Iron-magnesium silicate bioweathering on Earth (and Mars?)

We examined the common, iron-magnesium silicate minerals olivine and pyroxene in basalt and in mantle rocks to determine if they exhibit textures similar to bioweathering textures found in glass. Our results show that weathering in olivine may occur as long, narrow tunnels (1-3 microm in diameter and up to 100 microm long) and as larger irregular galleries, both of which have distinctive characteristics consistent with biological activity. These weathering textures are associated with clay mineral by-products and nucleic acids. We also examined olivine and pyroxene in martian meteorites, some of which experienced preterrestrial aqueous alteration. Some olivines and pyroxenes in the martian meteorite Nakhla were found to contain tunnels that are similar in size and shape to tunnels in terrestrial iron-magnesium silicates that contain nucleic acids. Though the tunnels found in Nakhla are similar to the biosignatures found in terrestrial minerals, their presence cannot be used to prove that the martian alteration features had a biogenic origin. The abundance and wide distribution of olivine and pyroxene on Earth and in the Solar System make bioweathering features in these minerals potentially important new biosignatures that may play a significant role in evaluating whether life ever existed on Mars.     

X-ray emission from cataclysmic variables

EXOSAT results on cataclysmic variables are reviewed. The long continuous X-ray observations afforded by this observatory, coupled with the sensitivity of its instruments to medium energy and very low energy X-rays, have enabled the rotational and orbital X-ray light curves of these stars to be measured in unprecedented detail. Examples are given of data on synchronously and asynchronously rotating magnetic systems, and on disc accreting stars. The impact of the new observations on our understanding of cataclysmic variables is discussed.     

Evidence for a Two-Stage Acceleration Process in Large Solar Energetic Particle Events

Using high-resolution mass spectrometers on board the Advanced Composition Explorer (ACE), we surveyed the event-averaged ∼0.1–60 MeV/nuc heavy ion elemental composition in 64 large solar energetic particle (LSEP) events of cycle 23. Our results show the following: (1) The Fe/O ratio decreases with increasing energy up to ∼10 MeV/nuc in ∼92% of the events and up to ∼60 MeV/nuc in ∼64% of the events. (2) The rare isotope ³He is greatly enhanced over the corona or the solar wind values in 46% of the events. (3) The heavy ion abundances are not systematically organized by the ion’s M/Q ratio when compared with the solar wind values. (4) Heavy ion abundances from C–Fe exhibit systematic M/Q-dependent enhancements that are remarkably similar to those seen in ³He-rich SEP events and CME-driven interplanetary (IP) shock events. Taken together, these results confirm the role of shocks in energizing particles up to ∼60 MeV/nuc in the majority of large SEP events of cycle 23, but also show that the seed population is not dominated by ions originating from the ambient corona or the thermal solar wind, as previously believed. Rather, it appears that the source material for CME-associated large SEP events originates predominantly from a suprathermal population with a heavy ion enrichment pattern that is organized according to the ion’s mass-per-charge ratio. These new results indicate that current LSEP models must include the routine production of this dynamic suprathermal seed population as a critical pre-cursor to the CME shock acceleration process.     

The Far Infrared Explorer (FIRE)

We describe the Far IR Explorer, a MIDEX-class orbital mission designed to survey the entire sky at millimeter and sub-millimeter wavelengths. The primary science goal of FIRE is to map the Cosmic Microwave Background with 20 resolution and 1 ppm precision. In addition, FIRE will measure diffuse radio and infrared emission from the Galaxy with unprecedented sensitivity, and will uniformly survey the entire sky to a limiting flux density of <100 mJy (3 ).     

Studying the evolution of the hot universe with the X-ray evolving universe spectroscopy mission – XEUS

Europe is one of the major partners building the International Space Station (ISS) and European industry, together with ESA, is responsible for many station components including the Columbus Orbital Facility, the Automated Transport Vehicle, two connecting modules and the European Robotic Arm. Together with this impressive list of contributions there is a strong desire within the ESA Member States to benefit from this investment by utilizing the unique capabilities of the ISS to perform world-class science. XEUS is one of the astronomical applications being studied by ESA to utilize the capabilities of the ISS. XEUS will be a long-term X-ray observatory with an initial mirror area of 6 m² at 1 keV that will be expanded to 30 m² following a visit to the ISS. The 1 keV spatial resolution is expected to be 2–5″ half-energy-width. XEUS will consist of separate detector and mirror spacecraft (MSC) aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting 0.1–2.5 keV sensitivity will then be 4 × 10⁻¹⁸ erg cm⁻² s⁻¹, around 200 times better than XMM-Newton, allowing XEUS to study the properties of the hot baryons and dark matter at high redshift.     

An EXOSAT observation of the peculiar X-ray binary 2S 0921-630 during optical eclipse

An x-ray observation of 2S 0921-630 has been made coincident with the time of optical eclipse of this 9-day binary. No significant reduction in X-ray flux is measured. This can be explained if the binary orbit is viewed almost exactly edge-on, so that the central X-ray emitting star is obscured by the accretion disk from direct view. The X-rays that are seen are scattered into the line of sight by material above and below the disk and the apparent size of the X-ray emission region is thus large compared to the size of the occulting star.     

Origin, Injection, and Acceleration of CIR Particles: Observations Report of Working Group 6

This report emphasizes new observational aspects of CIR ions revealed by advanced instruments launched on the Ulysses, WIND, SOHO, and ACE spacecraft, and by the unique vantage point of Ulysses which carried out the first survey of Corotating Interaction Region (CIR) properties over a very wide range of heliolatitudes. With this more complete observational picture established, this review is the basis to consider the status of theoretical models on origin, injection, and acceleration of CIR particles reported by Scholer, Mann et al. (1999) in this volume. This revised version was published online in August 2006 with corrections to the Cover Date.     

Special issue introduction: Approaching spatial uncertainty visualization to support reasoning and decision making

While research on uncertainty and decision-making has a long history across several disciplines, recent technological developments compel researchers to rethink how to best address and advance the understanding of how humans reason and make decisions under spatial uncertainty. This introduction presents a visual summary graphic to provide an overview of each article in this special issue. Upon viewing these visual summaries, the reader will find that each of these articles covers different topics in the uncertainty visualization domain, offering complementary research in this field. Extending this body of research and finding new ways to explore how these visualizations may help or hinder the analytical and reasoning process of humans continues to be a necessary step towards designing more effective uncertainty visualizations to support reasoning and decision-making.     

New atomic data for the FeXII coronal ion

Various FeXII spectroscopic lines in the UV and EUV range have been proved to be ideal diagnostic tools for measuring electron temperature, density and iron abundance in the solar corona. In the framework of the “IRON PROJECT” we have provided improved theoretical calculations of the atomic data required to analyse the intensity of these lines and to apply the results to SOHO (Solar Heliospheric Observatory) observations. Extensive configuration interaction and relativistic effects have been allowed for in the atomic structure computations which have provided energy levels and an extensive set of radiative data. The e-FeXII collisional problem has been tackled with the multichannel R-matrix method, a close-coupling calculation for the determination of electron impact collision strengths. Final results are presented for FeXII thermally averaged collision strengths, for fine-structure forbidden transitions within the ground configuration.     

The carbonaceous chondrites

The carbonaceous chondrites are a group of stony meteorites characterized by the presence of an appreciable amount of carbonaceous material other than free carbon (diamond and graphite). They have been divided into three subgroups known respectively as Type I, Type II, and Type III. Analyses of Type I meteorites show about 3–5% of carbon and 20% of combined water; they consist largely of hydrated magnesium-iron silicate, magnetite, and magnesium sulfate, contain no chondrules, and have a density about 2.2. Analyses of Type II meteorites show about 2–3% of carbon and 10–15% of combined water; they consist of a groundmass of hydrated magnesium-iron silicate enclosing chondrules of olivine and pyroxene which are almost iron-free, and have a density of 2.6–2.9. Analyses of Type III meteorites show about 0.5–2% of carbon and 2% combined water; they consist largely of olivine (often variable in composition, but averaging 30–40 mole per cent Fe₂SiO₄), with accessory pigeonite and sulfide minerals, and have a density about 3.4.The carbonaceous material and combined water in these meteorites are clearly of extraterrestrial origin, but their significance is not well understood. A biological origin has been claimed for some of the organic compounds on the basis of their composition, but this claim is the subject of considerable dispute. Microscopic objects with regular outline (organized elements) have been recognized in some of these meteorites; some investigators have claimed these to be extraterrestrial fossils, others have ascribed them to terrestrial contamination or considered them to be crystals or crystal aggregates of non-biological origin.