Two major types of volcanic units, older regional plains and younger lobate plains, make up 50% of the surface of Venus and represent different epochs of volcanism. The abundance of impact craters partially embayed from the exterior by each of these two types of units permits the testing of the key points of the model of equilibrium resurfacing. The proportion of craters embayed by the older re...

Introduction: One of the major and outstanding problem in Venus geology is: Does Venus possess a non-basaltic crustal component which may be an analog to the continental crust of Earth [e.g. 1]? Detailed photogeologic analysis of plains units that make up the majority of the surface of Venus strongly suggests that the plains were formed by eruptions of low-viscosity lavas [2-4]. Such a morpholo...

One of the main factors of water erosion is the natural characteristics of the soil called "erodibility" or"detachability". The present study aims to analyze the variations of soil erodibility factor in different plains and thefactors related to it. Erodibility is one the key factors in some models of erosion and sediment such as Universal SoilLoss Equation (USLE), Revised USLE (RUSLE), and Mod...

Introduction: Observations made by the Opportunity rover during its traverse south from Eagle crater show that the hematite bearing plains are an aeolian lag deposit consisting of hematite spherules and basal-tic sand, along with a nanophase iron oxide bearing dust component, that has been worked into ripples [1,2,3]. The hematite spherules, which have weathered out of the sulfate rich outcrop ...

[1] Detailed mapping has revealed several stratigraphic components among lobate plains in the vicinity of Sekmet Mons volcano (44.5 N. lat., 240.5 long.), located on the northern lowland plains of Kawelu Planitia on Venus. Volcanic effusion events produced discrete lobate plains throughout the area. Superposition of flow margins between adjacent lobate plains components indicate that the effusi...

Restriction-endonuclease-site variation of mitochondrial DNA (mtDNA) was used to investigate patterns of geographic and phylogenetic divergence within the rodent genus Onychomys. Onychomys has occupied arid habitats in the western North American deserts, shrub-steppes, and grasslands since the late Tertiary. A phylogenetic analysis of the total mtDNA restriction-site variation throughout the ra...

This study examines the spatial evolution of drought severity within the contiguous United States during the first six months of average Great Plains-centered drought events. It identifies Great Plains-centered drought events from 1895-1989 based on the drought history of the North Central, South Dakota and Low Rolling Plains, Texas climatic divisions. Time series of warmand cold-season average...

Birds of the Northern Hemisphere often harbour the genetic signature of postglaciation expansion but analyses identifying the location of refugia and the directionality of expansions are rare. Here we explore the evolutionary history of yellow warbler lineages, focusing on how these lineages recolonized their current range. We genotyped samples from 696 yellow warblers via direct sequencing of ...

Analysis of local and regional stratigraphic relationships has permitted the assessment of the nature of tectonic structures and their distribution throughout the observed history of Venus, spanning the past several hundreds of millions of years. We find that shortening characteristic of intensely deformed tessera terrain gave way to widespread distributed fracturing and extension within the te...