Previous Mars Research Articles

Development of the Mars Science Laboratory Heatshield Thermal Protection System

Early in the development of the Mars Science Laboratory thermal protection system on the heatshield, project management planned to use Lockheed Martin’s Super Light Ablator in honeycomb as the ablative material based on successful use on previous Mars entry heatshields and on stagnation arcjet tests at heating rates beyond the design levels. Because this heatshield would be the first to experience combined turbulent flow and high shear environments as it entered the Mars atmosphere, tests were performed in various arcjet facilities on flat-plate, wedge, and swept-cylinder specimen configurations in order to ascertain the effects of shear on the material. During the course of these tests, a set of conditions within the flight envelope was identified that resulted in catastrophic failure in the SLA-561V. Consequently, project management decided to replace the SLA-561V with the phenolic-impregnated carbon ablator, the material that had flown successfully on the Stardust mission and was undergoing intense testing and characterization for the Crew Exploration Vehicle Thermal Protection System Advanced Development Program. With only two years remaining before the expected launch date, and less than 18 months before the heatshield delivery date, the Mars Science Laboratory team developed and built NASA’s first tiled ablator flight heatshield that contributed to the outstanding success of the spacecraft’s entry, descent, and landing on 5 August 2012.

Uncertainty Quantification for Mars Entry, Descent, and Landing Reconstruction Using Adaptive Filtering

Mars entry, descent, and landing trajectories are highly dependent on the vehicle’s aerodynamics and the planet’s atmospheric properties during the day of flight. A majority of previous Mars entry trajectory and atmosphere reconstruction analyses do not simultaneously estimate the flight trajectory and the uncertainties in the atmospheric and aerodynamics models. Adaptive filtering techniques, when combined with traditional trajectory estimation methods, can improve the knowledge of the aerodynamic coefficients and atmospheric properties, while also estimating the confidence interval for these parameters. Simulated data sets with known truth data are used in this study to show the improvement in state and uncertainty estimation by using adaptive filtering techniques. Such a methodology can then be implemented on existing and future Mars entry data sets to determine the aerodynamic and atmospheric uncertainties and improve engineering design tools.

Laminar, Transitional, and Turbulent Heating on Mid Lift-to-Drag Ratio Entry Vehicles

The boundary-layer transition characteristics and convective aeroheating levels on mid lift-to-drag ratio entry vehicle configurations have been studied through wind-tunnel testing. Several configurations were investigated, including elliptically blunted cylinders with both circular and elliptically flattened cross sections, biconic geometries based on launch vehicle dual-use shrouds, and parametrically optimized analytic geometries. Vehicles of this class have been proposed for high-mass Mars missions, such as sample return and crewed exploration, for which the conventional sphere-cone entry-vehicle geometries of previous Mars missions are insufficient. Testing was conducted at Mach 6 over a range of Reynolds numbers sufficient to generate laminar, transitional, and turbulent flow. Transition onset locations, both straight-line and cross-flow, and heating rates were obtained through global phosphor thermography. Supporting computations were performed to obtain heating rates for comparison with the data. Laminar data and predictions agreed to well within the experimental uncertainty. Fully turbulent data and predictions also agreed well. However, in transitional flow regions, greater differences were observed.

The search for life on Earth and other planets

As the NASA rover Curiosity approaches Mars on its quest to look for signs of past or present life there and sophisticated instruments like the space telescopes Kepler and CoRoT keep discovering additional, more Earth-like planets orbiting distant stars, science faces the question of how to spot life on other planets. Even here on Earth biotopes remain to be discovered and explored.

The ExoMars rover locomotion subsystem

ExoMars is the European Space Agency (ESA) mission to Mars planned for launch in 2018, focusing on exobiology with the primary objective of searching for any traces of extant or extinct carbon-based micro-organisms. The on-surface mission is performed by a near-autonomous mobile robotic vehicle (also referred to as the rover) with a mission design life of 180 sols. The rover has a 6 × 6 × 6 with 6 wheel-walking drive configuration (all 6 wheels are driven, steered and have a ‘walking’ capability) and has flexible wheels providing enhanced traction compared to rigid wheels of the same diameter. The suspension is a passive ‘3-bogie’ system which offers the same 6 wheel contact on uneven ground and mobility performance as the NASA–JPL ‘rocker-bogie’ suspension used on previous Mars rovers, but permits elimination of the differential linkage present in that design. Mars presents several challenges to the rover locomotion subsystem with its rock-strewn surface, sand dunes, rocky outcrops, craters and slopes. The unknown nature of the terrain to be traversed imposes several constraints on the locomotion subsystem design that need to be evaluated and incorporated within the flight model for its successful operation on Mars. In addition, accommodation within the confines of the lander and successful egress from it over deflated airbags places stringent constraints on locomotion subsystem mass, stowage envelope, deployment and wheel design. This paper documents the evolution of the ExoMars rover vehicle locomotion configuration from an early design concept to the current mission baseline design. The discussion involves various tradeoffs supported by mechanical and terramechanical analyses, simulations and testing performed on full-scale locomotion breadboard models at single wheel level and system level.

Valles Marineris cloud trails

Distinctive cloud trails are identified in Mars Reconnaissance Orbiter Mars Color Imager (MARCI) images over specific locations associated with Valles Marineris and Noctis Labyrinthus and at perihelion solar longitudes (LS = 230°–260°). High‐contrast surface shadows are well defined, as cast from their eastern margins, supporting altitude and optical depth determinations. These relatively high altitude clouds (40–50 km) exhibit narrow latitudinal widths (25–75 km) in comparison to extended longitudinal dimensions (400–1000 km). MARCI multispectral imaging of cloud surface shadows in five wavelength channels (260, 320, 437, 546, and 653 nm) yields the wavelength dependence of cloud extinction optical depth, revealing a range of small cloud particle sizes (reff = 0.2–0.5 μm) and moderate cloud optical depths (0.03–0.10 visible and 0.1–0.2 ultraviolet). Local time and temporal sampling characteristics of MARCI cloud images indicate that these clouds develop very rapidly in afternoon hours (1300–1500 LT), reach their full longitudinal extents within <2 h time scales, and often reoccur on successive afternoons. Mars Global Surveyor Mars Orbital Camera imaging in previous Mars years indicates these clouds are annually repeating. These observed characteristics suggest a cloud formation mechanism that is specific to ∼50 km horizontal and vertical scales, transports water vapor and dust upward from lower levels, exists during the afternoon, and is likely associated with the mesoscale atmospheric circulations induced by the near‐equatorial canyons of Mars. Cloud particles formed in such updrafts would then be rapidly transported westward in the strong retrograde zonal circulation of the subsolar middle atmosphere in this season.

Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE

The Peneus and Amphitrites Paterae region of Mars displays large areas of smooth, geologically young terrains overlying a rougher and older topography. These terrains may be remnants of the mid-latitude mantle deposit, which is thought to be composed of ice-rich material originating from airfall deposition during a high-obliquity period less than 5 Ma ago. Within these terrains, there are several types of potentially periglacial features. In particular, there are networks of polygonal cracks and scalloped-shaped depressions, which are similar to features found in Utopia Planitia in the northern hemisphere. This area also displays knobby terrain similar to the so-called “basketball terrains” of the mid and high martian latitudes. We use recent high resolution images from the High Resolution Imaging Science Experiment (HiRISE) along with data from previous Mars missions to study the small-scale morphology of the scalloped terrains, and associated polygon network and knobby terrains. We compare these with the features observed in Utopia Planitia and attempt to determine their formation process. While the two sites share many general features, scallops in Peneus/Amphitrites Paterae lack the diverse polygon network (i.e. there is little variation in the polygon sizes and shapes) and large curvilinear ridges observed in Utopia Planitia. This points to a more homogeneous ice content within the substrate in the Peneus/Amphitrites Paterae region and implies that scallop formation is independent of polygon formation. This work shows that, as in Utopia Planitia, sublimation of interstitial ice is a likely process explaining the formation of the scalloped depressions in the region of Peneus/Amphitrites Paterae. Therefore, we provide a simplified scallop formation model based on sublimation of interstitial ice as proposed for Utopia Planitia. We also show that the differences in scallop morphologies between the two regions may be explained by differences in near-surface ice content, sublimation rates and age of formation of the scalloped terrains.

Refocusing NASA planetary science funding

NASA should invest more money in data analysis for its planetary science missions, even if it means delaying or canceling a future mission, members of the science committee of the NASA Advisory Council (NAC) uggested at a 12 October meeting.Science committee member Mark Robinson, director of the Center for Planetary Sciences at Northwestern University in Chicago, Ill., said that large amounts of data from NASA planetary science missions are accumulating, and the funds for data analysis often are inadequate to properly analyze all of it. For example, there is a large amount of currently unanalyzed Mars data that could be used in planning for the Mars Science Laboratory (expected to launch in 2009), and particularly for site selection. This includes data from the recently arrived Mars Reconnaissance Orbiter, which is likely to send more data to Earth in its first year than has been collected by all previous Mars missions combined.

Prediction of the structure of the martian upper atmosphere for the Mars Reconnaissance Orbiter (MRO) mission

Background: The Mars Reconnaissance Orbiter (MRO) spacecraft was launched toward Mars from the Kennedy Space Center in Florida on August 12, 2005, and arrived at Mars on March 10, 2006. Aerobraking in the Martian lower thermosphere (~100-200 km) is planned for 6-months after arrival, enabling the desired mapping orbit to be achieved. Knowledge of the Mars upper atmosphere structure is important for ensuring a safe and successful aerobraking process. Method: Previous Mars Global Surveyor (MGS) density data, acquired during Phase 2 (MGS2) aerobraking operations, is used to validate new coupled MGCM-MTGCM (General Circulation Model) simulations. Confidence gained from this analysis is used to make new predictions for anticipated MRO densities during its aerobraking phase. Specific Mars conditions approaching the aphelion season are prescribed in the MGCM-MTGCM inputs. 110) 30 ~ ( − S L Conclusion: Predicted densities for MRO are simulated to decrease toward the southern winter pole, in accord with the general trend observed during MGS2. However, it is clear that MRO predicted densities at 120 km are smaller than observed MGS2 densities (especially at similar latitudes near ). The distinct solar local time sampling planned for MRO, during a different interval of the solar cycle, may contribute to these differences. The new MRO MGCM-MTGCM predictions described in this paper are being used to support MRO aerobraking activities. 85 ~ S L

HEADING TO MARS

THE SEARCH FOR CLUES TO Mars's history is intensifying. A fleet of spacecraft from the U.S. and Europe is expected to arrive at the red planet over the next few weeks with instrument-laden rovers and a lander that will examine martian rocks for evidence of past water activity and even life. And the tools they're carrying have evolved since previous Mars missions. Along with standard instruments such as spectrometers and cameras, these craft are also toting microscopes and scratching tools to expose fresh rock. Beagle 2, a lander aboard the European Space Agency's Mars Express spacecraft, is scheduled to touch down on the martian surface on Dec. 25 in an ancient impact crater that may have been wet. After it comes to rest, Beagle 2 will begin examining the surrounding soil with its instruments. NASA's Mars Exploration Rover project features two rovers dubbed Spirit and Opportunity. Spirit is slated to land on Jan. 3 ...

Age relationship of basaltic and andesitic surface compositions on Mars: Analysis of high‐resolution TES observations of the northern hemisphere

Previous Mars Global Surveyor Thermal Emission Spectrometer (TES) results have identified two principal surface compositions on Mars; basaltic surfaces are found primarily in the southern highlands, while andesitic surfaces are found in the northern lowlands and in smaller concentrations distributed throughout the southern highlands. In 1 pixel‐per‐degree composition maps, the exact boundary between the basaltic and andesitic compositions is obscured by large amounts of equatorial surface dust. In this work, high‐resolution TES surface spectral data are used to identify and characterize isolated regions of basalt within the equatorial dust regions and northern lowlands (generally between 20°S–60°N, 0–360°W) in an effort to better understand the nature of the boundary between the two compositions. The purpose of refining this boundary is to more accurately determine the relationship of the compositional dichotomy with global surface morphology and derived crustal thickness. Results show that the basaltic surface composition is closely associated with the ancient cratered terrain morphology but is not well correlated with crustal thickness. The northern extent of the TES basalt composition is also established. With four exceptions, there are no significant concentrations (>∼30% surface cover) of basalt greater than ∼400 km2 in area within the northern plains. Three are located within or adjacent to knobby terrain, which has been suggested to be erosional remnants of the cratered highlands. The fourth exception is in Milankovic crater and may represent a local basalt flow or basaltic material excavated during crater formation. Results from this work suggest that there is a stratigraphic relationship between the basaltic and andesitic surface compositions, with younger andesitic materials overlying older basaltic materials throughout the equatorial and northern plains regions.

Gravity field of Mars: A 75th Degree and Order Model

Radiometric tracking data collected by NASA's Deep Space Network (DSN) for Mariner 9, Viking 1 and 2 orbiters, and Mars Global Surveyor (MGS) have been analyzed to determine the gravity field of Mars. The gravity solution (MGS75D) is a complete spherical harmonics model to degree and order 75. Also parts of the solution are the gravitational constants of Mars, Phobos, and Deimos. The significant improvement in the MGS75D Mars gravity model is mainly a consequence of globally distributed data set collected from the MGS mapping orbits, the use of optimal weighting and constrained least squares solution techniques, and improved force and measurement models in the orbit determination process. The gravity anomaly map reveals significantly more detail and larger amplitudes than any previous Mars gravity map over the major impact and volcanic areas on Mars. Olympus Mons remains the largest known gravity anomaly in our solar system and Isidis Planitia, the highest‐amplitude mascon. There are mascons in the Hellas, Argyre, and Utopia basins. Valles Marineris has distinctive negative anomalies, and all volcanic features are positive. Gravity anomalies over several craters have also been resolved. The overall correlation of the MGS75D gravity anomaly map with topography derived from the Mars Orbiter Laser Altimeter (MOLA) is very high, while the polar regions display relatively poor correlation.

Mars scientific investigations as a precursor for human exploration

In the past two years, NASA has begun to develop and implement plans for investigations on robotic Mars missions which are focused toward returning data critical for planning human missions to Mars. The Mars Surveyor Program 2001 Orbiter and Lander missions will mark the first time that experiments dedicated to preparation for human exploration will be carried out. Investigations on these missions and future missions range from characterization of the physical and chemical environment of Mars, to predicting the response of biology to the Mars environment. Planning for such missions must take into account existing data from previous Mars missions which were not necessarily focused on human exploration preparation. At the same time, plans for near term missions by the international community must be considered to avoid duplication of effort. This paper reviews data requirements for human exploration and applicability of existing data. It will also describe current plans for investigations and place them within the context of related international activities.

New gravity field for Mars fuels research

An new gravitational field model for Mars sheds new light on the structure and composition of many short‐wavelength features on the planet's surface. The model, Goddard Mars Model‐1 (GMM‐1) (Figure 1), holds great promise for future Mars research.Besides resolving more short‐wavelength features than previous Mars gravity models, most major features have higher magnitude anomalies. For example, GMM‐1 details the Valles Marineris canyon near the center of the map and reveals structures of several major impact basins and shield volcanos never before observed. Interestingly, several prominent anomalies in GMM‐1 fail to correlate with surface features. Two prominent anomalies of this type in the northern hemisphere (Ion=−160°, lat=+30° and Ion=105°, lat=+50°) may indicate features covered by volcanic flooding.

An improved gravity model for Mars: Goddard Mars model 1

Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, Goddard Mars Model 1 (GMM‐1). This model employs nearly all available data, consisting of approximately 1100 days of S band tracking data collected by NASA's Deep Space Network from the Mariner 9 and Viking 1 and Viking 2 spacecraft, in seven different orbits, between 1971 and 1979. GMM‐1 is complete to spherical harmonic degree and order 50, which corresponds to a half‐wavelength spatial resolution of 200–300 km where the data permit. GMM‐1 represents satellite orbits with considerably better accuracy than previous Mars gravity models and shows greater resolution of identifiable geological structures. The notable improvement in GMM‐1 over previous models is a consequence of several factors: improved computational capabilities, the use of optimum weighting and least squares collocation solution techniques which stabilized the behavior of the solution at high degree and order, and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models. The inclusion of X band tracking data from the 379‐km altitude, near‐polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM‐1, particularly at high latitudes where current data poorly resolve the gravitational signature of the planet.

Remote sensing of mars' ionosphere and solar wind interaction: Lessons from venus

Although the PHOBOS spacecraft will make some limited in-situ measurements of Mars' upper ionosphere during its transfer orbits, the major part of the mission will be limited to remote sensing by radio occultation and topside sounding methods. To “calibrate” the former as a means of studying the ionosphere and solar wind interaction, we have examined the Pioneer Venus Orbiter radio occultation experiment results in light of what we know from in-situ plasma and magnetic field data. This “calibration” can be used to reassess the data from previous Mars missions and to provide a basis for interpreting data from the upcoming PHOBOS mission. The resemblance between the available Mars radio occultation electron density profiles and those of Venus at solar minimum, and at solar maximum when the solar wind dynamic pressure is high, suggest that similar conditions of ionospheric magnetization exist at both planets. A key observation by the PHOBOS radio science experiments, which can be used to infer whether this ionospheric field is intrinsic or arises from the solar wind interaction, will be a determination of the sensitivity of the ionospheric profiles to varying solar wind conditions.