Microwave impedance spectroscopy of dense carbon nanotube bundles

We have performed impedance spectroscopy of dense carbon nanotube (CNT) bundles in the broad frequency range from 10 MHz to 67 GHz. Dense CNT bundles were formed on sharp tips from aqueous suspension by ac dielectrophoresis and incorporated into on-wafer test structures. The frequency response of the bundles can be fit to a model with frequency-independent elements in the entire frequency range up to 67 GHz strongly suggesting that CNT properties do not depend on the frequency throughout the whole frequency range. The measurements at microwave frequencies allowed separate characterization of the bundle/metal electrode contacts and the bundle bulk. Effects of different CNT fabrication and suspension processing routes on bundle characteristics were identified. We have also made a preliminary estimation of the average inductance per current carrying shell in the bundles. For good quality nanotube bundles, the inductance has been found to fall within the range from approximately 3.5 to 40 nH/microm. With decreasing nanotube quality, the implemented estimation procedure yields higher values with a large uncertainty. Systematic measurements of devices with individual nanotubes are required to provide more accurate data.     

Mars analysis by laser-induced breakdown spectroscopy (MALIS): influence of mars atmosphere on plasma emission and study of factors influencing plasma emission with the use of doehlert designs

A project called MALIS (Mars Analysis by Laser-Induced breakdown Spectroscopy) is under progress to perform in situ analysis of Mars soils and rocks. This paper reports on the behavior of plasma in Martian conditions, i.e., in a CO2 atmosphere at pressures between 5 and 12 mbar. Plasma expansion and lifetime have been studied in order to compare plasma evolution under standard conditions (air at atmospheric pressure) and in a Mars atmosphere. We have shown that the Mars environment favors plasma expansion and lifetime. The second part of the study concerns optimization of the emission signal from the plasma. An original approach has been chosen, as we used a Doehlert design for the first time in laser-induced breakdown spectroscopy (LIBS). The best conditions obtained are for a laser wavelength of 1064 nm with the maximum energy available due to space limitations, which is 40 mJ at 15 Hz. The other factors studied are delay, angle of incidence, and CO2 pressure. We have shown that these factors do not have the same influence depending on which spectroscopic line is used, i.e., the atomic line or the ionic line.     

The design concept of a static wide field-of-view polarization Michelson interferometer for Mars atmosphere survey

Passive optical remote sensing is one of the effective methods to measure the composition of the Martian atmosphere. A static wide field-of-view polarization Michelson interferometer is intended to be used to measure winds in the atmosphere of Mars. The highlight of the instrument is the application of a thin lens array and a polarizer array to obtain four interferograms simultaneously without moving parts; then the velocity and temperature can be deduced from the four interferograms. The thin lens array is used to divide the pupil, and this makes the optical system small and lightweight. Moreover, there is no influence on the recovered temperature and velocity when the lens array is misaligned. A fully compensation technology is applied to widen the field-of-view and fulfill achromatic and thermal compensation, and simulations show that the designed scheme responds well to theoretical expectation.     

Microwave assisted synthesis of flower-like ZnO and effect of annealing atmosphere on its photoluminescence property

Large scale flower-like ZnO microstructures were synthesized by microwave assisted hydrothermal method in short reaction time. These flower-like structures were composed of dozen of rods like building block units radiated from a centre. Similar morphology was not obtained in normal hydrothermal method. TEM microscopy study showed that individual rods of flower-like structures are single crystalline in nature and preferentially grown along [0001] direction. Growth mechanism showed that microwave induction and ethylenediamine (EDA) played an important role in the formation of flower-like ZnO microstructures. Photoluminescence property of flower-like ZnO microstructures showed deep level emission along with UV emission which indicates the presence of structural defects. The nature of defect responsible for deep level emission was examined by annealing the sample in different atmospheres. There was no significant effect of annealing the sample in air and argon atmospheres however in hydrogen atmosphere deep level emissions were passivated.     

Examining natural rock varnish and weathering rinds with laser-induced breakdown spectroscopy for application to ChemCam on Mars

A laser-induced breakdown spectroscopy (LIBS) instrument is traveling to Mars as part of ChemCam on the Mars Science Laboratory rover. Martian rocks have weathered exteriors that obscure their bulk compositions. We examine weathered rocks with LIBS in a martian atmosphere to improve interpretations of ChemCam rock analyses on Mars. Profile data are analyzed using principal component analysis, and coatings and rinds are examined using scanning electron microscopy and electron probe microanalysis. Our results show that LIBS is sensitive to minor compositional changes with depth and correctly identifies rock type even if the series of laser pulses does not penetrate to unweathered material.     

Combining preconcentration of air samples with cavity ring-down spectroscopy for detection of trace volatile organic compounds in the atmosphere

Quantitative detection of small volatile organic compounds in ambient air is demonstrated using a combination of continuous wave cavity ring-down spectroscopy (cw-CRDS) and the preconcentration of air samples with an adsorbent trap. The trap consists of a zeolite molecular sieve, selected for efficient trapping of the test compounds ethene (ethylene) and ethyne (acetylene). Upon heating of the trap, these organic compounds desorb into a small-volume ring-down cavity, and absolute concentrations are measured by CRDS at 6150.30 cm(-1) (ethene) and 6512.99 cm(-1) (ethyne) without the need for calibration. The efficiency of the trapping and desorption was tested using commercial standard gas mixtures and shown to be 100% in the case of ethene, whereas some ethyne is retained under the current operating conditions. Samples of indoor and outdoor air were analyzed for ethene content, and measurements were made of mixing ratios as low as 6 ppbv. Removal of water vapor and CO(2) from the air samples prior to trapping was unnecessary, and the selectivity of the trapping, desorption, and spectroscopic detection steps eliminates the need for gas chromatographic separation prior to analysis. With anticipated improvements to the design, measurements of these and other trace atmospheric constituents should be possible on time scales of a few minutes.     

Mars laser hygrometer

We have designed and built a miniature near-IR tunable diode laser (TDL) spectrometer for measuring in situ the water vapor mixing ratio either in the Martian atmosphere or thermally evolved from Martian soil or ice samples. The laser hygrometer uses a thermoelectrically cooled single-mode distributed-feedback TDL at 1.87 microm to scan over a selected vibration-rotation line of both H2O and CO2 near 5327.3 cm(-1). A working prototype that weighs only 230 g has been built and used to generate spectra whose analysis demonstrates precision sensitivities as fine as 1 part in 10(6) by volume in 1 s or 0.1 part in 10(6) in 10 s at Martian pressures and temperatures. Absolute uncertainties of approximately 5% are calculated.     

Mars 1064 nm spectral radiance measurements determined from the receiver noise response of the Mars Orbiter Laser Altimeter

A technique was developed to compute the radiance of the scene viewed by the optical receiver of the Mars Orbiter Laser Altimeter. The technique used the detection threshold and the false detection rate of the receiver to provide a passive radiometry measurement of Mars at the 1064 nm wavelength over a 2 nm bandwidth and subkilometer spatial resolution in addition to the altimetry and active radiometry measurements. The passive radiometry measurement is shown to have a 2% or better precision and has been stable over several Martian years. We describe the principle of operation of the instrument and its calibration and assess its performance from sample orbital measurements.     

Microwave sample preparation of facing materials for analysis using the method of atomic emission spectroscopy with inductively coupled plasma

A technique for microwave decomposition of the powder for plasma-jet hard-facing and determination of boron, iron (III), and chromium (III) by ICP-AES is presented. The solvent composition and parameters of the microwave decomposition of the samples in an autoclave are optimized. The detection limits for B, Cr (III) and Fe (III) are 3.0 × 10⁻³, 7.6 × 10⁻⁵, and 2.0 × 10⁻² wt %, respectively.     

Analysis of water ice and water ice/soil mixtures using laser-induced breakdown spectroscopy: application to Mars polar exploration

Recently, laser-induced breakdown spectroscopy (LIBS) has been developed for the elemental analysis of geological samples for application to space exploration. There is also interest in using the technique for the analysis of water ice and ice/dust mixtures located at the Mars polar regions. The application is a compact instrument for a lander or rover to the Martian poles to interrogate stratified layers of ice and dusts that contain a record of past geologic history, believed to date back several million years. Here we present results of a study of the use of LIBS for the analysis of water ice and ice/dust mixtures in situ and at short stand-off distances (< 6.5 m) using experimental parameters appropriate for a compact instrument. Characteristics of LIBS spectra of water ice, ice/soil mixtures, element detection limits, and the ability to ablate through ice samples to monitor subsurface dust deposits are discussed.     

Mars Helicopter Exceeds Expectations

On 19 April 2021,its twin rotors stirring the wispy Martian atmosphere,Ingenuity,the National Aeronautics and Space Administration(NASA)miniature helicopter,lif...     

The fluvial history of Mars

River channels and valleys have been observed on several planetary bodies in addition to the Earth. Long sinuous valleys on Venus, our Moon and Jupiter's moon Io are clearly formed by lava, and branching valleys on Saturn's moon Titan may be forming today by rivers of methane. But by far the most dissected body in our Solar System apart from the Earth is Mars. Branching valleys that in plan resemble terrestrial river valleys are common throughout the most ancient landscapes preserved on the planet. Accompanying the valleys are the remains of other indicators of erosion and deposition, such as deltas, alluvial fans and lake beds. There is little reason to doubt that water was the erosive agent and that early in Mars' history, climatic conditions were very different from the present cold conditions and such that, at least episodically, water could flow across the surface. In addition to the branching valley networks, there are large flood features, termed outflow channels. These are similar to, but dwarf, the largest terrestrial flood channels. The consensus is that these channels were also cut by water although there are other possibilities. The outflow channels mostly postdate the valley networks, although most are still very ancient. They appear to have formed at a time when surface conditions were similar to those that prevail today. There is evidence that glacial activity has modified some of the water-worn valleys, particularly in the 30-50° latitude belts, and ice may also be implicated in the formation of geologically recent, seemingly water-worn gullies on steep slopes. Mars also has had a long volcanic history, and long, sinuous lava channels similar to those on the Moon and Venus are common on and around the large volcanoes. These will not, however, be discussed further; the emphasis here is on the effects of running water on the evolution of the surface.