Sunday 30 September 2018

Asteroid 2018 SD2 passes the Earth.

Asteroid 2018 SD2 passed by the Earth at a distance of about 87 860 km (0.30 times the average  distance between the Earth and the Moon, or 0.006% of the distance between the Earth and the Sun), slightly after 6.05 am GMT on Tuesday 25 September 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 SD2 has an estimated equivalent diameter of 3-11 m (i.e. it is estimated that a spherical object with the same volume would be 3-11 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 50 and 30 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2018 SD2. Minor Planet Center.

2018 SD2 was discovered on 21 September 2018 (four days before its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2018 SD2 implies that the asteroid was the 54th object (object D2) discovered in the second half of September 2018 (period 2018 S).

2018 SD2 has a 318 day orbital period, with an elliptical orbit tilted at an angle of 0.25° to the plain of the Solar System which takes in to 0.78 AU from the Sun (78% of the distance at which the Earth orbits the Sun, and slightly more than the distance at which Venus orbits the Sun) and out to 1.04 AU (4% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in 18 May this year and the next predicted in July 2026. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2018 SD2 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. This also means that the asteroid has occasional close encounters with the planet Venus, with the last calculated to have occurred in September 2014, and the next predicted for November 2020.
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Thousands feared dead after Earthquake and tsunami hit Sulawesi.

832 people have now been confirmed dead and it is feared that the eventual total will reach into the thousands following an Earthquake on northern Sulawesi on Friday 28 September 2018, which triggered a tsunami. The event was recorded by the United States Geological Survey as a Magnitude 7.5 Earthquake at a depth of 10 km, roughly 78 km to north of the city of Palu, which occurred slightly after 6.00 pm local time (slightly after 10.00 am GMT), and was felt across the island of Sulawesi and on eastern parts of Borneo. The majority of the confirmed fatalities so far (821) have been in the city of Palu, but it is likely far more people have died in the Donggala Regency to the north of the city, where the Earthquake occurred and which was inundated by the tsunami after the event.

Debris in the streets of Palu, Sulawesi, following an Earthquake and tsunami on 28 September 2018. Haritsah Almudatsir/Jawa Pos.

The tectonic situation beneath Sulawesi is complex, as it is caught in the collisional zone between the Eurasian, Pacific and Australian Plates. The north of the island is located on a breakaway section of the Eurasian Plate, called the Sangihe Plate. To the east lies the remnant Molucca Sea Plate, which is being subducted beneath both the Sangihe Plate and the more easterly Halmahera Plate, leading to Earthquakes and volcanism on Sulawesi and the islands of the Sangihe Arc in the west and the islands of the Halmahera Arc in the east.

The approximate location of the 28 September 2018 Sulawesi Earthquake. USGS.

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement.. Eventually the pressure builds up to far and the overlying plate snaps back, causing an Earthquake and a tsunami. 

Simplified graphic showing tsunami generation along a convergent margin.NASA/JPL/CalTech.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.
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Begonia medogensis: A new species of Begonia from Tibet and Myanmar.

Begonia, Begonia spp., are perennial flowering plants related to Gourds, found in tropical and subtropical forests around the world, and popular as houseplants. They are typically ground-dwelling understory Plants, though some species are epiphytes (live on other Plants, usually in the canopy of trees). Begonias are monoecious, with both male and female flowers occurring on a single plant, and may be upright-stemmed, rhizomatous or tuberous.

In a paper published in the journal PhytoKeys on 2 July 2018, Jian-Wu Li of the Center for Integrative Conservation at the Xishuangbanna Tropical Botanical Garden, Yun-Hong Tan, also of the Center for Integrative Conservation at the Xishuangbanna Tropical Botanical Garden, and of the South Asia Biodiversity Research Institute of thr Chinese Academy of Sciences, Xi-Long Wang of the Tibet Plateau Institute of Biology, Cheng-Wang Wang of the School of Life Sciences at Nanchang University, and Xiao-Hua Jin of the Institute of Botany of the Chinese Academy of Sciences, describe a new species of Begonia from Medog County in Tibet and the Putao District of Kachin State in Myanmar.

The new species is named Begonia medogensis, meaning 'from Medog', as it was first identified in a subtropical semi-evergreen forest in Medog County, Tibet, and later found in a tropical montane forest in the Putao District of Kachin State in Myanmar. It is an erect rhizomatous perennial herb reaching up to a metre in height, with hairy, oval-to-lance-shaped leaves growing directly from the stems. It produces bracts of flowers from October to December, each of which bears 1-5 pink and white flowers, all of the same sex.

Begonia medogensis. Jian-Wu Li in Li et al. (2018).

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Saturday 29 September 2018

Almost 200 dead in Nigerian floods.

A total of 199 people have been reported dead in Nigeria after the Niger and Benue rivers burst their banks due to rains associated with an exceptionally severe rainy season, according to the National Emergency Management Agency. Ninety seven deaths have been reported in the states of Borno and Yobe in the northeast of the country, where a Cholera outbreak has infected over 3000 people. This outbreak has also hit the neighbouring nations of Niger, where 67 people have died and another 180 cases reported, as well as Cameroon and Chad. The flooding has made about 286 000 people homeless, mostly in southern Nigeria, as well as destroying large areas of crops and killing large amounts of livestock, raising the risk of future famine.

Flooding in Kara-Isheri, Ogun State, southwest Nigeria, on 20 Septmber 2018. Pius Utomi Ekpei/AFP.

West Africa has a distinct two season climatic cycle, with a cool dry season during the northern winter when prevalent winds blow from the Sahara to the northeast, and a warm rainy season during the northern summer when prevalent winds blow from the Atlantic Ocean to the southwest. These warm winds from the Atlantic are laden with moisture, which can be lost rapidly when the air encounters cooler conditions, such as when it is pushed up to higher altitudes by the Jos Plateau of central Nigeria and Shebshi Mountains on the border with Cameroon.

 Rainfall and prevalent winds during the West African dry and rainy seasons. Encyclopedia Britanica.

Cholera is caused by the Bacterium Vibrio cholerae, a Gram-negative, comma-shaped Gammaproteobacteria, related to other pathogenic Bacteria such as Yersinia pestis (Bubonic Plague), and Esherchia coli (food poisoning). The Bacteria produce proteins which can cause watery diarrhoea, which helps spread the disease, and can prove fatal in severe cases, as patients are killed by extreme dehydration.

 SEM image of Vibrio cholerae Bacteria. Kim et al. (2000).

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Napakimyrma paskapooensis: A new species of Relict Ant from the Palaeocene of Alberta, Canada.

Ants are a dominant group in almost all Insect communities today, but this does not appear to have been the case. Stem-group Ants (Ants not descended from the last common ancestor of all living Ants) are known in the fossil record from the Middle Cretaceous onwards, but Cretaceous Ants were rarer and less dominant members of the communities where they were found. Crown-group Ants (Ants descended from the last common ancestor of all living Ants) first appear in the Eocene, and rapidly rose to the ecological dominance we see today. Strangely there is a 23 million year gap between the last fossil Stem-group Ants, in amber from the 78-million-year-old Medicine Hat Formation of North America, and the appearance of the first Crown-group Ants in the 55-million-year-old Fur Formation of Denmark, a gap which encompasses the End Cretaceous Extinction and the entire Palaeocene Epoch. During this entire period only a single possible Ant fossil is known, a specimen from the Palaeocene of Menat in France, which might be an Ant or might be a Potter Wasp.

In a paper published in the journal Acta Palaeontologica Polonica on 27 July 2018, John Lapolla of the Department of Biological Sciences at Towson University and Phillip Barden of the Department of Biological Sciences at the New Jersey Institute of Technology, describe a new species of Relict Ant from the Palaeocene Paskapoo Formation in Alberta.

Relict Ants, Aneuretinae, are known only from a single species today, the Critically Endangered Sri Lankan Relict Ant, Aneuretus simoni, though nine fossil species have previously been described, leading entomologists to conclude that they were the last survivors of a group only distantly related to other Crown-group Ants, though modern DNA-based phylogenetic methods have shown them to be closely related to the much more widespread and diverse Dolichoderine Ants.

The Paskapoo Formation comprises a series of Middle-Late Palaeocene sandstones, gravels, mudstones and conglomerates, thought to have been laid down in a meandering river valley, with occasional palaeosols (fossil soils) and coal beds thought to have been laid down in wooded swamps on the river, which have produced numerous Insect and Plant fossils.

The new species is named Napakimyrma paskapooensis, where 'Napakimyrma' is a combination of the Cree 'Napaki', meaning 'flat' and the Greek 'Myrma', meaning 'Ant', to make 'Flat Ant', and 'paskapooensis' means 'from Paskapoo'. The species is described from a single worker Ant 6.8 mm in length, preserved as part and counterpart on a piece of split limestone. 

Relict Ant Napakimyrma paskapooensis from the Paleocene Paskapoo Formation at Dennis Wighton site 1 of Blackfalds Insect and Plant Site. Automontage generated photographs (A, B), line drawing (C). Lapolla & Barden (2018).

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Collapse at illegal sand mine in Kisumu County, Kenya, kills two children.

Two children have died following a collapse at an illegal sand mine in Kisumu County in western Kenya on Saturday 29 September 2018. The bodies were recovered by police after they were alerted to the incident by local residents and taken to the Jaramogi Oginga Odinga Teaching and Referral Hospital. The deceased have been identified as pupils at the Nyambo Primary School and Orongo Secondary School. Several other people working at the mine are reported to have fled the scene after collapse, including a relative of the dead children who was apparently in charge of the operation.

The scene of an illegal sand mine in Kisumu County, Kenya, where two children died in a collapse on 29 September 2018. Denish Ochieng/Standard.
Denish Ochieng/Standard
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This is the latest in a series of incidents at illegal sand mines in Kenya recently, fuelled by a demand for the material for the construction industry, Such mines often use child labour, as children will generally work for less than adults, and seldom take any form of health and safety considerations into account. 

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Delphinapterus leucas: Beluga Whale enters the Thames.

A Beluga Whale, Delphinapterus leucas, has been sighted in the Thames this week, having apparently wandered thousands of kilometres from its usual Arctic habitat. The animal was first observed on Thursday 27 September 2018, near Gravesend, and has remained in the area since. Divers from British Divers Marine Life Rescue have observed the animal and report that it is foraging and feeding normally, despite its unusual location, though the Port of London Authority is taking measures to keep sightseers away, as a Northern Bottle-nosed Whale, Hyperoodon ampullatus, that entered the river in 2006 died after beaching itself when it was startled by a boat.

A Beluga Whale, Delphinapterus leucas, in the Thames this week. Channel 4 News.

Beluga Whales typically live in the Arctic Ocean, where they reproduce during the summer months. When this environment largely freezes over during the winter, and the Whales migrate south into the North Atlantic and North Pacific. They do not, however, typically come as far south as the UK, with sightings in areas such as the Hebrides being considered exceptional. This has led to speculation that the animal may have become separated from its pod and disorientated during Atlantic Storm Ali which caused severe weather to the northeast Atlantic two weeks ago.

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