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At least 271 records · Page 15
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NASA NTRS2002

Mars Global Surveyor Data Analysis Program. Origins of Small Volcanic Cones: Eruption Mechanisms and Implications for Water on Mars

The goal of the proposed work was to determine the origins of small volcanic cones observed in Mars Global Surveyor (MGS) data, and their implications for regolith ice stores and magma volatile contents. For this 1-year study, our approach involved a combination of: Quantitative morphologic analysis and interpretation of Mars Orbiter Camera (MOC) and Mars Orbiter Laser Altimeter (MOLA) data; Numerical modeling of eruption processes responsible for producing the observed features; Fieldwork on terrestrial analogs in Iceland. Following this approach, this study succeeded in furthering our understanding of (i) the spatial and temporal distribution of near-surface water ice, as defined by the distribution and sizes of rootless volcanic cones ("pseudocraters"), and (ii) the properties, eruption conditions, and volatile contents of magmas producing primary vent cones.

Fagents, Sarah A.↗
NASA NTRS2002

Investigations of Martian Impact Crater Morphologies and Morphometries

We have made substantial progress towards completion of the original objectives and are continuing to include new data from the Mars Global Surveyor MOC and TES instruments as they become available (the MOLA instrument has ceased operation as of 2002). The project funding has been used to provide salary support to the PI and several undergraduate students, cover publication charges for two papers, reimburse travel expenses to conferences and workshops incurred by the PI and students, and cover a number of other expenses such as software upgrades and production costs of slides and color prints. This study is revising the PI's Catalog of Large Martian Impact Craters with information obtained from MGS and is utilizing data in the revised Catalog to investigate which planetary factors (such as location, elevation, terrain type, etc.) primarily affect the formation of specific ejecta morphologies and morphometries.

Barlow, Nadine G.↗
NASA NTRS2003

Sixth International Conference on Mars

This publication contains the extended abstracts that were accepted for presentation at the 6th International Conference on Mars, held in Pasadena, CA July 20-25, 2003. The file contains the preface, table of contents, program, abstracts, and indexes. The extended abstracts review and debate some of the key questions and controversies that have matured during the flood of MGS and Odyssey data. The papers are presented in PDF format and are indexed by abstract author, and program author.

Steven Mackwell↗
NASA NTRS2003

Water Ice Clouds in the Martian Atmosphere: A Comparison of Two Methods and Eras

Similar cloud features are seen in maps generated with each method with no obvious outliers. The temperature differencing method appears to possibly be somewhat more sensitive to weaker water ice signatures. We have also generated correlation plots comparing the two methods. At strong delta-T signals, the correlation between the two methods is quite good, and therefore extraction of opacities from earlier Viking data may be possible for these stronger detection levels. Weaker detections do not, however, show such a good correlation. We are currently analyzing why the correlation becomes poor at weak signal levels, though it may be due to the fact that the differencing method may be more sensitive to thin cloud hazes. Results of this ongoing analysis will be presented. A comparison of the Viking and Mars Global Surveyor (MGS) eras are also presented.

A S Hale↗
NASA NTRS2003

Modeling Near-Surface Temperatures at Martian Landing Sites

We have developed a process for deriving near-surface (approx. 1m) temperatures for potential landing sites, based on observational parameters from MGS TES, Odyssey THEMIS, and a boundary layer model developed by Murphy for fitting Pathfinder meteorological measurements. Minimum nighttime temperatures at the MER landing sites can limit power available, and thus mission lifetime. Temperatures are derived based on thermal inertia, albedo, and opacity estimated for the Hematite site in Sinus Meridiani, using predictions of 1-m air temperatures from a one-dimensional atmospheric model. The Hematite site shows 9 % probability of landing at a location with nighttime temperatures below the 97 C value considered to be a practical limit for operations.

T Z Martin↗
NASA NTRS2003

Mars: Updating Geologic Mapping Approaches and the Formal Stratigraphic Scheme

At the Fourth Mars Conference in 1989, Tanaka reviewed the stratigraphy and geologic history of Mars that had emerged based on systematic geologic mapping of the planet s surface using Viking data. This review looked at the stratigraphic column for Mars and assessed the global geologic history in terms of impact, fluvial, periglacial, aeolian, volcanic, and tectonic processes. Many significant new studies using Mars Global Surveyor (MGS) and now Mars Odyssey (MO) data are showing some important new insights and discoveries that are altering and deepening previous understandings. If we were to illustrate the current state of the science, we might compare it to a loose-leaf notebook in which pages are rapidly being added, removed, and rewritten, with plenty of room remaining. Much of the flux is due to new data, of course, but also much can be attributed to the re-examination of basic assumptions and approaches and our ability to employ ever more powerful computer techniques. Here, we will attempt to review, based on our experience, the areas where the most change seems to be occurring, what prospects we face in the immediate future, and where caution needs to be exercised.

K L Tanaka↗
NASA NTRS2003

Factors Controlling the Position of the Martian Magnetic Pileup Boundary

The magnetic pileup boundary (MPB) at Mars is the position where the dominant ion of the plasma changes from solar wind protons to heavy ions of planetary origin. As such, it is the obstacle to solar wind ions. We investigate the factors that influence the shape and position of the magnetic pileup boundary at Mars in order to better understand the Martian obstacle to the solar wind. Employing MGS data, we determine how the Martian MPB moves in response to factors including solar wind pressure and crustal magnetic fields. We also study the factors affecting the thickness of the MPB. Further, we compare the magnetic pileup boundary to the magnetic barrier at Venus. Direct comparison aids in our interpretation of the physics involved in the solar wind interaction with planets lacking a significant intrinsic magnetic field.

D H Crider↗
NASA NTRS2003

Mars Global Surveyor Radio Science Electron Density Profiles: Interannual Variability and Implications for the Neutral Atmosphere

The Mars Global Surveyor (MGS) Radio Science (RS) experiment employs an ultrastable oscillator aboard the spacecraft. The signal from the oscillator to Earth is refracted by the Martian ionosphere, allowing retrieval of electron density profiles versus radius and geopotential. The present analysis is carried out on five sets of occultation measurements: (1) four obtained near northern summer solstice (Ls = 74-116, near aphelion) at high northern latitudes (64.7-77.6N), and (2) one set of profiles approaching equinox conditions (Ls = 135- 146) at high southern latitudes (64.7-69.1S). Electron density profiles (95 to 200 km) are examined over a narrow range of solar zenith angles (76.5-86.9 degrees) for local true solar times of (1) 3-4 hours and (2) 12.1 hours. Variations spanning 1-Martian year are specifically examined in the Northern hemisphere.

S W Bougher↗
NASA NTRS2003

Post Impact Mars Climate Simulations Using a GCM

The first images returned by the Mariner 7 spacecraft of the Martian surface showed a landscape heavily scared by impacts. Mariner 9 imaging revealed geomorphic features including valley networks and outflow channels that suggest liquid water once flowed at the surface of Mars. Further evidence for water erosion and surface modification has come from the Viking Spacecraft, Mars Pathfinder and Mars Global Surveyor's (MGS) Mars Obiter Camera (MOC). This evidence includes apparent paleolake beds, fluvial fans and sedimentary layers (Cabrol and Grinn, 1999; Heberle et al., 2001). There is evidence for subsurface water as well. Rampart crates suggest an abundance of water in the near surface regolith (Mouginis-Mark, 1986). The estimated erosion rates necessary to explain the observed surface morphologies (Golombek and Bridges, 2000) present a conundrum. The rates of erosion appear to be highest when the early sun was fainter and only 75% as luminous as it is today. Furthermore the rates of erosion appear to correlate with the rate at which Mars was impacted (Carr and Waenke, 1992). All of this evidence suggests to a very different climate than what exists on Mars today.

A Colaprete↗
NASA NTRS2003

Operation of MRO's High Resolution Imaging Science Experiment (HiRISE): Maximizing Science Participation

Science return from the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) will be optimized by maximizing science participation in the experiment. MRO is expected to arrive at Mars in March 2006, and the primary science phase begins near the end of 2006 after aerobraking (6 months) and a transition phase. The primary science phase lasts for almost 2 Earth years, followed by a 2-year relay phase in which science observations by MRO are expected to continue. We expect to acquire approx. 10,000 images with HiRISE over the course of MRO's two earth-year mission. HiRISE can acquire images with a ground sampling dimension of as little as 30 cm (from a typical altitude of 300 km), in up to 3 colors, and many targets will be re-imaged for stereo. With such high spatial resolution, the percent coverage of Mars will be very limited in spite of the relatively high data rate of MRO (approx. 10x greater than MGS or Odyssey). We expect to cover approx. 1% of Mars at approx. 1m/pixel or better, approx. 0.1% at full resolution, and approx. 0.05% in color or in stereo. Therefore, the placement of each HiRISE image must be carefully considered in order to maximize the scientific return from MRO. We believe that every observation should be the result of a mini research project based on pre-existing datasets. During operations, we will need a large database of carefully researched 'suggested' observations to select from. The HiRISE team is dedicated to involving the broad Mars community in creating this database, to the fullest degree that is both practical and legal. The philosophy of the team and the design of the ground data system are geared to enabling community involvement. A key aspect of this is that image data will be made available to the planetary community for science analysis as quickly as possible to encourage feedback and new ideas for targets.

E Eliason↗
NASA NTRS2002

Age of the Mars Global Northerly Slope: Evidence From Utopia Planitia

Recent results from the Mars Orbiter Laser Altimeter (MOLA) experiment on Mars Global Surveyor (MGS) indicate that most of Mars is characterized by a very gentle, roughly northerly slope. Detailed mapping in north-central Arabia Terra combined with superposition relations and crater counts indicate that, in that region at least, this northerly slope must have been formed no later than Late Hesperian, with the most likely time of formation being Late Hesperian. Current research in Utopia Planitia intended as a test of extant models for the formation of giant polygons has turned up good evidence for a Late Hesperian age for the northerly tilt in this region as well, as will be discussed.

McGill, George E.↗
NASA NTRS2003

Thermal Emission Spectra of Altered Tephras and Constraints on the Composition of Martian Dust

We have begun to create a comprehensive set of thermal infrared (TIR, approx. 1650-200/cm, approx. 6-50 microns) spectra of palagonitic and hydrothermally altered soils that exhibit a range of mineralogical and chemical compositions for use in analyzing MGS TES data. Palagonite, a phyllosilicate-poor hydrolytically altered tephra, has been suggested as a possible component of the martian soil/dust based on visible and near infrared (VNIR) spectral similarities with martian dusty regions. The chemistry and crystallinity of altered tephras are highly variable depending on the parent material and local environmental conditions, and are important indicators of alteration processes.

Hamilton, Victoria E.↗
NASA NTRS2003

Application of THEMIS Data to an Investigation of a Long Lava Flow in the Tharsis Montes Region of Mars

The Tharsis region of Mars has long been known for the numerous lava flows radiating from the Tharsis Montes shield volcanoes. A 480-km-long flow southwest of Ascraeus Mons has been the subject of previous investigations using Viking and MGS data. The new data currently being obtained with the Thermal Emission Imaging System (THEMIS) on the Mars Odyssey spacecraft can shed new light on the volcanology of Martian lava flows, illustrated in this paper by two THEMIS images of the previously studied flow near Ascraeus Mons. The lava flow examined is on the western flank of the topographic saddle between the Ascraeus Mons and Pavonis Mons shield volcanoes. Flow morphology in the dust-covered Tharsis region is revealed in exquisite detail in daytime IR and VIS images from THEMIS, which will aid in documentation and analysis of lava flow features on Mars and improve constraints for volcanic modeling.

Zimbelman, J. R.↗
NASA NTRS2003

Water Ice Albedo Variations on the Martian Northern Polar Cap

The Viking Orbiters determined that the surface of Mars northern residual cap is water ice. Many researchers have related observed atmospheric water vapor abundances to seasonal exchange between reservoirs such as the polar caps, but the extent to which the exchange between the surface and the atmosphere remains uncertain. Early studies of the ice coverage and albedo of the northern residual Martian polar cap using Mariner 9 and Viking images reported that there were substantial internannual differences in ice deposition on the polar cap, a result which suggested a highly variable Martian climate. However, some of the data used in these studies were obtained at differing values of heliocentric solar longitude (L(sub s)). Reevaluation of this dataset indicated that the residual cap undergoes seasonal brightening throughout the summer, and indicated that this process repeats from year to year. In this study we continue to compare Mariner 9 and Viking Orbiter imaging observations and thermal data of the north residual polar cap to data acquired with Mars Global Surveyor s Mars Orbiter Camera (MOC) instrument. In the current study, our goal is to examine all released data from MGS MOC in the northern summer season, along with applicable TES data in order to better understand the albedo variations in the northern summer and their implications on water transport. To date, work has focused primarily on the MOC dataset. In 1999, data acquisition of the northern polar regions began at L(sub s) = 107, although there was little north polar data acquired from L(sub s)= 107 to L(sub s) = 109. We examined a total of 409 images from L(sub s) = 107 to L(sub s)=148. We have also examined data from 2000 from L(sub s)= 93 to L(sub s)= 110; additional progress is ongoing. Here we present a progress report of our observations, and continue to determine their implications for the Martian water cycle.

Hale, A. S.↗
NASA NTRS2003

Water Ice Clouds in the Martian Atmosphere: A Comparison of Two Methods

To date, the only two data sets offer the potential to examine year-to-year changes in cloud features over an entire Martian year: the Viking Infrared Thermal Mapper (IRTM) data set and the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data set. We have examined the TES data in the same way in which we examined the Viking IRTM data. This provides water-ice cloud information separated in time by 12 Martian years. Since the data are analyzed with the same method, we obtain a very accurate 'apples to apples' comparison, and can generate a historical record of the subtleties of this annual event. Consequently, it is desirable to compare their results to ours to see what differences exist.

Hale, A. S.↗
NASA NTRS2003

The Variability of Transverse Aeolian Ripples in Troughs on Mars

A precursory glance at MGS images of the surface of Mars show an abundance of aeolian transverse ridges. These ridges are located in a variety of geological terrains. Zimbelman and Wilson have separated the small-scale aeolian features of Syrtis Major into six categories: ripples associated with obstacles, ripple bands, ripple fields, ripple patches, isolated ripple patches and ripples associated with dunes. This paper focuses on one of these categories, that of ripple bands which tend to accumulate within linear troughs. As the origin of these features is still being studied (i.e. ripples versus dunes), we refer to them simply as transverse aeolian ridges.

Bourke, M. C.↗
NASA NTRS2003

Investigating the Martian Gullies for Possible Brine Origin: A Preliminary Search for Evaporite Minerals Using THEMIS Data

Photographs taken by both the Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor (MGS) spacecraft and the Thermal Emission Imaging System (THEMIS) aboard the Mars Odyssey (MO) spacecraft have shown the presence of young gullies on Mars. These gullies occur at middle and high latitudes (predominantly in the southern hemisphere) in the walls of both impact craters and canyons. They are thought possibly to be formed by the melting of ground ice, groundwater seepage (possibly as brines), surface runoff, or even liquid CO2, activated sporadically as a result of oscillations in Mars orbit. For this work, the hypothesis of gully formation being related to the outflow of brines will be investigated through the observation and study of spacecraft data. Brine rich fluids expunged from underground onto the walls of canyons and craters would either evaporate or freeze and sublimate. Removal of water from a brine by evaporation or sublimation would cause the solutes to precipitate as evaporite minerals on the canyon and crater walls or at the base of the walls, and possibly on the canyon and crater floors. Hence, the gully sites are ideal target areas to search for evaporites using THEMIS data. The objective of this work is to survey the recently acquired THEMIS data for spectral evidence of evaporite minerals, with a focus on areas of gully formation. Identifying salt mineral residues could provide chemical evidence in support of the brine origin of the Martian gullies.

Lane, M. D.↗
NASA NTRS2003

Geologic Mapping Applications Using THEMIS Data for the Medusae Fossae Formation, Mars

The Medusae Fossae Formation (MFF) is a regionally extensive deposit located along the equator of Mars between roughly 130 and 240 E longitude, the origin of which has stimulated a host of published hypotheses. A volcanic or aeolian origin appear most consistent with Viking and MGS data, but other hypotheses remain viable and new data, as from the Mars Odyssey spacecraft, is likely to stimulate additional hypotheses of origin. NASA is supporting geologic mapping of portions of the MFF deposits, but it is now quite clear that this on-going mapping will need considerable revision as data from the Thermal Emission Imaging System (THEMIS) on Mars Odyssey become available. The daytime IR THEMIS images hold particularly strong potential for providing a new base on which geologic mapping can be carried out, as illustrated by the examples discussed.

Zimbelman, J. R.↗