Carbon-rich particles in Comet Halley

The majority of particles detected in the coma of Comet Halley contain carbon atoms; many of these grains appear to consist preponderately or only of light elements. These light-element particles may be composed of organic compounds. Of the possible combinations of the elements hydrogen, carbon, nitrogen, and oxygen, numerous examples are found of particles containing the combinations (H,C,O,N), (H,C,N), (H,C,O), and (H,C). These results may bear on the recent detection of polyoxymethylene fragments, the observation of cyanojets (CN patterns consistent with release from solid particles), the possible presence of cyanopolyacetylenes or HCN polymer and the make-up of the CHON particles. If cometary matter could reach the surface of the earth without complete disruption, these diverse organic and mixed particles could create unique microenvironments, possibly with significant or even pivotal prebiotic chemical activity. Here a speculative insight into possible relationships between carbon in comets and carbon in life is given, as well as a brief overview of on-going analysis of data from the highly successful Particle Impact Analyzer (PIA) experiment flown on the Giotto spacecraft for the flyby of Comet Halley (development and implementation of PIA was under the direction of J. Kissel of the Max Planck Institute for Kernphysik, Heidelberg). PIA is a time-of-flight analyzer which obtains mass spectra of ions from individual particles impacting on a Pt-Ag foil target within the instrument

Mars aqueous chemistry experiment

The Mars Aqueous Chemistry Experiment (MACE) is designed to conduct a variety of measurements on regolith samples, encompassing mineral phase analyses, chemical interactions with H2O, and physical properties determinations. From these data, much can be learned or inferred regarding the past weathering environment, the contemporaneous soil micro-environments, and the general chemical and physical state of the Martian regolith. By analyzing both soil and duricrust samples, the nature of the latter may become more apparent. Sites may be characterized for comparative purposes and criteria could be set for selection of high priority materials on future sample return missions. Progress for the first year MACE PIDDP is reported in two major areas of effort: (1) fluids handling concepts, definition, and breadboard fabrication and (2) aqueous chemistry ion sensing technology and test facility integration. A fluids handling breadboard was designed, fabricated, and tested at Mars ambient pressure. The breadboard allows fluid manipulation scenarios to be tested under the reduced pressure conditions expected in the Martian atmosphere in order to validate valve operations, orchestrate analysis sequences, investigate sealing integrity, and to demonstrate efficacy of the fluid handling concept. Additional fluid manipulation concepts have also been developed based on updated MESUR spacecraft definition. The Mars Aqueous Chemistry Experiment Ion Selective Electrode (ISE) facility was designed as a test bed to develop a multifunction interface for measurements of chemical ion concentrations in aqueous solution. The interface allows acquisition of real time data concerning the kinetics and heats of salt dissolution, and transient response to calibration and solubility events. An array of ion selective electrodes has been interfaced and preliminary calibration studies performed

<i>Chirotherium barthii </i>Kaup 1835 from the Triassic of the Isle of Arran, Scotland

The mould of a track from SE Arran, and several in situ trackways and individual tracks, as well as a partial trackway on a loose block of Triassic sandstone, from western Arran, represent the first verifiable fossil tracks of Chirotherium from the Triassic of Scotland and support a Scythian (Lower Triassic) age for the base of the Auchenhew Beds. The grouping of the I–IV toes with toe V behind and lateral to the group is characteristic of Chirotherium-like tracks. A comparison with European and American Triassic trackways suggests that the tracks belong to the species Chirotherium barthii Kaup, 1835, first described from Hildburghausen, Germany

Mars Aqueous Chemistry Experiment (MACE)

The concept of an aqueous-based chemical analyzer for Martian surface materials has been demonstrated to be feasible. During the processes of analysis, design, breadboarding, and most importantly, testing, it has become quite apparent that there are many challenges in implementing such a system. Nonetheless, excellent progress has been made and a number of problems which arose have been solved. The ability to conduct this work under a development environment which is separate and which precedes the project-level development has allowed us to find solutions to these implementation realities at low cost. If the instrument had been selected for a mission without this laboratory pre-project work, the costs of implementation would be much higher. In the four areas covered in Sections D, E, F, and G of this Final Report, outstanding progress has been made. There still remains the task of flight-qualifying certain of the components. This is traditionally done under the aegis of a Flight Project, but just as the concept development can be done at much lower cost when kept small and focused, so could the qualification program of critical parts benefit. We recommend, therefore, that NASA consider means of such qualifications and brass-boarding, in advance of final flight development. This is a generic recommendation, but hardware such as the Mars aqueous chemistry experiment (MACE) and other similarly-new concepts are particularly applicable. MACE now has wide versatility, in being able to reliably dispense both liquids and solids as chemical reagents to an entire suite of samples. The hardware and the experiment is much simpler than was developed for the Viking Biology instrument, yet can accomplish all the inorganic chemical measurements that the Viking desing was capable of. In addition, it is much more flexible and versatile to new experiment protocols (and reagents) than the Viking design ever could have been. MACE opens up the opportunity for many different scientific disciplines to design sub- experiments and to benefit from the investigations that can be conducted. In this sense, it will have the value of a facility, although our recommendation would be that it be under the stewardship of a single lead investigator to insure that conflicting requirements not compromise the straight-forward design that have been achieved. MACE is an excellent candidate for upcoming Mars missions, including the Mars Surveyor Program (MSP) lander missions in 2001 and 2003. In addition, it could be used for any mission to the surface of any other planet or planetary body (including small bodies). An important next step is to encourage various investigators to propose specific uses for this experiment that specifically address their major scientific objectives for upcoming missions

Momentum-space engineering of gaseous Bose-Einstein condensates

We show how the momentum distribution of gaseous Bose--Einstein condensates can be shaped by applying a sequence of standing-wave laser pulses. We present a theory, whose validity for was demonstrated in an earlier experiment [L.\ Deng, et al., \prl {\bf 83}, 5407 (1999)], of the effect of a two-pulse sequence on the condensate wavefunction in momentum space. We generalize the previous result to the case of $N$ pulses of arbitrary intensity separated by arbitrary intervals and show how these parameters can be engineered to produce a desired final momentum distribution. We find that several momentum distributions, important in atom-interferometry applications, can be engineered with high fidelity with two or three pulses.Comment: 13 pages, 4 figure

Portable x-ray fluorescence spectrometer for environmental monitoring of inorganic pollutants

A portable x-ray fluorescence spectrometer has a portable sensor unit containing a battery, a high voltage power supply, an x-ray tube which produces a beam x-ray radiation directed toward a target sample, and a detector for fluorescent x-rays produced by the sample. If a silicon-lithium detector is used, the sensor unit also contains either a thermoelectric or thermochemical cooler, or a small dewar flask containing liquid nitrogen to cool the detector. A pulse height analyzer (PHA) generates a spectrum of data for each sample consisting of the number of fluorescent x-rays detected as a function of their energy level. The PHA can also store spectrum data for a number of samples in the field. A processing unit can be attached to the pulse height analyzer to upload and analyze the stored spectrum data for each sample. The processing unit provides a graphic display of the spectrum data for each sample, and provides qualitative and/or quantitative analysis of the elemental composition of the sample by comparing the peaks in the sample spectrum against known x-ray energies for various chemical elements. An optional filtration enclosure can be used to filter particles from a sample suspension, either in the form of a natural suspension or a chemically created precipitate. The sensor unit is then temporarily attached to the filtration unit to analyze the particles collected by the filter medium

A Comparison of Petersen Tags and Biological Stains Used With Internal Tags as Marks for Shrimp

During May 20-31, 1968, 14,301 brown shrimp (Penaeus aztecus) were marked and released in Biloxi Bay, Mississippi. Of these 7,023 were marked by injection with a combination of Niagara Sky Blue 6B stain and polyvinyl chloride (PVC) internal tags and 7,278 were marked with Petersen tags. The objectives of this experiment were to compare the two methods as marks for shrimp and to obtain information on growth rates and migrations. Eighteen weeks after release, 1,942 (28%) of those marked with the biological stain-internal tag combination and 2,286 (31%) of those marked with Petersen tags had been recovered. The difference in proportions recaptured (significant at P \u3c0.01) could have resulted from greater ease in recognition of the Petersen tag by commercial fishermen or from differential marking mortality, although no evidence was found that differential marking mortality occurred. Marking mortality was observed for both marks and appeared inversely related to size at time of marking. No significant differences were found between growth rates of shrimp marked with the biological stain-internal tag combination and those of shrimp marked with the Petersen tag, although most weekly average increments for stained shrimp were higher. Rates of return were similar in the vicinity of the release area, although a significantly higher proportion (P \u3c0.01) of returns from waters outside of Biloxi Bay were marked with Petersen tags. Again, this was attributed primarily to greater ease in recognition by commercial fishermen. It was concluded that the Petersen tag was the more effective of the two marks as it appeared to be recognized more readily over longer periods of time than the biological stain

Aqueous Alteration on Mars

Aqueous alteration is the change in composition of a rock, produced in response to interactions with H2O-bearing ices, liquids, and vapors by chemical weathering. A variety of mineralogical and geochemical indicators for aqueous alteration on Mars have been identified by a combination of surface and orbital robotic missions, telescopic observations, characterization of Martian meteorites, and laboratory and terrestrial analog studies. Mineralogical indicators for aqueous alteration include goethite (lander), jarosite (lander), kieserite (orbiter), gypsum (orbiter) and other Fe-, Mg-, and Ca-sulfates (landers), halides (meteorites, lander), phyllosilicates (orbiter, meteorites), hematite and nanophase iron oxides (telescopic, orbiter, lander), and Fe-, Mg-, and Ca-carbonates (meteorites). Geochemical indicators (landers only) for aqueous alteration include Mg-, Ca-, and Fe-sulfates, halides, and secondary aluminosilicates such as smectite. Based upon these indicators, several styles of aqueous alteration have been suggested on Mars. Acid-sulfate weathering (e.g., formation of jarosite, gypsum, hematite, and goethite), may occur during (1) the oxidative weathering of ultramafic igneous rocks containing sulfides, (2) sulfuric acid weathering of basaltic materials, and (3) acid fog (i.e., vapors rich in H2SO4) weathering of basaltic or basaltic-derived materials. Near-neutral or alkaline alteration occurs when solutions with pH near or above 7 move through basaltic materials and form phases such as phyllosilicates and carbonates. Very low water:rock ratios appear to have been prominent at most of the sites visited by landed missions because there is very little alteration (leaching) of the original basaltic composition (i.e., the alteration is isochemical or in a closed hydrologic system). Most of the aqueous alteration appears to have occurred early in the history of the planet (3 to 4.5 billion years ago); however, minor aqueous alteration may be occurring at the surface even today (e.g., in thin films of water or by acid fog)

Approximate Mean-field Equations of Motion for Quasi-two-dimensional Bose-Einstein Condensates

We present a method for approximating the solution of the three-dimensional, time-dependent Gross-Pitaevskii equation (GPE) for Bose-Einstein-condensate systems where the confinement in one dimension is much tighter than in the other two. This method employs a hybrid Lagrangian variational technique whose trial wave function is the product of a completely unspecified function of the coordinates in the plane of weak confinement and a Gaussian in the strongly confined direction having a time-dependent width and quadratic phase. The hybrid Lagrangian variational method produces equations of motion that consist of (1) a two-dimensional (2D) effective GPE whose nonlinear coefficient contains the width of the Gaussian and (2) an equation of motion for the width that depends on the integral of the fourth power of the solution of the 2D effective GPE. We apply this method to the dynamics of Bose-Einstein condensates confined in ring-shaped potentials and compare the approximate solution to the numerical solution of the full 3D GPE