Prehistoric meteor shower and evolution of life discovery


This video is called Late Ordovician Mass Extinction (Ordovician – Silurian).

From daily The Independent in Britain:

Scientists discover fragment of ‘missing link’ asteroid that led to explosion of life on Earth

James Vincent

Thursday 03 July 2014

Scientists in Sweden have discovered a never-before seen class of meteorite that could be the ‘missing link’ between a gigantic collision in the asteroid belt 470 million years ago and the subsequent explosion of diverse life forms here on Earth.

Although it’s usually thought that meteorite impacts are disastrous for species on Earth (the classic example is the colossal impact thought to have killed off the dinosaurs 66 million years ago) there’s plenty of evidence to suggest that these events can also be beneficial to the overall diversity on the planet.

It’s thought that just such an impact – or rather, a string of them – dramatically boosted biodiversity on the planet during the Ordovician Period some 470 million years ago. It’s believed that a collision of two asteroids (or possibly an asteroid and a comet) out in space caused a shower of meteors to rain down on Earth.

Over time fragments of this meteor shower have been found around the planet and dated to 470 million years ago – but until now scientists had not found any evidence of the ‘killer’ asteroid that started this chain of events.

During the Ordovician Period most life on Earth was found in the ocean, with jawless fish, molluscs and insect-like arthropods making up the bulk of the species roll-call. However, a study from 2008 showed that the planet went through a “major phase of biodiversification” at this time shortly after “the largest documented asteroid breakup event during the past few billion years”.

The evidence for this breakup comes from the abundance of L-chondrite meteorites – the second most common meteorite type – fragments of which first started appearing on Earth around 470 million years ago.

“Something we didn’t really know about before was flying around and crashed into the L-chondrites,” said Gary Huss, co-author of the study that analysed the sample (published in Earth and Planetary Science Letters). This newly-discovered fragment is thought to be that very object – the mysterious ‘bullet’.

The composition of the fragment differs from known meteorite samples and its exposure age – the length of time it sailed through space – places it at the ‘scene of the crime’ when meteors rained down on the planet during the Ordovician Period.

“It’s a very, very strange and unusual find,” Birger Schmitz, the lead author of the study, told Live Science. “I think [it] adds to the understanding that the meteorites that come down on Earth today may not be entirely representative of what is out there.”

It’s not clear exactly why the Ordovician meteor shower led to a greater variety of life on the plane although some more far-fetched theories suggest that life itself was ‘seeded’ by organisms hitching a ride on asteroids.

A more likely explanation is that the impact craters caused by the collisions provided perfect test-beds for developing life. When meteorites hit the surface of the planet they scooped out bubbling pools of minerals and nutrients that served – in Carl Zimmer’s words – as “natural beakers that synthesized new chemicals essential for life”. However, even this is still just a theory – and the impacts might have also fostered life by creating new habitats, like restructured shorelines.

If further geochemical tests on the newly discovered fragment confirm its suspected origins then scientists will have pinned down another piece of the solar system’s history – but figuring out what happened closer to home might be more difficult still.

440 million years old fossil on Dutch beach?


The Texel fossil, photo by Bram Fey

A week ago, Hannes and Klaas Fey were walking on the beach near the Slufter nature reserve on Texel island, the Netherlands. Then, they found a small fossil.

Arthur Oosterbaan of Ecomare museum thinks the fossil may be a Hindia fibrosa. A sponge from the Ordovician, about 440 million years old.

Maybe about 150,000 years ago, during the Ice Age, a glacier transported the little sponge fossil from Scandinavia to Texel.

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Trilobite fossils of Kangaroo Island, Australia


This video is called Kangaroo Island / Australia.

From the Australian Broadcasting Corporation:

Narration: Kangaroo Island, South Australia. A holiday destination renowned for its beaches and natural splendours.

And soon to be renowned for some of the weirdest relics of ancient marine life in the world. …

Narration: Here in Emu Bay on the island’s north coast an international team of palaeontologists hosted by the South Australian Museum are digging up fossils from the Cambrian Period. They’re around 520 million years old, a time when life had only just begun to diversify.

These animals were living on the floor of an ancient sea. Many of them were arthropods, the group that includes modern crabs, lobsters, spiders, centipedes and insects. And by far the most common type of fossil is this one – a trilobite.

Jim: This is the largest species of trilobite. They’re called trilobites because they’ve got three lobes to them. And you see those ridges? They’re the eye ridges. So this thing could see.

Narration: Diego Garcia– from the University of Madrid – has seen fossils like this before – in the Burgess Shales of western Canada.

Talking about Diego Garcia and islands: it is to be hoped that this scientist Diego Garcia will fare better than the inhabitants of Diego Garcia island in the Indian ocean, driven off their island in order to make space for a US military base, now also a torture prison.

Tiny Trilobites Drifted in Cambrian Currents: here.

Signs of violence on agnostid trilobites found in Cambrian rocks suggest they were attacking each other: here.

Fossils record reveals ancient migrations, trilobite mass matings: here.

A new species of the Lower Ordovician pliomerid trilobite Pseudocybele: here.

It’s easy to travel responsibly on Kangaroo Island, where conservation is key to the wildlife that abounds: here.

July 2011: Nearly 700 people have planted 120,000 seedlings to help restore and protect the habitat on Kangaroo Island, Australia. The annual Kangaroo Island Planting Festival attracted 676 volunteers this year – almost 200 more than last year – with more than 100 different species planted to establish new habitat in the lower Cygnet Valley: here.