P11E-01
New Insights About Mars From the Creation and Analysis of Mars Global Datasets
The past decade has brought a massive influx of new data from Mars and the moons of Jupiter and Saturn, and equally large volumes will soon be collected from Mercury and the Moon. This influx has created a need for efficient and effective tools to compile, synthesize, and analyze these data. We have attempted to address these needs in two basic directions; first to organize and synthesize the data, and second to create a GIS tools that can ingest and manipulate all of the available planetary data. To date this effort has focused on Mars, but the approach and methodology are easily applied to any solar system object. We have developed a Java-based software and database system called JMARS for creating, compiling, and analyzing global data sets. The effort was begun in direct response to the needs and uses of the Odyssey THEMIS experiment, and the first step has been to produce a global mosaic of 100-m resolution day and night IR imagery from the THEMIS instrument. This effort has required mosaicing and geo-referencing JMARS database includes these global maps, together with global mosaics from Viking and MG MOC, topographic elevation data from MGS MOLA, and global mineral, albedo, and thermal inertia maps from the MGS TES. In addition, the original images from each of these missions can easily imported, as can all of the available numeric data. The JMARS database includes special products such as the image products produced for the Mars Science Laboratory rover landing site selection and MOC THEMS VIS mosaics created for specific sites. The second phase has been the development GIS capabilities to display, layer, combine, and process all of the se data. An example of the analysis capability is the ability to obtain numeric elevation, temperature, albedo, mineral, and thermal inertia profiles on a 100-m resolution base map, while viewing individual high-resolution MOC imagery of any area of interest. JMARS performs basic image processing functions and can import and export data in a wide (and growing) variety of formats. Examples of the scientific applications from this approach include the global mapping of salt deposits, studies of the stratigraphic relationships among compositional units, mapping of specific olivine-bearing rock layers over 1,000's of km, the study of bedrock outcrops in relation to erosional processes, and the ability to investigate processes that produce m-scale morphologies in a regional geologic context. http://jmars.asu.edu
P11E-02
A Sulfur Dioxide Climate Feedback on Early Mars
Reconciling evidence for persistent liquid water during the late Noachian with our understanding of the evolution of the Martian atmosphere and of solar luminosity remains a challenge, despite several decades of research. An optically-thicker atmosphere to supply the necessary radiative forcing would result in the existence of a carbon cycle similar to Earth's, where the release of CO2 from volcanoes is balanced by burial of calcium carbonate through silicate weathering reactions that remove protons and release alkalinity to surface waters. Existence of such a carbon cycle on Mars, even for tens of millions of years, would yield carbonate sediments in far greater abundance than has been observed, as well as residual clay minerals. The high concentration of sulfur in Martian soils and rocks indicates that Martian volcanic emissions contained abundant sulfur volatiles in addition to CO2. However, the atmospheric and aquatic chemistry of SO2 under the reducing conditions of early Mars, in contrast with the presently oxidizing and biologically-catalyzed Earth, has not been thoroughly examined. We argue that these conditions may have allowed atmospheric concentrations of SO2 high enough to augment a thick CO2-H2O greenhouse. Furthermore, early Martian climate may have been stabilized by a feedback mechanism involving SO2 and the solubility of sulfite minerals instead of CO2 and the solubility of carbonates. We present the results of a one-dimensional radiative-convective model, demonstrating the radiative importance of SO2 to the planetary energy budget. We also use a simple geochemical model to show that the presence of SO2 in the early Martian atmosphere would have dominated the aquatic chemistry on the planet's surface, and may provide an explanation for how water could have persisted for millions of years without forming massive carbonate sediments, yet allowing the formation of clay minerals.
P11E-03
Occurrence and Stratigraphy of Phyllosilicate and Hydrated Silicate Minerals on Mars from OMEGA and CRISM
The OMEGA investigation on the Mars Express spacecraft identified phyllosilicates across a range of martian geologic terrains, but importantly the mineral occurrences were largely confined to Noachian-aged terrains. This led to the new paradigm that that an active hydrologic system was restricted to early Mars history. The order of magnitude increase in spatial resolution of the CRISM instrument on Mars Reconnaissance Orbiter over OMEGA is used here to assess mineralogic diversity and stratigraphic relationships in several phyllosilicate regions. CRISM data show definitive evidence for diagnostic Al-OH and Fe/Mg-OH absorptions of phyllosilicate minerals, similar to those seen by OMEGA, but reveal mineralogic diversity down to the fine spatial resolution of the instrument. Al-OH phyllosilicates have been confirmed in Mawrth Vallis and are identified for the first time in the Nili Fossae region, displaying spectra consistent with kaolinite, illite and/or muscovite. A diversity of Fe/Mg-OH phyllosilicates is observed; smectites such as nontronite and saponite are the most common, but chlorites are also present in some locations. A new spectral class of mineral is found interpreted to be hydrated volcanic or impact glass. This material is found in isolated regions in the Noachian highlands. Fe/Mg phyllosilicate and hydrated glasses are found in rims, ejecta, and central peaks of craters in the southern highland Noachian cratered terrain indicating excavation of altered crust from depth. Phyllosilicate is also found in deposits clearly laid by water in Jezero, Ritchy, and Holden crater. Stratigraphic relationships in the many regions show unaltered volcanic or igneous lithologies overlying phyllosilicate-bearing rocks indicating an abrupt cessation of widespread alteration in the late Noachian. The predominance of smectite clay signatures implies moderate to low temperatures of formation (<200°C) such as might have existed in the near surface or shallow crust. The formation of phyllosilicate and hydrated glass could have been a consequence of near surface weathering or low temperature hydrothermal processes in a cooling crust
P11E-04 INVITED
Deep Hydrothermal Circulation and Implications for the Early Crustal Compositional and Thermal Evolution of Mars
Both orbital remote sensing and geophysical observations indicate an important role for hydrothermal crustal cooling during the Noachian epoch. Orbital remote sensing shows that phyllosilicate minerals are common in Noachian-aged terrains but have not been observed in younger terrains (<3.8 Ga). Throughout the Noachian highlands, phyllosilicates are observed in deeply eroded terrains as well as in association with impact craters, in their walls, rims, ejecta, and in central peaks of craters as large as 45 km, corresponding to excavation depths of 4-5 km. CRISM and OMEGA mapping typically show phyllosilicate-bearing rocks occupy the lowest observable stratigraphic unit, and the most common alteration minerals are iron magnesium smectites which typically form at low pressures and temperatures <200oC. Widespread occurrences of phyllosilicates to depths of at least 4-5 km may provide evidence for deep crustal hydrothermal circulation during the Noachian. Geophysical evidence from surface deformation associated with faulting and from the analysis of the relationship of gravity and topography suggest elastic lithosphere thicknesses a large as ~30 km near the end of the Noachian, corresponding to surface heatflux of 20-40 mW/m2. Relaxation of elastic stresses due to thermally activated creep results in elastic lithosphere thicknesses sensitive to crustal temperatures. Plausible planetary thermal evolution models with chondritic abundances of heat producing elements predict a surface heat flux of 50-60 mW/m2 near the end of the Noachian. The difference in the heat flux required for planetary cooling and that inferred from elastic lithospheric thickness, suggests that a significant fraction of heatflow reaching the surface may be transported by hydrothermal convection rather than by conduction alone. Relaxation of crustal thickness variations due to lower crustal flow is sensitive to both the temperature and geothermal gradient at the crust-mantle boundary. In the presence of a low thermal conductivity regolith, thermal evolution models also indicate that crustal thickness variations created during the Noachian would not be preserved, even with a creep-resistant dry diabase rheology. Thus, a mechanism enhancing heat flux in the Noachian Martian crust is indicated. The studies to be reported will summarize these individual constraints on thermal structure and explore their combined implications for the depth and vigor of hydrothermal circulation during the early crustal evolution of Mars.
P11E-05
Juxtaposition of Layered Sulfate and Phyllosilicate Deposits, Meridiani Planum, Mars
Analysis of hyperspectral MRO CRISM and MEX OMEGA data from the fluvially-dissected Noachian cratered terrain to the south and west of the layered sedimentary sulfate deposits explored by the Opportunity rover shows clear evidence for phyllosilicate deposits. Specifically, exposures exhibit spectral features resulting from an Fe/Mg-OH vibration at ~ 2.3 microns and bound H2O at ~1.9 microns. In several locations, the phyllosilicates (ex. -3.1N°,-8.0E° and -3.4N°,-5.6E°) are located within ~20 kilometers of the edge of the hematite-bearing plains unit investigated by the Opportunity rover ~150km to the northeast. This is one of the few regions on Mars where a clear stratigraphic relationship between the phyllosilicate exposures and layered sulfates is observed, and this may record the transition to acid sulfate conditions on Mars. Continued analyses of the mineralogical composition and mapping of the spatial distribution of these phyllosilicate and sulfate deposits in Meridiani with CRISM, OMEGA, CTX, and HiRISE images will constrain the relative timing of the change in climatic and hydrologic regimes on Mars from fluvial conditions to an acid sulfate groundwater system. The spatial juxtaposition of phyllosilicate and sulfate deposits also provides a potentially important site for exploration by the Mars Science Laboratory, ExoMars, and other upcoming rover-based missions.
P11E-06
A Thermal Infrared View of Altered Noachian Martian Crust
Exposures of altered, ancient Martian crust seemingly represent a distant epoch in Mars" history where aqueous surface processes were active and the planet may have been habitable. In this study, thermal infrared remote sensing data are analyzed in order to better understand these deposits and the geological conditions under which they formed. Three questions are addressed: 1) On surfaces where VNIR datasets detect clay minerals, do thermal IR datasets also detect clays? 2) Aside from clay minerals, what other minerals are detected in the clay-bearing deposits based on thermal IR spectroscopy? 3) What are the thermophysical properties of clay mineral-bearing deposits? Thermal IR data used include TES and THEMIS datasets. To date, one deposit has been detected in the Mawrth Vallis region where thermal IR spectra have features attributable to trioctahedral clay minerals - possibly serpentine. Many other deposits (elsewhere in Mawrth Vallis and the Nili Fossae region) have subtle features at long wavelengths (> 20 microns) suggestive of Mg- and/or Fe-bearing clay mineralogy. Most of the deposits that show strong clay mineral signatures in the VNIR have basaltic character in the thermal IR. Thermal inertia values for these altered deposits are consistent with a combination of bedrock and sand at subpixel levels - consistent with the interpretation of the clay minerals as bulk component of in situ bedrock. Understanding the bulk composition of ancient, clay-bearing bedrock is critical to unraveling the geologic formation mechanisms of these deposits and their significance related to ancient Martian climate and habitability. In the Mawrth Vallis region, the basaltic signatures from clay-bearing deposits are relatively weak. In the Nili Fossae region, the basaltic signatures are stronger with surface mineralogy dominated by plagioclase feldspar, pyroxene, and in some cases, olivine. At this point, it is difficult to strongly constrain the abundance of clay minerals in these deposits form thermal IR data because of the complicating considerations for particle size variation and surface texture. However, thermal IR results seem to indicate that the Mawrth Vallis deposits are more completely altered than the Nili Fossae deposits because the Nili Fossae deposits have a stronger signature of primary mineralogy. This is consistent with an interpretation of Mawrth Vallis deposits as altered, processes sediments or metasomatized pyroclastics. Clay-bearing materials in the Nili Fossae area might include ancient altered sediments as well, but could also include exposures of deep, partially altered igneous or metamorphic crust.
P11E-07
Modal Mineralogy Of The Martian Phyllosilicate-rich Terrains And Implication For Their Formation
Using classical methods of spectral identification based on the absorption band depth of minerals, OMEGA has provided an unambiguous identification of phyllosilicates on the surface of Mars (Poulet et al. 2005, Nature, 438). First constraints on the conditions of their formation were derived (Chevrier et al., 2007, Nature, 448), however the complete story of their formation and their evolution will be fully understood if mineral abundances are known. The modal mineralogy of the phyllosilicate-rich terrains will be presented from the analysis of the OMEGA reflectance spectra using a nonlinear unmixing model based on the Shkuratov radiative transfer theory. Several occurences (regional deposits in Mawrth Vallis and in Nilo-Syrtis, numerous localized deposits in the two hemispheres) are studied in detail. Significant differences in mineral abundances between these regions are found. The modelling of the OMEGA spectra of the phyllosilicate-rich outcrops in Mawrth Vallis requires the largest amount of phyllosilicates (about 60% of nontronite and/or montmorillonite) mixed with hydroxides (ferrihydrite as a very likely end-member) and some non-phyllosilicate materials (plagioclase, Martian dust, pyroxenes). This suggests that the degree of alteration was stronger in Mawrth Vallis than anywhere on Mars. In the NiloSyrtis region, we observe significant spot-to-spot differences in modal mineralogy, and these differences are remarkably consistent with the geomorphology. In the second part of the paper, the modal mineralogy will be compared to kinetic-thermodynamic modeling of weathering of basalt and the implications for the formation of the phyllosilicate-rich terrains will be addressed.
P11E-08
Mars early geological and climatic evolution, derived from its surface mineralogy
The OMEGA/Mars Express reflectance spectroscopy of the Martian Surface, confirmed and detailed by CRISM/MRO, has identified and mapped diagnostic minerals tracing the specific processes that have modelled Mars History. Areas with their pristine mafic constituents are still present in most of the highly cratered terrains, as well as in lava outflows which exhibit a distinct composition characterizing their magmatic source. A major discovery is that of hydrated phyllosilicates within these early terrains, recording an era during which crustal aqueous alteration took place, possibly at the surface itself. Hydrated sulfates have also been identified, in specific areas with geomorphological context indicating a later formation. The location and the compositional diversity of both families of hydrated minerals (phyllosilicates and sulfates), coupled to the stratification evidences, enable to build a consolidated early climatic History that will be discussed in the framework of Mars global geophysical evolution.