Monday, 23 January 2017

Investigating the nature of Extreme Trans-Neptunian Objects (474640) 2004 VN112 and 2013 RF98.

Extreme Trans-Neptunian Objects are Outer Solar System bodies with orbits that never bring them closer to the Sun than 30 AU (i.e. 30 times as far from the Sun as the Earth), and an average distance from the Sun of greater than 150 AU. The first of these objects, (148209) 2000 CR105, was discovered in 2000, since when a total of 21 have been found. Curiously these bodies not appear to orbit in the plane of the Solar System, but rather follow highly eccentric orbits that are consistent with having been thrown from this plane by encounters with a large, undiscovered body, a body that has been referred to as Planet 9 or Planet X.

In a paper published on the online arXiv database at Cornell University Library on 10 January 2017, and submitted for publication in the Monthly Notes of the Royal Astronomical Society, Julia de León of the Instituto de Astrofísica de Canarias and the Departamento de Astrofísica at the Universidad de La Laguna, and Carlos and Raul de la Fuente Marcos of the Universidad Complutense de Madrid describe the results of a study of the visible spectra of two Extreme Trans-Neptunian Objects, (474640) 2004 VN112 and 2013 RF98, made with the OSIRIS camera-spectrograph at the 10.4 m Gran Telescopio Canarias.

(474640) 2004 VN112 was discovered on 6 November 2004 by the ESSENCE Supernova Survey using the 4 m Blanco Telescope at Cerro Tololo International Observatory. The  name 2004 VN112 implies that 2813th asteroid (asteroid N112) discovered in the first half of November 2004 (period 2004 V), while the longer designation 474640 implies that it was the 474 640th asteroid ever discovered. It is estimated to be between 130 and 300 km in diameter, and has an orbit calculated from 31 observations made over a period of fourteen years. This orbit is calculated to take 5629 years and is tilted at an angle of 26°, taking the asteroid from 47.3 AU from the Sun at its closest out to 586 AU from the Sun at its furthest. It is calculated that an object of this size in an orbit of this nature would be visible to the ESSENCE survey for only 2% of its orbit, which suggests that a significant number of similar asteroids could be awaiting discovery.

2013 RF98 was discovered on 12 September 2013 by the Dark Energy Camera on the Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in La Serena, Chile. The designation 2013 RF98 implies that it was the 2456th asteroid (asteroid F98) discovered in the first half of September 2013 (period 2013 R). It is estimated to be between 50 and 120 km in diameter, and has had an orbit described from 38 observations made over a period of 56 days. This orbit is calculated to take 6527 years and be tilted at an angle of 30°, taking the asteroid from 36.1 AU from the Sun at its closest out to 662 AU at its farthest.

2013 RF98, at center of circle, as seen on 11 October 2013 by the Dark Energy Camera. Dark Energy Survey.

These objects are considered to be part of the Scattered Disk, objects sufficiently distant from the Sun that they are not influenced by tidal forces exerted by the eight known planets. Nevertheless both objects are tilted strongly from the Plane of the Solar System, which implies that they have had their orbits perturbed by the influence of some large body, one of the pieces of evidence that led astronomers to propose that an undiscovered ninth planet may be present in the Outer Solar System. These orbits are not only inclined to the Plane of the Solar System, they are very similar, leading de León et al. to speculate that these bodies might share a common origin.

To this end they examined the visual spectra of the two objects with the OSIRIS Spectograph in March and August 2016. Since all materials reflect light at certain wavelengths (spectra), the visual spectra of an object will reflect the materials present on its surface. Thus if two objects have similar visual spectra, then they are likely to have similar compositions.

De León et al. calculated that the spectral slope for 474640 is 12±2 %/0.1 μm and that of 2013 RF98 is 15±2 %/0.1 μm. As with the orbital parameters, these are not identical, but are very similar (to give some comparison the Trans-Neptunian Dwarf Planets Eris, Pluto, Makemake and Haumea have spectral slopes in the range 0–10 %/0.1 μm, while Sedna has a spectral slope of 26-42 %/0.1 μm). This suggests these objects have surfaces with variety of pure ices (water, methane, carbon dioxide etc.) as well as carbon and possibly amorphous silicates, but not complex organic molecules.

 Comparison between the spectra of (474640) 2004 VN112 and 2013 RF98 smoothed by a Savitzky-Golay filter and scaled to match at 0.60 μm. The most prominent absorption band of pure methane ice at 0.73 μm is not seen on either spectra. De León et al. (2017).

Given the similarities between the orbits and spectra of the two objects, de León et al.conclude that the two bodies are likely to share a common origin. They therefore consider two possibilities; that the two bodies are the result of a single object breaking up close to perihelion (when bodies are at their closest to the Sun, and receiving their most heat and tidal stress from it), or that they were a single object or binary asteroid (i.e. two asteroids orbiting one-another) torn apart by repeated tidal stresses from an encounter with a larger body.

Of these hypotheses, de León et al. reject the idea that the two objects reject the idea that the two bodies might represent the remains of a single body torn apart by tidal forces close to perihelion, as two fragments of such a bodies which fragment at perihelion are should not return to perihelion at the same time on every passage (if they did there would be no tidal forces pulling them apart) so happening to see the two together close to perihelion within a year would be a remarkable coincidence.

In order to test the second hypothesis, de León et al.used a computer model, which was run several thousand times with varying parameters, in order to work out the most likely scenarios for such an encounter. They conclude that the most likely scenario would be one where the parent body of the two objects repeatedly encountered a planet with a mass 10-20 times that of the Earth on an orbit with an eccentricity of up to 40% (an orbit in which it is 40% closer to the Sun at its closest than at its furthest), inclined to the Plain of the Solar System by 20-40°. Such a planet could cause a binary asteroid pair of weekly consolidated asteroid to break apart and nudge the parts onto the observed orbits due to repeated encounters over a period of 5-10 million years.

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Sunday, 22 January 2017

Magnitude 4.8 Earthquake in Mendoza Province, Argentina.

The United States Geological Survey recorded a Magnitude 4.8 Earthquake at a depth of 22.4 km in Mendoza Province, Argentina, at about 6.30 am local time (about 9.30 am GMT) on Saturday 21 January 2017. There are no reports of any damage or injuries relating to this event, but people have reported feeling it in the cities of Mendoza and San Rafael.

The approximate location of the 21 January 2017 Mendoza Earthquake. USGS.

Mendoza Province is located on the eastern margin of the Andes Mountains, one of the most tectonically active mountain ranges in the world, and the plains to the east of these mountains. The Andes are being formed as the Nazca Plate to the west is subducted beneath the South American Plate. This causes quakes in a number of ways. Firstly there is friction between the two plates as the Nazca Plate passes under South America. Then there is crumpling and upthrust of the South American as it is pushed from the west by the Nazca Plate and from the east by the expansion of the Atlantic. Finally there is volcanic activity in the Andes, as lighter minerals in the Nazca Plate are melted by the heat of the Earth's interior, then rise up through the overlying South American Plate to form volcanoes. 

The subduction of the Nazca Plate beneath the South American Plate, and how it causes Earthquakes and volcanoes. Pacific Earthquake Engineering Research Center.

This means that Earthquakes, even large events, are quite common in the area, but since the province is on the eastern margin of the Andes, such quakes usually happen at considerable depth (the margin between the Nazca and South American plates is angled downwards, so that maximum seismic activity happens close to the surface on the coast of Chile and deep within the Earth beneath eastern Argentina), so that much of the energy from the quake is dissipated before it reaches the surface. 

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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Asteroid (265482) 2005 EE passes the Earth.

Asteroid (265482) 2005 EE passed by the Earth at a distance of about 10 240 000 km (26.6 times the average distance between the Earth and the Moon, or 6.84% of the distance between the Earth and the Sun), slightly before 6.25 am GMT on Sunday 15 January 2017. There was no danger of the asteroid hitting us, though were it to do so it would have presented a considerable threat. ((265482) 2005 EE has an estimated equivalent diameter of 110-360 m (i.e. it is estimated that a spherical object with the same volume would be 110-330 m in diameter), and an object of this size would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be 600-110 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 1.5-5 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.

 The calculated orbit of (265482) 2005 EE. Minor Planet Center.

(265482) 2005 EE was discovered on 1 March 2005 by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2005 EE implies that it was the fifth asteroid (asteroid E) discovered in the first half of March 2005 (period 2005 E), while the longer designation (265482) indicates that it was the 265 482nd asteroid discovered overall (asteroids are not given this longer designation immediately, to ensure that numbered objects are genuine asteroids that have not been previously described). 

(265482) 2005 EE is calculated to have a 438 day orbital period and an elliptical orbit tilted at an angle of 6.17° to the plain of the Solar System that takes it from 0.76 AU from the Sun (i.e. 76% of the average distance at which the Earth orbits the Sun, slightly outside the orbit of Venus) to 1.50 AU from the Sun (i.e. 150% of the average distance at which the Earth orbits the Sun, roughly the distance at which the planet Mars orbits the Sun). 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 extremely common, with the last having occurred in May 2016 and the next predicted in July 2021. (265482) 2005 EE  also has frequent close encounters with the planet Venus, with the last calculated to have happened in April 2013 and the next predicted for February 2036. As an asteroid possibly larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (265482) 2005 EE is also classified as a Potentially Hazardous Asteroid.
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Saturday, 21 January 2017

Motorcycle crash causes major sinkhole in Wichita, Kansas.

Local authorities are warning drivers to expect several days of disruption after a motorcycle struck a fire hydrant, leading to a water leak that washed away sediments beneath a major interchange, leading to a sinkhole that closed both roads. The motorcycle was reportedly being chased y the police when it hit the hydrant, having failed to stop after a traffic violation. The rider was taken to hospital with injuries described as ;serious but not life-threatening'.

Sinkhole in Wichita, Kansas, caused by a motorcycle crash. KSN.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace. Potash, a potassium salt, is readily soluble and can be dissolved quickly if water gains access to deposits, leading to the rapid formation of sinkholes.

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Landslide kills at least two in Hunan Province, China.

Two people are known to have died and missing after a landslide struck a hotel in Hubei Province, China on Friday 20 January 2016. About 3000 m² of rock, soil and other material slumped onto the three story Mirage Hotel in Nanzhang County at about 7.30 pm local time, causing the building to collapse and trapping fifteen people in the building, five people have since been pulled from the site, two of whom subsequently died in hospital.

Rescue workers at the Mitage Hotel in Hubei following a landslide on 20 January 2017. Peoples Daily.

Hubei province is noted for a large number of landslides, but these are generally associated with the summer monsoon. 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. However this landslide occurred in the drier winter months, and does not appear to be related to any extreme weather events, and its cause is being investigated by local authorities.

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Understanding the ecological niche of the Neanderthals.

The Neanderthals were an early Human group living in Europe during the Late Pleistocene, from about 250 000 to about 40 000 years ago. They are considered by some palaeoanthropologists to have been a separate species of Humans, closely enough related to Modern Humans to have occasionally interbred with us, while others see them as a distinct group of Modern Humans adapted to living in Pleistocene environments that have now disappeared. The traditional view of Neanderthals is of a cold-adapted group, able to survive in harsh, Ice Age environments that Modern Humans could not tolerate, but unable to compete with Modern Humans in the milder climate of the Holocene. However an expanding number of Neanderthal finds and work upon these has painted a different picture, with the Neanderthals reaching their maximum range of expansion during the Last Interglacial Climatic Optimum, 125-119 000 years ago, when temperatures were on average 2°C warmer than today across Europe, and the last Neanderthals having lived around the Mediterranean Basin close to the Last Glacial Maximum, 40 000 years ago, at a time when Modern Humans, with more advanced textile manufacturing capabilities, were already moving into parts of Central Europe.

In a paper published in the Journal of Biogeography on 9 August 2016, Blas Benito and Jens-Christian Svenning of the Section for Ecoinformatics & Biodiversity at Aarhus University, Trine Kellberg-Nielsen and Felix Riede of the Department of Archaeology, also at Aarhus University, Graciela Gil-Romera of the Quaternary Palaeoenvironments and Global Change Department at Campus Aula Dei, Thomas Mailund of the Bioinformatics Research Centre at Aarhus University, Peter Kjaergaard of the Natural History Museum of Denmark at the University of Copenhagen, and Brody Sandel, also of the Section for Ecoinformatics & Biodiversity at Aarhus University, describe the results of study of the distribution of Neanderthals in Europe and the Middle East during the Last Interglacial Climatic Optimum, made with the aim of understanding the optimum ecological niche of the group.

Neanderthals have traditionally been thought of as a cold-adapted Human group, but this may not be the case. Walking with Cavemen/BBC.

Benito et al. mapped the known distribution of Neanderthal sites in Europe and the Middle East against factors likely to have effected their distribution, notably maximum temperature of the warmest month, minimum temperature of the coldest month, annual precipitation, precipitation during the warmest quarter, topological variability and average slope. Neanderthal populations from Central Asia and Siberia were not included in this study as insufficient information on these was available.

Some previous studies have suggested that parts of Central Europe were covered by dense forests during the Last Interglacial Climatic Optimum, which would have excluded large game upon which Neanderthals were dependent, and therefore the Neanderthals themselves, from these areas. However more recent studies have suggested that these areas were covered not by a single homogenous dense forest, but by a more patchwork environment with forested and open areas, which would not have excluded big game, implying that if Neanderthals were absent from these areas it would have been for other reasons. Benito et al. observe that the addition of detailed mapping of vegetation in Europe during the Last Interglacial Climatic Optimum would have been useful, but that such information is not available at a sufficiently detailed level at the current time.

It has also been suggested that the biggest limiting factor for Neanderthals in Northern Europe would be a short growing season, which would have limited the available food for prey animals both large and small, thereby limiting the amount of food available to Neanderthals. At the other extreme Neanderthals could have been excluded from some more southerly areas by a warm dry climate, with low summer rainfall again limiting plant growth and available food for herbivorous animals, again limiting the Neanderthals by reducing their hunting opportunities. This latter theory has been undermined somewhat by the discovery of a large number of Neanderthal sites around the Mediterranean Basin, leading to suggestions that Neanderthals may have been able to cope with an absence of game animals in these regions by substituting seafood such as shelfish gathered on the shore.

Neanderthals were found to be able to tolerate a high temperature range, with a maximum average warmest month temperature of 38.4°C and an average minimum coldest month temperature of -19.3°C. Reasonably high rainfall levels also seemed to be important, with Neanderthals favouring areas with about 900 mm of rain per year and high summer rains. Neanderthals also favoured areas with high topological variability (on average 73.8%) and an average slope between 0.5 and 6.8°. In layman’s terms this means they needed a reasonably varied terrain, enabling foraging in a variety of habitats, and avoided both flatlands and mountainous regions. The absence of Neanderthals from mountain ranges such as the Alps and Pyrenees has been noted before, and it has been suggested that this may be due to the loss of archaeological remains by glacial scouring. However a number of recent finds of Pleistocene Cave Bears from sites in the Alps has suggested that such remains can survive here at least in caves, and Neanderthals are known to have taken advantage of such natural shelters just as Bears do.

Neanderthal sites in the European and Irano-Turanian Region used to calibrate the models and habitat suitability during the Last Interglacial Climatic Optimum. Site codes: (1) Lehringen; (2) Veltheim Steinm€uhle; (3) Neumark Nord; (4) Burgtonna; (5) Waziers; (6) Jaskinia Nietoperzowa; (7) Caours; (8) Gouberville; (9) Velykyj Glybochok; (10) Horka Ondrej; (11) Yezupil; (12) Subalyuk Cave; (13) Krapina; (14) Betalov Podmol; (15) Kabazi II; (16) Grotte Vauffrey; (17) Payre; (18) Abri des Pécheurs; (19) Oyambre; (20) El Castillo; (21) Lezetxiki; (22) Crvena Stijena; (23) Saccopastore; (24) Estragales; (25) Grotta del Cavallo; (26) Grotta Riparo del Poggio; (27) Gánovce; (28) Bolomor Cave; (29) La Carihuela; (30) Del Angel Cave; (31) Karain Cave; (32) Es Skhul; (33) Tabun. Benito et al. (2016).

The single highest factor affecting the distribution of Neanderthals turned out to be annual rainfall, followed by minimum winter temperature (undermining the idea that Neanderthals were a cold-adapted group). However at local level slope was the most important factor followed by summer rainfall and coldest winter temperature again.

This model indicates that the optimum environment for Neanderthals was found in Southern Europe and the Mediterranean Basin, in central and southern France, Italian Peninsula, the Mediterranean islands, along the Atlantic coast of the Iberian Peninsula, the southern coast of the Black Sea and the Levantine coasts of the Mediterranean Sea. A less optimal environment was found in inland areas of Southern Europe and coastal areas further north, such as the continental areas of the Iberian Peninsula, British Isles, Dinaric Alps, Balkan Mountains, continental areas of Anatolia and the southern coasts of the Baltic Sea. Others areas, such as high-altitude regions of the Alps and Pyrenees, across the Scandinavian Shield, and the current Arabian Desert, were highly unsuitable for Neanderthal occupation.

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Friday, 20 January 2017

Magnitude 5.7 Earthquake triggers deadly avalanche in Rieti Province, Italy.

The United States Geological Survey recorded a Magnitude 5.7 Earthquake at a depth of 10 km, roughly 5 km to the southwest of the town of Amatrice in Rieti Provice in Lazzio, Central Italy, at about 10.25 pm local time (about 9.25 pm GMT) on Wednesday 18 January 2017. The event has been followed by several serious aftershocks, which are reported to have caused damage to a large number of buildings, and in addition has been linked to an avalanche that stuck a hotel near Pescara in the Abruzzo Region, an event which is known to have killed at least four people, with about twenty still missing.

Rescue workers searching the scene of an avalanche in the Abruzzu Region of Italy on 18 January 2017. Vigili del Fuoco.

Historically Italy has suffered a number of devastating Earthquakes that lead to large numbers of casualties, though in recent decades the country has made serious attempts to prevent this, with better warning systems and tighter building regulations, though the large number of historic buildings in Italy, which cannot easily be replaced (and any attempt to do so would be unlikely to succeed due to their high cultural value), meaning that the country is unlikely to be completely risk free any time soon.

 Earthquake damage in a mountain village in central Italy following the 18 January 2017 event, AP.

Italy is in an unusual tectonic setting, with the west of the country lying on the Eurasian Plate, but the east of the country lying on the Adriatic Plate, a microplate which broke away from North Africa some time in the past and which is now wedged into the southern margin of Europe, underlying eastern Italy, the Adriatic Sea and the west of the Balkan Peninsula. This, combined with the northward movement of the African Plate into Italy from the south, leads to uplift in the Apennine Mountains that run the length of the country, and makes Italy extremely prone to Earthquakes. 

Map showing the tectonic plates underlying Italy and southern Europe, and the location of the l'Aquila Earthquake. Napoli Unplugged.

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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