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All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Evidence for a Hematite Ore Body on Mars

The Mars Global Surveyor (MGS) spacecraft was launched from Cape Kennedy in November 1996. MGS was put into orbit around Mars in September of 1997 and has since been sending back data from a suite of instruments, including the Thermal Emission Spectrometer (TES). The TES instrument is an interferometric spectrometer designed to map the surface mineralogy of Mars by measuring the midinfrared emitted radiation over the spectral region of about 1600 to 200 cm(exp -1) (about 6 to 50 microns). This mineralogically sensitive technique utilizes the characteristic intra- and inter-molecular vibrations of minerals that are manifested in the midinfrared spectra. These spectral "fingerprints" are unique because they are dependent upon chemical composition, crystal structure, crystal orientation, and other factors. Midinfrared spectral data received from the MGS-TES instrument have indicated the presence of a large deposit of hematite (alpha-Fe2O3) in Sinus Meridiani, Mars. This hematite ore body, that is accompanied by basalt, is really extensive, encompassing an area about 350 by 500 km. To better understand the geologic context of this large deposit, a detailed laboratory spectroscopic investigation was conducted using more than 20 hematite samples so that their spectra could be compared to the martian spectra. The samples included red and gray polycrystaline hand samples, gray single-crystal hand samples, and red and gray fine- and coarse-grained particulates. The laboratory analyses provided thermal emissivity spectra that, when compared to the hematite emissivity spectra from Mars, suggest the Sinus Meridiani hematite is possibly an exposure of oriented hematite grains. These grains are likely coarser that 10 microns (and may be much larger) and gray in color. The characteristic of oriented grains is suggested by the apparent crystal axis-dependence of the energy emitted from the surface of Mars. The strong degree of crystal alignment exhibited in the emissivity spectra of Mars suggests that these oriented hematite crystals most likely occur as bedrock of aligned specular hematite grains (possibly schistose in texture) or as a secondary coating on bedrock, rather than as discrete particles. We are investigating the nature of this vast hematite deposit in order to understand better the geologic setting and infer past conditions and geological evolution on Mars.

Morris, Richard V.↗
NASA NTRS2000

Evidence for a Hematite Ore Body on Mars

The Mars Global Surveyor (MGS) spacecraft was launched from Cape Kennedy in November 1996. MGS was put into orbit around Mars in September of 1997 and has since been sending back data from a suite of instruments, including the Thermal Emission Spectrometer (TES). The TES instrument is an interferometric spectrometer designed to map the surface mineralogy of Mars by measuring the midinfrared emitted radiation over the spectral region of approximately 1600 to 200 per centimeter (appjroximately 6 to 50 microns). This mineralogically sensitive technique utilizes the characteristic intra- and inter-molecular vibrations of minerals that are manifested in the midinfrared spectra. These spectral "fingerprints" are unique because they are dependent upon chemical composition, crystal structure, crystal orientation, and other factors. Midinfrared spectral data received from the MGS-TES instrument have indicated the presence of a large deposit of hematite (alpha-Fe2O3) in Sinus Meridiani, Mars. This hematite ore body, that is accompanied by basalt, is areally extensive, encompassing and area approximately 350 by 500 km. To better understand the geologic context of this large deposit, a detailed laboratory spectroscopic investigation was conducted using more than 20 hematite samples so that their spectra could be compared to the martian spectra. The samples included red and gray polycrystaline hand samples, gray single-crystal hand samples, and red and gray fine- and coarse-grained particulates. The laboratory analyses provided thermal emissivity spectra that, when compared to the hematite emissivity spectra from Mars, suggest the Sinus Meridiani hematite is possibly an exposure of oriented hematite grains. These grains are likely coarser that 10 microns (and may be much larger) and gray in color The characteristic of oriented grains is suggested by the apparent crystal axis-dependence of the energy emitted from the surface of Mars. The strong degree of crystal alignment exhibited in the emissivity spectra of Mars suggests that these oriented hematite crystals most likely occur as bedrock of aligned specular hematite grains (possibly schistose in texture) or as a secondary coating on bedrock, rather than as discrete particles. We are investigating the nature of this vast hematite deposit in order to understand better the geologic setting and infer past conditions and geological evolution on Mars.

Lane, M. D.↗
NASA NTRS1999

MOLA: The Future of Mars Global Cartography

The MGS Orbiter is carrying the high-precision Mars Orbiter Laser Altimeter (MOLA) which, when combined with precision reconstructed orbital data and telemetered attitude data, provides a tie between inertial space and Mars-fixed coordinates to an accuracy of 100 m in latitude / longitude and 10 m in radius (1 sigma), orders of magnitude more accurate than previous global geodetic/ cartographic control data. Over the 2 year MGS mission lifetime, it is expected that over 30,000 MOLA Global Cartographic Control Points will be produced to form the basis for new and re-derived map and geodetic products, key to the analysis of existing and evolving MGS data as well as future Mars exploration. Additional information is contained in the original extended abstract.

Duxbury, T. C.↗
NASA NTRS1999

Global Geometric Properties of Martian Impact Craters: A Preliminary Assessment Using Mars Orbiter Laser Altimeter (MOLA)

Impact craters on Mars have been used to provide fundamental insights into the properties of the martian crust, the role of volatiles, the relative age of the surface, and on the physics of impact cratering in the Solar System. Before the three-dimensional information provided by the Mars Orbiter Laser Altimeter (MOLA) instrument which is currently operating in Mars orbit aboard the Mars Global Surveyor (MGS), impact features were characterized morphologically using orbital images from Mariner 9 and Viking. Fresh-appearing craters were identified and measurements of their geometric properties were derived from various image-based methods. MOLA measurements can now provide a global sample of topographic cross-sections of martian impact features as small as approx. 2 km in diameter, to basin-scale features. We have previously examined MOLA cross-sections of Northern Hemisphere and North Polar Region impact features, but were unable to consider the global characteristics of these ubiquitous landforms. Here we present our preliminary assessment of the geometric properties of a globally-distributed sample of martian impact craters, most of which were sampled during the initial stages of the MGS mapping mission (i.e., the first 600 orbits). Our aim is to develop a framework for reconsidering theories concerning impact cratering in the martian environment. This first global analysis is focused upon topographically-fresh impact craters, defined here on the basis of MOLA topographic profiles that cross the central cavities of craters that can be observed in Viking-based MDIM global image mosaics. We have considered crater depths, rim heights, ejecta topologies, cross-sectional "shapes", and simple physical models for ejecta emplacement. To date (May, 1999), we have measured the geometric properties of over 1300 impact craters in the 2 to 350 km diameter size interval. A large fraction of these measured craters were sampled with cavity-center cross-sections during the first two months of MGS mapping. Many of these craters are included in Nadine Barlow's Catalogue of Martian Impact Craters, although we have treated simple craters smaller than about 7 km in greater detail than all previous investigations. Additional information is contained in the original extended abstract.

Garvin, J. B.↗
NASA NTRS2000

A Search for Unconfined Fluvial Outflow Deposits on Mars

Fluvial processes have been active during a large portion of Martian history, as evidenced by a variety of erosional features, ranging from concentrations of small channels to scour features generated by floods that affected enormous areas on Mars. Most research efforts prior to Mars Global Surveyor (MGS) focused on channelized reaches since these were some of the most convincing fluvial features on the planet. Since MGS reached its planned mapping orbit in 1999, a new era of Mars exploration has been opened. The m-scale resolution of the Mars Orbiter Camera (MOC), the precise elevation measurements of the Mars Orbiter Laser Altimeter (MOLA), and the compositional constraints derived from the Thermal Emission Spectrometer (TES) allows one now to search for deposits as well as erosional landforms. Here we describe our initial efforts at a search for deposits on Mars where flow was no longer confined within a topographic channel. We are using both new MGS and existing Viking data, in conjunction with field results of fluvial deposits in unconfined reaches from central Australia and elsewhere as analogues for the deposit characteristics to search for on Mars. Additional information is contained in the original extended abstract.

Zimbelman, J. R.↗
NASA NTRS2001

Observations Regarding Small Eolian Dunes and Large Ripples on Mars

Eolian bedforms occur at the interface between a planetary surface and its atmosphere; they present a proxy record of the influence of climate, expressed in sediment transport, over that surface. High resolution images (1.5 - 12 m/pixel) from the Mars Global Surveyor (MGS) Mars Orbiter Camera provide glimpses of the most recent events shaping the martian landscape. Thousands of images exhibit small transverse dunes or large eolian ripples that have crest-to-crest spacings of 10 to 60 m, heights of a few to 10 m. Bedforms of the size and patterns seen in the Mars photographs are rarely described among Earth's eolian landforms; in terms of size and morphology, most of these fall between traditional definitions of "ripples" and "dunes". Dunes are composed chiefly of materials transported by saltation, ripples are smaller forms moved along by the impact of saltating grains (traction). The largest reported eolian ripples on Earth (granule ripples, megaripples) are typically smaller than the bedforms observed on Mars; likewise, most dunes are typically larger. The small dunes and large ripples on Mars come in a variety of relative albedos, despite an early MGS impression that they are all of high albedo. Some ripples occur on the surfaces of sand dunes; these are most likely true granule ripples. However, most of these bedforms occur in troughs, pits, craters, and on deflated plains. Despite impressions early in the MGS mission, they do not occur everywhere (e.g., they are rare on the northern plains) but they do occur at a range of elevations from the highest volcanoes to the deepest basins. Where they occur on a hard substrate among larger sand dunes, the big dunes have over-ridden the smaller bedforms, indicating that the smaller features are older and perhaps indurated or very coarse-grained. At other locales, the small bedforms have been mantled by material settled from suspension, in other cases they are being exhumed and may be lithified. Still other examples are peppered with small impact craters, implying considerable age. These bedforms present a complicated record of the geologically-recent past, one that has involved changes in climate, sediment transport capabilities, and sediment sources and sinks over time.

Edgett, Kenneth S.↗
NASA NTRS2001

Radiometry Measurements of Mars at 1064 nm Using the Mars Orbiter Laser Altimeter

Measurements by the Mars Orbiter Laser Altimeter (MOLA) on board the Mars Global Surveyor (MGS) may be used to provides a radiometric measurement of Mars in addition to the topographic measurement. We will describe the principle of operation, a mathematical model, and the receiver calibration in this presentation. MOLA was designed primarily to measure Mars topography, surface roughness end the bidirectional reflectance to the laser beam. To achieve the highest sensitivity the receiver detection threshold is dynamically adjusted to be as low as possible while keeping a predetermined false alarm rate. The average false alarm rate 29 monitored in real time on board MOLA via a noise counter, whose output is fed to the threshold control loop. The false alarm rate at a given threshold is a function of the detector output noise which is the sum of the photo detector, shot noise due to the background light seen by the detector and the dark noise. A mathematical model has been developed that can be used to numerically solve for the optical background power given the MOLA threshold setting and the average noise count. The radiance of Mars can then be determined by dividing the optical power by the solid angle subtended by the MOLA receiver, the receiver optical band-width, end the Mars surface area within the receiver field of view. The phase angle which is the sun-Mars-MOLA angle is available from the MGS database. MOLA also measures simultaneously the bidirectional reflectance of Mars vie its 106-lum loser beam at nadir with nearly zero phase angle. The optical bandwidth of the MOLA receiver is 2um full width at half maximum (FWHM) and centered at 106-lum. The receiver field of view is 0.95mrad FWHM. The nominated spacecraft altitude is 100km and the ground track speed is about 3km/s. Under normal operation, the noise counter are read and the threshold levels are updated at 1Hz. The receiver sensitivity is limited by the detector dark noise to about 0.1nW, which corresponds to less than 2% the maximum radiance during daytime from the brightest area on Mars. The results from the mathematical model agree well with the prelaunch measurements at several calibrated optical power levels. The radiance of sunlit Mars estimated with this technique correlates well with the measurement from the MGS. Thermal Emission Spectrometer (TES) and the Hubble Space Telescope at similar wavelength.

Sun, Xiao-Li↗
NASA NTRS2002

The Crustal Thickness of Mars: Accuracy and Resolution

Since the arrival of the Mars Global Surveyor (MGS) spacecraft at Mars and its entry into its mapping orbit in February 1999, the radio tracking and altimetry data from the mission have been part of the systematic mapping of the planet and used to develop very precise models of the gravity field and topography of Mars. Until the altimetry function of Mars Orbiter Laser Altimeter (MOLA) failed on June 30, 2001, the instrument had acquired close to 700 million measurements of the planet's radius, the majority of which have been used to develop a model of the topography with horizontal resolution of about 500 m and radial accuracy of better than 1 m. Concurrently, Doppler and range tracking of MGS by the Deep Space Network at X-band frequencies, with accuracies of about 50 microns/s and about 5 m respectively, have provided orbital knowledge of MGS to the few meter level and enabled the gravity perturbations of the spacecraft to be used to develop a improved gravity models of Mars. The recent models have horizontal resolutions of about 200 km, or degree 65, when expressed in spherical harmonics, and have accuracies of the order of a few mGals at the poles and about 10 mGals at the equator at the highest resolution.

Smith, David E.↗
NASA NTRS2002

Light-Toned, Layered Outcrops of Northern Terra Meridiani Mars: Viking, Phobos 2, and Mars Global Surveyor Observations

Locating outcrops of sedimentary rock on Mars is an important step toward deciphering the planet's geologic and climatologic record. Sedimentary rock representing the earliest martian environments, are of particular interest in this context. This is a report about a vast exposure of material proposed to be martian sedimentary rock. The outcrops cover an area (approximately sq 300,000 km) roughly the size of the Colorado Plateau in North America (approximately 260,000 sq km). The materials occur in northern Terra Meridiani, near of one of the four sites being considered for a 2004 NASA Mars Exploration Rover (MER) landing. The landing ellipse, centered at deg S, deg W, lies in a region exhibiting smooth and rough (at meter scale) dark-toned surfaces, with scattered light-toned patches. Stratigraphically, the dark-toned materials at the MER site lie unconformably on top of a previously-eroded, light-toned surface; the light-toned patches in the landing ellipse are geologic windows down to this lower stratigraphic unit. North of the landing ellipse, the light-toned materials are well-exposed because the darker materials have been removed, stranding outlier remnants in a few locations. The light-toned materials are layered, vertically heterogeneous, and exhibit lateral continuity over hundreds of kilometers. Eroded layers produce cliffs; some outcrops are expressed as mesas, buttes, and spires; and impact craters ranging in diameter from a few meters to tens of kilometers are interbedded with the layers. The purpose of this report is to summarize the results of greater than 6 years of photogeologic investigation into the nature of the light-toned outcrops of northern Terra Meridiani. The work is a 'snapshot' of progress made toward eventual geologic mapping and establishment of the stratigraphic sequence for the materials through 30 September 2002, a day prior to the first release of Mars Odyssey Thermal Emission Imaging System (THEMIS) data to the NASA Planetary Data System (PDS). The main body of data examined were Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images acquired through 30 September 2002. The data also 2 include Viking orbiter images, a Phobos 2 Termoscan image, MGS Mars Orbiter Laser Altimeter (MOLA) topographic observations, and the products of published Viking Infrared Thermal Mapper (IRTM) and Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) analyses. Through September 2002, over 126,000 MOC images had been acquired, and greater than 600 of the MOC narrow angle (1.5-12 m/pixel) images occur within the portions of Terra Meridiani and southwestern Arabia Terra.

Edgett, Kenneth S.↗
NASA NTRS2003

Characteristics of Mini-Magnetospheres Formed by Paleo-Magnetic Fields of Mars

The intensely and non-uniformly magnetized crustal sources generate an effective large-scale magnetic field. In the Southern hemisphere the strongest crustal fields lead to the formation of large-scale mini-magnetospheres. In the Northern hemisphere, the crustal fields are rather weak and there are only isolated mini-magnetospheres. Re-connection with the interplanetary magnetic field (IMF) occurs in many localized regions. This may occur not only in cusp-like structures above nearly vertical field anomalies but also in halos extending several hundreds of kilometers from these sources. Re-connection will permit solar wind (SW) and more energetic particles to precipitate into and heat the neutral atmosphere. Electron density profiles of the ionosphere of Mars derived from radio occultation data obtained by the Radio Science Mars Global Surveyor (MGS) experiment are concentrated in the near polar regions. The effective scale-height of the neutral atmosphere density in the vicinity of the ionization peak has been derived for each of the profiles studied. The effective scale-heights have been compared with the crustal magnetic fields measured by the MGS Magnetometer/Electron Reflectometer (MAG/ER) experiment. A significant difference between the large-scale mini-magnetospheres and regions outside of them has been found. The neutral atmosphere is cooler inside the large-scale mini-magnetospheres. It appears that outside of the cusps the strong crustal magnetic fields prevent additional heating of the neutral atmosphere by direct interaction of the SW. The scale-height of the neutral atmosphere density derived from the experiment with the MGS Accelerometer has been compared with MAG/ER data. The scale-height was found to be usually larger than mean value near the boundaries of potential mini-magnetospheres and around cusps . It may indicate that the paleo-magnetic/IMF field re-connection is characteristic of the mini-magnetospheres at Mars.

N F Ness↗
NASA NTRS2004

Variability in Morphology and Thermophysical Properties of Pitted Cones in Acidalia Planitia and Cydonia Mensae

The northern plains of Mars contain a number of unique landforms and are unique in terms of their topography and composition . Much of the speculation about the northern plains centers on whether there was ever a northern ocean, and if there was, was it long-lived or ephemeral? The northern plains also hosts the Vastitas Borealis Formation which has been variously interpreted as the residue from a northern ocean , and pre-existing material reworked by cold-weather processes . In this work we examine a set of unusual features resident on the northern plains, the pitted cones originally recognized in Viking data . Our focus is on the pitted cones in Acidalia and Cydonia regions. The pitted cones of the northern plains have been hypothesized as being equivalent to terrestrial cinder cones , rootless cones , pingos , and mud volcanoes . To examine the Acidalia and Cydonia regions, multispectral data from the Mars Odyssey THEMIS, gridded topography from Mars Global Surveyor (MGS) MOLA, images from MGS MOC, and mineralogic and thermal inertia information from MGS TES have been assembled in a Geographic Information System. Analysis of MOC Narrow Angle camera images

Farrand, W. H.↗
NASA NTRS2004

An Improved Model of the Crustal Structure of Mars

The first reliable model of the structure of the crust and upper mantle of Mars from remote observations was produced using data from the Mars Orbiter Laser Altimeter (MOLA) and the Radio Science investigation of Mars Global Surveyor (MGS). That model assumed a uniform crustal density and solved for the global variations in crustal thickness using a gravity field derived from preliminary MGS tracking. In that study, spherical harmonic potential coefficients were derived to degree and order 80, but crustal structure was interpreted cautiously to degree 60, or 360 km wavelength, owing to the presence of noise. Tracking normal equations have since been generated to degree 75, to degree 80 (supplemented by altimetric crossovers), and recently to degree 90, using new constants for the orientation of the spin pole and the rotation rate of Mars provided by the IAU2000 rotation model. Gravity models now incorporate tracking data coverage from the Primary and Extended MGS missions and the early phases of the Mars Odyssey mission. In the present study we exploit these advances in gravity modeling to present a refined crustal inversion, which we also interpret in the context of Mars' internal structure and thermal evolution.

Zuber, M. T.↗
NASA NTRS2004

Improved Mars Upper Atmosphere Climatology

The detailed characterization of the Mars upper atmosphere is important for future Mars aerobraking activities. Solar cycle, seasonal, and dust trends (climate) as well as planetary wave activity (weather) are crucial to quantify in order to improve our ability to reasonably depict the state of the Mars upper atmosphere over time. To date, our best information is found in the Mars Global Surveyor (MGS) Accelerometer (ACC) database collected during Phase 1 (Ls = 184 - 300; F10.7 = 70 - 90) and Phase 2 (Ls = 30 - 90; F10.7 = 90 - 150) of aerobraking. This database (100 - 170 km) consists of thermospheric densities, temperatures, and scale heights, providing our best constraints for exercising the coupled Mars General Circulation Model (MGCM) and the Mars Thermospheric General Circulation Model (MTGCM). The Planetary Data System (PDS) contains level 0 and 2 MGS Accelerometer data, corresponding to atmospheric densities along the orbit track. Level 3 products (densities, temperatures, and scale heights at constant altitudes) are also available in the PDS. These datasets provide the primary model constraints for the new MGCM-MTGCM simulations summarized in this report. Our strategy for improving the characterization of the Mars upper atmospheres using these models has been three-fold : (a) to conduct data-model comparisons using the latest MGS data covering limited climatic and weather conditions at Mars, (b) to upgrade the 15-micron cooling and near-IR heating rates in the MGCM and MTGCM codes for ad- dressing climatic variations (solar cycle and seasonal) important in linking the lower and upper atmospheres (including migrating tides), and (c) to exercise the detailed coupled MGCM and MTGCM codes to capture and diagnose the planetary wave (migrating plus non-migrating tidal) features throughout the Mars year. Products from this new suite of MGCM-MTGCM coupled simulations are being used to improve our predictions of the structure of the Mars upper atmosphere for the upcoming MRO aerobraking exercises in 2006. A Michigan website, containing MTGCM output fields from previous climate simulations, is being expanded to include new MGCM-MTGCM simulations addressing planetary wave influences upon thermospheric aerobraking fields (densities and temperatures). In addition, similar MTGCM output fields have been supplied to the MSFC MARSGRAM - 200X empirical model, which will be used in mission operations for conducting aerobraking maneuvers.

Bougher, S. W.↗
NASA NTRS2004

A Martian Telecommunications Network: UHF Relay Support of the Mars Exploration Rovers by the Mars Global Surveyor, Mars Odyssey, and Mars Express Orbiters

NASA and ESA have established an international network of Mars orbiters, outfitted with relay communications payloads, to support robotic exploration of the red planet. Starting in January, 2004, this network has provided the Mars Exploration Rovers with telecommunications relay services, significantly increasing rover engineering and science data return while enhancing mission robustness and operability. Augmenting the data return capabilities of their X-band direct-to-Earth links, the rovers are equipped with UHF transceivers allowing data to be relayed at high rate to the Mars Global Surveyor (MGS), Mars Odyssey, and Mars Express orbiters. As of 21 July, 2004, over 50 Gbits of MER data have been obtained, with nearly 95% of that data returned via the MGS and Odyssey UHF relay paths, allowing a large increase in science return from the Martian surface relative to the X-band direct-to-Earth link. The MGS spacecraft also supported high-rate UHF communications of MER engineering telemetry during the critical period of entry, descent, and landing (EDL), augmenting the very low-rate EDL data collected on the X-band direct-to-Earth link. Through adoption of the new CCSDS Proximity-1 Link Protocol, NASA and ESA have achieved interoperability among these Mars assets, as validated by a successful relay demonstration between Spirit and Mars Express, enabling future interagency cross-support and establishing a truly international relay network at Mars.

telecommunications↗
NASA NTRS2010

Why Haven't Mars Rovers Landed Where They Were Expected to?

In a recent study (Desai, 2008) of the actual landing sites for the Mars Pathfinder, Mars Exploration Rovers and the Phoenix Mars Lander, data collected indicates that these missions landed at least 13 km downrange of their targeted landing sites. A direct reason is that density measurements taken during entry, descent and landing were consistently found to be lower than those predicted by Mars atmospheric models. The basis of this study is to further investigate this problem to see if certain aspects of current Mars atmospheric models need to be reevaluated. This study compared four different atmospheric profiles at nine pairs of comparable sites around Mars. The comparable sites are similar in location and Local True Solar Time; however they are from different Mars years. One year had normal conditions, while the other year experienced a global dust storm. Three of the atmospheric profiles were obtained by the Mars Global Surveyor (MGS); these data sets include a Radio Science profile and Thermal Emission Spectrometer data in limb and nadir projections. The three MGS data sets were selected from large observational databases to allow the sites to have data observed at nearcoincident times. The last atmospheric profile is from the Mars Global Reference Atmospheric Model (Mars-GRAM), an engineering level atmospheric model widely used for mission applications. Through careful data evaluation, several conclusions were drawn. Ratios among the data show that the three observed MGS profiles were consistent with each other, although they were recorded by three different methods. Mars-GRAM data had larger differences from the observed data. Mars-GRAM particularly had issues with consistently overestimating upper atmosphere atmospheric density, as noted in Desai s study. Differences between the observed atmospheric density profiles from the Mars-GRAM atmospheric density profile could be attributed to a temperature bias in the model, especially in the upper atmosphere.

Badger, Andrew M.↗
NASA NTRS2013

Mars-GRAM 2010: Additions and Resulting Improvements

The Mars Global Reference Atmospheric Model (Mars-GRAM) is an engineering-level atmospheric model widely used for diverse mission applications. Mars-GRAM has been utilized during previous aerobraking operations in the atmosphere of Mars. Mars-GRAM has also been used in the prediction and validation of Mars Pathfinder hypersonic aerodynamics, the aerothermodynamic and entry dynamics studies for Mars Polar Lander, the landing site selection process for the Mars Science Laboratory (MSL), the Mars Aerocapture System Study (MASS) as well as the Aerocapture Technology Assessment Group (TAG). Most recently, Mars-GRAM 2010 was used to develop the onboard atmospheric density estimator that is part of the Autonomous Aerobraking Development Plan. The most recent release of Mars-GRAM 2010 contains several changes including an update to Fortran 90/95 and the addition of adjustment factors. Following the completion of a comparison analysis between Mars-GRAM, Thermal Emission Spectrometer (TES), as well as Mars Global Surveyor (MGS), Mars Odyssey (ODY), and Mars Reconnaissance Orbiter (MRO) aerobraking density data, adjustment factors were added to Mars-GRAM 2010 that alter the input data from National Aeronautics and Space Administration (NASA) Ames Mars General Circulation Model (MGCM) and the University of Michigan Mars Thermospheric General Circulation Model (MTGCM) for the mapping year 0 user-controlled dust case. The addition of adjustment factors resolved the issue of previous versions of Mars-GRAM being less than realistic when used for sensitivity studies for mapping year 0 and large optical depth values, such as tau equal to 3. Mars-GRAM was evaluated at locations and times of TES limb observations and adjustment factors were determined. For altitudes above 80 km and below 135 km, Mars-GRAM (MTGCM) densities were compared to aerobraking densities measured by Mars Global Surveyor (MGS), Mars Odyssey (ODY), and Mars Reconnaissance Orbiter (MRO) to determine the adjustment factors. The adjustment factors generated by this process had to satisfy the gas law as well as the hydrostatic relation and are expressed as a function of height (z), Latitude (Lat) and areocentric solar longitude (Ls). The greatest adjustments are made at large optical depths such as tau greater than 1. The addition of the adjustment factors has led to better correspondence to TES Limb data from 0-60 km altitude as well as better agreement with MGS, ODY and MRO data at approximately 90-130 km altitude. Improved Mars-GRAM atmospheric simulations for various locations, times and dust conditions on Mars will be presented at the workshop session. The latest results validating Mars-GRAM 2010 versus Mars Climate Sounder data will also be presented. Mars-GRAM 2010 updates have resulted in improved atmospheric simulations which will be very important when beginning systems design, performance analysis, and operations planning for future aerocapture, aerobraking or landed missions to Mars.

Justh, Hilary L.↗
NASA NTRS1985

Laboratory infrared spectra of predicted condensates in carbon-rich stars

Laboratory spectra and mass absorption coefficients of MgS, CaS, FeS, SiS2, FeS2, Fe3C, and a commercial iron carbide are presented over the wavelength range 125-15 microns. These spectra confirm that MgS is the most likely source of the unidentified 30-micron emission in carbon-rich sources and that FeS, Fe3C, and 'iron carbide' cannot be responsible for this feature although they could contribute to the continuum in this region. CaS and FeS2 may contribute to the 30-micron feature; however, both higher resolution and higher precision astronomical observations are needed before their presence can be established. SiS2 has a peak near 22 microns and therefore cannot be a significant component of the dust in such regions.

Nuth, J. A.↗
NASA NTRS1988

Theoretical study of the alkali and alkaline-earth monosulfides

Ab initio calculations have been used to obtain accurate spectroscopic constants for the X2Pi and A2Sigma(+) states of the alkali sulfides and the X1Sigma(+), a3Pi, and A1Pi states of the alkaline-earth sulfides. In contrast to the alkali oxides, the alkali sulfides are found to have X2Pi ground states, due to the larger electrostatic interaction. Dissociation energies of 3.27 eV for BeS, 2.32 eV for MgS, 3.29 eV for CaS, and 3.41 eV for SrS have been obtained for the X1Sigma(+) states of the alkaline-earth sulfides, in good agreement with experimental results. Core correlation is shown to increase the Te values for the a3Pi and A1Pi states of MgS, CaS, and SrS.

Partridge, Harry↗