Sunday 31 July 2011

Discovery of Kepler 17-b, a new Hot Jupiter, announced.

The Kepler Space Telescope was launched by NASA in March 2009, with the express intention of looking for Earthlike planets. To this end it is located in Earth's trailing Lagrange point (i.e. it is situated on the same orbital pathway as Earth, but considerably behind us) to avoid interference from Earth and is aimed constantly at a single patch of the sky, taking in parts of the constellations of Cygnus, Draco and Lyra, to build up a very detailed picture of the stars there.

The Kepler Field of View, in relation to the Milky Way.

As well as some well publicized discoveries of rocky planets, Kepler has been building up a detailed picture of other objects in the field of view, including candidate planets of other types. One of these, KOI 203-b (KOI = Kepler Object of Interest), has been the subject of a study by a group of scientists led by Jean-Michel Désert of the Harvard-Smithsonian Centre for Astrophysics. Now that team have published a paper on the arXiv online forum maintained by Cornell University Library, in which they confirm KOI 203-b is a Hot Jupiter type planet, and rename it Kepler 17-b.

Kepler 17 (the star about which Kepler 17-b spins) is a dim star in the constellation of Cygnus. The study showed it is almost identical to our sun in mass and radius, though it is somewhat younger, ~2.9 billion years old as opposed to ~4.5 for our sun, and highly prone to sunspot activity. This sunspot activity made it hard to confirm that Kepler 17-b is in fact a planet rather than another sunspot, since both a sunspot and a planet are dark objects moving across the surface of the star. However repeated observations with the Kepler Space Telescope, the Hobby-Eberly Telescope, the Fred Lawrence Whipple Observatory, the Keck High Resolution Echelle Spectrometer and the Spitzer Space Telescope revealed that Kepler 17-b had a repeated cycle unlike that produced by a sunspot, and provided a limited amount of information about its atmosphere.

Kepler 17-b orbits its host star roughly once every 36 hours, in a roughly circular orbit, edge on to our solar system. It has a mass approximately 2.45 time that of Jupiter, and a radius approximately 1.3 times that of Jupiter. Its atmosphere is probably not inverted (i.e. it is probably warmer in the lower parts of the atmosphere, and cooler higher up), with gaseous Titanium Oxide and Vanadium Oxide present in the upper atmosphere. It is possible that the atmosphere is inverted (i.e. warmer above, cooler below) and that it contains gaseous Sodium and Potassium in its upper atmosphere.

Image of Kepler 17 (centre) taken with the Kepler Space Telescope.

See also Could there be life on Gliese 481d? and Exoplanets on Sciency Thoughts YouTube.

Magnitude 6.4 Earthquake off the Coast of Honshu, Japan. 31 July 2011

At 3.54 Japan Standard Time on the 31st July 2011 an earthquake with a magnitude of 6.4 on the Richter scale struck off the east coast of Honshu, Japan, 18 km from the city of Iwaki in Fukushima Coast. The earthquake, which took place at a depth of about 40 km, was felt across eastern Honshu and southern Hokkaido, but does not appear to have caused significant damage to buildings or infrastructure. No tsunami warning has been issued, nor have any deaths been reported. There have been a few reports of minor injuries, mainly to elderly residents of Fukushima Prefecture.

Map of Japan showing areas where the Earthquake was felt.

Japan is particularly prone to earthquakes; the Japan Meteorological Agency reported 21 earthquakes across the country on the 30th of July and another 21 on the 29th. The country has tight building regulations and a long history of planning for earthquakes, so quakes that would cause major problems in other countries often cause only minor damage in Japan. However the Japanese are not immune to earthquake damage, and really big quakes can overwhelm their defenses. On 11 March 2011 a magnitude 9 earthquake and associated tsunami caused widespread devastation, killing over 15 000 people, destroying several cities and causing a meltdown at the Fukushima Daiichi Nuclear Power Plant. The island of Honshu was moved 2.5 m to the east, relative to the rest of Japan.

Aerial footage of the March 2011 Tsunami.

Japan is so prone to earthquakes because it lies on the conjunction of three moving tectonic plates; the Eurasian, Philippine and Pacific. To the northwest the Eurasian Plate is eastward over the Philippine and Pacific Plates. To the south the Philippine plate is moving northward over the Pacific Plate but under the Eurasian Plate. To the east the Pacific Plate is moving west, but being forced under the Eurasian and Philippine Plates.

The movement of the Eurasian, Philippine and Pacific Plates under Japan.

To make matters worse the Eurasian Plate is somewhat fractured under Japan and East Asia. with two small breakaway plates; The Okhotsk Plate, which underlies northeast Honshu, Hokkaido and the Kamchatka Peninsula (Russia) and the Amurian Plate underlying the southwest of Honshu, Korea and Manchuria. The Okhotsk plate is moving southwest relative to the rest of Eurasia, and the Amurian south-southeast.

The Amurian and Okhotsk Plates under Japan.

This also makes Japan particularly prone to volcanic activity. As one plate is forced below another, rocks are melted by the heat of the earth's interior and rise as liquid magma through the overlying plates forming volcanoes. The complicated network of plates underlying japan leads to dozens of volcanoes all over the country, many of which are active.

Volcanoes of Japan.

The Japan Meteorological Agency currently has alerts out on a number of these volcanoes. Kirishimayama and Sakurajima in the southeast are both subject to Level 3 warnings; it is considered unsafe to approach the volcano. Miyakijima in the south and Suwanosejima Satsuma-Iojima in the southeast are subject to Level 2 warnings; it is unsafe to approach the crater. There is also a hazard warning on Ioto and Fukutoku-Oka-no-Ba in the Ogasawara Islands.

Friday 29 July 2011

Rock Carving on the Gower Peninsula; Britain's oldest art?

On Tuesday this week (26 July 2011) Bristol University announced the discovery of a carving of a speared reindeer in a cave on the Gower Peninsula. It is thought the carving could be over 14 000 years old and is possibly Britain's oldest known art.
The Gower Cave Carving.

The carving was discovered in September 2010 by Dr George Nash of the university's Department of Archaeology and Anthropology in an as yet undisclosed location in a cave on the peninsula. It is located in a very tight niche, where it is thought the artist would only have been able to use their right hand. The cave was already a known archaeological sight; in the 1950s researchers from the University of Cambridge found several hundred flint tools there, which were dated to 12 000-14 000 BC (i.e. 14 000 - 16 000 years ago).

The Gower Peninsula is also the location of Europe's oldest known ceremonial burial, the Red Lady of Paviland (actually a man), discovered in Goats's Hill Cave in 1823 by the Rev. William Buckland, the leading geologist and palaeontologist of the day (and inventor of the post-it note). At the time the skeleton, which was dyed red with ochre, was thought to be a Romano-British woman, but since discovered to be the skeleton of a young (at most 21 years old) man, dating from approximately 33 000 years ago.

The Red Lady of Paviland, now on display in the National Museum of Cardiff.

Cave paintings are not well known in the UK, but they have also been found in the Creswell Crags on the Nottinghamshire/Derbyshire border. The Creswell Crags caves appear to have been occupied on and off since about 43 000 BC, but the cave art is thought to be between 13 000 and 15 000 years old, so the Gower Peninsula claim for the oldest art is a a bit dubious. The Creswell Crags art is much more extensive with a number of carvings of animals and birds. They are also the most northerly cave paintings in Europe.
Bird carving from Creswell Crags.

Whichever of these is the older, the finds are important for what they tell us than because either one is the oldest; science is more than just a competition. Between 18 000 and 10 000 years ago Britain was suffering the most severe glaciation of the Devensian Ice Age, though this was not as severe as some previous ice ages, and did leave both the English Midlands and the South Wales coast free of permanent glaciation. Between 12 900 and 11 500 years ago a period called the Younger Dryas was causing particularly cold and dry conditions. It is notable that both the Gower and Creswell Crags art seem to pre-date this; the Younger Dyas may have been to severe for the artists, leading to a stop in British cave art soon after it started.

Despite Britain having been the subject of palaeoanthropological investigation longer than any other country, there is clearly still much to be found here.

Thursday 28 July 2011

2010 TK₇: Earth's Trojan Asteroid.

The term 'Trojan Asteroids' was first used by the Piedmontese astronomer and mathematician Joseph-Louis Lagrange to describe (at that time theoretical) asteroids traveling in the same orbit as Jupiter, but 60° degrees ahead and behind, which he predicted to be stable points. In total he came up with 5 'Lagrange Points' (now named in his honor); points at which the gravity of two bodies cancel one another out, resulting in no net force. L₁ is between a satellite and the body it is orbiting (bearing in mind planets are satellites of the sun), L₂ is on the opposite side of a satellite to the body it is orbiting, L₃ is 180° ahead of (or behind) an orbiting body, in the same orbit, L₄ is 60° ahead of an orbiting body in the same orbit and L₅ is 60° behind an orbiting body in the same orbit.

Jupiter's Lagrange Points.

Strictly speaking the term 'Trojan Asteroid' should be restricted to those sharing an orbit with Jupiter. Traditionally these are named after figures from the Trojan wars, those at the L₄ point being named after Greeks and those at the L₅ point being named after Trojans. Bodies orbiting in the same orbit as other planets should be referred to as 'Lagrangian Asteroids', but this is seldom adhered to.

In the 28 July edition of the journal Nature, a paper by a team lead by Martin Conners of of the Centre for Science at Athabasca University and the Department of Earth and Space Sciences at the University of California Los Angeles, report the discovery of a Trojan Asteroid at Earth's L₄ Lagrange point. The asteroid, 2010 TK₇ was discovered using the NASA Wide-field Infrared Survey Explorer space telescope in October 2010. 2010 TK₇ implies the 185th object discovered during period 'T' (1-15 October) in 2010. It is a rock with a diameter of about 300 m, which migrates back and forth between the Earth's L₃ and L₄ Lagrange points over a period of about 400 years.

NASA animation of the orbit of 2010 TK₇.

2010 TK₇ is not the only asteroid to have an orbital relationship with Earth.

3753 Cruithne was originally discovered in October 1986 by Duncan Waldron of the UK Schmidt Telescope at Sliding Spring Observatory. In 1997 a paper in the journal Nature by a team lead by Paul A. Weigart of the Department of Physics and Astronomy at York University and two co-authors described the orbital relationship between Earth and 3753 Cruithne. Essentially 3753 Cruithne is in an elliptical orbit about the sun intersecting the Earth's, with an year of 364 days, very similar to that of Earth. Seen from the Earth 3753 Cruithne seems to track a kidney shaped path ahead of us in our orbit, though due to the slightly shorter year it is slowly drawing ahead of us, and will eventually catch up with us from behind. When it does this an exchange of gravitational energy will slow it in its orbit so that it falls behind again, till Earth eventually catches up with it, when another exchange of gravitational energy will cause it to speed up again.

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The orbit of 3753 Cruithne as seen from outside the system.

The orbit of 3753 Cruithne as seen from Earth.

Wednesday 27 July 2011

New 'oldest bird' found in China.

For a hundred and fifty years Archaeopteryx lithographica has been the earliest known bird. The first specimen (actually a single feather) was found in 1861, in the Solnhofen limestone quarry in Bavaria, a fossil Lagerstatten (remarkable fossil bed) noted for exceptionally well preserved specimens; a number of other specimens followed. Archaeopteryx dates from the Late Jurassic, 150 million years ago. It shows clear dinosaurian affinities, but also has many birdlike features, most notably well developed flight feathers. It has been noted that had feathers not been found on Archaeopteryx, then it would probably been classified as a small dinosaur rather than a bird.

Archaeopteryx lithographica.

In the 27 July 2011 edition of the journal Nature a team lead by Xing Xu of the College of Life Science, Linyi Normal University announced the discovery of an earlier bird fossil. Xiaotingia zhengi, discovered in the Tiaojishan Formation in Liaoning, China is 155 million years old, or for convenience 'Early Late Jurassic'; fully five million years older than Archaeopteryx. Like Archaeopteryx, Xiaotingia shows both dinosaurian and avian features, though this is less remarkable than it was 150 years ago; many 'bird' features, such as feathers and wish-bones, are now known from a variety of dinosaurs. Nevertheless palaeobiological analysis of the fossil suggests that Xiaotingia is more closely related to modern birds than Archaeopteryx, and therefore can confidently be described as a bird.
Xiaotingia zhengi.

This is where things get a bit complicated. According to Xu et al. then if Xiaotingia is more closely related to modern birds than Archaeopteryx, than possibly Archaeopteryx should not be described as a bird. This is to do with the way birds are defined. If we define birds as modern birds plus all modern birds, plus their most recent common ancestor, then Archaopteryx is clearly not a bird as nobody thinks it is a direct ancestor of modern birds. Unfortunately all modern birds may well have had a quite recent common ancestor, which would mean that some Cretaceous fossils which are clearly very avian, such as Hesperornis might not be birds either.

So palaeontologists use a compromise definition, anything more closely related to modern birds than it is to Deinonychus (a dinosaur thought to be closely related to birds, but definitely not a bird) is a bird. This was fine up until now, as Archaopteryx seemed to be more like a modern bird than it seemed like Deinonychus. However Xiaotingia has more bird-like features than Archaeopteryx; producing a cladogram (family tree) for birds and bird-like dinosaurs including Xiaotingia moves Archaeopteryx closer to Deinonychus, and therefore away from the birds.

Deinonychus antirrhopus. Not a bird.

Ultimately though, this is about how we define birds as a group. Archaeopteryx clearly cannot be described as the earliest bird any more, but it should not be excluded from the group because of an artificial classification which was basically set up to rule it in and feathered maniraptiforms out. Only if good biological evidence that it is not sensible to describe Archaeopteryx as a bird comes to light should it be excluded. Sometimes technical definitions need to be tweaked to fit popular conceptions; if they did not then the definition of birds as we have it would not exist, so there is no reason to try to alter popular conceptions to fit the definition if it becomes obsolete.

See also The Ashdown Maniraptoran, An Australian Spinosaurid and Dinosaurs on Sciency Thoughts YouTube.

Earthquakes in the Gulf of California, 26 July 2011.

Just before 11.45 am local time a magnitude 5.9 earthquake struck 10 km beneath the Gulf of California (Sea of Cortez). This was followed by a magnitude 4.3 earthquake slightly before 1.00 pm, then a magnitude 5 quake at 1.40, then a magnitude 4 quake just before 9.45 pm. The quakes occurred roughly 125 NE of La Paz in Baja California State and 100 km SE of Los Mohis in Sinaloa State, Mexico, on the San Andreas Fault. There are no reports of any casualties, and no tsunami warning has been issued.

Map showing the location of the quakes (blue squares) and the San Andreas Fault (red line) in the Gulf of Mexico. From the United States Geological Survey

The San Andreas Fault runs along the length of the Gulf of Mexico, then northward through the US state of California. It is a transform, or strike slip fault caused by two plates (in this case the Pacific and the North American) moving past one another. Faults of this type are not particularly prone to causing tsunamis, but can trigger submarine landslides, which are a tsunami hazard. The main danger from this series of quakes is that by releasing pressure on one part of the fault, they increase it on another; thus the danger of a significant quake in the (populous) US State of California will have now increased.

The San Andreas Fault lies on the border between the north-moving Pacific Plate and the south-moving North American Plate.

The Gulf of Mexico is an extensional basin running along the southern part of the San Andreas Fault. The basin runs on-land as the Imperial Valley of Southern California; for this reason the southern part of the San Andreas Fault is sometimes known as the Imperial Fault. Extensional basins occur where two plates move apart from one-another, in this case the Pacific and North American. Potentially the Gulf of California could one day evolve into a new ocean, though this is not guaranteed, most extensional basins stop expanding before this happens.

See also Torino (Turin) rocked by mild earthquake, Earthquake on the Krygyzstan/Uzbekistan Border and Earthquakes on Sciency Thoughts YouTube.

Tuesday 26 July 2011

Volcanoes on the far side of the moon.

On 24 July 2011 an article appeared in the journal Nature Geoscience, reporting the discovery of shield volcanoes on an area of the far side of the moon called the 'Compton-Belkovich Thorium Anomaly' (CBTA). The article, by a team led by Bradley L. Jolliff of the Department of Earth and Planetary Sciences at Washington University in St. Louis, used data from the Lunar Reconnaissance Orbiter to build up a picture of the geochemistry and topology of the area, from which they draw the conclusion that the feature is in fact a cluster of shield volcanoes.

Wide angle photograph of the central part the CBTA.

This is not actually news, since the team had already announced the finding at the 42nd Lunar and Planetary Science Conference in March this year, but getting published in a prestigious journal seems to have brought the story to the attention of more of the press.

Shield volcanoes are made up of layers of lava from repeated eruptions, they tend to be dome shaped with low profiles, unlike the more classically cone shaped stratovolcanoes, which are made up of a mixture of lava and ash layers, but grow much larger. The largest known volcanoes are all shield volcanoes, such as Mauna Loa on Earth and Olympus Mons on Mars.

Shield volcanoes are well documented on the moon, where they are commonly referred to as 'lunar domes' due to their shape. Many lunar volcanoes are clustered around impact craters, suggesting that the impact event may have in some way triggered the eruption of the volcanoes. However this does not appear to be the case with the CBTA volcanoes.

Most of the moons surface is of course made up of volcanic material, since the only source of erosion is meteor impacts, which produce a regolith (soil) of rock fragments and dust, but nothing like the sedimentary processes seen on Earth. The lighter lunar terrae (highlands) are probably the result of the original cooling of the surface of the moon after its formation and the darker lunar mare (lowlands or oceans) appear to be later flood basalts. These mares are concentrated on the near side of the moon, though nobody is quite sure why; it was formerly thought that this was a tidal effect caused by the Earth's gravity, but it is now understood that the centrifugal forces caused by the moon's orbit should cancel this out.

The CBTA volcanoes appear to resemble none of these. They are apparently made up of evolved, silica rich volcanic material. This deserves a slight explanation. When lava cools different minerals solidify at different temperatures. Above 1000° basaltic lavas are formed, between 800° and 1000° andersitic Lavas and between 650° and 800° rhyolitic lavas. Thus the large plains of basalt that make up the lunar mare are assumed to be the result of vast amounts of very hot lava being expelled then cooling rapidly when exposed to the vacuum of space. The rhyolitic lavas of the CBTA must presumably have cooled beneath the surface for some time, so that the basaltic and andersitic components had precipitated out (solidified) before the rhyolitic components were ejected.

The location of the Compton-Belkovich Thorium Anomaly (C-B) on the moon; the yellow and green areas on the top left are the Lunar Maria, which are permanently turned towards the Earth.

Monday 25 July 2011

Is Mount Cleveland, Alaska, about to erupt?

On Wednesday the 20th July 2011 the Alaska Volcano Observatory issued an advisory warning on Cleveland Volcano in the Aleutian Islands, following the detection of thermal anomalies in satellite data. Since then the weather has prevented further satellite observations, and the warning remains in place.

Cleveland is located on the uninhabited Chuginadak Island, 1500 km southwest of Anchorage, and 75 km from the nearest settlement, Nikolski on Umnak Island, a village of 39 people. Due to its remote location it it seldom visited, and does not merit a network of seismometers, so there is not data available other than that from satellites.

Cleveland Volcano, in a remote part of the Aleutian Islands.

Cleveland has a history of sudden, explosive eruptions, it's last major eruption, in February 2001, threw ash 12 km into the air and produced a lava flow that reached the sea, so it is considered a hazard to aircraft.

Cleveland is a stratovolcano, a volcano formed by layers of ash and lava deposits with a classic cone shape. It rises 1730 m above the sea level, and is about 8 km across at the base. It shows little sign of erosion, and is probably no more than 10 000 years old. Due to its location it is completely treeless, and has little vegetation of any sort on its flanks, making its shape particularly notable.
An arial photograph of Mount Cleveland.

The Aleutians are a volcanic island arc, formed where the Pacific Plate is being subducted beneath the North American Plate; the arc actually continues onto land as the Aleutian Range, a string of volcanic mountains on the Alaskan Peninsula. As the Pacific Plate sinks into the Earth it is heated and partially melted; lighter minerals then rise up through the overlying North American Plate, forming volcanoes.

How volcanoes are formed by oceanic plate subduction.

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Torino (Turin) rocked by mild earthquake; 25 July 2011.

Just after 2.30 pm local time the northern Italian town of Turin was rocked by a small earthquake. No casualties are reported, but some there was some damage to houses and other buildings, phone lines were briefly cut and train services around the city were suspended while engineers ascertained that the tracks were safe.

Earthquake Location
Map showing the location of the quake, from the United States Geological Survey.

The epicenter of the quake (point on the ground directly above the centre of the quake) appears to have been about 22 km northwest of the city, with the quake occurring at a depth of between 5 and 25 km. The quake lasted about 20 seconds, and had a magnitude of between 4.3 and 4.8 on the Richter Scale; not really severe, but quite alarming. The quake was felt across a wide area of Piedmont (the north-easternmost province of Italy, of which Turin is the capital) and south-western France.

Italy is among the most earthquake-prone countries in Europe, though the Piedmont area is not particularly noted in this respect. The country has a complex geology. Part of the country is located on the European Plate, and part on the Apulian (or Adriatic) Plate; a micro-plate that broke away from northern Africa during the Cretaceous, and is now sandwiched between the African and European Plates, being pushed further into Europe by the northward movement of Africa. The borders of the Apulian Plate form the Apennine Mountains of central Italy, the Southern Alps and the Dinaric Alps (on the Balkan Peninsula).
The Apulian Plate, sandwiched between Africa and Europe.

This has given Italy a history of Earthquakes that dates back to classical times, with some major quakes taking place in the north. Until the late twentieth century these often lead to major loss of life and widespread destruction, as few buildings were earthquake-proofed and there was little infra-structure to deal with the aftermath of natural disasters.

In 1976 a magnitude 6.4 earthquake hit the Friuli region on the Slovenian border, killing 989 people, injuring 2400 and making 157 000 homeless. This lead to the creation of the Dipartimento della Protezione Civile, the Italian agency responsible for predicting, preventing, mediating and clearing up after major disasters. (This was also the only major earthquake that I have ever been involved in, at the age of seven).

Italian language documentary about the 1976 Friuli Earthquake.

Sunday 24 July 2011

Recent eruptions on Mount Etna.

On the 4th of July 2011 loud explosions were heard from a pit crater on the eastern flank of Mount Etna's southeastern cone (Etna has four cones, the southeast cone in the newest having only formed in 1978). That evening the cone was seen to be glowing, and over the next two days a series of small Strombolian eruptions (eruptions in which liquid lava is thrown into the air) were photographed by scientists from the Sezione di Cantania - Osservatorio Etneo. On the 7th these Strombolian eruptions became more intense, a number of volcanic tremors were felt and several small scoria (ash) cones started to form on the crater floor. Then, suddenly, all activity stopped.

On the morning of the 9th Strombolian eruptions and tremors started up again, then, at about noon, lava started to flow out of the crater and into the upper western part of the Valle de Bove, a horseshoe shaped caldera opening to the east. Later in the afternoon the Strombolian eruptions were replaced by a continual lava eruption. This was followed by the eruption of an ash plume that several kilometers into the air and rained ash down on several local towns, briefly closing Fontanarossa International Airport. Then, again, all activity abruptly ceased.

Strombolian eruption in Etna's southeast crater on the 9th of July 2011, by photographer Martin Rietz.

On the 11th July Strombolian activity started up again, this time on the westernmost cone, known as 'Bocca Nuova', the first lava eruptions from this cone since 2002. For the next two days these eruptions continued; lava bombs were observed being thrown high into the air and falling back into the crater, which remained incandescent throughout the nights. On the 13th a team of volcanologists visited Bocca Nuova, where they discovered a large vent had opened up in the floor of the crater, from which lava bombs were being thrown several tens of meters into the air.
Video footage taken at Bocca Nuovo by volcanologist Boris Behncke of the Institutio Nazionale di Geofisica e Vulcanologia Sezione di Catania.

On the fifteenth the volcanologists re-visited the crater. When they first arrived they found that activity was at a lower level than on the 13th, but within two hours it had risen higher than ever. To the west of the vent lava was issuing in a steady stream from beneath a sheet of solidified lava, and flowing into a depression in the western part of the crater.

On the 16th a series of loud explosions were heard from the southeastern crater, and ash was thrown from the crater on its eastern flank. This was followed on the 18th & 19th by a resumption of Strombolian eruptions in the crater, with lava being thrown 200-250 m in the air, and a number of lava flows were observed. A cloud of ash and gas was produced, and drifted to the east.

This all seems fairly dramatic, and has appeared in a number of news reports around the world. However for Etna this is all quite normal. There have been eruptions of one sort or another in every month since November 2010, when the volcano took a brief rest, having not erupted for the whole month of October (it erupted in September).

Etna first erupted about half a million years ago, beneath the sea off the east coast of Sicily, and has been going strong ever since. It now stands 3330 m above sea level, and covers 1200 km³. It is responsible for fertile soils across eastern Sicily. Records of eruptions on Etna go back to 1500 BC. It is Europe's second largest volcano, after Teide in the Canary Islands, and is one of the most active volcanoes in the world.

The location of Etna, in eastern Sicily.

Despite all this Etna has only ever caused 77 recorded deaths (the most recent being two tourists caught in a summit explosion in 1987) and relatively little destruction. In 1928 it destroyed the village of Mascali on its northeastern flank, though there were no reported casualties, the village being slowly overrun by a lava flow. In 1669 a much larger lava flow destroyed at least 10 villages, reaching the walls of the city of Catania, 40 km to the south, but again without loss of life. In 122 BC a heavy ash fall covered much of the region, causing several buildings to collapse in Catania. The destruction was deemed so severe by the Roman authorities that they granted the city a 10 year tax holiday. In about 6000 BC a landslide on the eastern flank of the volcano is thought to have caused a tsunami that caused destruction around much of the eastern Mediterranean.

Etna is located on the border of the African and European Plates, specifically where Africa is being subducted beneath the European Plate. As it is drawn into the Earth's interior material from the African Plate melts, and the lighter portions rise up through the overlying European Plate, causing a number of volcanoes including Etna and Vesuvius.

The subduction of the African Plate beneath the European Plate.

Earthquake on the Kyrgyzstan/Uzbekistan Border, 20 July 2011; at least 14 people dead.

Slightly after 1.30 am local time on the 20th July 2011 (or slightly after 7.30 pm on the 19th July GMT) an earthquake stuck in the Fergana Valley on the Kyrgyzstan/Uzbekistan border. It had a magnitude of 6.1 on the Richter Scale, and was at a depth of 16 km; shallow enough to have a considerable effect at the surface. Although the epicenter was on the Kyrgyrzstan side of the border, the majority of the damage seems to have occurred on the more densely populated Uzbek side of the border.
The geology of the area is complex; the Pamir Mountains to the southeast are being forced north into the Kazakh Shield to the northeast by the northward movement of India, far to the south. This causes shear in the Fergana Basin, as the rocks are twisted anti-clockwise, leading to thrust and strike-slip faulting. A thrust fault occurs where rocks are forced up and over one another; in this instance the faulting would be a blind-thrust; a thrust that happens beneath the surface, causing notable effects (e.g. earthquakes) but not visible faulting at the surface. A strike-slip fault occurs where two sections of rock slide past one-another. The earthquake in the Fergana Valley is likely to have been a combination of the two.
No fatalities were reported in Kyrgyrzstan, though 15 people were injured. Between 200 and 600 houses were damaged or destroyed in Batken Province (where the earthquake occurred) and (neighboring) Osh Province.

A single fatality was reported in Tajikstan, though this was caused by somebody jumping out of a window in panic, rather than directly by the earthquake. There are also reports of fractures to a dam under construction, delaying work while engineers investigate the situation.

Across the border in Uzbekistan the situation it much more serious (and confused). The city of Fergana (sometimes Ferghana or Farghona), capital of Fergana Province, with a population of 214 000, lies just 42 km from the epicenter of the quake (the point at ground level directly above the centre of the quake). For several hours the Uzbek authorities denied that anything had happened at all. It now appears that at least 13 people have been killed, and 86 injured, 35 requiring hospital treatment. At least 800 buildings have been destroyed, including several deemed to be of historic significance. It is likely that there will be further reports of injuries and possibly deaths as much of the population lives in remote villages in the mountainous region, and few buildings are earthquake proofed in any way.

There have been three other major earthquakes in the vicinity within the last 40 years, though none of these have caused any reported fatalities, though the wider region has suffered a number of significant quakes.

A series of earthquakes in 2006/2007/2008 destroyed a large number of buildings in Osh Province, displaced several thousand people and caused many fatalities. The worst of these, in October 2008, caused 15 fatalities (including 41 children), and destroyed the towns of Nura and Kura. This earthquake also caused damage in the Xingjiang Uyghur Autonomous Region of China.

In July 2006 a pair of magnitude 4.5 earthquakes in the Khatlon region of Tajikistan killed three people and injured 19 more. It also destroyed several thousand (non-earthquake-proofed) houses and caused a collapse in infrastructure that lead to a malaria epidemic, amongst other problems.

In 1985 a magnitude 7.4 earthquake in Wuquia County, Xingjiang, China, that was felt across the Fergana Basin and as far away as Pakistan. 65 deaths were reported.

In April 1966 a 7.5 magnitude earthquake destroyed Tashkent, the capital of Uzbekistan, making about 300 000 people homeless (figures on fatalities are not available; the Soviet Union was not keen on admitting to catastrophes at the time.

The aftermath of the 1966 Tashkent Earthquake.

In July 1949 a magnitude 7.4 earthquake in the Gharm Oblast region of Tajikistan (then the Tajik Soviet Socialist Republic), causing a series of landslides and killing over 7000 people (some estimates are as high as 28 000 fatalities).

In 1931 a magnitude in Fuyun County, Xingjiang caused a surface rupture 171 km long, with a maximum horizontal displacement of 14 m. This is now preserved as part of the Koktokay National Geopark. This quake caused about 10 000 fatalities.

In 1907 a 7.4 magnitude earthquake near Qaratog (sometimes Karatog) on the Tajikistan/Uzbekistan border caused between 12 000 and 15 000 fatalities.

See also The End of the Cretaceous and Earthquakes on Sciency Thoughts YouTube.

Saturday 23 July 2011

NASA sets its sights on Gale Crater, Mars.

On the 22nd of July this year NASA announced that it's next Mars rover, the Mars Science Laboratory, or Curiosity, will target Gale Crater, just south of the Martian equator on the fringes of Elysium Planitia. The Mars Science Laboratory is a car-sized rover intended for launch in November or December this year; it will cary the most advanced set of tools for the analysis of geological samples yet sent to Mars.
An artist's impression of the Mars Science Laboratory in action.

Gale Crater was chosen from a list of thirty potential landing sights due to it's extremely low elevation; water runs downhill so, logically, if Mars once had any liquid water, then the last places it endured would have been the lowest points, and anything being carried in the water would have a good chance of being carried to the lowest points on the planet. Evaporites (minerals formed when salt-laden water evaporates) have already been found on Mars; what the Mars Science Laboratory will be looking for in particular will be any organic compounds that could indicate that life once existed on the Red Planet.

Like many craters on bodies with little or no atmosphere Gale Crater (named after the Australian amateur astronomer Walter Frederick Gale) has a central peak. These are caused by material compressed during the original impact rebounding. In Gale Crater this is surrounded by an enormous mound of unidentified debris; in the southern part of the crater this is thought to be 4.5 k think, and overtops the rim of the crater. It is this unidentified debris that is of interest to scientists. It appears to be layered in structure, and may have been laid down over a period of 2 billion years (the crater itself is between 3.5 and 3.8 billion years old). Some scientists believe it is the eroded remains of an ancient sea- or lake-bed that once competely covered the crater.

3D Animation of the Gale Crater Landing Site.

The Mars Science Laboratory will be launched from Cape Canaveral Air Force Station in Florida between the 25 November and the 18 December 2011, using an Atlas V 541 Launch Vehicle, with four solid propellent rocket motors.

The Cruise Stage, weighing about 400 kg, will separate from the launch vehicle and carry the lander to Mars. It will have a propulsion system made up of eight thrusters fueled by hydrozene rocket fuel from two titanium tanks, and derive power from a large solar array. As well as carrying the probe to Mars the cruise stage will have to carefully monitor and regulate its temperature during the journey. To this end it has a system of coolant pipes, radiators and insulation blankets, monitored by a system of thermostats which can activate the cooling and heating systems as needed.

When the vehicle reaches Mars the Lander Stage will separate from the Cruise Stage and descend into the atmosphere, using a parachute to slow itself. As it nears the surface it will activate a set of four rocket motors, then detach itself from the parachute, decelerating as it descends the remaining distance. When it gets close enough to the surface it will hover on the rocket motors and lower the lander stage to the surface on a cable. The descent stage will then disconnect from the lander and accelerate away.

The lander itself is a car sized robot exploration vehicle with six independently controlled wheels on extended legs, designed to be able to get over obstacles 50 cm high. It will be fueled by a small nuclear power system with a plutonium power source. It has an array of cameras for navigation, hazard avoidance and scientific imaging, as well as an extendable arm, with a variety of scientific instruments.

Animation of the Mars Science Laboratory mission.

See also Pluto gains a forth moon, Visiting Vesta and Mars on Sciency Thoughts YouTube.

Thursday 21 July 2011

Pluto gains a fourth moon.

NASA scientists announced this week (20 July 2011) that they had discovered a new moon around the dwarf planet Pluto. The discovery was made by scientists using the Hubble Space Telescope in a set of five long exposure pictures taken over a period of two months and is referred to as 'P4' or 'S/2011 p1'. The moon has since been identified in earlier Hubble images, from 2006 and 2010.
The Pluto system as we currently understand it, incorporating the new moon P4.

Pluto was discovered in 1930 by Clyde Tombaugh, a young astronomer working at the Lowell Observatory in Arizona; its existence had been predicted as early as 1909, due to anomalies in the orbit of Neptune. At the time it was assumed that Pluto was a planet of some size, capable of disturbing the orbit of Neptune. Pluto spends part of its 248 earth year orbit inside the orbit of Neptune; this is not the same on every orbit, but alternates between a 20 and a 14 year stay.

In 1979 the first moon of Pluto was discovered by James Christy at the United States Naval Observatory. Dubbed 'Charon' it enabled scientists to make an estimate of the size of Pluto; to their surprise they found it has only 2% of the mass of Earth or 18% of that of the moon, making it far to small to affect the orbit of Neptune, re-starting the hunt for new planets in the outer solar-system. In fact it is now understood that (due to orbital effects) Pluto passes closer to Uranus than it ever does to Neptune. Charon is so large (relative to Pluto) that their mutual centre of gravity, the point about which they both rotate, is 2040 km above the surface of Pluto; they are the only known planet/moon system for which this is true (671 Patroclus is a pair of asteroids orbiting a mutual centre of gravity at Jupiter's trailing Lagrangian Point, but these are nothing like planets), and for this reason some scientists suggest they should be referred to as a pair of binary planets rather than a planet and its moon. Charon has a mass 2% that of the moon (1520 × 10¹⁸ kg) and a diameter of 1205 km. It orbits the systems centre of gravity at a distance of 17 530 km.

The Pluto/Charon system.

In 2004 another Pluto-like object was located in the outer solar system by a team led by Mike Brown at the California Institute of Technology (this is disputed; José Luis Ortiz Moreno of the Instituto de Astrofísica de Andelucía and his team at the Sierra Nevada Observatory in Grenada, Spain). Haumea has only a third the mass of Pluto, and orbits slightly further out, but it confirmed what scientists were beginning to suspect, that the outer solar system might contain a number of such objects.

An artists impression of Haumea. It is ellipsoid in shape and has a distinctive red patch. These cannot be directly imaged, but are the best interpretation of the available data on Haumea.

In 2005 Mike Brown's team working at Caltech's Palomar Observatory discovered two further objects in the outer solar system.

Makemake is similar to Haumea, roughly third the mass of Pluto, and further out, but the other new object, Eris, was more interesting. Eris is half again as far from the sun as Pluto - and a third again as big. Clearly if Pluto is a planet, then Eris is too.

Hubble images of Eris and it's moon Dysnomia.

Since it was likely that there are many more objects of this size in the outer solar system many astronomers were becoming uncomfortable with the term 'planet' to describe them. Thus in 2006 the International Astronomical Union settled on the term 'Dwarf Planet', to designate objects large enough to form a roughly spherical shape under their own gravity, but no so massive as to have cleared the area around their orbit of all other objects. Pluto, Haumea, Makemake, and Eris were placed in this category, as was Ceres in the asteroid belt. Ceres had also been classified as a planet at the time of its discovery in 1801, as were a number of other asteroids until the mid-nineteenth century, when it became clear that asteroids were too abundant to be classed as planets.

Also in 2005 two more moons of Pluto were discovered by the Hubble Space Telescope Pluto Companion Search Team. Nix and Hydra are further out and smaller than Charon, but orbit the same centre of gravity, so logically if Charon should be considered a planet, then so should Nix and Hydra. This is rather more problematic, as Nix is only 91 km in diameter and Hydra 114 km. Nix orbits the system's centre of gravity at 48 708 km and Hydra at 64 749 km.

The new moon, S/2011 p1, orbits the same centre of gravity as the rest of the system and therefore logically could also potentially be considered a planet, despite having a radius of between 14 and 34 km. It orbits between Nix and Hydra, at a distance of about 59 000 km.

Clearly the Pluto system is something very different to anything in the inner solar system, a cloud of objects more than a planet with satellites. Some scientists theorize that this may be the result of a collision early in the solar system's history, in the same way that Earth's moon (larger in comparison to its parent body than any other moon in the solar system except Charon) is thought to be the result of a collision between the early Earth and a Mars-sized object.

The images we have at the moment, even those taken with our best telescopes, are still pretty faint. In July 2015 NASA's New Horizon spacecraft is due to reach Pluto and will hopefully bring us far more information, and probably a good few more surprises.

See also Visiting Vesta and Dwarf Planets on Sciency Thoughts Youtube.