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NASA NTRS2003

Carbonate Platform Development and Stromatolite Morphogenesis: Constraints on Environmental and Biological Evolution

Work has been completed on the digital mapping of a terminal Proterozoic reef complex in Namibia. This complex formed an isolated carbonate platform developed downdip on a carbonate ramp of the Nama Group. The stratigraphic evolution of the platform was digitally reconstructed from an extensive dataset that was compiled by using digital surveying technologies. The platform comprises three accommodation cycles in which each subsequent cycle experienced progressively greater influence of a long-term accommodation increase. Aggradation and progradation during the first cycle resulted in a flat, uniform, sheet-like platform. The coarsening and shallowing-upward sequence representing the first cycle is dominated by columnar stromatolitic thrombolites and massive dolostones with interbedded mudstone-grainstone at the base of the sequence grading into cross-bedded dolostones. The second cycle features aggradation, formation of a distinct margin containing thrombolite mounds and domes, and the development of a bucket geometry. Columnar stromatolitic thrombolites dominate the platform interior. The final stage of platform development shows a deepening trend with initial aggradation and formation of well-bedded, thin deposits in the interior and mound development at the margins. While the interior drowned, the platform margin kept up with rising sea level and a complex pinnacle reef formed containing fused and coalesced thrombolite mounds flanked by bioclastic grainstones (containing Cloudina and Namacalathus fossils) and collapse breccias. A set of isolated large thrombolite mounds flanked by shales indicate the final stage of the carbonate platform. During a progressive increase in accommodation, a flat-topped isolated carbonate platform becomes aerially less extensive by either backstepping or formation of smaller pinnacles or a combination of both. The overall geometric evolution of the studied platform from flat-topped to bucket with elevated margins is recorded in many Proterozoic and Phanerozoic isolated carbonate platforms with similar dimensions. The terminal Proterozoic, microbial-dominated, isolated carbonate platform of this study clearly illustrates that the answer to accommodation changes was already familiar among carbonate platforms before the dawn of metazoan-dominated platforms.

Grotzinger, John P.↗
NASA NTRS2001

KT Boundary Impact Debris from DSDP Site 577

The KT boundary at DSDP Site 577 (Shatsky Rise, western North Pacific) is in a calcareous nannofossil ooze. It is bioturbated so Ir and impact debris are smeared across less than 15 cm of core. An absence of sulfides and chalcophile enrichment and the presence of Mn-micronodules indicate that this boundary did not experience anoxic conditions typical of many other calcareous KT sites. Because of its shallow burial (109 m) ejecta is extremely well preserved and has been the subject of numerous studies. Three high-temperature minerals have been identified at this site. Clinopyroxene (cpx), found only at Site 577 may be precursor to diagenetic sanidine in some European sites. Magnesioferrite spinel has the highest Fe2O3/FeO of any locality and can have and trace inclusions of Ni-magnesiowustite, which is known at only one other site (Site 596). Other debris described includes shocked quartz grains less than 200 microns, hollow spherules possibly related to impact melt glasses found near Chicxulub, and irregular Ir-rich particles that may be derived directly from meteoritic materials. The latter may be related to the fossil meteorite found at Site 576, just 500 km to the east. A large-volume (approx. 10 cc) sample was taken to systematically characterize debris. The less than 60 microns fraction of the carbonate-free sediment contained 44 mg of impact debris. 2700 particles less than l00 microns were classified based on color, shape, and morphology. About 55% are generally light colored, composed mostly of clays, and typically lack magnesioferrite spinel. Less than half of these are quite spherical; many have irregular shapes, possibly from fragmentation. Hollow spherules with smooth shiny surfaces are only 2% of the total but many fragments in the 60 - 100 microns fraction suggest that they were more abundant and that some may have been quite large; 800 microns or more. Cpx-bearing spherules, easily identified by green crystals at the surface, constitute only 2.5% of the total. Three cpx spherules are dumbbells. The other 40% of the debris is a complex assemblage of dark-colored particles, most of which have magnesioferrite spinel. We have currently separated these into 6 groups based on color and morphology, but this hardly describes the diversity of this group. They range from smooth and spherical to rough and irregular in shape. Some have a planar cleavage, similar to some broken cosmic spherules. 220 particles were irradiated for trace element analysis, as groups and as individual particles. It appears that every spherule type as at least a few ng/g Ir. Several of the spinel-bearing particles have been identified with high Ir (200-1500 ng/g), Cr (2-5 mg/g), and Ni (2-10 mg/g), consistent with results. It is hoped that some of these will yield potential fragments of the KT bolide. Only five have been sectioned to date and they are characterized by high concentrations of spinel; two contained traces of magnesiowustite. This debris constitutes a complex assemblage of ejecta materials. The light-colored, spinel-free particles likely derive mainly from target materials. A significant fraction of these are probably alteration products of cpx-spherules. The dark-colored debris is more likely to have high siderophile concentrations, and thus a high extraterrestrial component. However, the majority don't. Most of the larger spinel-bearing spherules have modest Ir concentrations (5-30 ng/g).

Kyte, Frank T.↗
NASA NTRS2003

Astrobiology: The Case for Venus

The scientific discipline of astrobiology addresses one of the most fundamental unanswered questions of science: are we alone? Is there life elsewhere in the universe, or is life unique to Earth? The field of astrobiology includes the study of the chemical precursors for life in the solar system; it also includes the search for both presently existing life and fossil signs of previously existing life elsewhere in our own solar system, as well as the search for life outside the solar system. Two of the promising environments within the solar system being currently considered are the surface of the planet Mars, and the hypothesized oceans underneath the ice covering the moon Europa. Both of these environments differ in several key ways from the environments where life is found on Earth; the Mars environment in most places too cold and at too low pressure for liquid water to be stable, and the sub-ice environment of Europa lacking an abundance of free energy in the form of sunlight. The only place in the solar system where we know that life exists today is the Earth. To look for life elsewhere in the solar system, one promising search strategy would be to find and study the environment in the solar system with conditions that are most similar to the environmental conditions where life thrives on the Earth. Specifically, we would like to study a location in the solar system with atmospheric pressure near one bar; temperature in the range where water is liquid, 0 to 100 C; abundant solar energy; and with the primary materials required for life, carbon, oxygen, nitrogen, and hydrogen, present. Other than the surface of the Earth, the only other place where these conditions exist is the atmosphere of Venus, at an altitude of about fifty kilometers above the surface.

Landis, Geoffrey A.↗
NASA NTRS2003

Thermographic Inspections Save Skins and Prevent Blackouts

Scanning thermography involves heating a component s surface and subsequently measuring the surface temperature, using an infrared camera to identify structural defects such as corrosion and disbonding. It is a completely noninvasive and noncontacting process. Scans can detect defects in conventional metals and plastics, as well as in bonded aluminum composites, plastic- and resinbased composites, and laminated structures. The apparatus used for scanning is highly portable and can cover the surface of a test material up to six times faster than conventional thermography. NASA scientists affirm that the technology is an invaluable asset to the airlines, detecting potential defects that can cause structural failure.In 1996, ThermTech Services, Inc., of Stuart, Florida, approached NASA in an effort to evaluate the technology for application in the power and process industries, where corrosion is of serious concern. ThermTech Services proceeded to develop the application for inspecting boiler waterwall tubing at fossil-fueled electric-generating stations. In 1999, ThermTech purchased the rights to NASA s patented technology and developed the specialized equipment required to apply the inspecting method to power plant components. The ThermTech robotic system using NASA technology has proved to be extremely successful and cost effective in performing detailed inspections of large structures such as boiler waterwalls and aboveground chemical storage tanks. It is capable of inspecting a waterwall, tank-wall, or other large surfaces at a rate of approximately 10 square feet per minute or faster.

Source record↗
NASA NTRS2003

Tharsis-triggered Flood Inundations of the Lowlands of Mars

Throughout the recorded history of Mars, liquid water has distinctly shaped its landscape, including the prominent circum-Chryse and the northwestern slope valleys outflow channel systems [1], and the extremely flat northern plains topography at the distal reaches of these outflow channel systems.Basing on the ideas of episodic greenhouse atmosphere and water stability on the lowlands of Mars [3], a conceptual scheme for water evolution and associated geomorphologic features on the northern plains can be proposed. This model highlights Tharsis-triggered flood inundations and their direct impact on shaping the northern plains, as well as making possible the existence of fossil and/or extant life.Possible biologic evolution throughout the resulting different climatic and hydrologic conditions would account for very distinct metabolic pathways for hypothesized organisms capable of surviving and perhaps evolving in each aqueous environment, those that existed in the dry and cold periods between the flood inundations, and those organisms that could survive both extremes. Terrestrial microbiota, chemolithotrophic and heterotrophic bacteria, provide exciting analogues for such potential extremophile existence in Mars, especially where long-lived, magmatic-driven hydrothermal activity is indicated [14].

Fairen, Alberto G.↗
NASA NTRS2002

Validated Numerical Models for the Convective Extinction of Fuel Droplets (CEFD)

The NASA Nebraska Space Grant (NSGC) & EPSCoR programs have continued their effort to support outstanding research endeavors by funding the Numerical Simulation of the Combustion of Fuel Droplets study at the University of Nebraska at Lincoln (UNL). This team of researchers has developed a transient numerical model to study the combustion of suspended and moving droplets. The engines that propel missiles, jets, and many other devices are dependent upon combustion. Therefore, data concerning the combustion of fuel droplets is of immediate relevance to aviation and aeronautical personnel, especially those involved in flight operations. The experiments being conducted by Dr. Gogos and Dr. Nayagam s research teams, allow investigators to gather data for comparison with theoretical predictions of burning rates, flame structures, and extinction conditions. The consequent improved fundamental understanding of droplet combustion may contribute to the clean and safe utilization of fossil fuels (Williams, Dryer, Haggard & Nayagam, 1997, f 2). The present state of knowledge on convective extinction of fuel droplets derives from experiments conducted under normal gravity conditions. However, any data obtained with suspended droplets under normal gravity are grossly affected by gravity. The need to obtain experimental data under microgravity conditions is therefore well justified and addresses one of the goals of NASA's Human Exploration and Development of Space (HEDS) microgravity combustion experiment.

Gogos, George↗
NASA NTRS2003

Laboratory Studies of Heterogeneous Chemical Processes of Atmospheric Importance

The objective of this study is to conduct measurements of chemical kinetics parameters for heterogeneous reactions of importance in the stratosphere and the troposphere. It involves the elucidation of the mechanism of the interaction of HC1 vapor with ice surfaces, which is the first step in the heterogeneous chlorine activation processes, as well as the investigation of the atmospheric oxidation mechanism of soot particles emitted by biomass and fossil fuels. The techniques being employed include turbulent flow- chemical ionization mass spectrometry and optical ellipsometry, among others. The next section summarizes our research activities during the first year of the project, and the section that follows consists of the statement of work for the second year.

Molina, Mario J.↗
NASA NTRS2002

Numerical Simulation of the Combustion of Fuel Droplets: Finite Rate Kinetics and Flame Zone Grid Adaptation (CEFD)

The NASA Nebraska Space Grant (NSGC) & EPSCoR programs have continued their effort to support outstanding research endeavors by funding the Numerical Simulation of the Combustion of Fuel Droplets study at the University of Nebraska at Lincoln (UNL). This team of researchers has developed a transient numerical model to study the combustion of suspended and moving droplets. The engines that propel missiles, jets, and many other devices are dependent upon combustion. Therefore, data concerning the combustion of fuel droplets is of immediate relevance to aviation and aeronautical personnel, especially those involved in flight operations. The experiments being conducted by Dr. Gogos and Dr. Nayagam s research teams, allow investigators to gather data for comparison with theoretical predictions of burning rates, flame structures, and extinction conditions. The consequent improved hndamental understanding droplet combustion may contribute to the clean and safe utilization of fossil hels (Williams, Dryer, Haggard & Nayagam, 1997, 72). The present state of knowledge on convective extinction of he1 droplets derives fiom experiments conducted under normal gravity conditions. However, any data obtained with suspended droplets under normal gravity are grossly affected by gravity. The need to obtain experimental data under microgravity conditions is therefore well justified and addresses one of the goals of NASA s Human Exploration and Development of Space (HEDS) microgravity combustion experiment.

Gogos, George↗
NASA NTRS2003

Issues and Concerns in Robotic Drilling

Exploration of the Martian subsurface will be essential in the search for life and water, given the desiccated and highly oxidized conditions on the surface. Discovery of these, at least in non-fossil form, is unlikely without drilling or other physical access to the subsurface. Hence subsurface access will be critical for both future in-situ science and Mars sample return. Drilling applications present many new challenges for diagnosis and control technology. Traditionally, diagnosis has concentrated on determining the internal state of a system, and detecting failures of system components. In the case of drilling applications, an additional challenge is to diagnose the interactions between the drill and its environment. This is necessary because particular observations of the drilling operation may be consistent with a number of possible problems, including faults in the equipment, but also changes in the material being drilled (for example, from rock to ice). The diagnosis of a particular observation may also depend on knowledge of geological formations previously encountered during drilling, and different remedial actions may be required for each diagnosis. Current 2009 Mars mission scenarios call for no more than 33 sols to be spent drilling. Yet they also call for a baseline of two 2m-deep holes in each of three target areas, for a total of six drilling operations. Using current levels of automation, it is estimated that 15-16 sols would be required to drill each hole. As a result of this, either the drilling part of the mission plan will need to be severely downscoped to no more than two holes total, or on-board automation and robotics must be increased in order to reduce the number of sols required per hole by removing ground control from the drilling control loop. This lecture will discuss salient issues and concerns of robotic drilling automation compares with other applications, and implementation constraints.

Glass, Brian↗
NASA NTRS2003

Chandra Observations of Magnetic White Dwarfs and their Theoretical Implications

Observations of cool DA and DB white dwarfs have not yet been successful in detecting coronal X-ray emission, but observations of late-type dwarfs and giants show that coronae are common for these stars. To produce coronal X-rays, a star must have dynamo-generated surface magnetic fields and a well-developed convection zone. There is some observational evidence that the DA star LHS 1038 and the DB star GD 358 have weak and variable surface magnetic fields. It has been suggested that such fields can be generated by dynamo action, and since both stars have well-developed convection zones, theory predicts detectable levels of coronal X-rays from these white dwarfs. However, we present analysis of Chandra observations of both stars showing no detectable X-ray emission. The derived upper limits for the X-ray fluxes provide strong constraints on theories of formation of coronae around magnetic white dwarfs. Another important implication of our negative Chandra observations is the possibility that the magnetic fields of LHS 1038 and GD 358 are fossil fields.

Musielak, Z. E.↗
NASA NTRS2003

Baseline Testing of the Club Car Carryall With Asymmetric Ultracapacitors

The NASA John H. Glenn Research Center initiated baseline testing of the Club Car Carryall with asymmetric ultracapacitors as a way to reduce pollution in industrial settings, reduce fossil fuel consumption, and reduce operating costs for transportation systems. The Club Car Carryall provides an inexpensive approach to advance the state of the art in electric vehicle technology in a practical application. The project transfers space technology to terrestrial use via non-traditional partners, and provides power system data valuable for future space applications. The work was done under the Hybrid Power Management (HPM) Program, which includes the Hybrid Electric Transit Bus (HETB). The Carryall is a state of the art, ground up, electric utility vehicle. A unique aspect of the project was the use of a state of the art, long life ultracapacitor energy storage system. Innovative features, such as regenerative braking through ultracapacitor energy storage, are planned. Regenerative braking recovers much of the kinetic energy of the vehicle during deceleration. The Carryall was tested with the standard lead acid battery energy storage system, as well as with an asymmetric ultracapacitor energy storage system. The report concludes that the Carryall provides excellent performance, and that the implementation of asymmetric ultracapacitors in the power system can provide significant performance improvements.

Eichenberg, Dennis J.↗
NASA NTRS2004

Environmental Effects on the Metallicities of Early-Type Galaxies

In this multi-year project to investigate the metal enrichment of early-type galaxies, we have used ROSAT, ASCA and now Chandra observations to study samples of galaxies. We have published two papers and a third paper that incorporates Chandra archival observations is nearing completion. Below, we briefly describe our findings. Our first paper "SN IA Enrichment in Virgo Early-type Galaxies from ROSAT and ASCA Observations" was published in the Astrophysical Journal (vol 539, 603) reported on the properties of nine X-ray bright elliptical galaxies in the Virgo cluster observed by ROSAT and ASCA. We measured iron abundance gradients as a function of radius in three galaxies. We found that the magnesium and silicon abundance gradients were in general flatter than those of iron. We suggest this is due to a metallicity dependence in the metal production rates of SN Ia's. We calculate SN Ia rates in the center of these galaxies that are comparable to those measured optically. Our second paper "ASCA Observations of Groups at Radii of Low Overdensity: Implications for Cosmic Preheating" also was published in the Astrophysical Journal (vol 578, 74). This paper reported on the ASCA spectroscopy of nine groups of galaxies. We found that the entropy profile in groups is driven by nongravitational heating processes, and could be explained by a short period of preheating by galactic winds. The third paper (in preparation) uses a sample of about 200 galaxies from both ROSAT and Chandra observations. In this paper we characterize both the nuclear and the extended X-ray emission for this sample. We will use these observations to determine the "on-time" of the X-ray emitting AGN and the fraction of "fossil groups" as well as to investigate how large AGN outbursts can sweep the galaxy of its hot ISM, thus leading to changes in the ISM metal enrichment.

Oliversen, Ronald J.↗
NASA NTRS2004

Over-Luminous Elliptical Galaxies

We have completed a first draft of a paper on the galaxy group ES03060170, the hottest known fossil group. We have submitted a first draft of the paper but the final completion is delayed due to several issues mentioned by the referee that we wish to revisit and discuss in more detail. The XMM data was combined with Chandra data which allowed a rich set of projects. The paper discusses the north-south elongation which is similar to that of the central dominant galaxy as well as the galaxy distribution. We detect an X-ray "finger" or small tail emanating from the central galaxy to the north, suggesting motion of the galaxy within the elongated gravitational potential. The overall agreement between XMM and Chandra data are excellent (although the XMM data extend to larger radii). Both data sets show a cool core centered on the dominant galaxy. Surprisingly, the temperature maps and detailed spectra indicate that the finger of gas is NOT cool, but has the same temperature as the ambient gas. We extracted surface brightness profiles, deprojected gas density profiles, cooling time profiles, and entropy profiles. There is a sharp discontinuity in gas temperature where the surface brightness profile starts to rise rapidly at 10 kpc. This produces a decrease in the cooling time and the gas entropy within 10 kpc. The central cooling time (within 10 kpc) is less than l0(exp 9) years and falls to almost half that value in the inner 5 kpc. Despite the very short cooling time, we find no evidence (even with the excellent statistics from XMM-Newton) for multi-phased gas, i.e., a cooling flow. We find two "edges" associated with the gas distribution (common in peaked X-ray groups and galaxies). On large scales, the temperature profile is flat and disagrees with the profile predicted by Loken et al. (2003) from detailed numerical simulations. We studied the galaxy distribution within one virial radius. The galaxy concentration associated with the group is detectable only within 0.3 of the virial radius (450 kpc) given the available depth of the optical galaxy catalogs at present. We have derived total mass and gas mass distributions (from the X- ray data) and find the gas fraction approaches a constant 8% (for Ho = 70).

Mushotzky, Richard↗
NASA NTRS2004

Over-Luminous Elliptical Galaxies

We have completed a first draft of a paper on the galaxy group ESO3060170, the hottest known fossil group. We have submitted a first draft of the paper but the final completion is delayed due to several issues mentioned by the referee that we wish to revisit and discuss in more detail. The XMM data was combined with Chandra data which allowed a rich set of projects. The paper discusses the north-south elongation which is similar to that of the central dominant galaxy as well as the galaxy distribution. We detect an X-ray 'finger' or small tail emanating from the central galaxy to the north, suggesting motion of the galaxy within the elongated gravitational potential. The overall agreement between XMM and Chandra data are excellent (although the XMM data extend to larger radii). Both data sets show a cool core centered on the dominant galaxy. Surprisingly, - the temperature maps and detailed spectra indicate that the finger of gas is NOT cool, but has the same temperature as the ambient gas. We extracted surface brightness profiles, deprojected gas density profiles, cooling time profiles, and entropy profiles. There is a sharp discontinuity in gas temperature where the surface brightness profile starts to rise rapidly at 10 kpc. This produces a decrease in the cooling time and the gas entropy within 10 kpc. The central cooling time (within 10 kpc) is less than 109 years and falls to almost half that value in the inner 5 kpc. Despite the very short cooling time, we find no evidence (even with the excellent statistics from XMM-Newton) for multi-phased gas, i.e., a cooling flow. We find two 'edges' associated with the gas distribution (common in peaked X-ray groups and galaxies). On large scales, the temperature profile is flat and disagrees with the profile predicted by Loken et al. (2003) from detailed numerical simulations. We studied the galaxy distribution within one virial radius. The galaxy concentration associated with the group is detectable only within 0.3 of the virial radius (450 kpc) given the available depth of the optical galaxy catalogs at present. We have derived total mass and gas mass distributions (from the X-ray data) and find the gas fraction approaches a constant 8% (for H0 = 70).

Mushotsky, Richard↗
NASA NTRS2003

Large-scale Distribution of CH4 in the Western North Pacific: Sources and Transport from the Asian Continent

Methane (CH4) mixing ratios in the northern Pacific Basin were sampled from two aircraft during the TRACE-P mission (Transport and Chemical Evolution over the Pacific) from late February through early April 2001 using a tunable diode laser system. Described in more detail by Jacob et al., the mission was designed to characterize Asian outflow to the Pacific, determine its chemical evolution, and assess changes to the atmosphere resulting from the rapid industrialization and increased energy usage on the Asian continent. The high-resolution, high-precision data set of roughly 13,800 CH4 measurements ranged between 1602 ppbv in stratospherically influenced air and 2149 ppbv in highly polluted air. Overall, CH4 mixing ratios were highly correlated with a variety of other trace gases characteristic of a mix of anthropogenic industrial and combustion sources and were strikingly correlated with ethane (C2H6) in particular. Averages with latitude in the near-surface (0-2 km) show that CH4 was elevated well above background levels north of 15 deg N close to the Asian continent. In the central and eastern Pacific, levels of CH4 were lower as continental inputs were mixed horizontally and vertically during transport. Overall, the correlation between CH4 and other hydrocarbons such as ethane (C2H6), ethyne (C2H2), and propane (C3H8) as well as the urban/industrial tracer perchloroethene (C2Cl4), suggests that for CH4 colocated sources such as landfills, wastewater treatment, and fossil fuel use associated with urban areas dominate regional inputs at this time. Comparisons between measurements made during TRACE-P and those of PEM-West B, flown during roughly the same time of year and under a similar meteorological setting 7 years earlier, suggest that although the TRACE-P CH4 observations are higher, the changes are not significantly greater than the increases seen in background air over this time interval.

Bartlett, Karen B.↗
NASA NTRS2004

Winds, Water Budgets and Stable Isotopes in Tropical Cyclones using TRMM and QUICKSCAT

Water vapor is the most abundant greenhouse gas in the atmosphere. Changes in its concentration and distribution are controlled by the hydrologic cycle. Because of its capacity to absorb and emit long wave radiation, release latent heat during condensation in storms and reflect short wave radiation when clouds form it has a major impact on Global climate change. The stable isotope ratios of water are H20 H2l6O and H0 H2l6O. These ratios change whenever water undergoes a phase change. They also change in both rain and water vapor whenever an air parcel is exposed to rain. In addition the relative changes in the two ratios differ as a &nction of the relative humidity. In short, the stable isotope ratios in water vapor in the atmosphere contain an integrated history of the processes affecting the concentration and distribution of water vapor in the atmosphere. Therefore the measurement and interpretation of changes in these stable isotope ratios are a powerful tool matched by no other method in tracing the transport history of water in the atmosphere. Our initial studies under this grant focused on the changes of the stable isotope ratios of precipitation and water vapor in tropical cyclones. The changes in time and space were found to be very large and to trace the transport of water in the storms reflecting changes in basic structural features. Because the stable isotope ratios of rains from tropical cyclones are so low flooding associated with land falling tropical cyclones introduces a negative isotopic spike into the coastal surface waters. In addition the stable isotope ratios of water vapor in the vicinity of tropical cyclones is anomalously low. This suggests that carbonate shelled organisms such as ostracoda living in coastal waters have the potential to record the isotopic spike and thereby provide a long term record of tropical storm activity in sediment cores containing fossil shells. Likewise, tree rings in coastal environments offer a similar potential. We have analyzed the oxygen isotopic composition of ostrcoda shells formed in the floodwaters of Tropical Storm Allison (2001) and discovered the negative isotopic 1 16 spike. Because we had learned that storm activity has a major impact on the stable isotope ratios of water vapor in the tropics and sub-tropics we decided to analyze the isotopic compositions of water vapor in different locations in the tropics. We did this in Puerto Escondido, Mexico in July 1998, near Kwajalein Island in the Pacific in 1999 as part of a TRMM summer field program and in 2001 in Key West, Florida as part of the CAMEX 4 summer field program. Our isotopic studies along with our earlier tropical cyclone studies showed that the low isotopic ratios in water vapor induced by exposure to rains the storms persisted for 48 hours often far away from the original storm site. We also noted that positive isotopic spikes were introduced into atmospheric water vapor if winds were high and extensive sea spray was present. These findings have a significant impact on the interpretation of the stable isotope studies of tropical ice cores found in the high mountain regions of the tropics. The assumption made in interpreting the ice core record is that the source water vapor evaporated from the sea surface is in near isotopic equilibrium with the seawater and undergoes a decrease during its transport that reflects the change in temperature from the sea surface to the site of the ice core. Because an additional isotopic depletion occurs at the sea surface source area that depends on the intensity, duration and size of the tropical rain system the isotopic variations found in the ice cores must take into account changes in past storm activity in the tropics. These systems must be an important source of water vapor to the ice cores because they charge the troposphere with water vapor to a far greater vertical height than evaporation in quiescent regions. Finally, an interest in increased heat transfer in thnterior of tropical cyclones resulting from greater amounts of sea spray is a topic of considerable interest to the research community. Increases in sea spray may be related to rapid changes in the intensity of hurricanes, a feature of hurricanes that currently is very poorly forecast. Project CBLAST of the Hurricane Research Division of NOAA is an active program that uses P3 research aircraft to evaluate this problem. An instrument has been designed and built at the University of Houston that will be placed on the P3 research aircraft during the 2004 hurricane season. It continuously measures the salt content of rain in hurricanes. Changes in the salt content of the rains should reflect the abundance of sea spray at the sea surface. In this way maps of sea spray intensity in hurricanes may be forthcoming. This should help computer modelers who simulate hurricanes to better understand the potential of changes in sea spray to change the intensity of hurricanes. The cost of designing, building and installing this instrument was borne largely by funding from this NASA grant. A list of presentations at national meetings and publications that were as the result of funding from this NASA grant are found in the report.

Lawrence, James R.↗
NASA NTRS2001

NASA's new Mars Exploration Program: the trajectory of knowledge

NASA's newly restructured Mars Exploration Program (MEP) is finally on the way to Mars with the successful April 7 launch of the 2001 Mars Odyssey Orbiter. In addition, the announcement by the Bush Administration that the exploration of Mars will be a priority within NASA's Office of Space Science further cements the first decade of the new millennium as one of the major thrusts to understand the "new" Mars. Over the course of the past year and a half, an integrated team of managers, scientists, and engineers has crafted a revamped MEP to respond to the scientific as well as management and resource challenges associated with deep space exploration of the Red Planet. This article describes the new program from the perspective of its guiding philosophies, major events, and scientific strategy. It is intended to serve as a roadmap to the next 10-15 years of Mars exploration from the NASA viewpoint. [For further details, see the Mars Exploration Program web site (URL): http://mars.jpl.nasa.gov]. The new MEP will certainly evolve in response to discoveries, to successes, and potentially to setbacks as well. However, the design of the restructured strategy is attentive to risks, and a major attempt to instill resiliency in the program has been adopted. Mars beckons, and the next decade of exploration should provide the impetus for a follow-on decade in which multiple sample returns and other major program directions are executed. Ultimately the vision to consider the first human scientific expeditions to the Red Planet will be enabled. By the end of the first decade of this program, we may know where and how to look for the elusive clues associated with a possible martian biological record, if any was every preserved, even if only as "chemical fossils.".

Space Flight↗
NASA NTRS2000

Microscopic physical biomarkers in carbonate hot springs: implications in the search for life on Mars

Physical evidence of life (physical biomarkers) from the deposits of carbonate hot springs were documented at the scale of microorganisms--submillimeter to submicrometer. The four moderate-temperature (57 to 72 degrees C), neutral pH springs reported on in this study, support diverse communities of bacteria adapted to specific physical and chemical conditions. Some of the microbes coexist with travertine deposits in endolithic communities. In other cases, the microbes are rapidly coated and destroyed by precipitates but leave distinctive mineral fabrics. Some microbes adapted to carbonate hot springs produce an extracellular polymeric substance which forms a three-dimensional matrix with living cells and cell remains, known as a biofilm. Silicon and iron oxides often coat the biofilm, leading to long-term preservation. Submicrometer mineralized spheres composed of calcium fluoride or silica are common in carbonate hot spring deposits. Sphere formation is biologically mediated, but the spheres themselves are apparently not fossils or microbes. Additionally, some microbes selectively weather mineral surfaces in distinctive patterns. Hot spring deposits have been cited as prime locations for exobiological exploration of Mars. The presence of preserved microscopic physical biomarkers at all four sites supports a strategy of searching for evidence of life in hot spring deposits on Mars.

NASA Center JSC↗