Lithopanspermia in Star Forming Clusters

This paper considers the lithopanspermia hypothesis in star forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to the field) due to the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed and number of members in the birth aggregate. The odds of any given ejected meteroid being recaptured by another solar system are relatively low. Because the number of ejected rocks per system can be large, virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that several million rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life bearing rocks is expected to occur 10 -- 16,000 times per cluster (under favorable conditions), depending on the ejection speeds. Only a small fraction of the captured rocks impact the surfaces of terrestrial planets, so that only a few lithopanspermia events are expected (per cluster).Comment: 27 pages including 5 figures; accepted to Astrobiolog

Provenance of sedimentary rocks

Understanding the origins, or provenance, of a sedimentary deposit is an important aspect of geology. Sedimentary rocks are derived from the erosion of other rocks and thus provide important records of the geological environment at the time they were deposited. Some minerals found in sedimentary rocks, such as zircon particles, can be dated using uranium-lead techniques to trace the age of their parent rock thus providing useful information about the geological environment. Statistical and mathematical analyses that can assist in the analysis of the distribution of ages of the zircon crystals are examined. Methods of defining a difference between the distributions of ages found in rock samples are proposed, and demonstrated in the division of multiple rock samples into clusters of similar types. A test for the existence of a cluster is developed, and statistics for comparing different rock samples examined. Estimating an accurate age for the sedimentary deposit itself proves to be difficult unless prior distributions providing significant extra information are available

A survey of lunar rock types and comparison of the crusts of earth and moon

The principal known types of lunar rocks are briefly reviewed, and their chemical relationships discussed. In the suite of low-KREEP highland rocks, Fe/(Fe + Mg) in the normative mafic minerals increases and the albite content of normative plagio-clase decreases as the total amount of normative plagioclase increases, the opposite of the trend predicted by the Bowen reaction principle. The distribution of compositions of rocks from terrestrial layered mafic intrusives is substantially different: here the analyses fall in several discrete clusters (anorthositic rocks, norites, granophyres and ferrogabbros, ultramafics), and the chemical trends noted above are not reproduced. It is suggested that the observed trends in lunar highland rocks could be produced by crystal fractionation in a deep global surface magma system if (1) plagiociase tended to float, upon crystallization, and (2) the magma was kept agitated and well mixed (probably by thermal convection) until crystallization was far advanced and relatively little residual liquid was left. After the crustal system solidified, but before extensive cooling had developed a thick, strong lithosphere, mantle convection was able to draw portions of the lunar anorthositic crust down into the mantle

XCBC and XNIT - tools for cluster implementation and management in research and training

The Extreme Science and Engineering Discovery Environment has created a suite of software designed to facilitate the local management of computer clusters for scientific research and integration of such clusters with the US open research national cyberinfrastructure. This suite of software is distributed in two ways. One distribution is called the XSEDE-compatible basic cluster (XCBC), a Rocks Roll that does an “all at once, from scratch” installation of core components. The other distribution is called the XSEDE National Integration Toolkit (XNIT), so that specific tools can be downloaded and installed in portions as appropriate on existing clusters. In this paper, we describe the software included in XCBC and XNIT, and examine the use of XCBC installed on the LittleFe cluster design created by the Earlham College Cluster Computing Group as a teaching tool to show the deployment of XCBC from Rocks. In addition, the demonstration of the commercial Limulus HPC200 Deskside Cluster solution is shown as a viable, off-the-shelf cluster that can be adapted to become an XSEDE-like cluster through the use of the XNIT repository. We demonstrate that both approaches to cluster management – use of SCBC to build clusters from scratch and use of XNIT to expand capabilities of existing clusters – aid cluster administrators in administering clusters that are valuable locally and facilitate integration and interoperability of campus clusters with national cyberinfrastructure. We also demonstrate that very economical clusters can be useful tools in education and research.This document was developed with support from National Science Foundation (NSF) grant OCI-1053575. The LittleFe project has been funded in part by a grant from Intel, Inc. to Charlie Peck as well as NSF grants 1258604 and ACI-1347089. This research has also been supported in part by the Indiana University Pervasive Technology Institute, which was established with a major grant from the Lilly Endowment, Inc

Xenocryst assimilation and formation of peritectic crystals during magma contamination: An experimental study

International audienceContamination of magmas by country rocks may contribute xenoliths and xenocrysts to the magma, but also melt and peritectic crystals that form through incongruent melting or dissolution of the original contaminants. Identifying contaminant-derived peritectic crystals and former melt components in igneous rocks is particularly challenging, but also particularly important, because their assimilation significantly affects melt composition and magma temperature. To facilitate the identification of peritectic crystals in igneous rocks, the aim of this study was to experimentally control partial assimilation of xenocrysts and examine the formation, textures, and composition of resulting peritectic crystals. Our experiments mimic contaminant melting and contamination of a partially crystallized basaltic andesite by melanorite- and monzodiorite-derived xenocrysts and micro-xenoliths. Micro-xenoliths and xenocrysts partially survive assimilation, and yet peritectic crystals form ~ 1/3 of all solid contaminants. Anhydrous xenocrysts either develop laterally continuous, subhedral to euhedral, and inclusion-poor overgrowths, or progressively decompose. Hydrous and partially altered xenocrysts decompose to peritectic crystals. The peritectic crystals form clusters of subhedral to euhedral, randomly-oriented olivine, clinopyroxene, olivine–plagioclase, and olivine–plagioclase–clinopyroxene that texturally resemble primary magmatic crystals. We propose that natural peritectic crystals with short residence times form clusters of one or more minerals with textures as those of our experiments, and that peritectic crystals with longer residence times likely anneal to subhedral or euhedral single crystals or coarse-grained mineral clusters. They hold crucial evidence for largely assimilated country-rock components and estimates of open-system magma evolution, but the longer their magma residence time the more easily they are overlooked

Polyhedral colloidal `rocks': low-dimensional networks

We introduce a model system of anisotropic colloidal `rocks'. Due to their shape, the bonding introduced via non-absorbing polymers is profoundly different from spherical particles: bonds between rocks are rigid against rotation, leading to strong frustration. We develop a geometric model which captures the essence of the rocks. Experiments and simulations show that the colloid geometry leads to structures of low fractal dimension. This is in stark contrast to gels of spheres, whose rigidity results from locally dense regions. At high density the rocks form a quasi one-component glass

Damage-cluster distributions and size effect on strength in compressive failure

We investigate compressive failure of heterogeneous materials on the basis of a continuous progressive damage model. The model explicitely accounts for tensile and shear local damage and reproduces the main features of compressive failure of brittle materials like rocks or ice. We show that the size distribution of damage-clusters, as well as the evolution of an order parameter, the size of the largest damage-cluster, argue for a critical interpretation of fracture. The compressive failure strength follows a normal distribution with a very small size effect on the mean strength, in good agreement with experiments