Changes in Surface Morphology of Calcite Exposed to the Oceanic Water Column

Reactions occurring on the surfaces of biogenic carbonate minerals can have important consequences for the biogeochemical cycle of carbon. In this study, carbonate mineral surface reactions with ambient seawater were investigated by atomic force microscopy (AFM). A sampling method was developed in which calcite surfaces were hung at discrete depths on a sediment trap array line for a three-day deployment period in subtropical North Pacific waters. Changes in surface morphologies were examined at nanometer resolution and evaluated using as a constraint the depth profile of calcite saturation in these waters. Evidence suggests that: (1) organic films which develop on carbonate surfaces exposed to shallow seawater may be responsible for the oversaturated state of the upper oceanic water column, (2) dissolution of carbonate minerals within the shallow warm layer of the ocean could be responsible for part of the alkalinity anomaly observed in the North Pacific.     

Young star clusters in the Large Magellanic Cloud: NGC 1805 and 1818

We present colour–magnitude diagrams for two rich (≈10⁴ M_⊙) Large Magellanic Cloud star clusters with ages ≈10⁷ yr, constructed from optical and near-infrared data obtained with the Hubble Space Telescope . These data are part of an HST project to study LMC clusters with a range of ages. In this paper we investigate the massive star content of the young clusters, and determine the cluster ages and metallicities, paying particular attention to Be-star and blue-straggler populations and evidence of age spreads. We compare our data with detailed stellar-population simulations to investigate the turn-off structure of ≈25 Myr stellar systems, highlighting the complexity of the blue-straggler phenomenon.     

Palomar and Table Mountain observations of 9P/Tempel 1 during the Deep Impact encounter: First results

We present the first results of the Palomar Adaptive Optics observations taken during the Deep Impact encounter with 9P/Tempel 1 in July 2005. We have combined the Palomar near-IR imaging data with our visual wavelength images obtained simultaneously at JPL's Table Mountain Observatory to cover the total wavelength range from 0.4 to 2.3 μm in the B, V, R, I, J, H, and K filter bands, spanning the dates from 2005 July 03-07. We also include in our overall analysis images taken on the pre-encounter dates of June 1 and June 15, 2005. The broad wavelength range of our observations, along with high temporal resolution, near-IR sensitivity, and spatial resolution of our imaging, have enabled us to place constraints on the temperature of the impact flash and incandescent plume of >700 K, and to provide mean dust velocities of order approximately 1.25 h after impact derived from our 1.64 μm observations. Our ejected dust mass estimates, as derived from our near-IR observations, are an order of magnitude less than those previously reported for visual wavelength observations.     

SciMeasure Wavefront Sensor Cameras and their Application in the Palomar Adaptive Optics System

SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory, has developed a very versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise. The overall architecture of this controller system will be discussed and its performance using both EEV CCD39 and MIT/LL CCID-19 detectors will be presented. This controller is used in the adaptive optics system, developed by JPL, for the 200′′ Hale telescope at Palomar Mountain. Early diffraction-limited science results, recently achieved by the AO system, are presented. We gratefully acknowledge the financial support of NASA through SBIR contracts NAS8–97195 and NAS8–98081.     

The binary star population of the young cluster NGC 1818 in the Large Magellanic Cloud

We determine the binary star fraction as a function of radius in NGC 1818, a young rich cluster in the Large Magellanic Cloud, using Hubble Space Telescope images in bands F336W (∼ U ) and F555W (∼ V ). Our sample includes binaries with M _primary ∼ 2–5.5 M_⊙ and M _secondary ≳ 0.7 M_primary. The binary fraction increases towards the cluster centre, from ∼ 20 ± 5 per cent in the outer parts, to ∼ 35 ± 5 per cent inside the core. This increase is consistent with dynamical mass segregation and need not be primordial. We compare our results with expectations from N -body models, and discuss the implications for the formation and early evolution of such clusters.     

Effect of Mars analogue dust deposition on the automated detection of calcite in visible/near-infrared spectra

We have developed an artificial neural net detector for use on board Mars rovers that correctly identifies calcite under Mars analogue dust (JSC Mars-1 regolith simulant) layers up to ∼100 μm thickness and 80% aerial coverage. Both the detector output and the band depth of the ∼2300 nm CO⁼₃ absorption are linearly related to the surface area of exposed calcite. This detector provides a means for rapid and robust automated recognition of calcite on Mars in areas of active aeolian erosion.     

Extragalactic integral field spectroscopy on the Gemini telescopes

We have been undertaking a programme on the Gemini 8‐m telescopes to demonstrate the power of integral field spectroscopy, using the optical GMOS spectrograph, and the new CIRPASS instrument in the near‐infrared. Here we present some preliminary results from 3D spectroscopy of extra‐galactic objects, mapping the emission lines in a 3CR radio galaxy and in a gravitationally lensed arc, exploring dark matter sub‐structure through observations of an Einstein Cross gravitational lens, and the star formation time‐scales of young massive clusters in the starburst galaxy NGC 1140. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)