The geology of Australian Mars analogue sites

Australia has numerous landforms and features, some unique, that provide a useful reference for interpreting the results of spacecraft orbiting Mars and exploring the martian surface. Examples of desert landforms, impact structures, relief inversion, long-term landscape evolution and hydrothermal systems that are relevant to Mars are outlined and the relevant literature reviewed. The Mars analogue value of Australia's acid lakes, hypersaline embayments and mound spring complexes is highlighted along with the Pilbara region, where the oldest convincing evidence of life guides exploration for early life on Mars. The distinctive characteristics of the Arkaroola Mars Analogue Region are also assessed and opportunities for future work in Australia are outlined.     

The Australian Ska New Technology Demonstrator Program

I present a brief overview of the SKA projects conducted under the Australian Major National Research Facilities program, and describe the largest of these projects – the SKA New Technology Demonstrator. The goal of this project is to construct an SKA technology demonstrator which will explore and evaluate a number of SKA technologies in a remote radio-quiet environment, while also achieving a restricted set of key science goals. Infrastructure and access to back-end facilities will also be provided for other international SKA groups who wish to evaluate or demonstrate technologies, or conduct science experiments, in a remote, radio-quiet, environment.     

Australian research effort for the SKA

The next generation radio telescope being planned is the Square Kilometer Array (SKA): an international project which is currently in the research and development phase. Australia is one of the partner countries in the SKA consortium; here I describe some of the SKA research being undertaken in Australia. This revised version was published online in July 2006 with corrections to the Cover Date.     

Testing technologies and strategies for exploration in Australian Mars analogues: A review

Australia is an ideal testing ground in preparation for the robotic and human exploration of Mars. Numerous sites with landforms or processes analogous to those on Mars are present and the deserts of central Australia provide a range of locations for free-ranging Mars analogue mission simulations. The latest developments in testing technologies and strategies for exploration in Australian Mars analogues are reviewed. These include trials of analogue space suits based on mechanical counter pressure technology and the development of an analogue, crewed, pressurized rover for long-range exploration. Field science activities and instrumentation testing relevant to robotic and future crewed missions are discussed. Australian-led human factors research undertaken during expeditions to Mars analogue research stations and expeditions to Antarctica are also reviewed. Education and public outreach activities related to Mars analogue research in Australia are also detailed.     

A study of “chorus” observed at Australian stations

The very-low-frequency emission known as “chorus” has been studied for four Australian recording stations. The phenomenon exhibits a maximum of occurrence at about geomagnetic latitude 60° and occurs only about one-tenth as frequently at geomagnetic latitude 45°. It was never definitely observed at geomagnetic latitude 35°. Marked diurnal variations are present with morning peaks for all stations and also an evening peak at Adelaide and Hobart. Analysis of the diurnal variations suggests that two different mechanisms are involved. The average strength of chorus increases with increasing value of K-index at lower latitude stations and shows a maximum at moderate values of the index for geomagnetic latitude 61°. This is interpreted as meaning that the region of maximum average-chorus-strength moves towards lower latitudes at times of magnetic disturbance.     

Paleoclimate implications of high latitude precession-scale mineralogic fluctuations during early Oligocene Antarctic glaciation: the Great Australian Bight record

Sediments from ODP Site 1128 in the Great Australian Bight record isotopic and mineralogic variations corresponding to orbital parameters and regional climate change during the early Oligocene climate transition and Oi1 glacial event. Bulk carbonate stable isotope analyses reveal prominent positive oxygen and carbon isotope shifts related to the inferred major increase in glaciation at approximately 33.6 to 33.48 Ma. The oxygen isotope excursion corresponds to a prolonged period of low eccentricity, suggesting ice-sheet growth during low seasonality conditions. The clay mineralogy is dominated by smectite throughout. The exclusive occurrence of highly crystalline smectite from 33.6 to 33.5 Ma suggests the occurrence of explosive volcanism that correlates with the positive oxygen isotope shift. The dominance of mixed-layer smectite from 33.5 to 33.4 Ma and an increase in illite following 33.4 Ma indicates a transition from cool, wet conditions to cool, dry conditions over Australia during the Oi1 glaciation. Clay mineralogy and carbonate percentages reveal precession-scale oscillations during the Oi1 event. Kaolinite varies inversely with smectite and percent carbonate. Variations in precipitation and runoff, and wind velocities during southern hemisphere summer perihelion and high eccentricity intervals may account for the precession-scale oscillations.     

The Effect Of Zonal Tides On The DynamicalEllipticity Of The EarthAnd Its Influence On The Nutation

In this paper, the expressions of variations of the dynamical ellipticity and the principal moments of inertia due to the deformations produced by the zonal part of the tidal potential are obtained. Starting from these expressions, we have studied from equations related to Hamiltonian theory, their effects on the nutation and finally we have evaluated numerically such influences, with a level of truncation at 0.1 μas. Thus we have shown that some coefficients are quite large with respect to the usual accuracy of up-to-date observations. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Availability of Phosphorus in The Bacterial Model of The Interstellar Grains

It is shown that phosphorus availability is in close balance with the phosphorus requirement of the bacterial grain model. This correspondence, which would be fortuitous if the interstellar grains were of inorganic origin, points to the correctness of the biological model. This revised version was published online in July 2006 with corrections to the Cover Date.     

The lunar exosphere: The sputtering contribution

We have extended our Monte Carlo model of exospheres [Wurz, P., Lammer, H., 2003. Icarus 164 (1), 1-13] by treating the ion-induced sputtering process from a known surface in a self-consistent way. The comparison of the calculated exospheric densities with experimental data, which are mostly upper limits, shows that all of our calculated densities are within the measurement limits. The total calculated exospheric density at the lunar surface of about 1×¹⁰⁷ m⁻³ as result of solar wind sputtering we find is much less than the experimental total exospheric density of about ¹⁰¹² m⁻³. We conclude that sputtering contributes only a small fraction of the total exosphere, at least close to the surface. Because of the considerably larger scale height of atoms released via sputtering into the exosphere, sputtered atoms start to dominate the exosphere at altitudes exceeding a few 1000 km, with the exception of some light and abundant species released thermally, e.g. H₂, He, CH₄, and OH. Furthermore, for more refractory species such as calcium, our model indicates that sputtering may well be the dominant mechanism responsible for the lunar atmospheric inventory, but observational data does not yet allow firm conclusions to be drawn.     

The Large-Scale Structures Of The Quiet-Sun Photosphere

The area density distribution of bright photospheric points on the quiet solar surface is not uniform. The distributions show some considerable pecularities. This article is a study of their characteristics during the four last solar activity minima in Bartels longitudes. The bright-photospheric-point distributions on the equatorial and polar solar surface exhibit a type of sectoral-hemispherical asymmetry. The density distributions vary a lot, but have the tendency to alternate with a period of 22 years. The phase origin of density concentrations is the first structural pecularity of the photospheric point distributions. The simultaneous appearance of bright regions on the equatorial and polar solar surface in spatial antiphase lock and, at the same time, the half-phase shift (11 years) between polar and equatorial cycles suggests a synchronous distribution process. This time synchronization is the second important pecularity of density concentrations. Therefore, the solar activity organization in minima occurs according to strict synchronization, like being under the control of a very precise clock.     

Primordial Angular Gradients In The Temperature Of The CMBR And The Density Fluctuations

A non-conventional approach is developed and used to find the primordial angular gradient, anisotropy, of the temperature of the Cosmic Microwave Background Radiation (CMBR), as well as the density fluctuations in an adiabatic expanding universe. The obtained results is a consequence of considering the magnitude of the angular gradient of the temperature of the CMBR as a constant function with respect to the proper time of the spatially perturbed FRW expanding universe. This revised version was published online in July 2006 with corrections to the Cover Date.     

On The Origin of The High-Perihelion Scattered Disk: The Role of The Kozai Mechanism And Mean Motion Resonances

We study the transfer process from the scattered disk (SD) to the high-perihelion scattered disk (HPSD) (defined as the population with perihelion distances q > 40 AU and semimajor axes a>50 AU) by means of two different models. One model (Model 1) assumes that SD objects (SDOs) were formed closer to the Sun and driven outwards by resonant coupling with the accreting Neptune during the stage of outward migration (Gomes 2003b, Earth, Moon, Planets 92, 29–42.). The other model (Model 2) considers the observed population of SDOs plus clones that try to compensate for observational discovery bias (Fernández et al. 2004, Icarus , in press). We find that the Kozai mechanism (coupling between the argument of perihelion, eccentricity, and inclination), associated with a mean motion resonance (MMR), is the main responsible for raising both the perihelion distance and the inclination of SDOs. The highest perihelion distance for a body of our samples was found to be q = 69.2 AU. This shows that bodies can be temporarily detached from the planetary region by dynamical interactions with the planets. This phenomenon is temporary since the same coupling of Kozai with a MMR will at some point bring the bodies back to states of lower-q values. However, the dynamical time scale in high-q states may be very long, up to several Gyr. For Model 1, about 10% of the bodies driven away by Neptune get trapped into the HPSD when the resonant coupling Kozai-MMR is disrupted by Neptune’s migration. Therefore, Model 1 also supplies a fossil HPSD, whose bodies remain in non-resonant orbits and thus stable for the age of the solar system, in addition to the HPSD formed by temporary captures of SDOs after the giant planets reached their current orbits. We find that about 12 – 15% of the surviving bodies of our samples are incorporated into the HPSD after about 4 – 5 Gyr, and that a large fraction of the captures occur for up to the 1:8 MMR (a ⋍ 120 AU), although we record captures up to the 1:24 MMR (a ≃ 260 AU). Because of the Kozai mechanism, HPSD objects have on average inclinations about 25°–50°, which are higher than those of the classical Edgeworth–Kuiper (EK) belt or the SD. Our results suggest that Sedna belongs to a dynamically distinct population from the HPSD, possibly being a member of the inner core of the Oort cloud. As regards to 2000 CR₁₀₅ , it is marginally within the region occupied by HPSD objects in the parametric planes (q,a) and (a,i), so it is not ruled out that it might be a member of the HPSD, though it might as well belong to the inner core.     

The Optical Layout Of The HEGRA Cherenkov Telescopes

The raytracing technique was used to derive a suitable design for the HEGRA system of Cherenkov telescopes, which is at present commissioned at La Palma. The reflectors with a diameter of 3.9 m consist of 30 spherical mirrors with focal lengths in the range of 4.88 – 4.94 m. It is shown that 93% of the photons from the Cherenkov light emitted by an extended air shower are contained in the camera pixels, 0.25° in diameter, for the full field of view of = ± 2.5°. The optical performance of the HEGRA design is compared to other layouts.     

度盘对径改正的几何原理

立足于实测，用平面几何的方法讨论子午环度盘对径改正的几何原理与测量设备，测量数据之间的关系     

The ``Great Debate': The case for AGNs

We summarize the evidence from multiwavelength observations that the dominant power source in the majority of ultraluminous infrared galaxies (ULIGs) may be an active galactic nucleus (AGN). In the broader context of the debate, we also show that –- 1. ULIGs are indeed a key stage in the transformation of merging gas-rich disks into ellipticals,2. ULIGs are plausibly the precursors of quasi-stellar objects (QSOs), and 3. ULIGs do appear to be local templates of the high luminosity tail of major gas-rich mergers at z 1–4.     

计算平均中子辐照量的新公式

根据13C辐射燃烧的低质量AGB(Asymptotic Giant Branch)星s-过程核合成模型,考察了氦壳层核合成区域中子辐照量分布(以下简称DNE)的特点.结果表明,该模型的DNE同以前的对流核合成模型一样仍然非常接近指数分布,但是每个脉冲的中子辐照量△r和平均中子辐照量To之间的关系却不再是To=-△T/lnr,而近似为To=-△r/ln{q[1.0020 0.6602(r-q) 4.6125(r-q)2-10.8962(r-q)3 13.9138(r-q)4]}(r为重叠因子, q为13C壳层占氦壳层的质量比例).该式从DNE角度将辐射s-过程恒星模型和经典模型统一起来.     

The complexH-function

The properties of theH -function for the complex albedo of single scattering are studied. It is shown that basically all the formulae derived for the real albedo of single scattering can be transferred into the complex-plane without alteration.An iterational procedure to find the numerical values of the complexH - function is set up. Some examples of the numerical results are given in the figures.