Thursday 30 April 2015

Stenaelurillus albus: A new species of Jumping Spider from the Western Ghats of India.


Jumping Spiders, Salticidae, are active predatory Spiders which hunt down and leap on prey rather than lying in wait in a web or other trap. Members of the genus Stenaelurillus are Jumping Spiders, found predominantly in Africa, with a few species also described from Eurasia and the Indian Subcontinent. They are distinguished by the presence of a pair of white stripes on their prosoma (back) and by large bristles around their eyes.

In a paper published in the journal ZooKeys on 26 March 2015, Pothalil Sebastian, Pradeep Sankaran, Jobi Malamel and Mathew Joseph of the Division of Arachnology at Sacred Heart College in Thevara, Kerala, describe a new species of Stenaelurillus from the Western Ghats of India.

The new species is named Stenaelurillus albus, meaning ‘white’ in reference to the colour of the tegulum (part of the male reproductive equipment). The species is described from seven male and eight female specimens collected at Kurisumudi in Ernakulam District. Males were 4.61–5.89 mm in length and had a distinctive uniform black abdomen, a colouration not seen in any other known member of the genus. Females were 5.43–6.82 mm in length, and had a dark abdomen with yellow markings, similar to other known species. All were collected on the ground, in a rocky area covered by leaf litter within a deciduous forest.

Stenaelurillus albus, male (left) and female (right), both in dorsal view. Sebastian et al. (2015).

See also…

Peacock Spiders of the genus Maratus are a group of Jumping Spiders, Salticidae, found only in Australia. They are small in size, typically less than 5 mm in length, though the males are brightly coloured and engage in elaborate courtship dances, which give...

Peacock Spiders, Maratus spp., are a group of small Jumping Spiders, Salticidae, found only in Australia. The group gets its name from the bright colours and elaborate courtship dances of the male Spiders...


Peacock Spiders, Maratus, are Jumping Spiders, Salticidae, endemic to Australia and distinguished by the bright colours and elaborate courtship dances of the males. The calcitrans group of Peacock Spiders currently comprises three members of the genus...
 
 
 
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Magnitude 1.9 Earthquake in Essex, southern England.

The British Geological Survey recorded a Magnitude 1.9 Earthquake at a depth of 6 km slightly to the northeast of the village of North Fambridge in Essex, England, slightly before 5.20 pm British Summertime (slightly before 6.20 pm GMT) on Thursday 23 April 2015. There are no reports of any damage or injuries associated with this event, though it is likely to have been felt locally.
 
 The approximate location of the 23 April 2015 Essex Earthquake. Google Maps.
 
Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England. However, while quakes in southern England are less frequent, they are often larger than events in the north, as tectonic presures tend to build up for longer periods of time between events, so that when they occur more pressure is released.
The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.
Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process.
 
(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East.
Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.
 
See also...
 
http://sciencythoughts.blogspot.co.uk/2015/04/magnitude-22-earthquake-near.htmlMagnitude 2.2 Earthquake near Peterborough in Cambridgeshire, England. The British Geological Survey recorded a Magnitude 2.2 Earthquake at a depth of 8 km about 10 km to the south of Peterborough in...
http://sciencythoughts.blogspot.co.uk/2015/03/homes-evacuated-after-sinkhole-opens-up.htmlHomes evacuated after sinkhole opens up in Swanley, southeast England.                        Two homes have been evacuated in the town of Swanley in Kent, southeast England after a sinkhole opened up on Thursday 26 March 2015 swallowing...
National geological surveys have traditionally produced two dimensional geological maps showing the outcropping of rock formations, combined with data...
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Assessing the composition of ices on the surface of Makemake.


The Dwarf Planet Makemake is one of the three largest Trans-Neptunian Objects, with a diameter of about 1400 km, along with Pluto and Eris (2370 km 2330 km respectively). Makemake is thought to have a roughly circular orbit, remaining at about 45.7 AU from the Sun, while those of Pluto and Eris are more eccentric, taking them substantially closer to and further away from the Sun during the course of a single orbit (Pluto even spends part of its orbit inside the orbit of Neptune). All of these bodies are thought to have icy surfaces, and while those of Eris and Pluto are thought to undergo substantial heating and cooling as their distance from the Sun varies, leading to significant reworking of surface ices, that of Makemake if thought to remain close to 37K throughout its orbital cycle. This in theory means that the surface of Makemake should have undergone little reworking, and could therefore preserve a composition from early in the history of the Solar System.

The orbit of Makemake.  JPL Small Body Database Browser.

In a paper published in the journal Astronomy & Astrophysics on 10 April 2015 and on the arXiv database at Cornell University Library on 9 April 2015, Vania Lorenzi of the Fundación Galileo Galilei, Noemi Pinilla-Alonso of the Department of Earth and Planetary Sciences at the University of Tennessee and Javier Licandro of the Instituto Astrofísico de Canarias and the Departamento deAstrofísica at the Universidad de La Laguna, describe the results of a spectrographic analysis of the surface of Makemake carried out with the medium-resolution spectrograph ISIS on the 4.2 m William Herschel Telescope at the Roque de LosMuchachos Observatory on La Palma Island in the Canaries.

While all ices reflect light, specific ices will only do so at specific wavelengths, enabling astronomers to determine the surface composition of remote icy objects by analysing the spectra of sunlight reflected from them.

Lorenzi et al. were able to observe Makemake for 6.3 hours, 82% of one of its rotational periods (a ‘day’ on the surface of the Dwarf Planet), obtaining good data that enabled them to assess the composition of 70% of its surface. They found that the studied surface was homogenous (unvarying), which supports the idea that it is relatively unperturbed. The surface of Makemake appears to be covered by granular ice, containing a mixture of methane (CH4) and nitrogen (N2).

See also…

For over a century Pluto was the only known bright object in the Solar System beyond Neptune, but in the past two decades a large number of such objects...
 
http://sciencythoughts.blogspot.co.uk/2014/09/observations-of-new-horizons-candidate.htmlObservations of New Horizons candidate bodies with the Hubble Space Telescope.      The New Horizons Spacecraft was launched in January 2006, and is due to pass through the Pluto System (Pluto is now recognized to be...
 
The dwarf planet Pluto will reach opposition slightly before 3.00 am GMT on Friday 4 July 2014; this means that it will be directly opposite the Sun in the sky when viewed from Earth, on this occasion in the...
 
 
 
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Asteroid 2015 HT10 passes the Earth.

Asteroid 2015 HT10 passed by the Earth at a distance of 627 100 km (1.63 times the average distance between the Earth and the Moon, or 0.42% of the average distance between the Earth and the Sun), at about 4.55 am GMT on Wednesday 29 April 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 HT10 has an estimated equivalent diameter of 9-30 m (i.e. it is estimated that a spherical object with the same volume would be 9-30  m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 32 and 16 km above the ground, with only fragmentary material reaching the Earth's surface.

  Image of 2015 HQ11 taken on 28 April 2015 from Ceccano in Italy. The asteroid is the point in the center of the picture. The longer lines are stars, their elongation being caused by the telescope traking the asteroid over the length of the exposure, in this case 120 seconds. Gianluca Masi/Virtual Telescope.

2015 HT10 was discovered on 21 April 2015 (eight days before its closest approach to the Earth) by the Dark Energy Camera on the Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in La Serena, Chile. The designation 2015 HT10 implies that it was the 269th asteroid (asteroid T10 ) discovered in the secondt half of April 2015 (period 2015 H).

2015 HT10 has an 1080 day orbital period and an eccentric orbit tilted at an angle of 4.59° to the plane of the Solar System, which takes it from 0.88 AU from the Sun (i.e. 88% of the average distance at which the Earth orbits the Sun) to 3.24 AU from the Sun (i.e. 324% of the average distance at which the Earth orbits the Sun, somewhat greater than twice 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 also means that close encounters between 2015 HT10 and the Earth are quite common, with thenext predicted for April 2018.

See also...

http://sciencythoughts.blogspot.co.uk/2015/04/asteroid-2015-hq11-passes-earth.htmlAsteroid 2015 HQ11 passes the Earth.     Asteroid 2015 HQ11 passed by the Earth at a distance of 490 100 km (1.27 times the average distance between the Earth and the Moon, or 0.33% of the average distance between the Earth and the Sun), slightly before 6.20 am GMT on Saturday 25 April...
Asteroid 2015 HH passed by the Earth at a distance of 4 513 000 km (11.7 times the average distance between the Earth and the Moon, or 3.02% of the average distance between the Earth and the Sun), slightly after 10.25 am GMT on Tuesday 14 April 2015. There was...
 
http://sciencythoughts.blogspot.co.uk/2015/04/lyrid-meteor-shower-to-peak-on-22-23.htmlLyrid Meteor Shower to peak on 22-23 April this year.                                                                    The Lyrid Meteors will be at peak visibility between 22 and 23 April this year, shortly after the New Moon on 19 April, which should ensure a good display in areas with clear skies. The meteors, which appear to radiate...
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Landslides kill fourteen in Salvador, Brazil.

Fourteen people have been confirmed dead after two landslides in the city of Salvador in Bahia State, Brazil, on Monday 27 April 2015. The incidents happened in the Barro Branco and Marotinho neighbourhoods, each claiming seven lives. The landslides occurred after over 200 mm of rain fell in the city in 24 hours, over two thirds of the typical rainfall for the entire month of April, and has reportedly caused 147 landslides and several building collapses, as well as widespread flooding, which has led to evacuations in some areas, including the Santo Antonio Hospital. 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. 

Local residents searching for survivors after the 27 April 2015 Salvador landslides. Felipe Oliveira/AFP.

Salvador has a wet tropical climate with high levels of rainfall all year round, though the wettest months are usually April and May with averages of 309.7 mm and 359.9 mm respectively. Landslides are a common event in the cities favelas (poor neighbourhoods) where building standards tend to be lower and population densities higher. The exceptionally high rainfall has continued through the week, with 142 mm of rain falling on 27-28 April, and local authorities are warning of the danger of more events.

The approximate location of the fatal 27 April 2015 Salvador landslides. Google Maps.

See also...

At least 44 people have died and over 65 000 have been driven from their homes as southeastern Brazil suffered the highest rainfall for 90 years this month. In...



Six members of the same family, including four children have been killed in a landslide in the town of Sardoá in eastern Minas Gerais State in southeastern Brazil on Tuesday 17 December 2013. The incident happened following several days of heavy rain, when part of...



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Wednesday 29 April 2015

Cretaceous Bone-eating Worms from England.


Siboglinid Worms are a distinctive group of Annelids which lack mouths and digestive tracts in their adult phases, instead being entirely dependent on symbiotic Bacteria which live within their tissues for nutrition. Members of the genus Osedax have a particularly novel lifestyle, even for Siboglinids, as they burrow into the bones of large vertebrates (principally Whales) on the seafloor with specialized root-lie structures on their tails, which enable them to extract collagen and lipids from the bone, these being metabolized by the symbiotic Bacteria. The foreparts of the Worms extend into the water column, and are crowned with respiratory palps.

The oldest known Osedax traced described to date come from Whale bones from the Oligocene. Attempts to determine when the Osedax Worms split from other members of the group using molecular dating techniques (which measure the rate of mutation on strands of non-coding DNA) have yielded two very different results; either the group appeared about 45 million years ago during the Eocene, at about the same time as Whales were first colonizing the seas, of they appeared 125 million years ago during the Cretaceous, long before the appearance of Whales, but in a time when a great variety of large Marine Reptiles could be found in the seas.

In a paper published in the journal Biology Letters on 15 April 2015, Silvia Danise of the School of Geography, Earth and EnvironmentalSciences at Plymouth University and the Department of Geology at the Universityof Georgia, and Nicholas Higgs of the Marine Institute at Plymouth University describe two instances of what appear to be Osedax traces on the bones of Marine Reptiles from the Late Cretaceous of England.

The first example comes from a Plesiosaur humerus from the Cambridge Greensand Member, which is thought likely to have been reworked from the older Gault Formation, making it about 100 million years old. This specimen has a heavily bio-eroded area around its centre, with two individual borings on the edge of this area that strongly resemble modern Osedax traces.

CT reconstruction of Plesiosaur bone (semi-transparent), with two Osedax borings reconstructed in orange. Danise & Higgs (2015).

The second example comprises a rib and shell plate of a Turtle from the Grey Chalk Subgroup at Burham in Kent. The shell plate is heavily eroded, with some intact burrows which Danise and Higgs identify as Osedex traces. The rib has a series of 15 tubular excavations, which are also attributed to Osedex.

Details of the bioeroded areas on (d) the Turtle rib and (e) the shell plate. Danise & Higgs (2015).

If these results are correct then they confirm the presence of Osedex Worms in the seas of the Late Cretaceous, and offer an explanation into how these Worms survived between the extinction of most of the Mesozoic Marine Reptiles at the end of the Cretaceous, and the appearance of the first Whales in the Eocene, roughly twenty million years later. Unlike other groups of Marine Reptiles, Turtles survived the End-Cretaceous Extinction and underwent a significant evolutionary radiation during the Palaeocene, when they appear to have lacked either large rivals or predators. Turtles typically have a significant amount of dense bone, and would provide a good source of nutrition for Osedex Worms in the absence of Whales or other large Marine Tetrapods.

See also…

http://sciencythoughts.blogspot.co.uk/2015/01/a-new-species-of-serpulid-worm-from.htmlA new species of Serpulid Worm from the Caribbean.                                                 Serpulids are distinctive Polychaete Worms found throughout the world’s oceans, from the intertidal zones to the deep seas. They live in calcareous tubes, which they cement to hard substrates, and are...
http://sciencythoughts.blogspot.co.uk/2014/04/a-new-species-of-earthworm-from-spain.htmlA new species of Earthworm from Spain Earthworms play a major role in the formation of soils in many parts of the world (though soils can and do form in there absence), ingesting and breaking larger...

http://sciencythoughts.blogspot.co.uk/2013/07/two-new-species-of-scolecodont-from.htmlTwo new species of Scolecodont from the Early Devonian of the Ukraine.               Scolecodonts are the fossilized remains of the chitinous teeth and jaw elements of Polychaete Worms. They are described as species since preservation of entire Worms more-or-less never happens. Scolecodonts are known in the fossil record from the Cambrian...

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Cryptic diversity in West African Torrent Frogs.


The West African Torrent Frog, Odontobatrachus natator, is found in fast moving streams and waterways in the forests of Guinea, Sierra Leone Liberia, and western Côte d’Ivoire, part of the Upper Guinean Biodiversity Hotspot. While it has been known to science for over a hundred years, a recent study has shown it to be sufficiently genetically isolated from all other Frogs to merit placing it in its own family, the Odontobatrachidae, this being the first family of Vertebrates discovered which is entirely restricted to West Africa.

In a paper published in the journal BMC Evolutionary Biology on 19 April 2015, Michael Barej and Johannes Penner of the Museum für Naturkunde Berlin at the Leibniz Institute for Evolution and Biodiversity Science, Andreas Schmitz of the Department of Herpetology and Ichthyology at the Natural HistoryMuseum of Geneva and Mark-Oliver Rödel, also of the Museum für Naturkunde Berlin at the Leibniz Institute for Evolution and Biodiversity Science examine the genetic diversity of West African Torrent Frogs in order to determine if they were truly all one widespread species or a cluster of morphologically indistinguishable cryptic species.

A West African Torrent Frog, Odontobatrachus natator. Barej et al. (2014).

Cryptic species are species which resemble one-another closely but which are reproductively isolated. These have been known about for a long time in groups such as calling Frogs and Songbirds, where morphologically identical populations can be separated on the basis of different mating calls, but the true extent of hidden diversity in many groups did not become apparent until genetic tools became available to study wild populations in the 1990s. The discovery of cryptic species can have profound implications for conservation efforts, as what was thought to be a single, widespread species with a large population can suddenly be found to be a cluster of species, each with very limited populations and ranges. Cryptic diversity seems to be particularly common among groups such as small Amphibians and Reptiles, but has been found even in large charismatic animals such as Elephants, Giraffes, Baboons and Hammerhead Sharks.

Barejet al. found that the population of Odontobatrachus natator contains six distinct genetic lineages, and though they do not go so far as to name them as new species from this preliminary study, they do indicate that further studies are likely to result in the group being divided into a number of separate species.

Tree resulting from partitioned Bayes and ML analyses of mitochondrial genes 16S, 12S, cytb and nuclear genes RAG1, SIA and BDNF (outgroups not shown). Barej et al. (2015).

The most widespread of these is found in western Guinea, across Sierra Leone and as far to the east as eastern Guinea and eastern Liberia. This includes the area from which the species was first described (Sierra Leone, unspecified), and will therefore retain the name Odontobatrachus natator however the group is subdivided in future. This population is considered to be of ‘Least Concern’ under the terms of the International Union for the Conservation of Nature’s Red List of ThreatenedSpecies.

The most closely related outgroup to this (and therefore the group least likely to subsequently be described as a separate species) was a population found only on the Freetown Peninsula in Sierra Leone. This population is referred to as Odontobatrachus natator (Freetown Peninsula), and while closely related to the larger population, does appear to be separate on the basis of the genes studies and is separated from the main population by a wide area of unsuitable habitat, which may have allowed reproductive isolation to develop. If this population is recognized as a separate species then it would be recognized as ‘Critically Endangered’ under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species, due to the limited geographical range it inhabits.

Environmental niche modelling map of genetically confirmed records of the Operational Taxonomic Units Odontobatrachus natatorand Odontobatrachus natator (Freetown Peninsula). Barej et al. (2015).

In addition four other distinctive genetic lineages are identified, and provisionally named as ‘Operation Taxonomic Units’ (OTUs) 1 to 4. These can be further groups as (OTU 1 and OUT 4) which are most closely related to one-another and the sister group to (Odontobatrachus natatorand Odontobatrachus natator (Freetown Peninsula)), and (OUT 2 and OUT 3) which are more closely related to one-another, and form an outgroup to all the other populations.

OTU 1 is found in the Simandou Range and the Massif du Ziama in south-eastern Guinea, and environmental niche modelling suggests that it may also occur westwards into parts of Sierra Leone. This population is considered to be ‘Vulnerable’ under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species.

Environmental niche modelling map of genetically confirmed records of Operational Taxonomic Unit 1. Barej et al. (2015).

OTU 2 was found in western Guinea, though Environmental Niche Modelling suggested that it may also be found as far east as central Sierra Leone, though Barej et al. deem this unlikely. This population is considered to be ‘Vulnerable’ under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species.

Environmental niche modelling map of genetically confirmed records of Operational Taxonomic Unit 2. Barej et al. (2015).

OTU 3 was also found in wesertn Guinea, though Environmental Niche Modelling suggests that it may be found as far east as central Sierra Leone and as far west as parts of Guinea Bissau, though againBarejet al. deem this unlikely.This population is considered to be ‘Endangered’ under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species.

Environmental niche modelling map of genetically confirmed records of Operational Taxonomic Unit 3. Barej et al. (2015).

OTU 4 was found in the Nimba Mountains of southeaster Guinea and the surrounding area, as well as in northeastern Liberia and the Mont Sangbé National Park in western Côte d’Ivoire. Environmental niche modelling suggested that this population could extend across much of eatern Guinea and northern Liberia, and even into eastern Sierra Leone. This population is considered to be ‘Endangered’ under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species.

Environmental niche modelling map of genetically confirmed records of Operational Taxonomic Unit 4. Barej et al. (2015).

Although this is only a preliminary study, the degree of genetic separation between the populations suggests that they may have diverged during the Plio-Pleistocene. This is consistent with palaeoclimatic models of West Africa, which suggest while the region was not directly affected by glaciation during the Pleistocene, glacial intervals at higher latitudes led to a cooler drier climate in which forests withdrew and grasslands expanded. During such periods forest species would have been restricted to isolated refugia, where populations cut off from one-another geographically could become permanently separated by genetic drift.

See also….

Robber Frogs of the genus Eleutherodactylus are found from Texas to Guatemala and Belize and across the islands of the Caribbean. The genus was formerly the most specious of any genus of Vertebrate Animals (i.e. it contained more species than any other Vertebrate...

In the late 1960s and early 1970s a series of anthropological excavations were carried out at Minatogawa Fissure on southern Okinawa Island, producing a number of Late Pleistocene Human...


Fanged Frogs, Limnonectes spp., are unique among Frogs in that the males are typically larger than the females, and frequently fight for territories, the females then mating with the males perceived as having the...

 

 

 

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Asteroid 2015 HQ11 passes the Earth.

Asteroid 2015 HQ11 passed by the Earth at a distance of 490 100 km (1.27 times the average distance between the Earth and the Moon, or 0.33% of the average distance between the Earth and the Sun), slightly before 6.20 am GMT on Saturday 25 April 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 HQ11 has an estimated equivalent diameter of 7-23 m (i.e. it is estimated that a spherical object with the same volume would be 7-23 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 37 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.

 Image of 2015 HQ11 taken on 25 April 2015 from Ceccano in Italy. The asteroid is the point indicated by the two lines at right angles in the center of the picture. The longer lines are stars, their elongation being caused by the telescope traking the asteroid over the length of the exposure, in this case 150 seconds. Gianluca Masi/Virtual Telescope.
 
2015 HQ11 was discovered on 23 April 2015 (two days before its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2015 HQ11 implies that it was the 291st asteroid (asteroid Q11 ) discovered in the secondt half of April 2015 (period 2015 H).

 The calculated orbit of 2015 HQ11. JPL Small Body Database.

2015 HQ11 has an 673 day orbital period and an eccentric orbit tilted at an angle of 8.21° to the plane of the Solar System, which takes it from 0.91 AU from the Sun (i.e. 91% of the average distance at which the Earth orbits the Sun) to 2.09 AU from the Sun (i.e. 209% of the average distance at which the Earth orbits the Sun, somewhat greater than 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 also means that close encounters between 2015 HQ11 and the Earth are quite common, with the last having occurred in March 2004 next predicted for September this year.

See also...

Asteroid 2015 HH passed by the Earth at a distance of 4 513 000 km (11.7 times the average distance between the Earth and the Moon, or 3.02% of the average distance between the Earth and the Sun), slightly after 10.25 am GMT on Tuesday 14 April 2015. There was...
 
http://sciencythoughts.blogspot.co.uk/2015/04/lyrid-meteor-shower-to-peak-on-22-23.htmlLyrid Meteor Shower to peak on 22-23 April this year.                                                                    The Lyrid Meteors will be at peak visibility between 22 and 23 April this year, shortly after the New Moon on 19 April, which should ensure a good display in areas with clear skies. The meteors, which appear to radiate...
http://sciencythoughts.blogspot.co.uk/2015/04/asteroid-2015-fl-passes-earth.htmlAsteroid 2015 FL passes the Earth.         Asteroid 2015 FL passed by the Earth at a distance of 7 597 000 km (19.8 times the average distance between the Earth and the Moon, or 5.08 % of the average distance between the Earth and the Sun), at about 0.50 am GMT on Saturday 11 April 2015. There was...
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