Sunday, 28 August 2011

A Eutherian Mammal from the Jurassic of China.

Modern mammals are divided into three groups by biologists: the monotremes which lay eggs, the marsupials which give birth to underdeveloped live young then raise these young in pouches, and the placental mammals which give birth to large, well developed young. Palaeontologists rarely get the opportunity to observe animals giving birth, so they use a different system of classification, based largely on dentition. This is complex, and includes many extinct groups, but the relevant bit here is that modern placental mammals are included in a group called the Eutheria, and modern marsupials are included in a group called the Metatheria.

It is not possible to determine how a fossil species carried its young, but palaeontologists are able to say that they believe any specimen they label a eutherian to be more closely related to modern placental mammals than it is to marsupials (the reverse is not true, since the eutherians are thought to have evolved from metatherians).

DNA evidence suggests that the eutherian and metatherian lines split around 160 million years ago, in the Middle-to-Late Jurassic, although fossil evidence of this has proved hard to find, since Mesozoic mammals were largely small, and tended to live in trees, giving them poor preservational potential.

Up until this year the oldest known eutherian mammal was Eomaia scansoria, a 10 cm long shrew-like mammal from the Early Cretaceous, described by a team lead by Qiang Ji of the Chinese Academy of Geological Sciences in a paper in the 15 March 2002 edition of the journal Nature.
A reconstruction of Eomaia scansoria by Mark Klinger of the Carnegie Museum of Natural History.

The 25 August edition of Nature contained a paper by a team lead by Zhe-Xi Luo of the Carnegie Museum, which describes a new eutherian mammal, Juramia sinensis, from the Middle Jurassic of Liaoning in northeastern China. At 160 million years old this fossil is pretty much at the predicted origin of the group. The specimen is about 40 mm long, which includes the skull and torso but no tail. Preservation of the specimen is excellent, showing the dentition clearly, and traces of fur around the body.

Like most other Mesozoic mammals Juramaia appears to have been arboreal (tree dwelling) and omnivorous. It was found in the Tiaojishan Formation which is known largely for plant fossils, but which has produced a number of other well preserved vertebrate fossils, including small dinosaurs and pterosaurs. It appears to have been a subtropical woodland environment with a rich, volcanic soil. The formation is contains a number of pyroclastic (volcanic) deposits which allow for good isotopic dating. The earliest levels of the Tiaojisha appear to be about 160 million years old, with the youngest being no more recent than 153 million years.
Reconstruction of Juramaia sinensis, again by Mark Klinger.

The fossil has been deposited at the Beijing Museum of Natural History.

See also New 'oldest bird' found in China and Mammals on Sciency Thoughts YouTube.

Quebec Earthquake, 27 August 2011

At about 2.25 am on Saturday 27 August 2011, the Canadian province of Quebec suffered a minor earthquake. The quake measured 3.0 on the Richter Scale and occurred at a depth of about 12.8 km, just about large and shallow enough to have been felt, but unlikely to have caused any damage. The epicenter of the quake was about 40 km to the east of Quebec City.

Quebeck sits on the Canadian Shield, an ancient part of the North American Plate, and should in theory be very tectonically stable. Nevertheless it has two distinct earthquake zones, the Charlevoix Seismic Zone in the northeast and the Western Quebec Seismic Zone in the west, though this earthquake occurred in southeast of the state, outside of both zones. The mechanism behind this seismic activity is not well understood, but is being monitored and studied by the Canadian National Seismograph Network. It is thought that this activity is caused by stresses on the North American Plate resulting from the expansion of the Atlantic and the subduction zones along the Pacific Coast.

There has only ever been one death reported due to an earthquake in eastern Canada, that of a young girl in Montreal in 1732, and this report is considered dubious.

Saturday, 27 August 2011

PSR J1719-1438b. The Diamond Planet.

A neutron star is a superdense object made almost entirely of neutrons packed together as they would be in an atom nucleus, but somehow able to group together in vast numbers in the absence of charged protons and electrons. Since neutrons have mass they are massive objects, typically 1.2-2.0 times the mass of the sun, but are very compact at most a few tens of thousands of kilometers across. Neutron stars are formed in the cores of massive stars as they go supernova; as the outer parts are blown away by the explosion the inner core is forced in upon itself and compressed into the neutron star. Since the stars that form them are invariably rotating, so are the neutron stars when they are formed, and because they have lost volume while retaining mass they spin much faster than their parent stars, just as an ice-skater spins faster when she pulls in her arms.

A pulsar is a neutron star which emits a beam of powerful electromagnetic radiation. This comes from a fixed point on the star, along its magnetic axis, and therefore spins with the star. This is only detectable while it is pointing at us, so many (some think all) objects that we see as neutron stars may be pulsars.

Two beams of radiation being emitted by a Pulsar. Unless the Pulsar is rotating at 180° to its polar access only one of these beams will be visible from any one fixed point in space.

Pulsars are named using the letters PSR (Pulsating Source of Radio) followed by their right ascension (celestial longitude) and declination (celestial latitude). If they are close to other pulsars in the sky (not necessarily close in space, but in a straight line from seen from Earth), then letters can be appended to the designation to help distinguish them, such as the J in PSR J1719-1438.

The pulsar PSR J1719-1438 was discovered in 2009 during a survey using the Parkes 64 m Radio Telescope in New South Wales, as part of the Parkes High Time Resolution Universe Legacy Survey for pulsars. It is a Millisecond Pulsar (MSP) a pulsar that spins faster than can be accounted for by the (theoretical) original mass of the star which produced it, in the case of PSR J1719-1438 rotating once every 5.7 milliseconds. Pulsars of this sort are thought to have had their rotation accelerated by the accretion of mass from a binary companion. Previous studies have shown many to have white dwarf companions (white dwarfs are stars that have stopped undergoing nuclear fusion, but which are still producing heat and light due to gravitational effects). PSR J1719-1438 is approximately 4000 light years from Earth, in the constellation of Serpens.

Image centered on PSR J1719-1438, taken with the Keck LRIS instrument.

This week a paper appeared in the 25 August edition of the journal Science, in which a team lead by Matthew Bailes of the Centre for Astrophysics and Computing at Swinburne University of Technology in Melbourne and the Department of Astronomy at the University of California, Berkeley, in which they describe the results of further study of PSR J1719-1438 using the Parkes Telescope and the Lovell Telescope at Jodrell Bank in Cheshire, England as well as the Keck 10 m Telescope in Hawaii, and the conclusions drawn from them.

Bailes et al. were able to detect a very slight wobble in the motion of PSR J1719-1438, regular enough to be the product of an orbiting body, and from this were able to make significant deductions about both bodies in the system.

For the sake of convenience standard astronomical nomenclature is used here, so that the pulsar is referred to as PSR J1719-1438A (a for the first body discovered in the system, capitalized because it is a star) and the orbiting body referred to as PSR J1719-1438b (b for the second body discovered in the system, but not capitalized, indicating a planet), although Bailes et al. do not use this nomenclature and the terms 'star' and 'planet' need to be used reservedly in this instance.

Bailes et al. calculate that PSR J1719-1438A is a body approximately 20 km across with a mass 1.4 times that of the sun. PSR J1719-1438b orbits this body once every 2.17 hours, at a distance of about 600 000 km, slightly less than the radius of the sun; the whole system could fit within the volume of our son. It has a volume roughly equal to that of Jupiter, but is roughly 20 times as dense, making it the densest planet yet discovered.

Bailes et al. propose that PSR J1719-1438b might by made up of crystalline carbon - diamond, which would fit the known data. Such an object could in theory be formed from the core of a white dwarf star, stripped of its outer layer.

PSR J1719-1438 is not the first pulsar known to host planets. The first confirmed planets to be discovered outside our own orbited the pulsar PSR B1257+12, approximately 2000 light years from Earth in the constellation of Virgo. This has three known planets, and one suspected.

PSR B1257+12A has a radius of about 15 km, and a mass of roughly 1.5 times that of our sun. PSR B1257+12b orbits this every 25 days at a distance of approximately 28 400 000 km. It has a mass of roughly 0.02 times that of the Earth, or a third that of Mercury. PSR B1257+12c orbits at a distance of 54 000 000 km, slightly closer to PSR B1257+12A than Mercury is to the sun. It has a mass of 4.3 times that of the Earth. PSR B1257+12d orbits at 69 000 000 km, slightly further out than Mercury, and has a mass of 3.9 times that of the earth. A possible fourth planet, PSR B1257+12e may orbit at roughly 450 000 000 km, which would be between the orbits of Mars and Jupiter in our system. This planet, if it exists has a mass of only 0.0004 times that of the Earth, roughly twice that of Ceres or Pluto in our system, and much smaller than our moon.

Comparison between the sizes of bodies in our solar system and the PSR B1257+12 system, and the distances between them (distances and size of planets are not to scale).

See also New Exoplanet: TrES-5, TrES-2b, the black planet and Exoplanets and Stars on Sciency Thoughts YouTube.

Tuesday, 23 August 2011

Colorado shaken by earthquake. 22 August 2011.

At about a quarter to midnight on Monday 22 August 2011 an earthquake occurred in Colorado, 15 km west-southwest of Trinidad, on the border with New Mexico, or 290 km south of Colorado, and was felt in Colorado, New Mexico and Kansas. The quake was shallow, at a depth of about 4 km and measured 5.3 on the Richter Scale; shallow and large enough to be dangerous. There are no reports of any casualties, but some minor damage to houses and roads has been reported.

The area is close to the Sangre de Cristo Fault, part of the Rio Grande Rift system. The Rio Grande Rift runs through Colorado and New Mexico and south into Mexico and Texas. It is effectively a split opening in the North American Continent, with the potential to form a new ocean (though most rifts of this kind do nothing of the sort), that has been drawing apart for about 35 million years. The Sangre de Cristo Fault forms part of the eastern boundary of this rift. As the fault opens, surface rocks in the central part sink downwards, tearing away from the rocks on either side.

Part of the Sangre de Cristo Fault, showing how the sediments to the west (right) are sinking down into the Rio Grande Rift.

Southern Colorado has a history of earthquakes, with some historical quakes having caused damage to towns and cities across the state. However, while it is clear that some of these earthquakes are natural, many have been attributed to drilling and blasting by the mining industry, which is extensive (and extremely financially important) within the state. Colorado produces coal, gold, molybdenum, silver, gypsum, limestone and uranium, amongst other resources. This quake is thought to be of natural origins.

Virginia Earthquake shakes Washington, New York. 23 August 2011.

A few minutes before 2.00 pm on 23 August 2011 the eastern coast of the United States was shaken by a rare earthquake. The quake was centered 14 km south of Mineral (141 km southwest of Washington DC), Virginia, and was felt as far south as South Carolina, as far north as New Hampshire and as far east as Oregon (this is slightly dubious). The quake was measured as 5.9 on the Richter Scale by the US Geological Survey, and was at a depth of about 0.1 km - very shallow and therefore potentially very dangerous, particularly in an area like the eastern US where buildings have limited earthquake protection. As yet there have been no reports of any casualties, but there has apparently been considerable damage to property in and around Mineral and there are reports of damage to the central spire of the National Cathedral in Washington DC. In addition the North Anna Nuclear Power Plant in Virginia was taken off line while it was checked for any damage, and buildings were briefly evacuated in several East Coast cities.

A magnitude 2.8 aftershock was felt locally at 2.46 pm. This was also a very shallow quake (~0.1 km) to the south of Mineral, although with slightly less than one thousandth of the energy this is much less likely to have caused any significant damage.

Virginia is a long way from any active tectonic margin, and is not known for its earthquakes. However the state does have two potentially hazardous faults, associated with the origins of the Appalachian Mountains during the Palaeozoic. This occurred when the ancient Iapetus Ocean closed, causing a collision between North America and Europe. When this happened the rocks that form the modern Blue Ridge Mountains were pushed up over the older rocks to the east. This lead to the formation of a fault on the eastern margin of the Blue Ridge Mountains, between the Blue Ridge rocks and the older sediments they overlay. In the West the rocks of the overlying Piedmont Province were also forced upwards, but have been slipping back, away from the Blue Ridge Province (this is a simplified explanation), creating a second major fault, between the Piedmont and Blue Ridge Provinces. It is on this fault that the earthquake occurred.

A cross section through the rocks of Virginia.

Earthquakes were reported in Virginia in 1774, 1811, 1812, 1828, 1833, 1852, 1861, 1875, 1897, 1898, 1908, 1910, 1918, 1919, 1929, 1959, 1977, 1978, 1980, 1981, 1983, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1991, 1992, 1993, 1994, 1994, 1995, 1996, 1997, 1998, 2000, 2001, 2003, 2004, 2006, 2007, 2009 and 2010. While many of these caused damage and alarm, only two fatalities have ever been attributed to an earthquake in Virginia, when a quake in 1833 caused a mine collapse at Brown's Coal Pits, near Dover Mills in the north of the state.

Sunday, 21 August 2011

New Exoplanet: TrES-5.

On the 17 August 2011 a team from the Trans-Atlantic Exoplanet Survey reported the discovery of a new 'Hot Jupiter' type exoplanet in a paper on the online arXiv forum, hosted by Cornell University Library. The planet orbits the star GSC 03949-00967, a G-type dwarf (the same sort of star as our sun) slightly under 90% of the mass and radius of our sun, roughly 1175 light years from our solar system in the constellation Cygnus, the faintest star about which is the faintest star about which an exoplanet has been discovered using Earth-based telescopes.

An artist's impression of a Hot Jupiter type planet.

The team was lead by Georgi Mandushev of the Lowell Observatory in Arizona, and first observed the planetary candidate in 2007 using the Planet Search Survey Telescope at Lowell Observatory and the STARE Telescope (STellar Astrophysics and Research on Exoplanets) in the Canary Islands. In order to confirm this was an exoplanet, and not a dim binary star or some sort of sunspot, follow up observations were made using the Hall and Perkins Telescopes at Lowell Observatory, and the Tillinghast Reflector Echelle Spectograph at Fred Lawrence Whipple Observatory in Arizona.

The paper refers to the planet as TrES-5 and the star as GSC 03949-00967 (GSC stands for 'Guide Star Catalogue', the numbers are co-ordinates in the sky), though strictly speaking the star should be referred to as either TrES-5A or GSC 03949-00967A and the planet as TrES-5b or GSC 03949-00967b if conventions on the naming of astronomical objects are followed.

Mandushev et al. calculate that TrES-5 has a mass of 1.8 times that of Jupiter and a radius 1.2 time that of Jupiter. This is roughly the radius we would expect for a planet of this mass, which is surprising as most 'Hot Jupiter' type planets have anomalously large radiuses; Mandushev et al. attribute this to the age of the system; the GSC 03949-00967 system is 7.38 billion years old, which may have allowed the planet to reach an equilibrium temperature distribution not seen in younger 'Hot Jupiter' planets. The planet takes 35 hours and 30 minutes to orbit its star, and does not show any appreciable eccentricity in its orbit.

See also TrES-2b, the black planet, The discovery of Kepler 17-b and Exoplanets on Sciency Thoughts YouTube.

Saturday, 20 August 2011

Earthquake in Vanuatu, 21 August 2011.

Just before 5.20 am on Sunday 21 August 2011 (6.20 pm on Saturday 20 August, GMT) a large earthquake occurred roughly 40 km south-southwest of the Island of Efate, Vanuatu. This was recorded as a magnitude 7.0 quake at a depth of 28.5 km by the United States Geological Survey and a magnitude 7.4 magnitude quake at a depth of 36 km by the Vanuatu Meteorological Services. This was followed by a magnitude 5.0 quake an hour later. The Pacific Tsunami Warning Centre did not issue an ocean-wide tsunami alert, but did warn of the possibility of a local tsunami; the Vanuatu Meteorological Services also issued a tsunami waring. A small tsunami wave, just over 1 m high was observed on Efate about an hour after the initial quake. The tsunami warning has now been lifted; there are no reports of any damage or casualties on Efate.

The location of the quake.

Vanuatu is a chain of 80 volcanic islands on the boundary between the Pacific and Australian plates. The Australian plate is being subducted beneath the Pacific at a rate of 9 mm a year, making the area highly prone to earthquakes. There are 13 active volcanoes in the islands, although there is none on Efate, despite it being thought to be less than 3 million years old. The nearest is North Vate on Nguna Island, 6 km to the north.

Is the Moon younger than we think?

Current theory suggests that the moon was formed early in the history of the solar system when a Mars sized planet (sometimes referred to as Theia) collided with the early earth, throwing a large chunk of the earth's crust into orbit about the planet. This then coalesced into a single body over a period of about 100 million years (0.1 billion years). The surface of the moon is thought to have solidified by about 4.5 billion years ago.

An initial collision with a Mars-sized body would have left the Earth with a ring of debris, that later coalesced to form the Moon.

This date was reached by examining the isotope ratios of minerals in volcanic rocks recovered from the moon by the NASA Apollo Missions between 1969 and 1972. This works roughly like this: Volcanic rocks form from the solidification of liquid magma. As the Magma cools, different minerals form at different temperatures, and each of these minerals has a known chemical composition at the time of formation. Some of these minerals contain unstable, radioactive isotopes, that decay to form other elements over time, elements that would not have been present when the minerals formed since they have different chemical properties to the original elements. Since radioactive isotopes decay at a known rate, it is possible to calculate the age of a mineral crystal by measuring the ratio of the original isotope to the decay product. The most familiar example is uranium, which decays to form lead over time, but the process also works with elements have both stable and unstable isotopes (hence isotope dating) as long as it is possible to measure the amount of the unstable isotope rather than the overall amount of the element (not hard if you have access to a mass spectrometer).

In this weeks edition of the journal Nature (17 August 2011), a paper by a team lead by Lars E. Borg of the Chemical Sciences Division at Lawrence Livermore National Laboratory details an examination of a piece of anorthosite (a type of volcanic rock) recovered by the Apollo 16 mission from the Descartes Highlands (roughly in the middle of the lunar disk when seen from Earth).

Apollo 16.

The (light) Lunar Highlands are generally considered to be the older part of the lunar surface; the (dark) Lunar Maria/Lowlands are thought to be later flood basalts. The piece of rock in examined by Borg et al. had large crystals, implying that it formed slowly deep beneath the surface of the moon (rock crystalizing at the surface would be exposed to the vacuum of space, causing it to solidify rapidly, forming small crystals), then was brought to the surface by some process, possibly the impact that formed the nearby Descartes Crater. This study was able to examine the presence of three product elements (lead, samarium and neodymium) giving a good correlation for the results.

Borg et al. derived an age of 4.3 billion years for the Descartes Highlands anorthosite, 200 million years (0.2 billion years) younger than the current estimated age of the surface of the moon. From this date Borg et al. deduce that the moon is either younger than current theories imply, or that it formed in a different way.

There are a couple of problems with this reasoning.

Current theory implies that the lunar highlands formed about 4.5 billion years ago, and that the Maria/Lowlands are younger flood basalts. This implies that while the surface of the moon had solidified 4.5 billion years ago, there was still liquid magma beneath the surface (where the anorthosite sample is thought to have formed). Current estimates for the age of the Lunar Maria rage from 3.5 to 4.2 billion years old; comfortably younger than the new date. A paper in the 24 July 2011 edition of Nature Geoscience by a team lead by Bradley L. Jolliff of the Department of Earth and Planetary Sciences at Washington University in St Louis reported the likely presence of shield volcanism in the highlands of the far side of the moon, implying that liquid magma may have been present beneath the surface even more recently.

Earlier this month the 4 August edition of the journal Nature contained a paper by Martin Jutzi and Eric Asphaug of the Earth and Planetary Science Department at the University of California Santa Cruz suggested a new theory of lunar formation. This theory suggested that the Lunar Maria formed earlier than the Highlands, which are the result of later accretion of material from a second Earth-orbiting satellite. This theory would allow for a younger date for the anorthosite minerals, although the large crystal sizes in the sample suggest it was formed bellow the surface of a reasonably large body, less likely on the smaller, unconsolidated object implied from Jutzi and Asphaug's theory.

Seen in this light the data from the Descartes Highland anorthosite tends to support the current theory of lunar development, rather than the new theory.

Saturday, 13 August 2011

A Pregnant Plesiosaur.

The plesiosaurs were a group of marine reptiles that appeared in the Middle Triassic, about 230 million years ago and went extinct in the KT extinction at the end of the Cretaceous, 65 million years ago. They are thought to have evolved from Nothosaurs, a group of semi-aquatic marine reptiles. The plesiosaurs are thought to have been fully aquatic from the outset. The term sauropterygians is used to include the nothosaurs and the plesiosuars, plus the pachypleurosaurs; lizard-like aquatic reptiles. The sauropterygians are thought to be related to the squamates - snakes and lizards.

A reconstruction of Pistosuarus, generally considered to be the earliest plesiosaur. It does not appear to be well suited to life on land.

The plesiosaurs are split into two taxonomic groups, the plesiosaurs proper and the pliosaurs (plus a few early species of uncertain affinities). The pliosuars were aquatic reptiles with short necks, elongated heads and powerful jaws, with many conical teeth (ideal for seizing large prey). They ranged from 4 m to 25 m in length and appeared in the Late Triassic, persisting till the end of the Cretaceous.

Reconstruction of a pliosaur attacking a mosasaur (large Mesozoic marine lizard) by paleo-artist Dan Varner.

The plesiosaurs proper are divided into five families, the Elasmosaurs, the Plesiosuarids, the Polycotylids, the Cimoliasaurs, and the Cryptoclids.

The elasmosaurs appeared in the Late Triassic; they had very elongate necks and small heads. The earliest species were about 3 m long, but some later species reached 14 m in length.

Reconstruction of Elasmosaurus by artist Doug Henderson.

The plesiosaurids currently include the single genus Plesiosaurus, the genus after which the whole group has been named. Since almost all plesiosaurs have started in this group then been moved out it is quite likely that this group will be further revised. Plesiosaurus was a long-necked, small headed form, though not as extreme as the Elasmosaurs. It is from the Lower Jurassic.
Reconstruction of Plesiosaurus by artist Adam Stuart Smith.

The polycotylids are a Cretaceous group with long snouts and short necks, superficially resembling the pliosaurs.

Reconstruction of Polycotylus by illustrator Carl Buell.

The cimoliasuars are probably an artificial group. The group includes a number of incomplete skeletons of plesiosaurs from the Jurassic and Cretaceous, as well as one (dubious) Palaeogene specimen. Cimoliasaurs tend to have intermediate neck and snout lengths.

The cryptoclidids are a group of medium sized plesiosaurs with long necks and broad, flat heads. They ranged from the Middle Jurassic to the end of the Cretaceous.

A reconstruction of Cryptoclidus, by palaeo-artist Alain Bénéteau.

A paper in the 12 August 2011 edition of the journal Science Robin O'Keefe of the Department of Biology at Marshall University and Luis Chiappe of the Natural History Museum of Los Angeles County describes for the first time a specimen of a plesiosaur which is apparently pregnant. If correct this settles a long standing dilemma for plesiosaur specialists. Plesiosaurs are clearly not not well adapted to land dwelling, so scientists had long suspected that they might be able to reproduce without venturing onto land. However no evidence of this had ever been found (unlike in ichthyosaurs, where the phenomenon is well documented), and not all reptiles have the potential to bear live young.

All crocodiles, most turtles and some birds and squamates (snakes and lizards) have temperature-dependent sex determination. This system uses an outside factor, temperature, to determine sex; above a certain temperature embryos will develop as one sex, bellow it as the other. This works fine for an egg-laying reptile, particularly one with a large brood size where there will be a temperature difference within the nest, but a large marine reptile is very likely to maintain a constant body temperature, which would result in all embryos developing as the same sex - not a good survival strategy.

Mammals, birds and most squamates use chromosomal sex determination. Under this system a species has sex two chromosomes. One chromosome is present in all individuals, the other only in individuals of one sex. Thus mammals have X and Y chromosomes; females have two X chromosomes males an X and a Y. Everyone inherits an X chromosome from their mother, and either an X or a Y chromosome from their father. All mammals develop as females, unless they have a Y chromosome.

This works well for mammals; the Y chromosome leads to the production of hormones that modify a potentially female animal to become male, but not so well for birds. Birds have sex chromosomes referred to as Z and W. A bird with two Z chromosomes in male, one with a Z and a W is female. In birds the presence of a W chromosome leads to the production of hormones that turn a potentially male individual female. This prevents the emergence of live births in birds; a baby bird developing inside its mother would be exposed to female hormones and develop as a female regardless of its chromosomes.

The sauropterygans (nothosaurs and plesiosaurs) are thought to be closely related the squamates, where chromosomal sex determination is the commonest method of sex determination, so it would not be surprising if this was the case in plesiosaurs.

In 2009 a paper in the Zoological Journal of the Linnean Society detailed a long-term study of sex-determination in squamates by Martina Pokorná and Lukáš Kratochvíl of the Department of Ecology at Charles University in Prague, which strongly indicated that the ancestral state in squamates was temperature dependent sex-determination, and that chromosomal sex determination has evolved several times within the group. Both the XY and ZW systems of sex determination are present within the squamates, and are likely to have evolved separately from a non-chromosomal system. This implies that the common ancestor of the sauropterygans and squamates used a temperature dependent sex determination system; the most that can be said is that the groups clearly had the potential to develop chromosomal sex determination.

The pregnant specimen described by O'Keefe and Chiappe (LACM 129639) was discovered in Kansas in the 1980s, and has been in the collection of the Natural History Museum of Los Angeles County ever since. It is not immediately obvious that this is a pregnant specimen; the fetus is not intact could potentially be the last meal of the adult rather than its young, though the pregnancy theory is supported by the absence of more common food material such as belemnites (Mesozoic molluscs) etc.

LACM 129369.

In addition LACM 129369 is a Polycotylus latippinis from the very end of the Cretaceous. P. latippinis is a highly derived species, not thought to be ancestral to any other form of plesiosaur, so it cannot be used to directly infer that other species bore live young. It would clearly have been useful to a plesiosaur, and it is considered likely that the ability arose in a nothosaur ancestor of the plesiosaurs. However this remains just as much a theory as it did before the re-examination of specimen LACM 129369.

A reconstruction of Polycotylus as a live-birthing animal, by science illustrator Stephanie Abramowicz.

See also The Weymouth Pliosaur and Reptiles on Sciency Thoughts YouTube.

Friday, 12 August 2011

TrES-2b, the black planet.

TrES-2b was discovered by the in 2006 by the Trans-Atlantic Exoplanet Survey, using telescopes at the Palomar Observatory in California and the Lowell Observatory in Arizona. It was the second planet discovered by the survey, hence its name, TrES from Trans-Atlantic Exoplanet Survey, 2 for the second planet discovered and b for a planet which is the second object in the system (a second star would get the designation B). The discovery was announced in a paper in The Astrophysical Journal by a team lead by Francis T. O'Donovan of the California Institute of Technology. The Trans-Atlantic Exoplanet Survey used simultaneous observations several relatively small (& therefore cheap) telescopes to identify regular drops in light intensity from stars, which might indicate planets passing in front of the star. The discovery was confirmed by the Keck Observatory.

TrES-2b was discovered by the very slight dimming it causes when it passes in front of its host star.

The planet orbits the star GSC 03549-02811, a yellow-dwarf main sequence star 718 light years away in the constellation of Drago. For this reason the planet could be referred to as GSC 03549-02811b and the star as GSC 03549-02811A, but this is unwieldily so it is not normally used. GSC stands for Guide Star Catalogue, a catalogue of stars designed for the Hubble Space Telescope. The numbers are co-ordinates, rather than numbers from a list, enabling the list to (potentially) include every object in the sky.

TrES-2b was the first transiting exoplanet (planet detected transiting across the disk of its star) discovered within the Kepler Field. This is the area of space which the Kepler Space Telescope is permanently trained upon. Unlike Hubble, Kepler does not move. It points permanently at the same point in space to build up a very detailed picture of the star systems in its field, and any planets they have. Since the Kepler team were forwarded as to the existence of TrES-2b, they were able to quickly identify it when Kepler came on line in 2009. Thus it was the first planet imaged by Kepler and is sometimes referred to as Kepler-1b (making the star Kepler-1A).

In February 2009 a team led by Sebastian Daemgen of the Max-Planck-Institut für Astronomie published a paper in the journal Astronomy & Astrophysics in which they announce the discovery of a second star in the TrES system using the Calar Alto telescope in Almeria, Spain. This second star is a dim K-type star orbiting TrES-2A at a distance of 232 AU (i.e. 232 times as far from the main star as Earth is from the sun, or nearly 5 times as far away as Pluto at its furthest from the sun). Since it was more distant than and discovered after TrES-2b it was given the designation TrES-2C, though it is unusual for a star to have a designation lower than a planet in the same system. A K-type star is a star with a surface temperature between 3700 and 5200 K; in contrast our sun is a G-type star, which implies a star with a temperature between 5,200 and 6000 K. K-type stars tend to be older stars running out of fuel or much smaller stars that have never got as hot as our sun, as is the case with TrES-2C.

TrES-2b is a 'hot jupiter' type planet; a gas giant twice the mass of Jupiter orbiting its star at a tenth of the distance at which Mercury orbits the sun.

In August 2011 The Royal Astronomical Society issued a press release announcing a forthcoming paper in the journal Monthly Notices of the Royal Astronomical Society, in which a team led by David Kipping of the Harvard-Smithsonian Center for Astrophysics detail the results of a long-term spectrographic study of TrES-2b using the Kepler Space Telescope. This has revealed that the planet is inexplicably dark in the visible part of the spectrum, emitting almost no light whatsoever. The planet is known to have a surface temperature of around 1000°C, and to have an atmosphere containing gaseous sodium, potassium and titanium oxide, all of which absorb light in the visible part of the spectrum and emit it at other wavelengths, but this cannot account for the darkness of the planet, which remains a mystery.

An artists impression of TrES-2b.

Earthquake in Mojen, northern Iran. 12 August 2011.

Just after 2 am local time on Friday the 12 August 2011 the Iranian town of Mojen, in Semnan to the southeast of the Caspian Sea, was shaken by a large earthquake. This was registered as a magnitude 5.0 on the Richter Scale at a depth of about 10 km, by the United States Geological Survey, and a magnitude 4.9 quake by the Institute of Geophysics at the University of Tehran. There are no reports of any damage or casualties, however Mojen is built on a steep hillside, from traditional mud-brick and wood materials, and a quake of this size would have caused considerable shaking at ground level, so it is likely that damage to buildings and injuries or even deaths may yet be reported.

Short video about Mojen.

Iran is one of the most earthquake-prone countries on earth. Iran, along with Afghanistan and western Pakistan, is part of a southern extension of the Eurasian Plate caught between the northeast moving Arabian Plate and the northwest moving Indian Plate. This has lead to the creation of a mountainous, earthquake-prone region called the Iranian Plateau. Although it is called a plateau it is not flat, just uplifted.

Relief map of the Iranian Plateau. Grey areas are highest, green lowest. Red dots indicate historic earthquakes, the red star the approximate position of the August 12 quake.

Despite Iran's oil wealth successive regimes have failed to invest in earthquake protection, resulting in a long history of devastating earthquake damage.

In 2003 an earthquake hit the city of Bam killing over 25 000 people, and injuring over 30 000 more, as well as destroying most of the city. This provoked a brief thaw in relations with the west as over 40 nations sent rescue teams into the area. Many of the casualties were caused by collapsing mud-brick buildings, which when shaken disintegrated so thoroughly as to exclude all air from the collapsed building, trapping and asphyxiating the sleeping victims; like the Mojen earthquake the Bam earthquake took place at about 2.oo in the morning. This similarity of building materials and timing raises concern for people caught in the Mojen earthquake.

The aftermath of the 2003 Bam Earthquake.

A similar earthquake in the northwest of the country in 1990 caused over 40 000 deaths and 60 000 injuries. This quake destroyed the cities of Rudbar, Manjil and Lushan, as well as over 700 villages, and left half a million people homeless. Again most of the fatalities were attributed to collapsing mud-brick buildings at night; this quake to place at 0.30 am.

The aftermath of the 1990 Manjil-Rudbar Earthquake.

Fukushima shaken by large earthquake. 12 Augsut 2011

Just after 3.20 am on Friday 12 August the Japanese prefecture of Fukushima was shaken by a large earthquake. At its epicenter (the point on the ground directly above the quake) this measured 5- on the Japan Meteorological Agency's Seismic Intensity Scale, which measures the effects of an earthquake rather than the amount of energy released. A 5- indicates people running out of buildings in panic, things falling from shelves, damage to non-earthquake resistant buildings and automatic gas cutoff devices present in Japanese buildings activating.

The location of the 12 August earthquake, and where it was felt.

There are differences of opinion about how deep the quake was, and how large it was on the Richter Scale (which does register energy released). The Japan Meteorological Agency (which also monitors earthquakes, volcanoes, tsunamis etc.) registered this quake as a magnitude 6 quake at a depth of 50 km, whereas the United States Geological Survey recorded this as a magnitude 5.2 quake at a depth of 9.9 km. Since the Richter scale is logarithmic (a magnitude 6 quake is 10 times as powerful as a magnitude 5 quake) and rock absorbs a lot of energy, either of these proposed quakes could have produced the observed effects.