99 research outputs found
The value of returning a sample of the Martian atmosphere
No full textThe elemental and isotopic abundances of major species in the Martian atmosphere have been determined, but analyses often lack sufficient precision, and those of minor and trace species are frequently not well known. Many important questions about the evolution and current state of Mars require the kind of knowledge that can be gained from analysis of a returned sample of the Martian atmosphere. Key target species include the noble gases, nitrogen, and various species containing carbon, hydrogen, and oxygen, such as methane. More detailed analyses will no doubt provide measurements of other species that will allow insights of their own. These volatiles can constrain the origin of the Martian atmosphere, exchange of volatiles between the surface and interior, polar processes, and (in the case of methane) the possibility of extant biology on Mars
Abundance of He-3 and other solar-wind-derived volatiles in lunar soil
No full textVolatiles implanted into the lunar regolith by the solar wind are potentially important lunar resources. Wittenberg et al. (1986) have proposed that lunar He-3 could be used as a fuel for terrestrial nuclear fusion reactors. They argue that a fusion scheme involving D and He-3 would be cleaner and more efficient than currently-proposed schemes involving D and T. However, since the terrestrial inventory of He-3 is so small, they suggest that the lunar regolith, with concentrations of the order of parts per billion (by mass) would be an economical source of He-3. Solar-wind implantation is also the primary source of H, C, and N in lunar soil. These elements could also be important, particularly for life support and for propellant production. In a SERC study of the feasibility of obtaining the necessary amount of He-3, Swindle et al. (1990) concluded that the available amount is sufficient for early reactors, at least, but that the mining problems, while not necessarily insurmountable, are prodigious. The volatiles H, C, and N, on the other hand, come in parts per million level abundances. The differences in abundances mean that (1) a comparable amount of H, C, and/or N could be extracted with orders of magnitude smaller operations than required for He-3, and (2) if He-3 extraction ever becomes important, huge quantities of H, C, and N will be produced as by-products
Dataset supporting the University of Southampton Doctoral Thesis "Development of poly(lactic-co-glycolic acid) electrospun membranes for incorporation into 3-D co-culture models of the airway-blood barrier"
No full textDataset supporting the University of Southampton Doctoral Thesis "Development of poly(lactic-co-glycolic acid) electrospun membranes for incorporation into 3-D co-culture models of the airway-blood barrier"
This dataset contains raw data and associated graphs and statistics in GraphPad Prism (version 10.2.0) files. Separate files are included for each results chapter.
Thesis_R1 - data for figures in the first results chapter, thesis chapter 3 - Development of an Electrospinning System and the Generation of PLGA Membranes
THesis_R2 - data for figures in the second results chapter, thesis chapter 4 - Biological characterisation of Epithelial Barrier Formation on Electrospun PLGA Membranes
Thesis_R3 - data for figures in the third results chapter, thesis chapter 5 - Development of a 3-D Co-culture Model using Electrospun Membrane
Data collection as described in associated thesis. Statistics are included with the data entry.
Software required to open filed: Graphpad Prism v10.2.0 (392)
The data is embargoed until 20/01/2025.
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Scientific Value of Including an Atmospheric Sample as part of Mars Sample Return
No full textThe Perseverance rover is meant to collect samples of the martian surface for eventual return to Earth. The headspace gas present over the solid samples within the sample tubes will be of significant scientific interest for what it reveals about the interactions of the solid samples with the trapped atmosphere and for what it will reveal about the martian atmosphere itself. However, establishing the composition of the martian atmosphere will require other dedicated samples. The headspace gas as the sole atmospheric sample is problematic for many reasons. The quantity of gas present within the sample tube volume is insufficient for many investigations, and there will be exchange between solid samples, headspace gas, and tube walls. Importantly, the sample tube materials and preparation were not designed for optimal Mars atmospheric gas collection and storage as they were not sent to Mars in a degassed evacuated state and have been exposed to both Earth’s and Mars’ atmospheres. Additionally, there is a risk of unconstrained seal leakage in transit back to Earth, which would allow fractionation of the sample (leak-out) and contamination (leak-in). The science return can be improved significantly (and, in some cases, dramatically) by adding one or more of several strategies listed here in increasing order of effectiveness and difficulty of implementation: (1) Having Perseverance collect a gas sample in an empty sample tube, (2) Collecting gas in a newly-designed, valved, sample-tube-sized vessel that is flown on either the Sample Fetch Rover (SFR) or the Sample Retrieval Lander (SRL), (3) Adding a larger (50-100 cc) dedicated gas sampling volume to the Orbiting Sample container (OS), (4) Adding a larger (50-100 cc) dedicated gas sampling volume to the OS that can be filled with compressed martian atmosphere
, edited by Peter W. Reiners and Todd A. Ehlers
No full textBook Review: Low-Temperature Thermochronology: Techniques, Interpretations, and Applications, Peter W. Reiners, Todd A. Ehlers (Eds.). Mineralogical Society of America, Reviews in Mineralogy and Geochemistry, vol. 58 (2005).The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202
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Dynamical History of the Asteroid Belt and Implications for Terrestrial Planet Bombardment
No full textThe main asteroid belt spans ~2-4 AU in heliocentric distance and is sparsely populated by rocky debris. The dynamical structure of the main belt records clues to past events in solar system history. Evidence from the structure of the Kuiper belt, an icy debris belt beyond Neptune, suggests that the giant planets were born in a more compact configuration and later experienced planetesimal-driven planet migration. Giant planet migration caused both mean motion and secular resonances to sweep across the main asteroid belt, raising the eccentricity of asteroids into planet-crossing orbits and depleting the belt. I show that the present-day semimajor axis and eccentricity distributions of large main belt asteroids are consistent with excitation and depletion due to resonance sweeping during the epoch of giant planet migration. I also use an analytical model of the sweeping of the ν6 secular resonance, to set limits on the migration speed of Saturn.After planet migration, dynamical chaos became the dominant loss mechanism for asteroids with diameters D>10 km in the current asteroid belt. I find that the dynamical loss history of test particles from this region is well described with a logarithmic decay law. My model suggests that the rate of impacts from large asteroids may have declined by a factor of three over the last ~3 Gy, and that the present-day impact flux of D>10 km objects on the terrestrial planets is roughly an order of magnitude less than estimates used in crater chronologies and impact hazard risk assessments.Finally, I have quantified the change in the solar wind 6Li/7Li ratio due to the estimated in-fall of chondritic material and enhanced dust production during the epoch of planetesimal-driven giant planet migration. The solar photosphere is currently highly depleted in lithium relative to chondrites, and 6Li is expected to be far less abundant in the sun than 7Li due to the different nuclear reaction rates of the two isotopes. Evidence for a short-lived impact cataclysm that affected the entire inner solar system may be found in the composition of implanted solar wind particles in lunar regolith
In search of stardust: Amazing micrometeorites and their terrestrial imposters, by Jon Larsen. Minneapolis, Minnesota: Voyageur Press, 2017, 152 p., hardcover (ISBN-13: 978-0760352649, ISBN-10: 076035264X).
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