Study of sampling systems for comets and Mars

Several aspects of the techniques that can be applied to acquisition and preservation of samples from Mars and a cometary nucleus were examined. Scientific approaches to sampling, grounded in proven engineering methods are the key to achieving the maximum science value from the sample return mission. If development of these approaches for collecting and preserving does not preceed mission definition, it is likely that only suboptimal techniques will be available because of the constraints of formal schedule timelines and the normal pressure to select only the most conservative and least sophisticated approaches when development has lagged the mission milestones. With a reasonable investment now, before the final mission definition, the sampling approach can become highly developed, ready for implementation, and mature enough to help set the requirements for the mission hardware and its performance

Mapping Riparian Vegetation in the Lower Colorado River Using Low Resolution Satellite Imagery

In the Western United States, monitoring water usage is a complex task carried out by the U.S. Bureau of Reclamation (USBR). It may be argued that USBR\u27s greatest challenge is equitably distributing the waters of the Colorado River, particularly the Lower Colorado River, where water rights have been established and contested several times. To help meet the demands of water management in the Lower Colorado River Basin, USBR estimates the amount of water lost from the basin each year via evapo-transpiration by riparian vegetation in the Lower Colorado River riparian zone. Key components of those estimates include maps of the vegetation itself, which provide a measure of the acreage covered by each dominant species. Previous mapping efforts have relied extensively on costly in-situ field measurements using the Anderson-Ohmart Classification scheme (which was developed for habitat evaluation, not species identification) and data-dense high resolution aerial photographs. This study employs low resolution Landsat imagery and simple classification and clustering algorithms to identify heterogeneous species assemblages in the Lower Colorado River as possible alternatives to Anderson-Ohmart and/or high resolution aerial photographs. Our results show that the method developed here is able to identify heterogeneous riparian species assemblages, but certain vegetative species can be mapped with greater accuracy than others. Pending an error assessment to be carried out in a future field season, we believe our method to be an inexpensive, relatively simple update to USBR\u27s existing mapping procedure

Mapping Riparian Vegetation in the Lower Colorado River Using Low Resolution Satellite Imagery

In the Western United States, monitoring water usage is a complex task carried out by the U.S. Bureau of Reclamation (USBR). It may be argued that USBR\u27s greatest challenge is equitably distributing the waters of the Colorado River, particularly the Lower Colorado River, where water rights have been established and contested several times. To help meet the demands of water management in the Lower Colorado River Basin, USBR estimates the amount of water lost from the basin each year via evapo-transpiration by riparian vegetation in the Lower Colorado River riparian zone. Key components of those estimates include maps of the vegetation itself, which provide a measure of the acreage covered by each dominant species. Previous mapping efforts have relied extensively on costly in-situ field measurements using the Anderson-Ohmart Classification scheme (which was developed for habitat evaluation, not species identification) and data-dense high resolution aerial photographs. This study employs low resolution Landsat imagery and simple classification and clustering algorithms to identify heterogeneous species assemblages in the Lower Colorado River as possible alternatives to Anderson-Ohmart and/or high resolution aerial photographs. Our results show that the method developed here is able to identify heterogeneous riparian species assemblages, but certain vegetative species can be mapped with greater accuracy than others. Pending an error assessment to be carried out in a future field season, we believe our method to be an inexpensive, relatively simple update to USBR\u27s existing mapping procedure

Excitation of the electric pygmy dipole resonance by inelastic electron scattering

To complete earlier studies of the properties of the electric pygmy dipole resonance (PDR) obtained in various nuclear reactions, the excitation of the 1$^-$ states in $^{140}$Ce by $(e,e')$ scattering for momentum transfers $q=0.1-1.2$~fm$^{-1}$ is calculated within the plane-wave and distorted-wave Born approximations. The excited states of the nucleus are described within the Quasiparticle Random Phase Approximation (QRPA), but also within the Quasiparticle-Phonon Model (QPM) by accounting for the coupling to complex configurations. It is demonstrated that the excitation mechanism of the PDR states in $(e,e')$ reactions is predominantly of transversal nature for scattering angles $\theta_e \approx 90^o-180^o$. Being thus mediated by the convection and spin nuclear currents, the $(e,e')$ like the $(\gamma,\gamma')$ reaction, may provide additional information to the one obtained from Coulomb- and hadronic excitations of the PDR in $(p,p')$, $(\alpha,\alpha')$, and heavy-ion scattering reactions. The calculations predict that the $(e,e')$ cross sections for the strongest individual PDR states are in general about three orders of magnitude smaller as compared to the one of the lowest $2^+_1$ state for the studied kinematics, but that they may become dominant at extreme backward angles.Comment: Prepared for the special issue of EPJA on the topic "Giant, Pygmy, Pairing Resonances and related topics" dedicated to the memory of Pier Francesco Bortigno

The ground state of relativistic ions in the limit of high magnetic fields

We consider the pseudorelativistic no-pair Brown-Ravenhall operator for the description of relativistic one-electron ions in a homogeneous magnetic field B. It is shown for central charge not exceeding Z=87 that their ground state energy decreases according to the square root of B as B tends to infinity, in contrast to the nonrelativistic behaviour.Comment: 15 page

Using the UM dynamical cores to reproduce idealised 3D flows

We demonstrate that both the current (New Dynamics), and next generation (ENDGame) dynamical cores of the UK Met Office global circulation model, the UM, reproduce consistently, the long-term, large-scale flows found in several published idealised tests. The cases presented are the Held-Suarez test, a simplified model of Earth (including a stratosphere), and a hypothetical tidally locked Earth. Furthermore, we show that using simplifications to the dynamical equations, which are expected to be justified for the physical domains and flow regimes we have studied, and which are supported by the ENDGame dynamical core, also produces matching long-term, large-scale flows. Finally, we present evidence for differences in the detail of the planetary flows and circulations resulting from improvements in the ENDGame formulation over New Dynamics.Comment: 34 Pages, 23 Figures. Accepted for publication in Geoscientific Model Development (pre-proof version

Habitable Climate Scenarios for Proxima Centauri b With a Dynamic Ocean

The nearby exoplanet Proxima Centauri b will be a prime future target for characterization, despite questions about its retention of water. Climate models with static oceans suggest that an Earth-like Proxima b could harbor a small dayside region of surface liquid water at fairly warm temperatures despite its weak instellation. We present the first 3-dimensional climate simulations of Proxima b with a dynamic ocean. We find that an ocean-covered Proxima b could have a much broader area of surface liquid water but at much colder temperatures than previously suggested, due to ocean heat transport and depression of the freezing point by salinity. Elevated greenhouse gas concentrations do not necessarily produce more open ocean area because of possible dynamic regime transitions. For an evolutionary path leading to a highly saline present ocean, Proxima b could conceivably be an inhabited, mostly open ocean planet dominated by halophilic life. For an ocean planet in 3:2 spin-orbit resonance, a permanent tropical waterbelt exists for moderate eccentricity. Simulations of Proxima Centauri b may also be a model for the habitability of planets receiving similar instellation from slightly cooler or warmer stars, e.g., in the TRAPPIST-1, LHS 1140, GJ 273, and GJ 3293 systems.Comment: Submitted to Astrobiology; 38 pages, 12 figures, 5 table