Micrometeorite craters and related features on lunar rock surfaces

Craters in the 0.4 mm and larger size class were observed on six Apollo 12 whole rock surfaces (12017, 12021, 12038, 12047, 12051 and 12073). Craters on crystalline surfaces are characterized by a central, glass-lined cavity, a concentric zone of shock fractured, high albedo material and a concentric spallation area. The crater geometries observed are similar to craters produced on glasses and crystalline materials in the laboratory with projectile velocities exceeding 10 km/sec. The high projectile velocities required and the presence of a distinct demarcation line between cratered and uncratered surfaces on individual rocks indicate that most of the microcraters are produced by primary cosmic particles. These discrete impact events account for most of the erosion and fragmentation of lunar surface rocks.     

Sovereign rights and responsibilities: Applying public trust principles to the management of EEZ space and resources

Since the United States proclaimed its 200 nautical mile Exclusive Economic Zone in 1983, US agencies have given little attention to the need to develop effective management principles and strategies for the resources of this vast ocean area. Instead, they have relied upon existing programs and authorities to oversee the development of ocean energy and fisheries. This approach has been criticized by marine policy analysts because it perpetuates the existing, fragmented single-sector ocean regime characterized by inconsistent policies and endemic use conflicts.This paper proposes the adoption of certain principles deriving from the common law public trust doctrine in the management of EEZ resources and space. Historically, the public trust doctrine protected the public's rights and interests in nearshore resources and uses (commerce, navigation, and fishing). These traditional public rights were held by the crown or the government in trust for the people and could not be readily destroyed even though shorelands and coastal waters subject to the public trust might be conveyed into private ownership. In modern times the doctrine has been expanded in the United States to protect public rights in other uses and activities (e.g. conservation, scenic and ecological values, and preservation of open space and habitat) and extended geographically to apply to inland rivers, streams, and lakes.The public trust doctrine already applies in many states to the space, resources, and uses of the territorial sea. Because of the overlap of EEZ and territorial sea resources and uses, this paper considers the advantages of applying public trust principles and concepts to managing the EEZ. These principles include the need to preserve trust lands, waters, and resources for public use and benefit. The doctrine also provides a basis for distinguishing between, and ranking, public uses of trust resources, and imposes both substantive and procedural standards against which the conduct of the govermental trustees of trust, resources may be measured.The authors contrast the public trust doctrine with the ‘public trust’ deriving from the property clause of the US Constitution, and conclude that the broad discretion afforded federal officals under the latter is inconsistent with effective environmental management. Finally, the authors recommend a set of ‘presumptions’ derived from public trust principles that federal courts might follow to resolve serious EEZ space and resource-use conflicts.     

Burrow morphologies in north-central Pacific sediments

An examination of split core photographs from the north-central Pacific reveals the presence of three different burrow morphologies. Simple burrows occur throughout the region. Halo burrows are present in water deeper than 4,000 m (3,000 m along the equator) and removed from continental areas. Imbricate burrows are uncommon and have an irregular distribution. Organisms responsible for the burrows are interpreted as surface to near-surface feeders which do not penetrate deeply into the sediments. Thus, the zone of sediment mixing caused by burrowing ranges from 10 to 30 cm and averages 20 cm.     

Visualization of three-dimensional datasets

The effective visualization of three-dimensional (3d) datasets, both observationally and computationally derived, is an increasing problem in solar physics. We present here plots of computational data derived from the 3d reconstruction of the magnetic field of a loop system, rendered as anaglyphs. By combining images of the same 3d object from two slightly different angles a realistic and useful 3d effect is obtained, aiding data visualization. The application of the same technique to real solar data (such as from the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO)) is discussed.     

Heterogeneity in mycorrhizal inoculum potential of flood-deposited sediments

Riparian areas are diverse systems where flooding creates new sites for establishment of vegetation. Symbioses with soil microorganisms, such as mycorrhizal fungi, affect vascular plant growth and community composition. It is unknown, however, how mycorrhizal fungi are dispersed along rivers and what potential they have to inoculate roots of plants establishing on recently deposited sedimentary surfaces of flood plains. We measured AMF inocula in sediment deposited by an average spring flood along an expansive riverine flood plain in Montana, USA, to determine whether AMF inocula were present in sediments and what types of propagules (spores, hyphae, or colonized root fragments) contribute to AMF infectivity. Flood-deposited sediments contained sufficient inocula for AMF to colonize host plants (Sorghum sudanense) grown in a greenhouse, and both AMF hyphal lengths and spore densities were correlated with infectivity. Availability of mycorrhizal inocula, which is patchily distributed in this system, may lead to microsites that differ in ability to support establishment and growth of early-successional plants.     

A Widebinary Solar Companion as a Possible Origin of Sedna-like Objects

Sedna is the first inner Oort cloud object to be discovered. Its dynamical origin remains unclear, and a possible mechanism is considered here. We investigate the parameter space of a hypothetical solar companion which could adiabatically detach the perihelion of a Neptune-dominated TNO with a Sedna-like semimajor axis. Demanding that the TNO’s maximum value of osculating perihelion exceed Sedna’s observed value of 76 AU, we find that the companion’s mass and orbital parameters (m _c , a _c , q _c , Q _c , i _c ) are restricted to $$m_c>rapprox 5\hskip.25em\hbox{M}_{\rm J}\left(\frac{Q_c}{7850\hbox{ AU}} \frac{q_c}{7850\hbox{ AU}}\right)^{3/2}$$ during the epoch of strongest perturbations. The ecliptic inclination of the companion should be in the range $45{\deg}\lessapprox i_c\lessapprox 135{\deg}$ if the TNO is to retain a small inclination while its perihelion is increased. We also consider the circumstances where the minimum value of osculating perihelion would pass the object to the dynamical dominance of Saturn and Jupiter, if allowed. It has previously been argued that an overpopulated band of outer Oort cloud comets with an anomalous distribution of orbital elements could be produced by a solar companion with present parameter values $$m_c\approx 5\hskip.25em\hbox{M}_{\rm J}\left(\frac{9000\hbox{ AU}}{a_c}\right)^{1/2}.$$ If the same hypothetical object is responsible for both observations, then it is likely recorded in the IRAS and possibly the 2MASS databases.