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Chondroids are any kind of nebular particle that would melt to become chondrules. We describe the petrography and basic chemistry of chondroids in LEW86018 (L3.1). Additional information is contained in the original extended abstract.
Sulfuric acid (H2SO4), formed in commercial aircraft operations via fuel-S (goes to) SO2 (goes to) SO3 (goes to) H2SO4 plays an important role in the formation of contrails. It is believed that the first step occurs inside the combustor, the second step in the engine exit nozzle, and the third step in the exhaust plume. Thus, measurements of the sulfur oxidation rates are critical to the understanding of contrail formation. Field measurements of contrails formed behind commercial aircraft indicate that significantly greater conversion of fuel-bound sulfur to sulfate aerosol occurs than can be explained by our current knowledge of contrail physics and chemistry. The conversion of sulfur from S(IV) to S(VI) oxidation state, required for sulfate aerosol formation, is thermodynamically favored for the conditions that exist within jet engines but is kinetically disfavored. The principal reaction pathway is O+SO2+M (goes to) SO3+M. The rates of this reaction have never been measured in the temperature and pressure regimes available to aircraft operation. In the first year (FY02) of this project, we performed a series of experiments to elucidate the rate information for the O+SO2+M (goes to) SO3+M reaction. The work performed is described following the proposed work plan. Because we used the H2/O2 system for an O-atom source and rate coefficients were obtained via computer simulation, construction of a reaction mechanism and either recalculation or estimation of thermodynamic properties of H(x)SO(y) species are described first.
Several isolated deposits of gray, crystalline hematite on Mars were discovered using data returned from the Thermal Emission Spectrometer (TES) instrument aboard the Mars Global Surveyor spacecraft. Christensen et al. provided five testable hypotheses regarding the formation of crystalline hematite on Mars: 1) low-temperature precipitation of Fe oxides/hydroxides from standing, oxygenated, Fe-rich water, followed by subsequent alteration to gray hematite, 2) low-temperature leaching of iron-bearing silicates and other materials leaving a Fe-rich residue laterite-style weathering) which is subsequently altered to gray hematite, 3) direct precipitation of gray hematite from Fe-rich circulating fluids of hydrothermal or other origin, 4) formation of gray hematitic surface coatings during weathering, and 5) thermal oxidation of magnetite-rich lavas. Since this initial work, several authors have examined the hematite deposits to determine their formation mechanism. Lane et al. cited the absence of a 390/ cm absorption in the martian hematite spectrum as evidence for platy hematite grains. Their model for the formation of the deposits includes deposition of any of a variety of iron oxides or oxyhydroxides by aqueous or hydrothermal fluids, burial and metamorphosis to gray platy hematite grains, and exhumation in recent times. Based on a detailed geomorphic examination of the Sinus Meridiani region, Hynek et al. conclude that the most likely method of hematite formation was either emplacement by a hydrothermal fluid or oxidation of a magnetite-rich pyroclastic deposit. Similarly, Arvidson et al., favor a model involving the alteration of pyroclastic deposits by aqueous or hydrothermal fluids. Finally, based on geochemical modeling and an examination of Aram Chaos, Catling and Moore favor emplacement by hydrothermal fluids with a minimum temperature of 100 C. Comparison of the average martian hematite spectrum measured by TES to hematite emissivity spectra for a variety of naturally occurring hematites shows small but potentially important differences. In particular, band shapes, positions and relative band emissivities of hematite spectra vary over the range of samples. These differences imply that the natural variability of thermal infrared hematite spectra has not been fully characterized, especially with respect to the reaction pathway and crystal structure.
The organic inventory initially available to protostellar disks is the first step on the long chemical path to the development of Life. The early earth may have obtained most its volatile material from the arrival of meteorites and comets at its surface. Determining the most likely distribution of meteoritic and cometary organic molecules that could seed primitive planets is a major goal since it sets the initial conditions for, at least part of, the phase of prebiotic chemical evolution. Observations and measurements of the chemical composition of primitive Solar System organics, and of dense molecular clouds, should allow the construction of coherent theoretical picture of the development of organic complexity from interstellar biogenic material to the beginning of prebiotic evolution.
The present sequential mission oriented approach to robotic planetary exploration, could be changed to an infrastructure building approach where a robotic presence is permanent, self sustaining and growing with each mission. We call this self-sustaining robotic ecology approach robosphere and discuss the technological issues that need to be addressed before this concept can be realized. One of the major advantages of this approach is that a robosphere would include much of the infrastructure required by human explorers and would thus lower the preparation and risk threshold inherent in the transition from robotic to human exploration. In this context we discuss some implications for space architecture.
This paper extends the work of our previous study, which showed the potential of using precipitation in the eastern Indian Ocean to predict when an El Nino would begin. The paper begins by showing the successful prediction of the 2002-03 El Nino. However, precipitation is really used as a substitute for wind (storms are usually accompanied by heavy wind), because a popular hypothesis is that winds (especially % winds out of the West) stir up the ocean surface in the western Pacific sending currents of warm waters to the east Pacific where El Ninos form. This paper shows that it is typical for storms that produce strong winds in the western Pacific to have traveled from the Indian Ocean. We begin in the Indian Ocean looking at strong bursts of wind over several days. The number of windy days seems to increase in the months prior to El Nino. We examined these relationships in detail for November 2001 to April 2002, before the recent El Nino, using NASA's TRMM and QuikSCAT data. We found in one case that a warming of the eastern Indian Ocean occurred about 25 days before heavy rainfall formed. As the stormed moved eastward it was followed (6 days later) by strong winds out of the West. The entire storm system (and warming of the sea) moved eastward through a small strip of water between Indonesia and Australia, before reaching the western Pacific. Thus, this paper increases our understanding of the physical processes leading to the formation of El Nino.
In the past two years, NASA has begun to develop and implement plans for investigations on robotic Mars missions which are focused toward returning data critical for planning human missions to Mars. The Mars Surveyor Program 2001 Orbiter and Lander missions will mark the first time that experiments dedicated to preparation for human exploration will be carried out. Investigations on these missions and future missions range from characterization of the physical and chemical environment of Mars, to predicting the response of biology to the Mars environment. Planning for such missions must take into account existing data from previous Mars missions which were not necessarily focused on human exploration preparation. At the same time, plans for near term missions by the international community must be considered to avoid duplication of effort. This paper reviews data requirements for human exploration and applicability of existing data. It will also describe current plans for investigations and place them within the context of related international activities. c 2000 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved.
For more than 15 years, Spacelab, has provided a laboratory in space for an international array of experiments, facilities, and experimenters. In addition to continuing this important work, Spacelab is now serving as a crucial stepping-stone to the improved science, improved operations, and rapid access to space that will characterize International Space Station. In the Space Station era, science operations will depend primarily on distributed/remote operations that will allow investigators to direct science activities from their universities, facilities, or home bases. Spacelab missions are a crucial part of preparing for these activities, having been used to test, prove, and refine remote operations over several missions. The knowledge gained from preparing these Missions is also playing a crucial role in reducing the time required to put an experiment into orbit, from revolutionizing the processes involved to testing the hardware needed for these more advanced operations. This paper discusses the role of the Spacelab program and the NASA Marshall Space Flight Center- (MSFC-) managed missions in developing and refining remote operations, new hardware and facilities for use on Space Station, and procedures that dramatically reduce preparation time for flight.
No abstract available
MODIS data from NASA's Terra and Aqua satellites are being sent to several NWS Forecast Offices in real time to assist in the preparation of short-term weather forecasts. The MODIS imagery, in channels similar to those of the planned GOES-R instrument, is reformatted, sectorized, and ingested directly in Advanced Weather Interactive Processing System (AWIPS). A number of products derived from the imagery are available in near real-time as well. This transition activity, from research to operations, serves to prepare forecasters for the next generation satellite observing capabilities through real-time, hands on applications to their forecast problems. The presentation will provide examples of this transition activity and a preliminary assessment on the utility of several of the MODIS products for improving short-term forecasts.
The involvement of coenzyme A in many enzyme reactions suggests that it acted in this capacity very early in the development of life on Earth. Particularly relevant in this regard is its role in the activation of amino acids and hydroxy acids in the biosynthesis of some peptide antibiotics--a mechanism of peptide synthesis that forms the basis for the proposal that a thioester world could have preceded the RNA world. The components of coenzyme A have been shown to be probable prebiotic compounds: beta-alanine, pantoyl lactone and cysteamine and possibly adenosine. We show here that the pantetheine moiety of coenzyme A (which also occurs in a number of enzymes) can be synthesized in yields of several per cent by heating pantoyl lactone, beta-alanine and cysteamine at temperatures as low as 40 degrees C. These components are extremely soluble and so would have been preferentially concentrated in evaporating bodies of water, for example on beaches and at lagoon margins. Our results show that amide bonds can be formed at temperatures as low as 40 degrees C, and provide circumstantial support for the suggestion that pantetheine and coenzyme A were important in the earliest metabolic systems.
No abstract available
Five small (55 days old, 196 +/- 5 g) (mean +/- SE) and five large (83 days old, 382 +/- 4 g) Sprague-Dawley strain, specific pathogen-free rats were exposed to a 7-day spaceflight and 12-h postflight recovery period. As measured in 3-micron sections, periodontal ligament (PDL) fibroblastlike cells were classified according to nuclear size: A + A' (40-79), B (80-119), C (120-169), and D (greater than or equal to 170 microns 3). Since the histogenesis sequence is A----A'----C----D----osteoblast, the relative incidence of A + A' to C + D is an osteogenic index. No difference in A + A' or C + D cells in small rats may reflect partial recovery of preosteoblast formation (A----C) during the 12-h postflight period. Large flight rats demonstrated increased numbers of A + A', indicating an inhibition of preosteoblast formation (A----C). At least in the older group, a 7-day flight is adequate to reduce PDL osteogenic potential (inhibition in PDL osteoblast differentiation and/or specific attrition of C + D cells) that does not recover by 12-h postflight.
No abstract available
Sulfuric acid (H2SO4), formed in commercial aircraft operations via Fuel-S (right arrow) SO2 + SO3 (right arrow) H2SO4, plays an important role in affecting the global climate change through atmospheric chemical reactions and radiative forcing. Measurement of the sulfur oxidation rates is critical to the understanding of the contrail formation. The principle reaction pathway is SO2 + O + M (right arrow) SO3 + M. Although there are many measurements for the rates of this reaction, it has never been measured in the temperature and pressure regime available to aircraft operation. In this investigation, a series of experiments were performed behind the reflected shock waves in a shock tube. OH radicals were produced in lean, shock heated SO2/H2/O2/Ar mixtures. The reaction progress was followed using OH absorption spectroscopy at 310 nm. The data were analyzed with the aid of computer modeling/simulation. The mean value of the rate coefficients of R21 determined is k(sub 21,0)/[M]= 3.9 x 10(exp 15) cm(sup 6) per square mole per second at T = 960 - 1150 K and rho = 16-30 micromole per cubic centimeter with uncertainty limits of plus or minus 30%. A non-Arrhenius fit to our data together with all existing data gives k(sub 21,0)/[M] = 1.3 x 10(exp 24) T (exp -2.5) exp(-2350 K/T) cm(sup 6) per square mole per second at T = 300 - 2500 K with the same uncertainty limits given above. The calculated conversion of S(IV)(SO2) to S(VI) (SO3 + H2SO4) was about 2% in our experimental conditions.
Discussions of future human expeditions into the solar system generally focus on whether the next explorers ought to go to the Moon or to Mars. The only mission scenario developed in any detail within NASA is an expedition to Mars with a 500-day stay at the surface. The technological capabilities and the operational experience base required for such a mission do not now exist nor has any self-consistent program plan been proposed to acquire them. In particular, the lack of an Abort-to-Earth capability implies that critical mission systems must perform reliably for 3 years or must be maintainable and repairable by the crew. As has been previously argued, a well-planned program of human exploration of the Moon would provide a context within which to develop the appropriate technologies because a lunar expedition incorporates many of the operational elements of a Mars expedition. Initial lunar expeditions can be carried out at scales consistent with the current experience base but can be expanded in any or all operational phases to produce an experience base necessary to successfully and safely conduct human exploration of Mars. Published by Elsevier Ltd.
The James Clerk Maxwell Telescope has been used to obtain submillimeter and millimeter continuum photometry of a sample of 30 IRAS sources previously studied in molecular lines and centimeter radio continuum. All the sources have IRAS colours typical of very young stellar objects (YSOs) and are associated with dense gas.
This paper will discuss the basic mission and system elements of the Venus Sample Return (VSSR) mission.