Arguably, the most striking geochemical distinction between Earth and the Moon has been the virtual lack of water (hydrogen) in the latter. This conclusion was recently challenged on the basis of ...geochemical data from lunar materials that suggest that the Moon's water content might be far higher than previously believed. We measured the chlorine isotope composition of Apollo basalts and glasses and found that the range of isotopic values from -1 to +24 per mil (per thousand) versus standard mean ocean chloride is 25 times the range for Earth. The huge isotopic spread is explained by volatilization of metal halides during basalt eruption--a process that could only occur if the Moon had hydrogen concentrations lower than those of Earth by a factor of approximately 10⁴ to 10⁵, implying that the lunar interior is essentially anhydrous.
Here, absolute cross sections for the addition of s- and d-wave neutrons to 14C and 14N have been determined simultaneously via the (d,p) reaction at 10 MeV/u. The difference between the neutron and ...proton separation energies, ΔS, is around -20 MeV for the 14C+n system and +8 MeV for 14N+n. The population of the 1s1/2 and 0d5/2 orbitals for both systems is reduced by a factor of approximately 0.5 compared with the independent single-particle model, or about 0.6 when compared with the shell model. This finding strongly contrasts with results deduced from intermediate-energy knockout reactions between similar nuclei on targets of 9Be and 12C. The simultaneous technique used removes many systematic uncertainties.
As part of the Australian spectroscopic dark energy survey (OzDES) we are carrying out a large-scale reverberation mapping study of ≥500 quasars over five years in the 30 deg2 area of the Dark Energy ...Survey (DES) supernova fields. These quasars have redshifts ranging up to 4 and have apparent AB magnitudes between 16.8 mag < r < 22.5 mag. The aim of the survey is to measure time lags between fluctuations in the quasar continuum and broad emission-line fluxes of individual objects in order to measure black hole masses for a broad range of active galactic nuclei (AGN) and constrain the radius–luminosity (R–L) relationship. Here we investigate the expected efficiency of the OzDES reverberation mapping campaign and its possible extensions. We expect to recover lags for ∼35–45 per cent of the quasars. AGN with shorter lags and greater variability are more likely to yield a lag measurement, and objects with lags ≲6 months or ∼1 yr are expected to be recovered the most accurately. The baseline OzDES reverberation mapping campaign is predicted to produce an unbiased measurement of the R–L relationship parameters for H β, Mg ii λ2798, and C iv λ1549. Extending the baseline survey by either increasing the spectroscopic cadence, extending the survey season, or improving the emission-line flux measurement accuracy will significantly improve the R–L parameter constraints for all broad emission lines.
We demonstrate a new technique for obtaining fission data for nuclei away from β stability. These types of data are pertinent to the astrophysical r process, crucial to a complete understanding of ...the origin of the heavy elements, and for developing a predictive model of fission. These data are also important considerations for terrestrial applications related to power generation and safeguarding. Experimentally, such data are scarce due to the difficulties in producing the actinide targets of interest. The solenoidal-spectrometer technique, commonly used to study nucleon-transfer reactions in inverse kinematics, has been applied to the case of transfer-induced fission as a means to deduce the fission-barrier height, among other variables. The fission-barrier height of ^{239}U has been determined via the ^{238}U(d,pf) reaction in inverse kinematics, the results of which are consistent with existing neutron-induced fission data indicating the validity of the technique.
The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical r process in producing nuclei heavier than A∼190. Despite their importance, the structure ...and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in ^{207}Hg have been probed using the neutron-adding (d,p) reaction in inverse kinematics. The radioactive beam of ^{206}Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of ^{207}Hg marks a first step in improving our understanding of the relevant structural properties of nuclei involved in a key part of the path of the r process.
The Martian meteorites record a wide diversity of environments, processes, and ages. Much work has been done to decipher potential mantle sources for Martian magmas and their interactions with ...crustal and surface environments. Chlorine isotopes provide a unique opportunity to assess interactions between Martian mantle‐derived magmas and the crust. We have measured the Cl‐isotopic composition of 17 samples that span the range of known ages, Martian environments, and mantle reservoirs. The 37Cl of the Martian mantle, as represented by the olivine‐phyric shergottites, NWA 2737 (chassignite), and Shergotty (basaltic shergottite), has a low value of approximately −3.8‰. This value is lower than that of all other planetary bodies measured thus far. The Martian crust, as represented by regolith breccia NWA 7034, is variably enriched in the heavy isotope of Cl. This enrichment is reflective of preferential loss of 35Cl to space. Most basaltic shergottites (less Shergotty), nakhlites, Chassigny, and Allan Hills 84001 lie on a continuum between the Martian mantle and crust. This intermediate range is explained by mechanical mixing through impact, fluid interaction, and assimilation‐fractional crystallization.
Executive Summary
Return of samples from the surface of Mars has been a goal of the international Mars science community for many years. Affirmation by NASA and ESA of the importance of Mars ...exploration led the agencies to establish the international MSR Objectives and Samples Team (iMOST). The purpose of the team is to re‐evaluate and update the sample‐related science and engineering objectives of a Mars Sample Return (MSR) campaign. The iMOST team has also undertaken to define the measurements and the types of samples that can best address the objectives.
Seven objectives have been defined for MSR, traceable through two decades of previously published international priorities. The first two objectives are further divided into sub‐objectives. Within the main part of the report, the importance to science and/or engineering of each objective is described, critical measurements that would address the objectives are specified, and the kinds of samples that would be most likely to carry key information are identified. These seven objectives provide a framework for demonstrating how the first set of returned Martian samples would impact future Martian science and exploration. They also have implications for how analogous investigations might be conducted for samples returned by future missions from other solar system bodies, especially those that may harbor biologically relevant or sensitive material, such as Ocean Worlds (Europa, Enceladus, Titan) and others.
Summary of Objectives and Sub‐Objectives for MSR Identified by iMOST
Objective 1
Interpret the primary geologic processes and history that formed the Martian geologic record, with an emphasis on the role of water.
Intent
To investigate the geologic environment(s) represented at the Mars 2020 landing site, provide definitive geologic context for collected samples, and detail any characteristics that might relate to past biologic processesThis objective is divided into five sub‐objectives that would apply at different landing sites.
1.1 Characterize the essential stratigraphic, sedimentologic, and facies variations of a sequence of Martian sedimentary rocks.
Intent
To understand the preserved Martian sedimentary record.
Samples
A suite of sedimentary rocks that span the range of variation.
Importance
Basic inputs into the history of water, climate change, and the possibility of life
1.2 Understand an ancient Martian hydrothermal system through study of its mineralization products and morphological expression.
Intent
To evaluate at least one potentially life‐bearing “habitable” environment
Samples
A suite of rocks formed and/or altered by hydrothermal fluids.
Importance
Identification of a potentially habitable geochemical environment with high preservation potential.
1.3 Understand the rocks and minerals representative of a deep subsurface groundwater environment.
Intent
To evaluate definitively the role of water in the subsurface.
Samples
Suites of rocks/veins representing water/rock interaction in the subsurface.
Importance
May constitute the longest‐lived habitable environments and a key to the hydrologic cycle.
1.4 Understand water/rock/atmosphere interactions at the Martian surface and how they have changed with time.
Intent
To constrain time‐variable factors necessary to preserve records of microbial life.
Samples
Regolith, paleosols, and evaporites.
Importance
Subaerial near‐surface processes could support and preserve microbial life.
1.5 Determine the petrogenesis of Martian igneous rocks in time and space.
Intent
To provide definitive characterization of igneous rocks on Mars.
Samples
Diverse suites of ancient igneous rocks.
Importance
Thermochemical record of the planet and nature of the interior.
Objective 2
Assess and interpret the potential biological history of Mars, including assaying returned samples for the evidence of life.
Intent
To investigate the nature and extent of Martian habitability, the conditions and processes that supported or challenged life, how different environments might have influenced the preservation of biosignatures and created nonbiological “mimics,” and to look for biosignatures of past or present life.This objective has three sub‐objectives:
2.1 Assess and characterize carbon, including possible organic and pre‐biotic chemistry.
Samples
All samples collected as part of Objective 1.
Importance
Any biologic molecular scaffolding on Mars would likely be carbon‐based.
2.2 Assay for the presence of biosignatures of past life at sites that hosted habitable environments and could have preserved any biosignatures.
Samples
All samples collected as part of Objective 1.
Importance
Provides the means of discovering ancient life.
2.3 Assess the possibility that any life forms detected are alive, or were recently alive.
Samples
All samples collected as part of Objective 1.
Importance
Planetary protection, and arguably the most important scientific discovery possible.
Objective 3
Quantitatively determine the evolutionary timeline of Mars.
Intent
To provide a radioisotope‐based time scale for major events, including magmatic, tectonic, fluvial, and impact events, and the formation of major sedimentary deposits and geomorphological features.
Samples
Ancient igneous rocks that bound critical stratigraphic intervals or correlate with crater‐dated surfaces.
Importance
Quantification of Martian geologic history.
Objective 4
Constrain the inventory of Martian volatiles as a function of geologic time and determine the ways in which these volatiles have interacted with Mars as a geologic system.
Intent
To recognize and quantify the major roles that volatiles (in the atmosphere and in the hydrosphere) play in Martian geologic and possibly biologic evolution.
Samples
Current atmospheric gas, ancient atmospheric gas trapped in older rocks, and minerals that equilibrated with the ancient atmosphere.
Importance
Key to understanding climate and environmental evolution.
Objective 5
Reconstruct the processes that have affected the origin and modification of the interior, including the crust, mantle, core and the evolution of the Martian dynamo.
Intent
To quantify processes that have shaped the planet's crust and underlying structure, including planetary differentiation, core segregation and state of the magnetic dynamo, and cratering.
Samples
Igneous, potentially magnetized rocks (both igneous and sedimentary) and impact‐generated samples.
Importance
Elucidate fundamental processes for comparative planetology.
Objective 6
Understand and quantify the potential Martian environmental hazards to future human exploration and the terrestrial biosphere.
Intent
To define and mitigate an array of health risks related to the Martian environment associated with the potential future human exploration of Mars.
Samples
Fine‐grained dust and regolith samples.
Importance
Key input to planetary protection planning and astronaut health.
Objective 7
Evaluate the type and distribution of in‐situ resources to support potential future Mars exploration.
Intent
To quantify the potential for obtaining Martian resources, including use of Martian materials as a source of water for human consumption, fuel production, building fabrication, and agriculture.
Samples
Regolith.
Importance
Production of simulants that will facilitate long‐term human presence on Mars.
Summary of iMOST Findings
Several specific findings were identified during the iMOST study. While they are not explicit recommendations, we suggest that they should serve as guidelines for future decision making regarding planning of potential future MSR missions.
The samples to be collected by the Mars 2020 (M‐2020) rover will be of sufficient size and quality to address and solve a wide variety of scientific questions.
Samples, by definition, are a statistical representation of a larger entity. Our ability to interpret the source geologic units and processes by studying sample sub sets is highly dependent on the quality of the sample context. In the case of the M‐2020 samples, the context is expected to be excellent, and at multiple scales. (A) Regional and planetary context will be established by the on‐going work of the multi‐agency fleet of Mars orbiters. (B) Local context will be established at field area‐ to outcrop‐ to hand sample‐ to hand lens scale using the instruments carried by M‐2020.
A significant fraction of the value of the MSR sample collection would come from its organization into sample suites, which are small groupings of samples designed to represent key aspects of geologic or geochemical variation.
If the Mars 2020 rover acquires a scientifically well‐chosen set of samples, with sufficient geological diversity, and if those samples were returned to Earth, then major progress can be expected on all seven of the objectives proposed in this study, regardless of the final choice of landing site. The specifics of which parts of Objective 1 could be achieved would be different at each of the final three candidate landing sites, but some combination of critically important progress could be made at any of them.
An aspect of the search for evidence of life is that we do not know in advance how evidence for Martian life would be preserved in the geologic record. In order for the returned samples to be most useful for both understanding geologic processes (Objective 1) and the search for life (Objective 2), the sample collection should contain BOTH typical and unusual samples from the rock units explored. This consideration should be incorporated into sample selection and the design of the suites.
The retrieval missions of a MSR campaign should (1) minimize stray magnetic fields to which the samples would be exposed and carry a magnetic witness plate to record exposure, (2) collect and return atmospheric gas sample(s), and (3) collect additional dust and/or regolith sample mass if possible.
The combination of passive drug permeability, affinity for uptake and efflux transporters as well as gastrointestinal metabolism defines net drug absorption. Efflux mechanisms are often overlooked ...when examining the absorption phase of drug bioavailability. Knowing the affinity of antimalarials for efflux transporters such as P-glycoprotein (P-gp) may assist in the determination of drug absorption and pharmacokinetic drug interactions during oral absorption in drug combination therapies. Concurrent administration of P-gp inhibitors and P-gp substrate drugs may also result in alterations in the bioavailability of some antimalarials. In-vitro Caco-2 cell monolayers were used here as a model for potential drug absorption related problems and P-gp mediated transport of drugs. Artemisone had the highest permeability at around 50 x 10(-6) cm/sec, followed by amodiaquine around 20 x 10(-6) cm/sec; both mefloquine and artesunate were around 10 x 10(-6) cm/sec. Methylene blue was between 2 and 6 x 10(-6) cm/sec depending on the direction of transport. This 3 fold difference was able to be halved by use of P-gp inhibition. MRP inhibition also assisted the consolidation of the methylene blue transport. Mefloquine was shown to be a P-gp inhibitor affecting our P-gp substrate, Rhodamine 123, although none of the other drugs impacted upon rhodamine123 transport rates. In conclusion, mefloquine is a P-gp inhibitor and methylene blue is a partial substrate; methylene blue may have increased absorption if co-administered with such P-gp inhibitors. An upregulation of P-gp was observed when artemisone and dihydroartemisinin were co-incubated with mefloquine and amodiaquine.
ICP registration using invariant features Sharp, G.C.; Lee, S.W.; Wehe, D.K.
IEEE transactions on pattern analysis and machine intelligence,
2002-Jan., 2002-01-00, 20020101, Volume:
24, Issue:
1
Journal Article
Peer reviewed
Investigates the use of Euclidean invariant features in a generalization of iterative closest point (ICP) registration of range images. Pointwise correspondences are chosen as the closest point with ...respect to a weighted linear combination of positional and feature distances. It is shown that, under ideal noise-free conditions, correspondences formed using this distance function are correct more often than correspondences formed using the positional distance alone. In addition, monotonic convergence to at least a local minimum is shown to hold for this method. When noise is present, a method that automatically sets the optimal relative contribution of features and positions is described. This method trades off the error in feature values due to noise against the error in positions due to misalignment. Experimental results suggest that using invariant features decreases the probability of being trapped in a local minimum and may be an effective solution for difficult range image registration problems where the scene is very small compared to the model.
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