Saturday, 20 April 2019

Asteroid 2019 GT19 passes the Earth.

Asteroid 2019 GT19 passed by the Earth at a distance of about 805 100 km (2.09 times the average distance between the Earth and the Moon, or 0.54% of the distance between the Earth and the Sun), at about 3.15 am GMT on Thursday 11 April 2019. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2019 GT19 has an estimated equivalent diameter of 5-19 m (i.e. it is estimated that a spherical object with the same volume would be 5-19 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 40 and 23 km above the ground, with only fragmentary material reaching the Earth's surface.

Short clip showing image of 2019 GT19 captured on 12 April from the Siding Spring Observatory in Australia. The moving object is the asteroid, the elongate objects are stars; each frame is made up of a composite of several images with the camera moving between frames to keep the stars in the same position. Japan Space Agency.

2019 GT19 was discovered on 12 April 2019 (the day after its closest approach to the Earth) by the Japan Space Agency's Janess-G 0.25 m telescope at Siding Spring Observatory in Australia. The designation 2019 GT19 implies that it was the 475th asteroid (asteroid T19 - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc., which means that T19 = 19 + (24 X 19) = 4755) discovered in the first half of April 2019 (period 2019 G).

 The position and calculated orbit of 2019 GT19. JPL Small Body Database.

2019 GT19 is calculated to have an 526 day orbital period and an eccentric orbit tilted at an angle of 7.76° to the plane of the Solar System, which takes it from 0.80 AU from the Sun (i.e. 80% of the the average distance at which the Earth orbits the Sun) to 1.74 AU from the Sun (i.e. 174% of the average distance at which the Earth orbits the Sun, more than the distance at which the planet Mars orbits). 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 the Earth are quite common, with the last calculated to have happened in October 2011 and the next predicted for November 2021. 

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Avalanche believed to have killed three top climbers in Alberta, Canada.

Three of the world's top professional climbers are believed to have died following an avalanche near Banff in Alberta, Canada, this week. Austrians David Lama, 28, and Hansjoerg Auer, 35, and American Jess Roskelley, 36, failled to check in with Parks Canada at an appointed time during an attempt to climb the notoriously difficult east face of Howse Peak in Banff National Park, sponsored by clothing company North Face. This prompted a fly-over of the area, which found evidence of a large avalanche on the slope, with scattered equipment among the debris. Attempts to get a rescue team to the site on the ground are being hampered by bad weather in the area.

Austrian climber David Lama, believed to have been killed in an Avalanche on Howse Peak, near Banff, Alberta, this week. Manuel Ferrigato/Red Bull/Associated Press.

Avalanches are caused by the mechanical failure of snowpacks; essentially when the weight of the snow above a certain point exceeds the carrying capacity of the snow at that point to support its weight. This can happen for two reasons, because more snow falls upslope, causing the weight to rise, or because snow begins to melt downslope, causing the carrying capacity to fall. Avalanches may also be triggered by other events, such as Earthquakes or rockfalls. Contrary to what is often seen in films and on television, avalanches are not usually triggered by loud noises. Because snow forms layers, with each layer typically occurring due to a different snowfall, and having different physical properties, multiple avalanches can occur at the same spot, with the failure of a weaker layer losing to the loss of the snow above it, but other layers below left in place - to potentially fail later.

 Diagrammatic representation of an avalanche, showing how layering of snow contributes to these events. Expedition Earth.

Howse Peak rises to 3295 m above sealevel, and 1600 m above the surrounding plain, making it the highest mountain in the Waputik Mountains (a subrange of the Rockies) and the 46th highest peak in Alberta.  The mountain has a subarctic climate with temperatures reaching as low as -20°C in winter, when significant snow can accumulate, feeding a glacier on the western flank, as well as the Howse, Mistaya, and Blaeberry rivers. In spring the the area encounters warmer weather, leading to significant melting and frequent avalanches. 

Howse Peak, to the left, in August 2012. Murray Foubister/Flikr/Wikimedia Commons.

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Friday, 19 April 2019

Small Theropod tracks preserved in exquisite detail from the Early Cretaceous of South Korea.

Small Dinosaur tracks assigned to Minisauripus have been described from a number of locations in China and Korea since the ichnogenus was first described in 1995 (trackways and other animal traces are often placed in to ichnospecies and ichnogenera by scientists that study them, a form of taxonomy that follows the same form as the classification of living species, and which, if unable to record actual biological relationships, at least serves to group traces according to shared similarities). The first instances of these tracks were originally ascribed to a small Ornithopod Dinosaur, and were thought to be of Late Cretaceous age, but further examination of both the tracks and the local geology suggests that they were made by a small Theropod, and are of Early Cretaceous age, with all subsequently discovered examples being of similar age.

In a paper published in the journal Scientific Reports on 14 February 2019, Kyung Soo Kim of the Department of Science Education at Chinju National University of Education, Martin Lockley of the Dinosaur Trackers Research Group at the University of Colorado Denver, Jong Deock Lim of the Korean Cultural Heritage Administration, and Lida Xing of the School of the Earth Sciences and Resources at the China University of Geosciences, describe a new instance of Minisauripus from the Jinju Formation of South Korea, exposed during excavations at the Ppuri Industrial Complex in Jinju Innovation City.

The Jinju Formation has already yielded a number of significant trackways from other, nearby, locations, which are housed in the nearby Jinju Pterosaur Footprint Museum. The new material comprises a thin slab of fine grey sandstone covered by a thin black mudstone drape, less than a millimetre thick, on which a pair of Minisauripus tracks are preserved as impressions, a larger counterpart slab in which these, plus two other similar tracks, making a four imprint trackway are preserved in negative epirelief, and a third slab with a single footprint impression, which was probably part of the same trackway. The counterpart slab also preserves two Pterosaur manus (hand) impressions, a number of invertebrate traces ascribed to large Nematode Worms, and some raindrop marks.

(A) Counterpart slab CUE JJ_M01 showing trackway with four consecutive Minisauripus track casts TL1-TR2. (B) Natural impression slab (CUE JJ_M02) showing tracks TL2 and TR2. (C) Isolated track specimen (CUE JJ_M03). Kyung Soo Kim in Kim et al. (2019).

The trackways are all very well preserved, with the exception of one of the negative relief tracks, which is partially obscured by an overlying Pterosaur track. The prints average 2.38 cm in length and 1.93 cm in width. The average step length (one footprint to the next) is 20.03 cm, while the average stride length (one footprint to the next made by the same foot) is 39.60 cm. All of the footprints preserve skin traces from the entire foot, something unknown on any other Dinosaur footprint of any size. This applies to both the impressions and the negative epirelief prints, which effectively form a mould of the foot of the living animal. The traces show evidence of skin between digits II and III, and II and IV, which may indicate evidence of skin between the digits, or of loose skin on the side of the digits that was pushed down between the toes when the foot was fully flat.

(A,B) Natural impression (A) and cast (B) of track TL2 showing area enlarged in frame (F). Note skin traces in hypex area between digits II and III. (C) Natural cast of track TR1, showing area enlarged in frame (E). Note narrow, digit II intersecting raindrop impressions. (D) Isolated track t. Note skin traces in hypex area between digits II and III. (E) and (F) details of skin trace ornament in 2.0 × 2.0 mm areas of digits IV and II respectively from tracks TL2 and TR1. Casts show in frames (B)-(F) are essentially replicas of the living foot. Kyung Soo Kim in Kim et al. (2019).

The Pterosaur tracks are larger than those of the Dinosaur, measuring 14 cm long and 7 cm wide, and 13 cm long and 8 cm wide. Both are manus (hand) prints, with no sign of marks made by the pes (foot); the prints are not orientated in the same direction, and are probably not part of a single trackway.

The size of the Minisauripus footprints (2.38 cm in length) is taken to indicate an animal with a hip height of about 10.71 mm, which again, assuming a fairly standard Theropod body shape would indicate an animal about 28.4 cm long, and weighing a few tens of grams (about the size of a Blackbird). The stride length is estimated to indicate a walking speed of between 2.27 and 2.57 m per second (8.19 and 9.27 km per hour). The presence of skin traces without any smudging suggests that the foot was placed firmly down on the ground and lifted without any sliding, either in one solid step or with a rolling movement in which the back of the foot hit the ground before the back, but no movement of the foot on the ground occurred.

The consistent small size of Minisauripus footprints across a wide area of China and Korea, with no similar larger footprints, strongly suggests they were made by a full-sized animal, rather than a juvenile member of a larger species. The small size might potentially represent a Bird rather than a non-Avian Theropod, but no Bird with a foot similar to Minisauripus is known from the Early Cretaceous.

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Fireball meteor over New Jersey.

The American Meteor Society has received reports of a bright fireball meteor being seen over the southern New Jersey, slightly before 11.00 pm on Tuesday 16 April 2019 Eastern Standard Time (slightly before 3.00 am on Wednesday 17 April GMT). The meteor was also seen from Washington DC, Delaware, Maryland, North Carolina, New Jersey, Pennsylvania, South Carolina, Virginia and West Virginia, with the majority of the reports came from Maryland. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry. 

The 16 April 2019 meteor seen from Fenwick Island, Delaware. E Kozy/American Meteor Society.

A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry. This object appeared to move north-to-south, passing over New Jersey, and the Atlantic Ocean off the coasts of Delaware and Maryland, where it disappeared. Many witnesses reported that the meteor had a greenish tinge, which is likely to indicate the meteor had a high iron-nickel content.

Map showing areas where sightings of the meteor were reported, and the apparent path of the object (blue arrow). American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).
 The 16 April 2019 meteor seen from Mathius, West Viginia. E Abel/American Meteor Society.
These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.
Witness reports can help astronomers to understand these events. If you witness a fireball-type meteor over the US you can report it to the American Meteor Society here
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Mulleroconis hyalina & Palaeoconis azari: Two new species of Dustywings from Cretaceous Burmese Amber.

The Dustrywings, Coniopterygidae, are small (usually under 5 mm) Insects related to Lacewings and Ant-lions. They are numerous and widespread, being found in woodland all over the world, where they feed on small Arthropods, such as Mites, Aphids and Scale Insects, living on trees and shrubs. Largely because of their affinity for woodland and small size, they have an excellent fossil record, with the group appearing in the Late Jurassic and specimens preserved in amber being found across much of the globe from the Cretaceous onwards.

In a paper published in the journal ZooKeys on 5 March 2019, Dominika Ružičková of the Department of Zoology at Charles University, André Nel of the Institut de Systématique, Évolution, Biodiversité at the Muséum national d’Histoire naturelle, and Jakub Prokop, name two new species of Dustywings from Cretaceous Burmese Amber.

Middle Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna. This amber is thought to have started out as the resin of a Coniferous Tree, possibly a Cypress or an Araucaria, growing in a moist tropical forest. This amber has been dated to between 105 and 95 million years old, based upon pollen inclusions, and to about 98.8 million years by uranium/lead dating of ash inclusions in the amber.

The first new species is named Mulleroconis hyalina, where ‘Mulleroconis’ means ‘Müller’s dust’ in honour of Patrick Müller, who collected the specimen from which the species is named from the Hukawng Valley in Myanmar and donated it to the Museum für Naturkunde in Berlin, and ‘hyalina’ means 'glassy' in reference to the appearance of the wings. The species is described from a single male specimen 1.17 mm in length, preserved within a piece of pale-yellow transparent amber. The head of this specimen is poorly preserved, the abdomen large and the legs slender. The forewings are about 1.46 mm long and 0.65 mm wide, while the hindwings are about 1.25 mm long and 0.55 mm wide.

Mulleroconis hyalina. (A) Specimen in dorsal view. (B) Detail of wing venation. Scale bar is 100 μm. Ružičková et al. (2019). 

The second new species is named Palaeoconis azari, where ‘Palaeoconis’ means ‘ancient dust’ and ‘azari’ honours palaeoentomologist Dany Azar of the Lebanese University. This species is named from a single male specimen 1.93 mm in length preserved within a piece of transparent yellow amber. This specimen has well developed compound eyes and antennae with 21 segments. The abdomen is large and broad, the legs long and slender. The forewings are about 2.19 mm long and 0.93 mm wide, the hindwings about 2.12 mm long and 0.54 mm wide.

Palaeoconis azari. (A) Specimen in lateral view. (B) Wing venation and spots. (C) Detail of forewing venation with stiff seta on vein M. (D) Head from dorso-lateral view showing antennae, terminal segment of maxillary palp and eye. Scale bars are 500μm (A) and (B) and 50 μm in (D). Ružičková et al. (2019).

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Magnitude 6.1 Earthquake beneath eastern Taiwan.

The Taiwan Central Weather Bureau reported a Magnitude 6.1 Earthquake at a depth of 18.8 km roughly 10.6 km to the northeast of the city of Hauling in eastern Taiwan slightly after 1.00 pm local time (slightly after 5.00 am GMT) on Wednesday 3Friday 18 April 2019. Fifteen injuries have been reported following this event, including two tourists hit by a rockfall while hiking in the Taroko Gorge National Park, and minor damage was reported in a number of locations, including burst water pipes near Hualing rail station and minor structural damage to buildings in Taipei. The quake was felt across Taiwan, and in parts of the Chinese mainland.

Damage to a private apartment in Taipei caused by an Earthquake on 18 April 2019. AP.

Taiwan has a complex tectonic setting, lying on the boundary between the Eurasian and Philippine Plates, with the Eurasian Plate being subducted beneath the Philippine Plate in the South and the Philippine Plate being subducted beneath the Eurasian in the East. Subduction is not a smooth process even in simple settings, with plates typically sticking together as pressure from tectonic expansion elsewhere builds up, then suddenly breaking apart and shifting abruptly, causing Earthquakes.

 The motion of the tectonic plates beneath Taiwan. The University of Memphis.

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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