Topography and Geologic Characteristics of Aeolian Grooves in the South Polar Layered Deposits of Mars

The topographic and geologic characteristics of grooves and groove-like features in the south polar layered deposits near the Mars Polar Lander/Deep Space 2 landing sites are evaluated using Mariner 9 images and their derived photoclinometry, normalized using Mars Orbiter Laser Altimeter data. Although both Mariner 9 and Viking images of the south polar layered deposits were available at the time of this study, Mariner 9 images of the grooves were selected because they were generally of higher resolution than Viking images. The dimensions and slopes of the grooves, together with orientations that nearly match the strongest winds predicted in the Martian Global Circulation Model and directions inferred from other wind indicators, suggest that they formed by aeolian scour of an easily erodible surface. Most grooves are symmetric and V-shaped in transverse profile, inconsistent with an origin involving extensional brittle deformation. Although the grooves strike along slopes and terraces of the south polar layered deposits, the variable depths and lack of terracing within the grooves themselves indicate that any stratigraphy in the uppermost 100 m of the polar layered deposits is composed of layers of similar, and relatively low, resistance. The grooves do not represent landing hazards at the scale of the Mariner 9 images (72-86 m/pixel) and therefore probably would not have affected Mars Polar Lander and Deep Space 2, had they successfully reached the surface.     

Inorganic chemical investigation by x-ray fluorescence analysis: The Viking Mars Lander

The inorganic chemical investigation added in August 1972 to the Viking Lander scientific package will utilize an energy-dispersive X-ray fluorescence spectrometer in which four sealed, gas-filled proportional counters will detect X-rays emitted from samples of the Martian surface materials irradiated by X-rays from radioisotope sources (⁵⁵Fe and ¹⁰⁹Cd). The output of the proportional counters will be subjected to pulse-height analysis by an on-board step-scanning single-channel analyzer with adjustable counting periods. The data will be returned to Earth, via the Viking Orbiter relay system, and the spectra constructed, calibrated, and interpreted here. The instrument is inside the Lander body, and samples are to be delivered to it by the Viking Lander Surface Sampler. Calibration standards are an integral part of the instrument.The results of the investigation will characterize the surface materials of Mars as to elemental composition with accuracies ranging from a few tens of parts per million (at the trace-element level) to a few percent (for major elements) depending on the element in question. Elements of atomic number 11 or less are determined only as a group, though useful estimates of their individual abundances maybe achieved by indirect means. The expected radiation environment will not seriously hamper the measurements. Based on the results, inferences can be drawn regarding (1) the surface mineralogy and lithology; (2) the nature of weathering processes, past and present, and the question of equilibrium between the atmosphere and the surface; and (3) the extent and type of differentiation that the planet has undergone.The Inorganic Chemical Investigation supports and is supported by most other Viking Science investigations.     

Horizon Topography and the Location Of Viking Lander 2

The location of Viking Lander 2 on Mars is determined by matching features seen on the horizon with hills visible in Viking Orbiter images. Three possible positions are found, with one being preferred, confirming and refining the position determined previously by radio tracking. The often stated opinion that a lobe of ejecta from the large crater Mie is visible in lander images is shown to be false. The most prominent hill on the eastern horizonis Goldstone, a pedestal crater 8 km from the lander. Another hill16 km from the preferred position is just visible to the north. The image processing procedures used to enhance visibility of low relief features on the horizon should be useful for several future missions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Convective vortices on Mars: a reanalysis of Viking Lander 2 meteorological data, sols 1-60

Dust devil data from Mars is limited by a lack of data relating to diurnal dust devil behaviour. Previous work looking at the Viking Lander meteorological data highlighted seasonal changes in temporal occurrence of dust devils and gave an indication of typical dust devil diameter, size, and internal dynamics. The meteorological data from Viking Lander 2 for sols 1 to 60 have been revisited to provide detailed diurnal dust devil statistics. Results of our analysis show that the Viking Lander 2 experienced a possible 38 convective vortices in the first 60 sols of its mission with a higher occurrence in the morning compared to Earth, possibly as a result of turbulence generated by the Lander body. Dust devil events have been categorised by statistical confidence and intensity. Some initial analysis and discussion of the results is also presented. Assuming a similar dust loading to the vortices seen by Mars Pathfinder, it is estimated that the amount of dust lofted in the locality of the Lander is approximately 800 ± 10 kgsol⁻¹km⁻².     

Inference of dust opacities for the 1977 Martian great dust storms from Viking Lander 1 pressure data

A δ-Eddington radiative transfer algorithm is used to compute the thermal tidal heating of a dusty Martian atmosphere for a given set of dust optical depth, effective single scattering albedo, and phase function asymmetry parameter. The resulting thermal tidal forcing is used in a classical atmospheric tidal model to compute the amplitudes of the surface pressure oscillations at the Viking Lander 1 site for the two 1977 Martian great dust storms. Parametric studies show that the dust opacities and optical parameters derived from the Viking Lander imaging data are roughly representative of the global dust haze needed to reproduce the tidal surface pressure amplitudes also observed at Lander 1, except that the model-inferred asymmetry parameter is smaller during the onset of a great storm. The observed preferential enhancement during dust-storm onset of the semidiurnal tide at Viking Lander 1 relative to its diurnal counterpart is shown to be due primarily to the elevation of the tidal heating source in a very dusty atmosphere, although resonant enhancement of the main semidiurnal tidal mode makes an important secondary contribution.     

Viking 1 Lander on the surface of mars: Revised location

Late in 1977, the periapsis altitude of the Viking Orbiters was lowered from 1500 to 300 km. The higher resolution of pictures taken at the lower altitude (8 m/pixel) permitted a more accurate determination of the location of the Viking 1 Lander by correlating topographic features seen in the new pictures with the same features in lander pictures. The position of the lander on Viking Orbiter picture 452B11 (NGF Rectilinear) is line 293, sample 1099. This location of the Viking 1 Lander has been used in a revision of the control net of Mars (M.E. Davies, F.Y. Katayama, and J.A. Roth, R2309 NASA, The Rand Corp., Feb. 1978). The new areographic coordinates of the lander are lat 22.483° N and long 47.968° W. The new location is estimated to be accurate to within 50 m.     

Crater streaks in the Chryse Planitia region of Mars: Early Viking results

High-resolution images of Chryse Planitia and eastern Lunae Planum from the early revolutions of Viking Orbiter I permit detailed analyses of crater-associated streaks and interpretation of related eolian processes. A total of 614 light and dark streaks were studied and treated statistically in relation to: (1) morphology, morphometry, and orientation, (2) “parent” crater size and morphology, (3) terrain type in which they occured, (4) topographic elevation, and (5) meteorological data currently being acquired by Viking Lander I. Three factors are apparent: (1) light streaks predominate, (2) most streaks form in association with fresh bowl-shaped craters, and (3) most light streaks are of the “parallel” type, whereas dark streaks are approximately evenly divided between convergent and parallel forms; moreover, very few light or dark streaks are divergent or fan-shaped. Light streaks have an average azimuth of 218° (corresponding to winds from the northeast), which approximates the orientation of 197 ± 14° for eolian “drifts” observed by the Viking Lander imaging team (Binder et al., 1977). This lends support to the hypothesis that light streaks are deposits of windblown sediments. Dark streaks are oriented at an azimuth of 42° (approximately opposite that of light streaks) and are nearly in line with the dominant wind direction currently recorded by the Viking meteorology instruments (Hess et al., 1977). Although the size of the sample area is not uniform among the various terrain types, the highest frequency of streaks per unit area occurs in the knobby terrain. This is partly explained by the probable production of fine-grained material (weathered from the knobs) to form streaks and other eolian features, and the higher wind turbulence generated around the knobs. The lowest frequency of streaks occurs on the elevated plateaus. The light streaks in Chryse Planitia appear to be relatively stable and to result from deposition of windblown material during times of relatively high velocity northeasterly winds. Dark streaks are more variable and probably result from erosion by southwesterly winds. Both types will be monitored during the extended Viking mission and the results compared with lander data.     

Surface erosion caused on Mars from Viking descent engine plume

During the Martian landings the descent engine plumes on Viking Lander 1 (VL-1) and Viking Lander 2 (VL-2) eroded the Martian surface materials. This had been anticipated and investigated both analytically and experimentally during the design phase of the Viking spacecraft. This paper presents data on erosion obtained during the tests of the Viking descent engine and the evidence for erosion by the descent engines of VL-1 and VL-2 on Mars. From these and other results, it is concluded that there are four distinct surface materials on Mars: (1) drift material, (2) crusty to cloddy material, (3) blocky material, and (4) rock.Work performed as part of NASA contract W 14,575.     

A sophisticated lander for scientific exploration of Mars: scientific objectives and implementation of the Mars-96 Small Station

A mission to Mars including two Small Stations, two Penetrators and an Orbiter was launched at Baikonur, Kazakhstan, on 16 November 1996. This was called the Mars-96 mission. The Small Stations were expected to land in September 1997 (Ls approximately 178 degrees), nominally to Amazonis-Arcadia region on locations (33 N, 169.4 W) and (37.6 N, 161.9 W). The fourth stage of the Mars-96 launcher malfunctioned and hence the mission was lost. However, the state of the art concept of the Small Station can be applied to future Martian lander missions. Also, from the manufacturing and performance point of view, the Mars-96 Small Station could be built as such at low cost, and be fairly easily accommodated on almost any forthcoming Martian mission. This is primarily due to the very simple interface between the Small Station and the spacecraft. The Small Station is a sophisticated piece of equipment. With the total available power of approximately 400 mW the Station successfully supports an ambitious scientific program. The Station accommodates a panoramic camera, an alpha-proton-x-ray spectrometer, a seismometer, a magnetometer, an oxidant instrument, equipment for meteorological observations, and sensors for atmospheric measurement during the descent phase, including images taken by a descent phase camera. The total mass of the Small Station with payload on the Martian surface, including the airbags, is only 32 kg. Lander observations on the surface of Mars combined with data from Orbiter instruments will shed light on the contemporary Mars and its evolution. As in the Mars-96 mission, specific science goals could be exploration of the interior and surface of Mars, investigation of the structure and dynamics of the atmosphere, the role of water and other materials containing volatiles and in situ studies of the atmospheric boundary layer processes. To achieve the scientific goals of the mission the lander should carry a versatile set of instruments. The Small Station accommodates devices for atmospheric measurements, geophysical and geochemical studies of the Martian surface and interior, and cameras for descent phase and panoramic views. These instruments would be able to contribute remarkably to the process of solving some of the scientific puzzles of Mars.     

Surface features of Phobos and Deimos

Viking Orbiter images have provided nearly complete coverage of the two satellites of Mars and have been used to construct maps of the surface features of Phobos and Deimos. The satellites have radically different appearances although nearly all features on both objects were formed directly or indirectly by impact cratering. Phobos has an extensive network of linear depressions (grooves) that probably were formed indirectly by the largest impact recorded on Phobos. Deimos lacks grooves as well as the large number of ridges that occur on Phobos. Craters on Deimos have substantial sediment fill; those on Phobos have none. Evidence of downslope movement of debris is prominent on Deimos but is rare on Phobos. Many of the differences between Phobos and Deimos may be caused by modest differences in mechanical properties. However, the lack of a very large crater on Deimos may be responsible for its lack of grooves.     

Mars: Hellas Planitia gravity analysis

Doppler radio tracking data from Viking Orbiter 1 has provided new detailed observations of gravity variations over Hellas Planitia. Line-of-sight Bouguer gravity definitely indicates that isostatic adjustment has occurred. Two theoretical models were tested to obtain fits to the gravity data. Results for a surface deficit model, and a model with a surface deficit and a mass excess at depth are displayed. The mass-at-depth model produced very marked improvement in the data fit as compared to the surface deficit model. The optimum depth for the mass excess is 130 km.     

Comparison of Viking Lander Descent Data and MOLA Topography Reveals Kilometer-Scale Offset in Mars Atmosphere Profiles

Each Viking Lander measured a topographic profile during entry. Comparing to MOLA, we find a vertical offset of 1-2 km in the Viking trajectory. Hence, Viking atmospheric densities and pressures at a given altitude are 10-20% too large.     

Exploratory experiments of impact craters formed in viscous-liquid targets: Analogs for Martian rampart craters?

Exploratory experimental impact studies have been performed using “soupy” mud as a target material. Although differing in details, the results appear to support the hypothesis that ejecta deposits around a class of Martian craters recently revealed in high-resolution Viking Orbiter images were emplaced as a flow of fluidized materials.     

Location of Viking 1 Lander on the surface of Mars

A location of the Viking 1 Lander on the surface of Mars has been determined by correlating topographic features in the lander pictures with similar features in the Viking orbiter pictures. Radio tracking data narrowed the area of search for correlating orbiter and lander features and an area was found on the orbiter pictures in which there is good agreement with topographic features on the lander pictures. This location, when plotted on the 1:250,000 scale photomosaic of the Yorktown Region of Mars (U.S. Geological Survey, 1977) is at 22.487°N latitude and 48.041°W longitude.     

Rosetta—one comet rendezvous and two asteroid fly-bys

One of the two planetary cornerstone missions of the European Space Agency is the Rosetta mission to comet 67P/Churyumov-Gerasimenko. Rosetta is a rendezvous mission with a comet nucleus, which combines an Orbiter with a Lander. It will monitor the evolution of the comet nucleus and the coma as a function of increasing and decreasing solar flux input along the comet’s pre- and post-perihelion orbit. Different instrumentations will be used in parallel, from multi-wavelength spectrometry to in-situ measurements of coma and nucleus composition and physical properties. Rosetta will go in orbit around the nucleus of its target comet 67P/Churyumov-Gerasimenko, when it is still far from the Sun and accompany the comet along its way to perihelion and beyond. In addition the Rosetta Lander Philae will land on the nucleus surface, before the comet is too active to permit such a landing (i.e. at around r = 3 AU) and examine the surface and subsurface composition of the comet nucleus as well as its physical properties.     

Photogrammetric application of viking orbital photography

Special techniques are described for the photogrammetric compilation of topographic maps and profiles from stereoscopic photographs taken by the two Viking Orbiter spacecraft. These techniques were developed because the extremely narrow field of view of the Viking cameras precludes compilation by conventional photogrammetric methods. The techniques adjust for internal consistency the Supplementary Experiment Data Record (SEDR—the record of spacecraft orientation when photographs were taken) and the computation of geometric orientation parameters of the stereo models. A series of contour maps of Mars is being compiled by these new methods using a wide variety of Viking Orbiter photographs, to provide the planetary research community with topographic information.     

Recession of Martian north polar cap: 1979–1980 Viking observations

The 1979–1980 regression curve for the north polar cap of Mars, determined from Viking orbiter images, is compared to Viking observations of the same season 1 (Martin) year earlier and to telescopic observations. Differences between the two years cannot unambigously be attributed to dynamical effects because of uncertainties introduced by limited longitudinal coverage.     

Possible pingo fields in the Utopia basin, Mars: Geological and climatical implications

The presence of pingos on Mars has been hypothesized since the period of the Viking mission. In fact, a diverse range of pingo-like features has been found at various martian sites including Elysium, Chryse and Utopia Planitiae in the northern lowlands. Due to the morphology and the geological setting, some of those features were interpreted in different ways, creating some controversies, as happened in Athabasca Valles. This reflects the complexity of interpreting these features by remote sensing and multiple plausible interpretations of the same feature. With the objective of identifying new possible pingos or rootless cones on Mars, we selected a study area in Utopia Planitia (10-55° N, 210-260° W) where the presence of both features is possible due to its geological history (volcanic and hydrological). We analyzed more than 2100 Mars Orbiter Camera (MOC)-narrow angle images in addition to Viking, Thermal Emission Imaging System (THEMIS), and High Resolution Stereo Camera (HRSC) images, together with Mars Orbiter Laser Altimeter (MOLA)-derived Digital Elevation Models (DEMs) with a Geographic Information System (GIS). We found in 94 MOC-narrow angle images dome, cone, and ring-shaped features. We analyzed them from morphological and morphometrical points of view in order to compare them with relevant features on Mars and Earth. We tested different possible origins for those features following the approach of multiple working hypotheses. We conclude that the dome, cone, and ring-shaped features could be pingos, which is in agreement with their geological settings. Regarding the driving heat source for the formation of the purported pingos, we propose the existence of a heat source, possibly a magma chamber, underneath the surface of the Utopia basin. Together with possible climatic shifts, the past activities of the heat source may have caused melting of ground ice. The pingo growth due to freezing of the water would have occurred during the following cold climatic conditions.     

New observations of Warrego Valles, Mars: Evidence for precipitation and surface runoff

Most valley networks have been identified primarily in the heavily cratered uplands which are Noachian in age (>3.5 Gyr). A striking exception to this general observation is Warrego Valles located on the southeastern part of the Tharsis bulge. Recent data obtained by the Mars Orbiter Laser Altimeter, the Thermal Emission Imaging System (THEMIS) spectrometer and the Mars Orbiter Camera give new insight into the formation of valley networks and the early Mars climate. We focus our study on the southern Thaumasia region especially on Warrego Valles and determine the organisation of valleys in relation to regional topography and structural geology. Warrego Valles is the most mature valley network that incised the southern side of Thaumasia highlands. It developed in a rectangular-shaped, concave-up drainage basin. Four times more valleys are identified in THEMIS infrared images than in Viking images. Valleys exist on both sides of the main tributary contrary to what was visible in Viking images. Their distribution is highly controlled by topographic slope, e.g. there is a parallel pattern on the sides and dendritic pattern on the central part of Warrego Valles. We quantitatively analyse valley morphology and morphometry to determine the processes responsible for valley network formation. Warrego Valles displays morphometric properties similar to those of a terrestrial fluvial valley network. This valley network is characterised by seven Strahler's orders, a bifurcation ratio of 3, a length ratio of 1.7, a drainage density of 0.53 km⁻¹ and a ruggedness number of 3.3. The hypsometric curve and integral (0.46) indicate that Warrego Valles reached the mature Davis’ stage. Valleys have undergone external degradation since their incision, which masks their main morphological characteristics. Our study supports the assertion that valley networks formed by fluvial processes controlled by an atmospheric water cycle. Further, they seem to develop by successive stages of erosion that occurred during Noachian through the late Hesperian.     

The global martian volcanic evolutionary history

Viking mission image data revealed the total spatial extent of preserved volcanic surface on Mars. One of the dominating surface expressions is Olympus Mons and the surrounding volcanic province Tharsis. Earlier studies of the global volcanic sequence of events based on stratigraphic relationships and crater count statistics were limited to the image resolution of the Viking orbiter camera. Here, a global investigation based on high-resolution image data gathered by the High-Resolution Stereo Camera (HRSC) during the first years of Mars Express orbiting around Mars is presented. Additionally, Mars Orbiter Camera (MOC) and Thermal Emission Imaging System (THEMIS) images were used for more detailed and complementary information. The results reveal global volcanism during the Noachian period (>3.7 Ga) followed by more focused vent volcanism in three (Tharsis, Elysium, and Circum-Hellas) and later two (Tharsis and Elysium) volcanic provinces. Finally, the volcanic activity became localized to the Tharsis region (about 1.6 Ga ago), where volcanism was active until very recently (200-100 Ma). These age results were expected from radiometric dating of martian meteorites but now verified for extended geological units, mainly found in the Tharsis Montes surroundings, showing prolonged volcanism for more than 3.5 billions years. The volcanic activity on Mars appears episodic, but decaying in intensity and localizing in space. The spatial and temporal extent of martian volcanism based on crater count statistics now provides a much better database for modelling the thermodynamic evolution of Mars.