Hydrothermal Alteration of Ultramafic Rocks in Ladon Basin, Mars - Insights From CaSSIS, HiRISE, CRISM, and CTX

The evolution of the Ladon basin has been marked by intense geological activity and the discharge of huge volumes of water from the Martian highlands to the lowlands in the late Noachian and Hesperian. We explore the potential of the ExoMars Trace Gas Orbiter/Color and Stereo Surface Imaging System color image data set for geological interpretation and show that it is particularly effective for geologic mapping in combination with other data sets such as HiRISE, Context, and Compact Reconnaissance Imaging Spectrometer for Mars. The study area displays dark lobate flows of upper Hesperian to early Amazonian age, which were likely extruded from a regional extensional fault network. Spectral analysis suggests that these flows and the underlying rocks are ultramafic. Two distinct altered levels are observed below the lobate flows. The upper, yellow-orange level shows hundreds of structurally controlled narrow ridges reminiscent of ridges of listwanite, a suite of silicified, fracture-controlled silica-carbonate rocks derived from an ultramafic source and from serpentine. In addition to serpentinite, the detected mineral assemblages may include chlorite, carbonates, and talc. Kaolin minerals are detected in the lower, white level, which could have formed by groundwater alteration of plagioclase in the volcanic pile. Volcanism, tectonics, hydrothermal activity, and kaolinization are interpreted to be coeval, with hydrothermal activity and kaolinization controlled by the interactions between the aquifer and the hot, ultramafic lobate flows. Following our interpretations, East Ladon may host the first listwanite ridges described on Mars, involving a hydrothermal system rooted in a Hesperian aquifer and affecting ultramafic rocks from a magmatic source yet to be identified

CP Studies and Non-Standard Higgs Physics

There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. These non-standard Higgs scenarios have important implications for collider physics as well as for cosmology, and understanding their phenomenology is essential for a full comprehension of electroweak symmetry breaking. This report discusses the most relevant theories which go beyond the Standard Model and its minimal, CP-conserving supersymmetric extension: two-Higgs-doublet models and minimal supersymmetric models with CP violation, supersymmetric models with an extra singlet, models with extra gauge groups or Higgs triplets, Little Higgs models, models in extra dimensions, and models with technicolour or other new strong dynamics. For each of these scenarios, this report presents an introduction to the phenomenology, followed by contributions on more detailed theoretical aspects and studies of possible experimental signatures at the LHC and other colliders.Comment: Report of the CPNSH workshop, May 2004 - Dec 2005, 542 pages. The complete report as well as its individual chapters are also available from http://kraml.home.cern.ch/kraml/cpnsh/report.htm

A Numerical Model for the Differentiation of Enceladus

The past close encounters of the CASSINI spacecraft in the Saturnian system have provided unprecedented insight into the geodynamics of small and mid-sized icy satellites. The newly determined average density and equilibrium shape of the most enigmatic satellite Enceladus implies that its interior is composed of ice and rock at nearly equal shares and at least partially differentiated. Characteristic features at the surface of Enceladus further suggest that this satellite has been geologically active during the recent past. Gaseous plumes of water vapor and nitrogen as recently observed by the Cassini spacecraft indicate that Enceladus is still active even at the present time. In the present study, we consider a plausible range of interior structure models that satisfy Enceladus’ average density to investigate under which conditions early and/or late differentiation could have run to completion. Our 2D-finite-element numerical model describes viscous Stokes flow and simulates the sinking of numerous rock particles through viscous water ice. The model aims at determining the timescales at which the internal differentiation of small and mid-sized icy bodies would proceed. Depending on rheology or particle size we found a wide range of possible differentiation times for Enceladus. Corresponding to recent convection models, which may explain the heat source for the plume activity, or tidal dissipation models, we can constrain our model variety

Sinking FE-Diapirs: A model for planetary core formation

The formation of a planetary core in terrestrial planets ist still not well understood. However, core formation is generally thought to have occured concurrently with or soon after planet formation and, therefore, determines the initial conditions for thermal evolution models to a significant extent. A possible scenario for the formation of a planetary core is the settling of iron melt diapirs in a solid matrix. Since the iron has a higher density than the underlying planetary mantle, it may sink in a Rayleigh-Taylor instability. Because the viscosity contrast is essentially infinite, the sinking melt diapirs will take the shape of a sphere. The size of the diapirs can be approximated using a wavelength analysis of the Rayleigh-Taylor instability. we have modelled the falling of an iron sphere through a silicate mantle with temperatures and stress dependent viscosity using a 2-D finite element software package (FEATFLOW) written by S. Turek. From these models the effect of the temperature and stress dependence of the silicate rock viscosity on the sinking rate can be estimated. Our models show that the implementation of a viscosity reducing rheology can easily reduce the drag force by several orders of magnitude. Equating the drag force with the body force woll allow to determine the terminal velocity of the diapir. In our models a viscosity contrast of 10_3 yields a terminal velocity which points to a core formation time of approximately 30 Ma for the Earth. The results are consistent with differentiation times of iron an sd silicate phases derived from isotope measurements in cosmochemistry

Thermal Evolution of the Moon and a Possible Explanation for Deep Moonquakes

The Moonquakes were first detected by the sensitive seismometers placed during the Apollo missions at four relatively densely spaced locations on the lunar surface. Because winds, sea waves, and road traffic do not shake the Moon, the lunar seismometers can detect quite weak Moonquakes even at 1000 km depth. The sheer existence of moonquakes is somewhat surprising, since the Moon is believed to be geologically inactive by today. In contrast to the Earth, were plate motions cause dislocations and build up stresses, which are released through earthquakes, the Moon’s interior is significantly less active. However, if no interior processes were going on, no moonquakes could be detected. The physical cause of both deep and shallow moonquakes remains unresolved today because it is difficult to reconcile them with models of the lunar thermal evolution and mantle flows. The monthly and bi–weekle periods in quake frequency hint to a connection to tidal deformation, may be as a cause, or just a trigger. The depth range of 930 to 960 km, which is compatible with most of the deep quakes, should also gibe a hint. We have set up a three dimensional thermal convection model to investigate the thermal evolution of the Moon.We find that the Moons history is dominated by the growth of a massive lithosphere, which constricts the effective transport of heat through convection due to its stiffness. Heat can then only be transported through thermal conduction. Henceforth the lithosphere serves as an insulating shell and keeps the lunar interior relatively warm. Although the hot thermal boundary at the core mantle boundary breaks down after about 0.5 Ga, the Moon’s lower mantle is being heated internally due to radioactive heat sources. The convection velocities become smaller with ongoing time, but even today a slight movement in the lower mantle is present. Although the strain rate build up due to convection might not be efficient enough to release moonquakes from the detected magnitude, the addition of monthly tidal forces from the Earth might be sufficient. The slow convection in the present lunar interior could then be understood as ’baseline’ strain for tidally triggered moonquakes