived radii to produce topographic data. The use of Mosaiced Digital Image Models (MDIMs), created from Viking Orbiter images, and MOLA data to provide horizontal and vertical control is reviewed. We describe procedures to adapt a commercial digital photogrammetric workstation to work with planetary data.

Geology and insolation-driven climatic history of Amazonian north polar materials on Mars

Mariner 9 and Viking spacecraft images revealed that the polar regions of Mars, like those of Earth, record the planet's climate history. However, fundamental uncertainties regarding the materials, features, ages and processes constituting the geologic record remained. Recently acquired Mars Orbiter Laser Altimeter data and Mars Orbiter Camera high-resolution images from the Mars Global Surveyor spacecraft and moderately high-resolution Thermal Emission Imaging System visible images from the Mars Odyssey spacecraft permit more comprehensive geologic and climatic analyses. Here I map and show the history of geologic materials and features in the north polar region that span the Amazonian period (approximately 3.0 Gyr ago to present). Erosion and redeposition of putative circumpolar mud volcano deposits (formed by eruption of liquefied, fine-grained material) led to the formation of an Early Amazonian polar plateau consisting of dark layered materials. Crater ejecta superposed on pedestals indicate that a thin mantle was present during most of the Amazonian, suggesting generally higher obliquity and insolation conditions at the poles than at present. Brighter polar layered deposits rest unconformably on the dark layers and formed mainly during lower obliquity over the past 4-5 Myr (ref. 20). Finally, the uppermost layers post-date the latest downtrend in obliquity <20,000 years ago.

Observations of lower hybrid cavities in the inner magnetosphere by the Cluster and Viking satellites

Abstract. Observations by the Viking and Cluster satellites at altitudes up to 35000km show that Lower Hybrid Cavities (LHCs) are common in the inner magnetosphere. LHCs are density depletions filled with waves in the lower hybrid frequency range. The LHCs have, until recently, only been found at altitudes up to 2000km. Statistics of the locations and general shape of the LHCs is performed to obtain an overview of some of their properties. In total, we have observed 166 LHCs on Viking during 27h of data, and 535 LHCs on Cluster during 87h of data. These LHCs are found at invariant latitudes from the auroral region to the plasmapause. A comparison with lower altitude observations shows that the LHC occurrence frequency does not scale with the flux tube radius, so that the LHCs are moderately rarer at high altitudes. This indicates that the individual LHCs do not reach from the ionosphere to 35000km altitude, which gives an upper bound for their length. The width of the LHCs perpendicular to the geomagnetic field at high altitudes is a few times the ion gyroradius, consistent with observations at low altitudes. The estimated depth of the density depletions vary with altitude, being larger at altitudes of 20000-35000km (Cluster, 10-20%), smaller around 1500-13000km (Viking and previous Freja results, a few percent) and again larger around 1000km (previous sounding rocket observations, 10-20%). The LHCs in the inner magnetosphere are situated in regions with background electrostatic hiss in the lower hybrid frequency range, consistent with investigations at low altitudes. Individual LHCs observed at high altitudes are stable at least on time scales of 0.2s (about the ion gyro period), which is consistent with previous results at lower altitudes, and observations by the four Cluster satellites show that the occurrence of LHCs in a region in space is a stable phenomenon, at least on time scales of an hour.

Detection of methane in the martian atmosphere: evidence for life?

Using the Fourier Transform Spectrometer at the Canada–France–Hawaii Telescope, we observed a spectrum of Mars at the P-branch of the strongest CH 4 band at 3.3 μm with resolving power of 180,000 for the apodized spectrum. Summing up the spectral intervals at the expected positions of the 15 strongest Doppler-shifted martian lines, we detected the absorption by martian methane at a 3.7 sigma level which is exactly centered in the summed spectrum. The observed CH 4 mixing ratio is 10 ± 3 ppb . Total photochemical loss of CH 4 in the martian atmosphere is equal to 2.2 × 10 5 cm −2 s −1 , the CH 4 lifetime is 340 years and methane should be uniformly mixed in the atmosphere. Heterogeneous loss of atmospheric methane is probably negligible, while the sink of CH 4 during its diffusion through the regolith may be significant. There are no processes of CH 4 formation in the atmosphere, so the photochemical loss must therefore be balanced by abiogenic and biogenic sources. Outgassing from Mars is weak, the latest volcanism is at least 10 million years old, and thermal emission imaging from the Mars Odyssey orbiter does not reveal any hot spots on Mars. Hydrothermal systems can hardly be warmer than the room temperature at which production of methane is very low in terrestrial waters. Therefore a significant production of hydrothermal and magmatic methane is not very likely on Mars. The calculated average production of CH 4 by cometary impacts is 2% of the methane loss. Production of methane by meteorites and interplanetary dust does not exceed 4% of the methane loss. Methane cannot originate from an extinct biosphere, as in the case of “natural gas” on Earth, given the exceedingly low limits on organic matter set by the Viking landers and the dry recent history which has been extremely hostile to the macroscopic life needed to generate the gas. Therefore, methanogenesis by living subterranean organisms is a plausible explanation for this discovery. Our estimates of the biomass and its production using the measured CH 4 abundance show that the martian biota may be extremely scarce and Mars may be generally sterile except for some oases.

The Swedish Small Satellite Program for Space Plasma Investigations

The success of the Swedish small satellite program, in combination with an active participation by Swedish research groups in major international missions, has placed Sweden in the frontline of experimental space research. The program started with the development of the research satellite Viking which was launched in 1986, for detailed investigations of the aurora. To date, Sweden has developed and launched a total of six research satellites; five for space plasma investigations; and the most recent satellite Odin, for research in astronomy and aeronomy. These fall into three main categories according to their physical dimension, financial cost and level of ambition: nano-satellites, micro-satellites, and mid-size satellites with ambitious scientific goals. In this brief review we focus on five space plasma missions, for which operations have ended and a comprehensive scientific data analysis has been conducted, which allows for a judgement of their role and impact on the progress in auroral research. Viking and Freja, the two most well-known missions of this program, were pioneers in the exploration of the aurora. The more recent satellites, Munin, Astrid, and Astrid-2 (category 1 and 2), proved to be powerful tools, both for testing new technologies and for carrying out advanced science missions. The Swedish small satellite program has been internationally recognized as cost efficient and scientifically very successful.

Optical properties of dust and the opacity of the Martian atmosphere

Particulate component of the Mars atmosphere composed by micron-sized products of soil weathering and water ice clouds strongly affects the current climate of the planet. In the absence of a dust storm so-called permanent dust haze with τ ≈ 0.2 in the atmosphere of Mars determines its thermal structure. Dust loading varies substantially with the season and geographic location, and only the data of mapping instruments are adequate to characterize it, such as TES/MGS and IRTM/Viking. In spite of vast domain of collected data, no model is now capable to explain all observed spectral features of dust aerosol. Several mineralogical and microphysical models of the atmospheric dust have been proposed but they cannot explain the pronounced systematic differences between the IR data ( τ = 0.05–0.2) and measurements from the surface (Viking landers, Pathfinder) which give the typical “clear” optical depth of τ ≈ 0.5 from one side, and ground-based observations in the UV–visible range showing much more transparent atmosphere, on the other side. Also the relationship between τ 9 and the visible optical depth is not well constrained experimentally so far. Future focused measurements are therefore necessary to study Martian aerosol.

Identifying Wrinkle Ridges from Mars MGS and Viking Mission Data: Using GRASS GIS in Planetary Geology

AbstractDuring the past few decades, numerous missions to Mars have sent information about the red planet. The missions have shown that Mars has ice on its poles and that ice could be present all over the planet subsurface. The presence of ice on the subsurface could drive particular geological structures called ‘wrinkle ridges’. In this work, Viking image data and the latest Mars Global Suveyor (MGS) data have been imported and stored in a common geospatial database using GRASS GIS as a tool for planetary geology. This study has focused on a subregion of Solis Planum where wrinkle ridges have been localised and both Viking images and MGS altimetry and imagery data are available. Raster data at different resolutions and with different projection parameters have been imported into GRASS GIS and projected in a common reference system. Raw, unprojected data have been processed and rectified using the GRASS image modules. Imagery data have been used to detect planimetric features, whereas basic morphometrical analysis has been performed from the gridded elevation data coming from MGS Mars Orbiter Laser Altimeter.

Impact melts and glasses on Mars

Dark mobile materials on Mars are widely considered to be volcanically derived windblown particulates. Such a conclusion is consistent with the large volcanic edifices on Mars and the assumption that a volatile‐rich crust would not favor significant impact melt generation. Several post‐Viking discoveries, however, provide new perspectives for reconsidering alternative origins not only for some of the mobile dark veneers but also certain materials at the Pathfinder and Viking landing sites. First, certain dark materials on Mars do not exhibit the expected mafic absorption features in their reflectance spectra. Second, the Pathfinder mission revealed unexpected feldspathic compositions of vesicular blocks that lead to a preliminary conclusion that they represent andesites or basaltic andesites, rather than basalts. Third, recent discoveries of Holocene to Miocene impacts in Argentine loessoid deposits provide new insights for the nature of melts generated from eolian sediments. Fourth, global dispersal of impact melt products are now recognized in the terrestrial record throughout the Cenozoic. Consequently, the generation and preservation of impact glass on Mars should be reconsidered. Possible occurrences include possible tektite‐like strewnfields downrange from recent oblique impacts, dark avalanches emerging from backwasting cliffs of easily eroded unconformable deposits, global dispersal of glassy ejecta from Hesperian and Amazonian craters of Chicxulub scale, and dark mobile veneers emerging from Noachian craters. We propose that the mobile dark materials comprising many of the named features of Mars as well as some blocks at the Pathfinder/Viking landing sites may represent impact‐melt products.

Slope streak formation and dust deposition rates on Mars

The Mars Orbiter Camera (MOC) has imaged, sometimes repeatedly, mass movements known as slope streaks, which are abundant in the dust‐covered regions on Mars. They are among the few known examples of contemporary surface changes. A survey of 173 collocated image pairs indicates that these features are currently forming at a high rate of ∼7% per existing streak, per Martian year. Either there is a complete turnover within a few decades or the streak population is currently increasing rapidly. Large spatial, as well as possible temporal, variations in the formation rate are obtained from these data. Streaks do not appear to fade over time periods comparable to their inverse formation rate of ∼28 years, as seen by analysis of Viking Orbiter images containing streaks that are still visible in MOC images. Gradual or stochastic variations in dust deposition may be needed to explain observations of changes in the formation rate, and its current imbalance with the fading rate.

Large-scale fault kinematic analysis in Noctis Labyrinthus (Mars)

Noctis Labyrinthus (Mars) is characterized by many tectonic features, which represent brittle deformation of the crust. This tectonic setting was analysed by remote sensing of the Viking Mars Digital Image Model (MDIM) mosaic and Mars Orbiter Camera (MOC) global mosaic, in order to identify deformational events. The main features are normal faults producing horst-graben structures, strike-slip faults, and related en-echelon and pull-apart basins. Using the criterion of cross-cutting relationships and analysis of secondary structures, to infer sense of movement of faults, two deformational phases were identified in the Noctis Labyrinthus area. The first, D1, located mainly in the northern part, is characterized by transtensional faults (Noachian). The second, D2, recorded in the southern part of the Noctis Labyrinthus by an orthorhombic extensional fault pattern along NNE and WNW trends, is related to the Valles Marineris formation (Late Noachian–Early Hesperian). A third tectonic event, D3, represented by the partly known dextral NW strike-slip faults cross-cutting the Valles Marineris Canyon System (Late Hesperian?-Amazonian?), was not found in Noctis Labyrinthus at the scale and resolution considered.

Mars-like soils in the Atacama Desert, Chile, and the dry limit of microbial life.

The Viking missions showed the martian soil to be lifeless and depleted in organic material and indicated the presence of one or more reactive oxidants. Here we report the presence of Mars-like soils in the extreme arid region of the Atacama Desert. Samples from this region had organic species only at trace levels and extremely low levels of culturable bacteria. Two samples from the extreme arid region were tested for DNA and none was recovered. Incubation experiments, patterned after the Viking labeled-release experiment but with separate biological and nonbiological isomers, show active decomposition of organic species in these soils by nonbiological processes.

The Temperature Regime of the Surface Layer of the Phobos Regolith in the Region of the Potential Fobos–Grunt Space Station Landing Site

Because of the absence of the atmosphere, the short duration of the Phobos day (7.7 hours), and the presence of a highly porous and fine-grained soil on the Phobos surface, all components of the future Russian Fobos–Grunt lander will operate under frequent and sharp temperature changes: from positive to extremely low negative temperatures. As a consequence, information about the temperature regime directly on the surface of the Martian satellite and in the near-surface layer appears to be extremely important. The proposed publication contains both the information about the thermophysical properties of the surface regolith of Phobos, derived from observations made with the Mariner 9 orbiter, the Viking orbiter, the Fobos-2 spacecraft, and the Mars Global Surveyor orbiter, and the results of the numerical modeling of the thermal regime of the surface regolith layer (on diurnal and seasonal time scales) in the area of the potential Fobos–Grunt landing site. We performed this modeling by taking into account the seasons on Mars and the effects due to the eclipse of Phobos by Mars.

Eos Chasma, Mars: Regional setting for a potential landing site for astrobiology

The floor of Eos Chasma, centered at about 13.4°S and 41.5°W at an elevation of −3.5 km, is proposed as a future landing site on Mars. Deposits in this area were derived from a variety of sources, including chaotic terrain (interpreted to reflect the release of subsurface water) and possible paleolake materials, which could shed light on the astrobiological potential of Mars, climate history, and the evolution of the surface. Analyses of the physical properties of the proposed site suggest a rock abundance of 10–18% (based on Viking Orbiter Infrared Thermal Mapper data), set in a matrix of medium to coarse sands (based on Mars Global Surveyor Thermal Emission Spectrometer data), sparse covering by dust (based on albedo measurements), and a surface roughness of &lt;1 to 1.7 m (derived from the Mars Orbiter Laser Altimeter). Although these attributes are within the engineering constraints for current lander designs, models of the atmosphere suggest that wind shear (generated primarily by the proximity to local topography, i.e., the Chasma canyon wall) might preclude the site with current landing systems.

Continual geological activity in Athabasca Valles, Mars

Comprehensive studies of the stratigraphic relationships in the Athabasca Valles region have been performed on imagery from the Viking Orbiters and the Mars Orbiter Camera (narrow and wide angle) on board Mars Global Surveyor as well as by making use of topographic data derived from the Mars Global Surveyor Laser Altimeter (MOLA) instrument. From superimposed crater frequencies we have derived absolute surface ages by applying the Hartmann and Neukum [2001] cratering chronology model. The main channel has been incised into the Cerberus volcanic plains with an average plains age of 3.4 Ga. The main fluvial or glacial erosion processes ended 2.6 Ga ago. This result shows that the age of the valley system itself is older than commonly believed. One major possible fluvial event occurred in the topographically lower volcanic plains southwest of the valley 1.6 Ga ago. The valley itself was covered by lava episodically and ending 0.9 Ga and in case of a few younger episodes 30 Ma ago. The surface texture south of the valley system suggests a younger, possibly fluvial overprinting of the volcanic texture 30 Ma ago. The latest volcanic activity is dated to about 3 Ma ago. With the latter ages we have been able not only to confirm earlier age estimates by Berman and Hartmann [2002] but also to show that the valley system itself has undergone over a period of two billion years active geological cycles which were dominated by volcanic processes at the end.

Rock size‐frequency distributions on Mars and implications for Mars Exploration Rover landing safety and operations

The cumulative fractional area covered by rocks versus diameter measured at the Pathfinder site was predicted by a rock distribution model that follows simple exponential functions that approach the total measured rock abundance (19%), with a steep decrease in rocks with increasing diameter. The distribution of rocks &gt;1.5 m diameter visible in rare boulder fields also follows this steep decrease with increasing diameter. The effective thermal inertia of rock populations calculated from a simple empirical model of the effective inertia of rocks versus diameter shows that most natural rock populations have cumulative effective thermal inertias of 1700–2100 J m−2 s−0.5 K−1 and are consistent with the model rock distributions applied to total rock abundance estimates. The Mars Exploration Rover (MER) airbags have been successfully tested against extreme rock distributions with a higher percentage of potentially hazardous triangular buried rocks than observed at the Pathfinder and Viking landing sites. The probability of the lander impacting a &gt;1 m diameter rock in the first 2 bounces is &lt;3% and &lt;5% for the Meridiani and Gusev landing sites, respectively, and is &lt;0.14% and &lt;0.03% for rocks &gt;1.5 m and &gt;2 m diameter, respectively. Finally, the model rock size‐frequency distributions indicate that rocks &gt;0.1 m and &gt;0.3 m in diameter, large enough to place contact sensor instruments against and abrade, respectively, should be plentiful within a single sol's drive at the Meridiani and Gusev landing sites.

Mars: Dust devil track survey in Argyre Planitia and Hellas Basin

Dust devils and dust devil tracks have been frequently observed in Viking Orbiter and Mars Orbiter Camera (MOC) images, but the parameters that control their distribution have been poorly constrained. Here we investigate the abundance of dust devil tracks in two large study areas, Argyre Planitia and Hellas Basin, using a survey of over 3000 MOC narrow‐angle (NA) images. We report the effect of season, elevation, and surface properties on track distribution using measurements of dust devil track density (the number of dust devil tracks per square kilometer). In both areas, dust devil tracks occur predominantly in summer and are rarely observed in winter. The lifetime of dust devil tracks is inferred to be short (i.e., less than a few months). There is no unambiguous correlation of abundance with elevation; rather the spatial distribution follows albedo patterns, suggesting that dust availability controls the abundance of dust devil tracks. We estimate the total dust lifting potential of dust devils using the average dust devil track density for Argyre and Hellas and conclude that, unless the average dust devil track is greater than 20 m wide, longer than 2 km, and more than 40 μm deep, they cannot account for the estimated global sedimentation rate. In addition, by comparing 2 Mars years of observations, we find no evidence of an increase in dust devil track density prior to the global dust storm that occurred in June 2001. We conclude that dust devils did not trigger this storm.