Sunday 30 March 2014

Magnitude 4.5 Earthquake in Logan County, Oklahoma.

The United States Geological Survey recorded a Magnitude 4.5 Earthquake at a depth of 3.8 km in the northwest of Logan County, Oklahoma, slightly before 9.10 am local time (slightly before 2.10 pm GMT) on Sunday 30 March 2014. This is a fairly large quake, and was felt across much of central, eastern and northern Oklahoma, as well as southern Kansas, although there are no reports of any damage or injuries.

The approximate location of the 30 March 2014 Logan County Earthquake. Google Maps.

Oklahoma is naturally prone to Earthquakes, particularly in the southwest of the state, near the Meers Fault Zone, but since 2009 has suffered a sharp increase in the number of small quakes in the central and northeast parts of the state. While most of these quakes have been quite small, a few have been large enough to potentially cause problems, and any unexplained increase in seismic activity is a cause for concern. 

In a paper published in the journal Geology on 26 March 2013, a team of geologists led by Katie Keranen of the ConocoPhillips School of Geology and Geophysics at the University of Oklahoma linked one of the largest of these quakes, a Magnitude 5.7 event in November 2011 which caused damage locally and was felt across 17 states, to the practice of pumping liquids (usually brine) into injection wells, which is common in the hydrocarbons industry and used to displace oil or gas, which can then be extracted from nearby extraction wells (where this is done in bursts at pressure to intentionally break up rock it is called hydraulic fracturing, or fracking). Significantly they suggested that the practice could lead to quakes years or even decades after the actual injection.

Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) you can report it to the USGS here.

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The nature of the Chicxulub impactor.

65 million years ago, at the end of the Cretaceous, the Earth underwent the last of the five great mass extinctions recorded in the fossil record. While this is by no means the largest of these events, it is the most familiar to the general public, as it was responsible for the extinction of, amongst other things, the non-Avian Dinosaurs and the large marine Reptiles of the Mesozoic Era. For many years the exact nature of this event was a mystery to scientists, and while many theories were proposed, prior to the 1980s few of these were grounded in any actual data. 

In 1980, a team of scientists led by Luis Alvarez of the Lawrence Berkeley Laboratory at the University of California, Berkeley proposed in a paper in the journal Science that the extinction might have been brought about by the extinction could have been caused by the impact of a large extra-terrestrial body with the Earth, based upon the discovery of a distinct layer of iridium-rich sediments at the top of Cretaceous strata in several parts of the world (iridium is rare in terrestrial rocks, but present at much higher levels in many meteorites). This is a dramatic theory, and quickly caught the imagination of the world’s media and the non-scientific public. What is more, unlike many other theories proposed for the end-Cretaceous extinction, it was possible to look for evidence to either support or undermine the theory, an important test in the eyes of the scientific community. Since this time the impactor theory has become one of two main rival explanations for the end-Cretaceous mass extinction (the other being flood-volcanism in the Deccan Traps in India).

An artists impression of the theoretical end-Cretaceous impact event. Don Davis.

In order to make calculations about the energy released by a collision with an extra-terrestrial object, the size and nature of this object need to be estimated with some degree of accuracy (exact details about an object destroyed 65 million years ago in a huge explosion are unlikely to be forthcoming), something which was not possible in the 1980s, though a number of theories were put forward. In 1983 Alvarez proposed in a paper in the Proceedings of the National Academy of Sciences of the United States if America that this object was a large asteroid, while in 1984 David Raup and John Sepkoski of the Department of Geophysical Sciences at the University of Chicago proposed in a paper in the Proceedings of the National Academy of Sciences of the United States of America that the repeated nature of mass extinctions in the fossil record might periodic in nature, and that this periodicity might have an extra-terrestrial cause and in 1987 a team of scientists led by Piet Hut of the The Institute for Advanced Study in Princeton, New Jersey proposed in a paper in the journal Nature that this repeated nature of mass extinctions in the fossil record might be due to repeated encounters with a cometary cloud. While the idea that the Earth’s mass extinctions have a regular and predictable nature with an extra-terrestrial cause is no longer taken seriously, the question of whether such an impact could have been caused by an asteroid or a comet is still debatable.

In 1991 a team of scientists led by Alan Hildebrand of the Department of Planetary Sciences at the University of Arizona published a paper in the journal Geology in which they announced the discovery of a large impact crater, between 180 and 200 km in diameter, buried beneath Tertiary deposits near Chicxulub on the Yutican Peninsula in Mexico, which they proposed might be direct evidence of an Alvarez-type impact at the end of the Cretaceous (though some geologists still dispute that this crater does actually date from the end of the Cretaceous; if it is simply of Late Cretaceous origin, pre-dating the end of the period by hundreds of thousands of years, then it is irrelevant).

Gravity map of the Chicxulub Crater. Virgil Sharpton/Lunar and Planetary Institute.

A simplified section through the geology of the Chicxulub Crater. David Kring/NASA/University of Arizona Space Imagery Center.

 In a paper published on the arXiv database at Cornell University Library on 19 March 2014, Hector Javier Durand-Manterola and Guadalupe Cordero-Tercero of the Instituto de Geofísica at the Universidad Nacional Autonoma de México, attempt to calculate the nature and size of the object which caused the Chicxulub Crater, based upon the calculating the amount of energy necessary to cause a crater of this size, and the concentration of iridium in the sedimentary layer that marks the end of the Cretaceous.

Using four different methods to calculate the mass of the object which caused the Chicxulub crater, all of which rely on scaling up the levels of energy known to have been released from nuclear explosions which caused craters of known sizes, Durand-Manterola and Cordero-Tercero calculate  that the object must have had a mass of between 5 700 000  and 460 000 000 megatons, and a diameter of between 5.1 and 80.9 km. 

Within this range exactly how much energy would have been needed to cause the crater depends upon the nature of the object involved in the impact; Durand-Manterola and Cordero-Tercero considered three possibilities, an iron asteroid, a stony asteroid and an (icy) comet, with the most energy being needed to cause the crater with a comet and the least with an iron asteroid. This is because an iron meteorite would be more than three times as dense as the limestone which the object is thought to have impacted, a stony asteroid slightly denser than the limestone and an icy comet considerably less dense (it would take more energy to break a window with a snowball than with a stone of equal mass). Thus if the object was an icy comet it would need to have been either considerably larger or considerably faster than if it was a stony or iron asteroid.

Durand-Manterola and Cordero-Tercero consider that the ratio of iridium to dust in the terminal Cretaceous boundary layer is closer to that found in comets than in either iron or stony asteroids, and therefore propose that the object was a comet (comets are thought to contain considerably less iridium by mass than either type of asteroid), moreover they suggest that the overall levels of iridium are low enough to suggest the object was towards the smaller end of the calculated possible range for the size of the original object, suggesting that the impact must have occurred at an exceptionally high velocity. For this reason they suggest that the impact may have been caused by a long period comet originating in the Öpik-Oort cloud.

This last set of calculations seem slightly optimistic from a geological point of view; it is highly unlikely that the iridium:dust ratio in the terminal Cretaceous layer would reflect that seen in the original impactor, and quite possible that the level of iridium in the layer could have been either concentrated or diluted by sedimentary processes; the iridium and dust are both thought to have passed from the impact site into the atmosphere, then the hydrosphere, then the sedimentary record. Passage through the atmosphere and hydrosphere are both known to sort particles my mass and surface area (feathers fall through the atmosphere more slowly than stones, and more massive particles sink more rapidly through water than less massive ones). Furthermore a considerable amount of debris is likely to have originated at the impact site, rather than in the impactor. 

It should also be noted that volcanism is also known to produce iridium, although at rather lower concentrations than would be predicted from an asteroid impact. While the iridium layer at the end of the Cretaceous is rather more concentrated than would be expected from a volcanic eruption, which is generally considered to be evidence for an extra-terrestrial origin for the layer, Durand-Manterola and Cordero-Tercero’s calculations suggest that the layer is considerably less dense than would be predicted from an asteroid impact, and therefore, if accurate, would tend to suggest that the iridium layer should be seen as rather less conclusive evidence.

See also…

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Saturday 29 March 2014

Five new species of cave-dwelling Armoured Spiders from southern China.

Armoured Spiders (Tetrablemmidae) are found throughout the tropics, but are at their most diverse and abundant in Southeast Asia. Most species are small, and dwell in leaf litter and soil, including the soil built up around epiphytic plants in the canopies of rainforests. Some cave dwelling species are also known. Armoured Spiders are easy to identify as such since they only have four eyes, a trait otherwise seen only in the Caponiid Spider genera Nopsides and Notnops, which do not resemble Armoured Spiders and which have limited geographical distributions (in Mexico and Chile respectively). Armoured Spiders do not build webs.

In a paper published in the journal ZooKeys on 13 March 2014, Yucheng Lin of the Key Laboratory of Bio-resources and Eco-environment at Sichuan University and Shuqiang Li of the Institute of Zoology of the Chinese Academy of Sciences describe five new species of cave-dwelling Armoured Spiders from southern China.

The first new species is named Sinamma oxycera, where 'Sinamma' is a combination of 'Sina' (China) and '-mma' the suffix of the genus Tetrablemma from which the group gets its name, and 'oxycera' means 'sharp horn' in Greek, a reference to a structure on the head of the male. The species is named from two male and one female specimens found in the Longmolai Cave in Guangxi Province. These are reddish brown Armoured Spiders 1.59 mm in length, the males of which have a distinctive horn-like structure on the head, upon which the eyes are mounted.
Sinamma oxycera, male (A-B, E, G) and female (C-D, F, H) (G, H) Frontal view, (A, C) dorsal view (B, D) ventral view (E, F) lateral view G, H) anterior view. Lin & Li (2014).

The second new species described is placed in the genus Singaporemma and given the specific name banxiaoensis, meaning 'from Banxiao'; the species is described from 16 specimens collected from Banxiao Cave in Guangxi Province. Singaporemma banxiaoensis is a brownish yellow 1.00-1.14 mm Armoured Spider, the females being slightly larger than the males. Both sexes have white eyespots.

Singaporemma banxiaoensis male (A-B, E, G) and female (C-D, F, H) (G, H) Frontal view (C, D) dorsal view (B. D) ventral view (E, F) lateral view (G, H) anterior view. Lin & Li (2014).

The third new species is also placed in the genus Singaporemma and is given the specific name wulongensis, meaning 'From Wulong'; the species is described from 29 specimens collected from Xiaodong Cave in Wulong County, Chonqing Municipality. Singaporemma wulongensis is a 1.14-1.30 mm reddish-brown Armoured Spider, the females being slightly larger and slightly paler in colours than the males.

Singaporemma wulongensis male (A-B, E, G) and female (C-D, F, H). (G-H) Frontal view (A, C) dorsal view (B, D) ventral view (E, F) lateral view (G, H) anterior view. Lin & Li (2014).

The fourth new species is placed in the genus Tetrablemma and given the specific name menglaensis, meaning 'from Mengla'; the species is described from three specimens collected in the Yeniu Cave System in
Mengla County in Yunnan Province. Tetrablemma Menglaensis is a 1.18-1.27 reddish-brown Armoured Spider, the females being slightly larger than the males. The males have a horn-like tubercle on the head, upon which the eyes are mounted.

Tetrablemma menglaensis male (A-B, E, G) and female (C-D, F, H). (G, H) Frontal view (A, C) dorsal view (B, D) ventral view (E, F) lateral view (G, H) anterior view. Lin & Li (2014).

The final new species is also placed in the genus Tetrablemma, and is given the specific name ziyaoensis, meaning 'from Ziyao'; the species is described from three specimens collected from Yinhe Cave, near Ziyao village in Guangxi Province. Tetrablemma ziyaoensis is a 1.13-1.21 mm reddish-brown Armoured Spider, the females being slightly larger than the males.

Tetrablemma ziyaoensis male (A-B, E, G) and female (C-D, F, H) (G, H) Frontal view (A, C) dorsal view (B, D) ventral view (E, F) lateral view (G, H) anterior view. Lin & Li (2014).

Distribution records of five new tetrablemmid species from China. (1) Singaporemma banxiaoensis (2) Singaporemma wulongensis (3) Sinamma oxycera (4) Tetrablemma menglaensis (5) Tetrablemma ziyaoensis.

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Friday 28 March 2014

Eruptive activity on Mount Merapi, Java.

Mount Merapi, a volcano in central Java considered to be one of Indonesia's most active, underwent a brief outburst of volcanic activity between 1.12 and 1.16 pm local time (6.12 and 6.16 am GMT) on Thursday 27 March 2014, during which it generated a number of small Earthquakes, as well as emitting volcanic gas and ejecting ash and gravel from its crater. The events have caused some concern locally, and been related to an Earthquake that occurred in the same region on Monday 24 March.

Mount Merapi on Thursday 27 March 2014. Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi.

Mount Merapi lies in a densely populated area of Java, on the borders of Central Java and Yogyakarta Provinces, only 28 km to the north of Yogyakarta city. It has been erupting more-or-less continuously since 1548, and has been responsible for numerous fatalities, most recently in 1994 when a pyroclastic flow (avalanche of hot gas and ash) killed 27 people, mostly in the town of Muntilan, to the west of the volcano. Since then Merapi has undergone tow major eruptive episodes, in 2006 and 2010, without any further loss of life, largely due to prompt evacuations by Indonesian authorities.

The Indo-Australian Plate, which underlies the Indian Ocean to the south of Java, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Java and neighbouring Sumatra, along the Sunda Trench, passing under Java, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fuelling the volcanoes of Java and Sumatra.

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Thursday 27 March 2014

A new species of Hydrangea from Mexico and Central America.

Hydrangeas are perennial woody plants related to Dogwoods and Silkleafs. Most species form small shrubs, but some grow to tree sizes, and there are some lianas (woody vines) in the group. Hydrangeas are most abundant and diverse in eastern Asia, but they are found as far west as the Himalayas, and also throughout the Americas. Most Hydrangeas have white flowers, but some species produce pink or blue flowers in response to changes in soil pH, a trait which has made them popular with gardeners. As such they have been introduced to many parts of the world beyond their home ranges, in some places, most notably the Azores, becoming destructive invasive species.

In a paper published in the journal Phytotaxa on 17 March 2014, Marie-Stéphanie Semain of the  Instituto de Ecología of the Centro Regional del Bajío in Mexico and the Research Group on Spermatophytes at the Department of Biology at the University of Gent, Francisco Hernández Najarro of the Herbario of the Secretaria de Medio Ambiente e Historia Natural and Esteban Manuel Martínez Salas of the Herbario Nacional de México at the Departmento de Botánica at the Instituto de Biologica at the Universidad Nacional Autónoma de México describe a new species of Hydrangea from Mexico and Central America.

The new species is given the name Hydrangea albostellata, a reference to the white hairs present on the leaves and flowering stems of the plant. It is a climbing liana reaching 35 m in height, with male and female flowers born on separate plants. Hydrangea albostella is found in cloud forests at altitudes of between 1200  and 2300 m from Chiapas State in southeastern Mexico through Central America as far as Costa Rica.

Branch of
Hydrangea albostellata with four inflorescences, all inflorescence bracts already shed in lower right one where the flower buds are visible, lower left inflorescence partially opened, apical inflorescences still covered by all inflorescence bracts. Semain et al. (2014).

Climbing a 
Hydrangea host tree with specific equipment (note, the Hydrangea is the vine on the tree, not the tree being climbed). Samain et al. (2014).

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Wednesday 26 March 2014

Dinosaur remains from northwestern Saudi Arabia.

Dinosaurs are the most distinctive element of Mesozoic Vertebrate faunas, arising in the Triassic, and coming to dominate all known terrestrial ecosystems during the Jurassic and Cretaceous, before disappearing abruptly (other than the still extant Birds) at the end of that period. Despite this widespread distribution, very few Dinosaur remains are known from the Middle East, with a few scattered remains recorded from Oman, Jordan, Yemen, Egypt and Lebanon, and, to date, only two recorded Dinosaur finds from Saudi Arabia, and unidentified Sauropod, possibly a Titanosaur, and some other unidentified bones, all from the late Cretaceous Adaffa Formation of the Midyan Peninsula, in the northwest of the country, collected between 2004 and 2008 by a joint expedition of the Saudi Geological Survey and the Egyptian Geological Museum.

In a paper published in the journal PLoS One on 26 December 2013, a team of scientists led by Benjamin Kear of the Department of Earth Sciences at Uppsala University formerly describe these Dinosaur  specimens for the first time.

Geological map of northeast of Saudi Arabia, showing outcrops of the Addafa Formation. Kear et al. (2014).

The material comprises seven caudal (tail) vertebrae, plus two other fragments, from a Sauropod Dinosaur, plus two Theropod teeth, collected from a limestone outcrop 11 km northeast of Al Kuraybah. The specimens were disarticulated, apparently due to water turbulence, but are thought to come from only two animals (i.e. one Sauropod and one Theropod). The most complete vertebra has a length of 105 mm and a height of 133 mm, and does indeed appear to be from a Titanosaur. Both of the teeth are fragmentary in nature, though they are distinctively Theropod in nature, flattened with a serrated cutting edge, and are thought to most likely be from an  Abelisaurid.

Dinosaur remains from the Adaffa Formation of Saudi Arabia. Titanosaurian distal caudal vertebra in: (A) anterior; (B) lateral; and (C) posterior views. Abelisaurid teeth including: (D) crown fragment with enlargement of the distal denticles; and maxillarydentary tooth shown in distal (E) and lateral (F) views with enlargements of the distal carina and baso-apical enamel ridges. Kear et al. (2014)

See also A dwarf Tyrannosaurid from the Late Cretaceous of northern Alaska, Bite marks on the bones of Late Cretaceous juvenile Ornithischian Dinosaurs from Utah, A new species of Theropod Dinosaur from the Late Jurassic of Portugal, A new species of Titanosaur from the Early Cretaceous of Texas and The foot of a small Alvarezsauroid Dinosaur from Inner Mongolia, China.

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Tuesday 25 March 2014

Three new species of Braconid Wasps from the Andean forests of Ecuador.

Braconid Wasps are parasitoid Wasps (i.e. Wasps whose larvae mature inside the living bodies of other insects, which generally die as a result) related to the more familiar Ichneumon Wasps, but much smaller. They have a formidable appearance, but are in fact stingless, making them harmless to non-host species. There are about 150 000 known species found across the globe. They have a fossil record dating back to the Early Cretaceous, though this is somewhat patchy.

In a paper published in the journal Zootaxa on 17 March 2014, Helmuth Aguirre and Scott Shaw of the University of Wyoming Insect Museum and the Department of Ecosystem Science and Management at the University of Wyoming describe three new species of Braconid Wasps from the Andean Forests of Ecuador. All three new species are placed in the genus Meteorus, and are parasitoids of Actiid Moths

The first new species is named Meteorus anuae, after the entomologist Anu Veijalainen, an expert on Peruvian Ichneumon Wasps. The species is described from fifteen individuals, reared from cocoons found on Actiid Moth caterpillars collected from False Nettles (Boehmeria pavonni) close to the Yanayuca Biological Station in the cloud forests of the High Andes (at about 2163 m). Meteorus anuae is a 4 mm orange and brown Braconid Wasp.
The Braconid Wasp Meteorus anuae, female specimen in lateral view. Aguirre & Shaw (2014).

The second new species is named Meteorus juliae, after Julia Stigenberg, an expert on Braconid Wasps in northern Europe. Meteorus juliae is described from specimens raised from larvae found parasitizing Arctiid Moth larvae collected from Sodiro (Dendrophorbium lloense), a herbaceous flowering plant, also near the Yanayacu Biological Station. It is a 4 mm yellow and brown Braconid Wasp.

The Braconid Wasp Meteorus julae, female specimen in lateral view. Aguirre & Shaw (2014).

The final new species is named Meteorus mirandae, after Miranda Bryant Talluto, an entomologist studying Braconid Wasps in the Ecuadorian cloud forests. The species is described from five specimens raised from caterpillars of the Arctiid Moth Saurita mosca collected from the Fern Diplazium costale and the Bamboo Chusquea scandens and an unnameed species of Arum, around the Yanayacu Biological Station. Meteorus mirandae is a 3.7-4.1 mm yellow and brown Braconid Wasp.

Meteorus mirandae, female specimen in lateral view. Aguirre & Shaw (2014).

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Sunday 23 March 2014

A new species of Sweeper from the Comoro Islands.

Sweepers (Pempheridae) are small nocturnal Fish found in the Western Atlantic and Indo-Pacific. They are members of the Perch order, Perciformes, with deeply keeled flattened bodies and large eyes. Some species are eaten and some others caught for use in aquaria. 

In a paper published in the journal Zootaxa on 21 March 2014, Randall Mooi of the Manitoba Museum and the Department of Biological Sciences at the University of Manitoba and John Randall of the Bishop Museum in Honolulu describe a new species of Sweeper from the Comoro Islands.

The new species is placed in the genus Pempheris and given the specific name bexillon, meaning banner or flag in Greek, a reference to the brightly coloured dorsal fin of the new species. Pempheris bexillon is described from 11 specimens caught around the Comoro Islands, and a further 12 specimens from around the Mascarine Islands and Madagascar, at depths of less than 100 m. It is a 129-151 mm Sweeper with a distinctive yellow and black dorsal fin.

Pempheris bexillon in left lateral view. Mooi & Randall (2014).

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The March Equinox.

The March Equinox fell on 20 March this year. The Earth spins on its axis at an angle to the plain of the Solar System. This means that the poles of the Earth do not remain at 90° to the Sun, but rather the northern pole is tilted towards the Sun for six months of the year (the northern summer), and the southern pole for the other six months (the southern summer). This means that twice a year neither pole is inclined towards the Sun, on days known as the equinoxes.

How the combination of the Earth's equatorial plane (red circle) and the plane of the Earth's orbit (green circle) creates the Solstices and Equinoxes that we observe. Ohio State University.

The equinoxes fall each year in March and September, with the March Equinox being the Spring (or Vernal) Equinox in the Northern Hemisphere and the Autumn Equinox in the Southern Hemisphere, while the September Equinox is the Autumn Equinox in the Northern Hemisphere and the Spring Equinox in the Southern Hemisphere. On these two days the day and night are both exactly twelve hours long at every point on the planet, the only days on which this happens.

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At least three people dead following Washington State landslide.

Three people are known to have died, and several more are in critical conditions, following a landslide near the town of Oso in Snohomish County in Washington State, about 55 km north of Seattle, that occurred slightly before 11.00 am local time on Saturday 22 March 2014. The landslide completely blocked State Route 530 as well as destroying six houses and blocking the North Fork of the Stillaguamish River, prompting an evacuation of nearby communities at risk of flooding. Those recieving hospital treatment for critical injuries are known to include an 81-year-old-man, a 58-year-old-man and a six-month-old boy. Rescuers are still searching for more people at the site of the event.

The aftermath of the 22 March 2014 Snohomish County landslide. Marcus Yam.

The landslide was over 40 m wide and 50 m deep. It is thought to have been caused by heavy rainfall which lead to the ground becoming waterlogged. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

The approximate location of the 22 March 2014 Snohomish County landslide. Google Maps.

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A preserved Passerine Bird’s foot from the late Oligocene of Poland.

Passerines (Perching Birds) are the most numerous and successful group of Birds in the modern world, with over half of all known Bird species being Passerines, including Finches, Thrushes, Sparrows, Warblers and Crows. Despite their success the group do not have an extensive fossil record, largely due to their small and delicate bones. The oldest putative Passerine fossils are from the early Eocene of Australia.

In a paper published in the journal Palaeontologica Electronica on 27 January 2014, Zbigniew Bochenski and Teresa Tomek of the Institute of Systematics and Evolution of Animals of the Polish Academy of Sciences and Ewa Swidnicka of the Department of Palaeozoology at the University of Wrocław, describe the preserved foot of a Passerine Bird preserved as part and counterpart on shale slabs from the late Oligocene Menilite Formation of the Outer Carpathians in southeastern Poland, dated to about 25 million years old.

The specimen comprises the entire foot and lower leg of a Passerine Bird, roughly 15 mm in length. It is not formally described as a new species, as the isolated foot of a Passerine Bird is not considered to be sufficient for species identification, although it is not thought to belong to any of the (few) known Oligocene Bird species.

Foot of a passerine bird foot from southeastern Poland, Hłudno, late Oligocene, approximately 25 million years old. (1) Main slab; (2),Counter slab; (3) Interpretative drawings of the main slab and counter slab. Abbreviations: (d) I, pp – digit I, proximal phalanx; d I, up – digit I, ungual phalanx; d II, p1 – digit II, phalanx 1; d II, p2 – digit II, phalanx 2; d II, up – digit II, ungual phalanx; d III, p1 – digit III, phalanx 1; d III, p2 – digit III, phalanx 2; d III, p3 – digit III, phalanx 3; d III, up – digit III, ungual phalanx; d IV, p1 – digit IV, phalanx 1; d IV, p2 – digit IV, phalanx 2; d IV, p3 – digit IV, phalanx 3; d IV, p4 – digit IV, phalanx 4; d IV, up – digit IV, ungual phalanx; omt I – os metatarsale I; tmt – tarsometatarsus; tbt – tibiotarsus (fragment of the condylus lateralis). Bochenski et al. (2014).

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The origin of Ceres.

Ceres is the largest body in the Main Asteroid Belt, comprising roughly 1/3 of all the mass of the belt. It has the designation (1) Ceres, indicating that it was the first asteroid discovered  (by Giuseppe Piazzi in 1801), but has recently been declared to be a Dwarf Planet, due to its large size, a designation that places it in the same class of bodies as the Trans-Neptunian Objects Pluto, Haumea, Eris and Makemake. As such it is the subject of considerable interest to planetary scientists, and was one of two bodies chosen to be visited by NASA’s Dawn Mission, along with (4) Vesta, the second largest body in the Main Asteroid Belt.

The results of the Dawn Mission have revealed striking differences between the two bodies, with Vesta having a subspherical shape and a cratered, volcanic surface (much as was expected from an asteroid), but Ceres has an (unexpected) smooth, icy surface and a more-or-less spherical shape. Moreover Ceres is considerably less dense than Vesta (at 2.077 g cm¯³ compared to 3.456 g cm¯³ for Vesta), suggesting that the ice forms a significant proportion of its mass, rather than simply being a thin surface layer, and several points of cryovolcanic activity, where water vapour is being released from the surface at a rate of about 6 kg s¯¹ have been discovered.

The surface of Ceres. NASA/JPL/Dawn Mission.

The surface of Vesta. NASA/JPL/Dawn Mission.

In a paper published on the arXiv online database at Cornell University Library on 20 March 2014, Yury Rogozin of the VEDA LLC in Moscow speculates that Ceres may have begun it existence not as a Main Asteroid Belt object, but as the moon of a now destroyed planet beyond the snowline of the early Solar System (the snowline being the point beyond which it was cool enough for water-ice to form, not possible within the inner Solar System due to the heat from the early Sun), and that it may have reached its current position by interaction with the gravity of the giant planet Jupiter.

Rogozin cites as evidence of this the theory that the planets Mercury and Mars may also have started out as the satellites of larger bodies (a theory which is not currently widely supported among planetary scientists). That theory goes something like this: Mercury and Mars are significantly smaller than the other two rocky planets, Earth and Venus, but are of comparable size to the larger moons of the Solar System, such as Earth’s Moon, the four Galilean moons of Jupiter, Titan etc. Furthermore Mercury and Mars have greater orbital eccentricities than any other planets in the Solar System (i.e. their distance from the Sun varies more than that of other planets). This theory speculates that Mercury is an escaped moon of Venus, and that Mars was formerly a moon of the planet Phaeton, which existed within what is now the Main Asteroid Belt, but which was destroyed by the gravitational influence of Jupiter early in the history of the Solar System.

Rogozin reasons that Mercury is in a 5:2 orbital resonance with Venus (i.e. it completes five orbits four every two orbits of Venus), and Mars is in a 5:2 resonance with the (hypothetical) orbit of the former planet Phaeton. Therefore Ceres could be in a 5:2 orbital resonance with another now destroyed planet, which Rogozin names Yurus, which would therefore have had a semi major axis (average orbital distance from the Sun) of 5.0951 AU (i.e. 5.0951 times the distance at which the Earth orbits the Sun), and an orbital period of 11.5 years.

The orbit of Ceres. JPL Small Body Database Browser.

Rogozin further suggests that the destruction of a large icy planet in such an orbit might account for the large volumes of water present on Earth and now believed to formerly have been present on Mars, both planets which are thought to have formed within the snow line, and which might therefore be expected to be largely waterless.

While the idea that Ceres may have formed beyond the early Solar System’s snow line has some merit, the existence of the planet Yurus seems highly speculative. The separation of Mercury and Mars from the other rocky planets as moon-like objects is not widely supported among planetary scientists. While Mercury is of similar size to several moons, Mars is in fact of intermediate size between these bodies and the larger rocky planets, and studies of other stellar systems have revealed a variety of rocky planets of intermediate sizes. Therefore most planetary scientists now either regard the four rocky planets as a discreet group, or use a grouping of ‘rocky worlds’ which includes the four planets, plus the fifteen largest moons in the Solar System.

The destruction of a large icy planet at a distance of 5.0951 AU from the Sun would be easy to explain, due to the closeness of such a planet to the orbit of Jupiter, a body which will excerpt considerable tidal stress on any nearby body, which has a semi major axis of 5.204267 AU, and which at its perihelion (the closest point in its orbit to the Sun) is only 4.950429 AU from the Sun; however the formation of a planet in such a position would require considerable explanation for the same reason, and explanation that Rogozin does not provide. The presence of water on Earth and Mars is more usually explained by hypothesizing a large number of comet impacts during the early history of the Solar System (the Early Bombardment Theory); comets that are thought to have formed in the outer parts of the Solar System, safely beyond the snow line.

Furthermore the speed at which a body orbits the Sun, and its distance from the Sun, are usually thought to be connected, with bodies that accelerate or slow in their orbits correspondingly moving towards or away from the Sun. Orbital resonances are usually explained by the exchange of inertia between bodies. A faster body approaching a slower body in a similar orbit will impart some of its inertia to it via tidal exchange, causing the slower body to accelerate and the faster body to slow down. The bodies will continue to exchange energy each time they pass, with one body accelerating and the other slowing each time they pass, until they reach a stable resonance. 

Several bodies within the Solar System (and in other known planetary systems) are in such resonances, most notably the three inner Galilean moons of Jupiter, which have a 4:2:1 orbital resonance. Where two bodies are in similar orbits but cannot reach a stable resonance, it is predicted that one of them will be expelled into a quite different orbit. Thus an origin of Ceres as a fifth large moon of Jupiter, unable to form a stable resonance with the other four Galilean moons and therefore expelled from the Jovian system by tidal forces, would present an alternative theory for the origin of Ceres (and an equally hypothetical one). The presence of an icy body in the Jovian system requires no explanation, as Jupiter is beyond the snow line, and has several icy moons.

The icy surface of the Jovian moon Europa. NASA/Galileo.

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Saturday 22 March 2014

Six killed by landslide at Myanmar jade mine.

Six people have been killed and another four injured in a landslide at an unlicensed jade mine near Hpakant in Kachin State in northeast Myanmar (Burma) on Monday 17 March 2014. The victims were reportedly working a rock face when it collapsed upon them.

The approximate location of the 17 March 2014 Kachin State jade mine landslide. Google Maps.

Myanmar is the world's largest producer of jade, though this is largely produced (along with other precious and semi-precious minerals) at unregulated (and illegal) artisanal mines in the north of the country, from where it is smuggled into neighbouring China. Accidents at such mines are extremely common, due to the more-or-less total absence of any safety precautions at the site. At many sites this is made worse by the unregulated use of explosives to break up rocks, often leading to the weakening of rock faces, which can then collapse without warning.