Tuesday 28 February 2017

Neptune reaches Solar Conjunction.

The planet Neptune will reach Solar Conjunction (i.e. was directly on the other side of the Sun from the Earth) at  2.46 am GMT on Thursday 2 March 2017. This means that it will both be at its furthest from the Earth this year, about 30.94 AU (30.94 times the average distance between the Earth and the Sun, or about 4 332 000 000 km), and completely obscured by the Sun.

Neptune imaged from the Voyager 2 spacecraft in August 1989. NASA/JPL/Caltech.

Since the orbits of the planets are not in complete alignment, Neptune will not be completely behind the Sun at conjunction but passes within 50 arc minutes of it (the sky, imagined as a sphere around the Earth, is split into 360 degrees, and each of these is split into 60 arc minutes), though this still means it cannot be observed due to the glare of the Sun.

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Monday 27 February 2017

Elephas cf. E. planifrons: A new Elephant specimen from the Early Pleistocene of Jammu and Kashmir, India.

The Indian Elephant, Elephas maximus, is the last surviving member of a genus that ranged from East Africa to Sulawesi in the Pliocene. Four members of this genus are known in the fossil record of India, Elephas maximus plus the Pliocene Elephas planifrons and Elephas hysudricus and the Pleistocene Elephas namadicus (sometimes placed in the genus Palaeoloxodon, along with the extinct European Straight-tusked Elephant). However there is also a large collection of Elephant remains collected from the Plio-Pleistocene Siwalik deposits of Jammu and Kashmir by the Geological Survey of India, many of which have never been described, making it possible that the full history of the group that is not understood.

In a paper published in the journal Vertebrata PalAsiatica on 1 December 2016, Som Nath Kundal, Gyan Bhadur and Sandeep Kumar of the Department of Geology of the University of Jammu describe a partial tooth assigned to the genus Elephas from the Early Pleistocene Siwalik deposits of Jammu and Kashmir.

The specimen comprises a single partial third molar with broken roots obtained from a mudstone horizon underlying a volcanic ash layer in the Nagrota Formation from a river cutting close to the village of Nangal, 15 km northwest of Samba city. The volcanic ash layer has been dated to 2.48 million years ago, making it Early Pleistocene in origin.

Left M3 of Elephas sp. from Nangal in Jammu and Kashmir. (A) Occlusal view; (B) labial view; (C) lingual view. Kundal et al. (2016).

Kundal et al. carried out a morphometric analysis (a tool used by palaeontologists, archaeologists, anthropologists and forensic pathologists to analyse and compare specimens) on the tooth, comparing it to the four Elephas species known from India, from which they conclude that the specimen falls within the range of Elephas planifrons, a species previously known from the Pliocene only (3.6 to 2.6 million years ago), extending the range of this species into the Early Pleistocene.

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Asteroid 2017 DB passes the Earth.

Asteroid 2017 DB passed by the Earth at a distance of 700 400 km (1.82 times the average distance between the Earth and the Moon, 0.47% of the average distance between the Earth and the Sun), slightly before 4.35 pm GMT on Monday 20 February 2017. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2017 DB has an estimated equivalent diameter of 7-24 m (i.e. it is estimated that a spherical object with the same volume would be 7-24 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 37 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2017 DB. Minor Planet Center.

2017 DB was discovered on 16 February 2017 (four days before its closest approach to the Earth) by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation 2017 DB implies that the asteroid was the second object (object B) discovered in the second half of February 2017 (period 2017 D).

2017 DB has a 453 day orbital period and an eccentric orbit tilted at an angle of 7.01° to the plane of the Solar System, which takes it from 0.86 AU from the Sun (i.e. 86% of he average distance at which the Earth orbits the Sun) to 1.44 AU from the Sun (i.e. 1.44% of the average distance at which the Earth orbits the Sun, slightly inside the orbit of the planet Mars). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that close encounters between the asteroid and Earth are common, with the last having occurred in August 2012 and the next predicted in September this year. 

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Poropoea africana: A new species of Trichogrammatid Wasp from Gabon.

Trichogrammatid Wasps are among the smallest of Insects, with adults often smaller than a millimetre in length. They are parasitiods, with a larval stage that grows inside the eggs of other Insects, typically Beetles. In many species the males never emerge, mating with their own sisters within the egg, The adults are poor fliers, and largely just drift on winds, eventually settling and seeking eggs in which to deposit their larvae on foot. Members of the genus Poropoea are known from across Eurasia and North America, with some species known from Africa and Madagascar. They target Leaf-rolling Weevils, Attelabidae, which are often serious agricultural pests, which opens the possibility of using these Wasps as biological control agents.

In a paper published in the journal ZooKeys on 23 February 2017, Stefania Laudonia and Gennaro Viggiani of the Department of Agriculture at the University of Naples Federico II and Silvano Biondi of Vicenza, describe a new species of Trichogrammatid Wasp from the Ivindo National Park in Ogooué-Ivindo Province in north-eastern Gabon.

The new species is named Poropoea africana, in reference to the continent where it was found. It is described from two adult females that emerged from the eggs of the Weevil species Paratomapoderus brachypterus. These were 1.18 mm in length and black in colour with red eyes and yellow markings on their limbs. 

Poropoea africana, female specimen. Laudonia et al. (2017).

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Persistent organic pollutants in animals in the deepest ocean trenches.

The presence of man-made chemicals is known to be a problem in a wide variety of environments, not just locations where Humans are present, but in remote areas such as the Arctic and High Himalayas. Such pollution in the world’s oceans is of particular concern, with visible concentrations of plastics on the ocean gyres and remote areas of the seafloor, and man-made chemicals, many with known ill-effect, recorded in a wide variety of marine organisms, including many species that form part of our own diet. The only areas where such pollutants have not been found are the deep ocean trenches that form in the subduction zones where one tectonic plate is pushed under another, though this is not evidence of actual absence, as these areas have not to date been sampled for such chemicals.

In a paper published in the journal Nature Ecology & Evolution on 13 February 2017, Alan Jamieson of the Oceanlab of the Institute of Biological and Environmental Sciences at the University of Aberdeen and the School of Marine Science and Technology at Newcastle University, Tamas Malkocs and Stuart Piertney of the Institute of Biological and Environmental Sciences at the University of Aberdeen, Toyonobu Fujii, also of the Oceanlab of the Institute of Biological and Environmental Sciences at the University of Aberdeen, and Zulin Zhang of Environmental and Biochemical Sciences at The James Hutton Institute, describe the results of a study that looked for two persistent organic pollutants in benthic Amphipod Crustaceans collected from the Mariana and Kermadec Trenches in the Pacific.

The Mariana Trench in the North Pacific is considered to be the deepest point in all the world’s oceans, and is a highly oligotrophic (low nutrient) environment, while the Kermadec Trench of the South Pacific is only slightly shallower and is more eutrophic (i.e. more nutrients are available). Amphipods were collected from both trenches using traps deployed by deep sea landers. Two species of Amphipods, Hirondellea dubia and Bathycallisoma schellenbergi, were collected from the Kermadec Trench at depths of between 7227 and 10 000 m, while a single species, Hirondellea gigas, was collected from the Mariana Trench at depths of between 7841 and 10 250 m.

Specimens of Hirondellea gigas, an Amphipod Crustacean from the Mariana Trench. Alan Jamieson.

These were tested for two persistent organic pollutants known to bioaccumulate in food chains, being absorbed by organisms close to the bottom and becoming more concentrated with each step up the chain. These were polychlorinated biphenyls (PCBs), which were used in the manufacture of electronic goods between the 1930s and 1970s, and polybrominated diphenyl ethers (PBDEs), which are used as flame retardants. Both are extremely hard to break down in natural environments, and have previously been recorded from coastal sediments, open ocean waters and the polar regions.

Both PCBs and PBDEs were present in the majority of samples from both locations. PCBs were found in Amphipods from the Mariana Trench at concentrations of 147.3-905 nanograms per gram, and in the Kermadec Trench at concentrations of 18.03-42.85 in the Kermadec, while PBDEs were present at concentrations of 5.82-28.93 in the Mariana Trench and 13.75-31.02 in the Kermadec Trench. There was no clear correlation between depth and pollutant concentration, though in both locations the highest chemical concentrations were found in Amphipods captured near the shallower end of the range, at 7841 m in the Mariana Trench and 7227 in the Kermadec Trench.

The PCB levels in the Mariana Trench were notably higher than those in the Kermadec, and indeed in comparison to samples from shallow and surface environments. Crabs from paddy fields on the Liaohe River, considered to be one of the most polluted in China, only have PCB levels about one fiftieth that seen in the Mariana Trench, while highly polluted coastal sediments from Guam, Japan and Australia had levels of 314, 240 and 160 nanograms per gram respectively.

This high concentration is remarkable, and requires explanation. Jamieson et al. consider a number of possibilities. Firstly the Mariana Trench is close to the highly polluted North Pacific Subtropical Gyre (also known as the ‘Great Pacific Garbage Patch’) a massive patch of plastic debris which partially overlies the trench. This can potentially lead to degraded plastic debris and plastic derived chemicals sinking directly into the Trench. Secondly the chemicals may be derived from carrion falls into the trench (a major source of food for benthic Amphipods) which have high levels of plastic-derived chemicals. However the consistently high PCB levels across the nutrient poor Mariana Trench make this seem unlikely. Thirdly it is possible that the species present in the Mariana Trench (Hirondellea gigas) is particularly prone to bioaccumulating PCBs due to some aspect of their physiology, though this would be surprising given the ecological similarity of the Mariana Amphipods to the Kermadec species, this also seems unlikely.

Instead Jamieson et al. suggest that high levels of PCBs may be accumulating in the Mariana Trench due to the topology of the Trench itself. The Trench is generally seen as an exceptionally deep structure, with the bottom remote from surface waters, and often depicted with a comparison to Mount Everest (which would not reach the sea surface if it sat in the Mariana Trench). However it is not as deep as part of the Mississippi River is wide, nor Manhattan Island is long, so the waters at the bottom of the Trench cannot be seen as truly separate from those at the surface. Studies made in the Japan Trench following the 2011 Fukushima Dia-ichi nuclear disaster suggested that particulate matter in the ocean sank at rates of 64–78 m per day, which would enable material derived from the North Pacific Subtropical Gyre to reach the deepest parts of the Mariana Trench in under 170 days. Such material settling on the seafloor of the ocean plains would be subject to further movement by deep ocean currents, eventually spreading more-or-less evenly across these vast areas, but chemicals sinking into the Mariana Trench would become concentrated, as the depth of the trench protects its contents from the ocean currents.

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Magnitude 4.5 Earthquake in Sánchez Ramírez Province, Dominican Republic.

The United States Geological Survey recorded a Magnitude 4.5 Earthquake at a depth of 60.3 km roughly 5 km to the southwest of the town of Cevicos in Sánchez Ramírez Province in the Dominican Republic, slightly after 9.00 pm local time on Sunday 26 February 2017  (slightly after 1.00 am on Monday 27 February GMT). There are no reports of any damage or injuries associated with this event, but people have reported feeling it across much of Hispaniola (the island upon which Haiti and the Dominican Republic sit).

 The approximate location of the 26 February 2017 Dominican Republic Earthquake. USGS.

The Dominican Republic forms the eastern part of the island of La Hispaniola, in the Greater Antilles. The island has a complex geological structure, with parts of it lying on three different tectonic plates, and two plate margins running east-to-west across the island. The northernmost part of the island lies on the North American Plate. This is divided from the Gonâve Microplate by the Septentrional Fault Zone, which runs through Rio San Juan, along the north coast of the Dominican Republic and Haiti, then across the Windward Passage and along the south coast of Cuba. The Gonâve Microplate is moving east relative to the North American Plate, pushed by the Mid-Cayman Spreading centre to the west of Jamaica. To the south the Gonâve Microplate is separated from the Caribbean Plate by the Enriquilo-Plantain Garden Fault Zone, which runs across Southern Haiti and the Dominican Republic. To the west the fault runs through central Jamaica. The Caribbean Plate is rotating clockwise, effectively moving east relative to the Gonâve Microplate.

 Plate movements and fault zones around the Gonâve Microplate. Mike Norton/Wikimedia Commons.

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Sunday 26 February 2017

German archaeologists kidnapped in Nigeria.

Two German archaeologists working at Jenjela village in Kaduna State were snatched by unidentified gunmen on Wednesday 22 February 2017. Two local men, identified as Anas Ibrahim and Adamu Abdulrahim, who tried to intervene were killed during the incident. The gunmen demanded payment of a ransom of 60 million Niara (about US$ 200 000) for the release of Peter Breunig and Johannes Buringer of the Goethe University in Frankfurt. The men were released late on Saturday 25 February, after an operation by local security services. No ransom is reported to have been paid, and details of any arrests made have not been released. The men are recovering from their ideals at the German Embassy in Abuja.

Peter Breunig of Goethe University with an artifact from a Nigerian archaeological site. Daily Post.

Kidnapping is a common problem in Nigeria, with foreigners often targeted as they are perceived as wealthier than the local population. It is one of a number of law and order problems that have developed as a rapidly rising population finds it cannot sustain itself through traditional activities such as agriculture, but wealth generated by new industries such as oil has failed to reach much of the population.

The archaeologists were investigating the Iron Age Nok Culture of Nigeria, which flourished in the area around the Benue Plateau between about 500 BC and 200 AD, and which is noted for its clay figurines of people and animals, which are considered to be cultural forebears of the later bronze figures of southwest Nigeria.

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