Benthic marine litter in four Gulfs in Greece,Eastern Mediterranean; abundance,composition and source identification

The types, abundance, distribution and sources of benthic marine litter found in four Greek Gulfs (Patras, Corinth, Echinades and Lakonikos) were studied using bottom trawl nets. Mean distribution and weight densities range between 72–437 Item/km² and 6.7–47.4 kg/km². Litter items were sorted into material and usage categories. Plastic litter (56%) is the most dominant material category followed by metal (17%) and glass (11%). Beverage packaging (32%) is the dominant usage category followed by general packaging (28%) and food packaging (21%). Based on the typological results three dominant litter sources were identified; land-based, vessel-based and fishery-based. Application of factor analysis (R- and Q-mode) conducted on both material and usage litter datasets confirmed the existence of the three dominant litter sources. Q-mode analysis further resulted in the quantification of the litter sources; land-based ones provided the majority (69%) of the total litter items followed by vessel-based (26%) and fishery-based (5%) sources. Diverse environmental parameters influence significantly these amounts among the four Gulfs.     

How to build a continental scale fireball camera network

The expansion of the Australian Desert Fireball Network has been enabled by the development of a new digital fireball observatory based around a consumer digital camera. The observatories are more practical and much more cost effective than previous solutions whilst retaining high imaging performance. This was made possible through a flexible concurrent design approach, a careful focus on design for manufacture and assembly, and by considering installation and maintenance early in the design process. A new timing technique for long exposure fireball observatories was also developed to remove the need for a separate timing subsystem and data integration from multiple instruments. A liquid crystal shutter is used to modulate light transmittance during the long exposure which embeds a timecode into the fireball images for determining fireball arrival times and velocities. Using these observatories, the Desert Fireball Network has expanded to cover approximately 2.5 million square kilometres (around one third of Australia). The observatory and network design has been validated via the recovery of the Murrili Meteorite in South Australia through a systematic search at the end of 2015 and the calculation of a pre-atmospheric entry orbit. This article presents an overview of the design, implementation and performance of the new fireball observatories.     

Effects of sea states on seafloor compliance studies

Gas hydrates affect the bulk physical properties of marine sediments, in particular, elastic parameters. Shear modulus is an important parameter for estimating the distribution of hydrates in the marine sediments. However, S-wave information is difficult to recover without proper datasets. Seafloor compliance, the transfer function between pressure induced by surface gravity waves and the associated seafloor deformation, is one of few techniques to study shear modulus in the marine sediments. The coherence between recorded time series of displacement and pressure provides a measure of the quality of the calculated transfer function, the seafloor compliance. Thus, it is important to understand how to collect high coherence datasets. Here we conducted a 10-month pilot experiment using broadband seismic sensors and differential pressure gauges. We found that data collected in shallow water depth and during rough seas gave high coherence. This study is the first time long-term data sets have been employed to investigate seafloor compliance data quality and its dependence on sea state. These results will help designing future large-scale compliance experiments to study anomalously high shear moduli associated with the presence of gas hydrate or cold vents, or alternatively anomalously low shear moduli, associated with partial melt and magma chamber.     

Discovery of asteroid 1976 AA

Asteroid 1976 AA was discovered as a result of a continuing systematic search for planet-crossing asteroids. It is the first asteroid to be thoroughly investigated by means of photometry and radiometry on its discovery apparition. It is also the first asteroid found with a semimajor axis and period less than that of the Earth and the first Earth-crossing asteroid which does not cross the orbit of either Mars or Venus. We estimate that there might be several tens of objects to absolute magnitude 18, which are exclusively Earth crossing. Some of these objects might be exceptionally easy to reach by spacecraft.     

The discovery of 1982 DB,the most accessible asteroid known

A small Apollo object was found while photographing the split comet DuToit 2-Hartley on February 27/28, 1982. Designated 1982 DB, this Earth-crossing asteroid passed the Earth at a distance of 4.08 million km about 1 month prior to its discovery. Asteroid 1982 DB has been determined to be the most accessible near-Earth minor planet known. It provides many excellent opportunities for rendezvous and sample return missions, and a rare dual rendezvous mission with 1980 AA as the second target. For a mission to be realized, opportunities to observe 1982 DB during future apparitions must be taken.     

Social networks and undocumented Mozambican migration to South Africa

This paper analyses the social networks which facilitate and sustain undocumented migration from Mozambique to South Africa. A key contention is that the migrant social networks are not limited to a spatially bounded area; transcend geography, location and territory; can be considered as spatial conveyors of social capital; and operate transnationally at three different locations: in the sending communities, on borders and in the destination areas. In the sending communities, interpersonal relationships are based on bonds of kinship, and friendship through which the migrants get moral and material support for the movement. At the borders migrants establish connections with border agents, guides, and conveyors who support them in entering South Africa and provide transportation to their preferred destinations. At the destination areas the newcomers have also counted on the bonds of kinship and friendship among former immigrants, who assist them on their arrival with accommodation and food as well as in the process of getting jobs and documentation. In South Africa undocumented migrants were subjected to high levels of xenophobia, exploitation and deportation, structural, sociopolitical forces against which social networks are largely ineffective. However, through the social networks the undocumented Mozambican labour migration to South Africa has become a self-sustained circular process that is difficult to control.