History of Extra-terrestrial Impacts Revealed in Ancient Sediments

Research by NASA and international scientists concludes giant asteroids, similar or larger than the one believed to have killed the dinosaurs, hit Earth billions of years ago with more frequency than previously thought.

Extra-terrestrial Impacts

To cause the dinosaur extinction, the killer asteroid that impacted Earth 66 million years ago would have been almost 6 miles (10 kilometres) in diameter.  By studying ancient rocks in Australia and using computer models, researchers estimate that approximately seventy asteroids the same size or larger impacted Earth 1.8 to 3.8 billion years ago.  During the same period, approximately four similarly-sized objects hit the moon.

The Archean Eon represents a period in the Earth’s history from approximately four billion to 2.5 billion years ago.  The Archean, in relation to other Eons assigned to the modern geological time-scale is the largest Eon in terms of the period of time covered.  It is also the most difficult to define, essentially the beginning of the Eon being set by geologists to mark the end of the so-called “Great Extra-terrestrial Bombardment, otherwise known as the Late Heavy Bombardment” and the end to coincide with the change in the fundamental nature of the planet’s atmosphere with the increase in oxygen levels.

Late Heavy Bombardment

NASA scientists collaborating with a number of other international research bodies have concluded that the “Great Extra-terrestrial Bombardment” may have been more intense than previously thought.

Commenting on the study, the paper having been published in the scientific journal “Nature”, Yvonne Pendleton, Director of NASA’s Lunar Science Institute based in California stated:

“This work demonstrates the power of combining sophisticated computer models with physical evidence from the past, further opening an important window to Earth’s history.”

Evidence for these impacts on Earth comes from thin rock layers that contain debris of nearly spherical, sand-sized droplets called spherules.  These millimeter-scale clues were formerly molten droplets ejected into space within the huge plumes created by mega-impacts on Earth.  The hardened droplets then fell back to Earth, creating thin but widespread sedimentary layers known as spherule beds.

William Bottke of the Southwest Research Institute, in the aptly named Boulder (Colorado), said:

“The beds speak of an intense period of bombardment of Earth.  Their source long has been a mystery.”

The team’s findings support the theory Jupiter, Saturn, Uranus and Neptune formed in different orbits nearly 4.5 billion years ago, migrating to their current orbits about 4 billion years ago from the interplay of gravitational forces in the young solar system.  This event triggered a solar system-wide bombardment of comets and asteroids, the young planet Earth and its recently formed satellite we now call the moon were not spared and suffered from this barrage as space rocks were sent hurtling towards the inner solar system.

In the paper, the team created a model of the ancient main asteroid belt and tracked what would have happened when the orbits of the huge, gas-giant planets changed.  They discovered the innermost portion of the belt became destabilised and could have delivered numerous big impacts to Earth and the moon over long time periods.

Twelve Mega-impacts

The team has concluded that at least twelve mega-impacts produced spherule beds during the so-called Archean period 2.5 to 3.7 billion years ago, a formative time for life on Earth.  Ancient spherule beds are rare finds, rarer than rocks of any other age.  Most of the beds have been preserved amid mud deposited on the sea floor below the reach of waves.

The impact believed to have killed the dinosaurs was the only known collision over the past half-billion years that made a spherule layer as deep as those of the Archean period.  The relative abundance of the beds supports the hypothesis for many giant asteroid impacts during Earth’s early history.

The frequency of the impacts indicated in the computer models matches the number of spherule beds found in terrains with ages that are well understood.  The data also hint at the possibility that the last impacts of the Late Heavy Bombardment on Earth made South Africa’s Vredefort crater and Canada’s Sudbury crater, both of which formed about two billion years ago.

Bruce Simonson, a geologist from Oberlin College (Ohio) stated:

“The Archean beds contain enough extraterrestrial material to rule out alternative sources for the spherules, such as volcanoes.”

The impact study team also included scientists from Purdue University in West Lafayette, Indiana.; Charles University in Prague, (Czech Republic); Observatorie de la Cote d’Azur in Nice, France; and Academia Sinica in Taipei, Taiwan.

Sourced from a Press Release – NASA

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Chechnya’s Giant Dinosaur Egg Discovery – Doubts Raised

Earlier this week we were sent some pictures taken by a team of scientists who were examining what was thought by a number of observers to be the fossilised remains of dinosaur eggs.  Construction workers undertaking the building of a new road were blasting their way through a hillside near the Chechen border with Georgia when the discovery of more than forty, strange, spherical objects embedded in the hillside was made.  The strange objects, ranging in size from a few centimetres across to a whopping 1.02 metres were described as being dinosaur eggs and their discovery led to a “scramble” amongst scientists to learn more.

Dinosaur Eggs

The Chechnya region has suffered in the past twenty years or so as separatist movements fought with Russia in a bid to form an independent state.  The war torn region has had millions of pounds of state aid poured into it in a bid to improve the living conditions for the local population, the road building project was one such regional development measure, however, the planners did not “eggspect” to have a dinosaur egg hunt on their hands.

Keen to take advantage of the find, a number of local businessmen have expressed an interest in developing guided tours to the remote hillside to view the “dinosaur eggs”.  The discovery has certainly attracted the attention of the local population with many of the curious venturing up the hillside to take a closer look at the objects.

Commenting on the strange phenomena a senior geologist at the Chechen State University stated:

“We’ve found about forty eggs so far, the exact number has not been established and there could be many more under the ground.”

Some scientists are claiming that the eggs were laid by a huge long-necked dinosaur known as a sauropod, the largest, land living animals known to science.   A number of samples and specimens have been sent to palaeontologists based in the city of Yessentuki in southern Russia’s Stavropol Region for a more thorough examination.

Other scientists have cast doubt about whether these are dinosaur eggs.  Chechyna is located in the south-eastern corner of Europe and the geology of the area is extremely complicated.  The northern Caucasus mountain range runs throughout this region, the result of extensive tectonic activity between the Eurasian and the Arabian plates.  The scientists claim that the strata within which the eggs were found dates to around sixty million years ago.  The  dinosaurs are believed to have died out many millions of years before.  The extensive seismic and volcanic activity may have led to a considerable amount of re-distribution and re-deposition but palaeontologists and geologists are sceptical whether such “fossils” such as massive eggs would have survived these physical processes.

Although once underwater, part of the massive Tethys Ocean, the region has been mountainous for much of the Cretaceous, leading scientists to question how such large animals such as sauropods, (titanosaurs) could have roamed a mountainous region and laid eggs on the sides of steep slopes.

Scientists Question Claims

The size of the objects have also led scientists to question the validity of the claim.  Contrary to popular believe, dinosaur eggs were not enormous, in fact given the size of some of the adults that laid the eggs, dinosaur eggs were not disproportionately any bigger than the eggs of many birds.  Egg size is limited by a number of factors.  It is not merely due to the ability of an egg to pass through the oviduct of the adult attempting to lay, but also if the eggs of the largest dinosaurs were more than one metre in diameter, their weight would mean that the egg shell would have to be very thick.  The thickened egg shell would interrupt gaseous exchange and any dinosaur attempting to hatch would have had an extremely difficult job.

Some of the largest dinosaur eggs known, do come from Europe, but not the Caucasus mountains, they were found in France.  A number of football-sized eggs were discovered in France in the 19th Century.  They are believed to have been laid by a Late Cretaceous (Maastrichtian faunal stage) titanosaur known as Hypselosaurus.

To read more about Hypselosaurus and to see a picture of the dinosaur eggs that some scientists ascribe to this genus: The Big Eggs of a Dinosaur.

However, the largest of the French eggs, some thirty centimetres in diameter are dwarfed by the strange eggs of Chechyna.  The objects are simply too big to be regarded as eggs.

Yuri Gubin from the Moscow Museum of Palaeontology has cast doubt about the authenticity of the find, he stated:

“The boundary between the shell and inner structure are clearly seen on the dinosaur eggs.  I haven’t mentioned it on the discovery of the Chechen specialists, I think it’s a kind of sphere-like rocks.  You can’t imagine how many such “eggs” were brought to our museum by Moscow residents”.

Photographs show a close up of some of the giant “dinosaur eggs”, however if you look closely a number of interesting points, challenging the validity of the dinosaur egg theory can be made.  Firstly one of the arrows points to an exposed area that shows the internal structure of the so-called egg.  Although it is difficult to see all the detail clearly, the  internal structure is not typical of what would be expected inside a fossilised egg, for example there is no evidence of a fossilised embryo.  The shape of the object is very nearly round, most dinosaur eggs are not that spherical in shape.  In addition, one of the arrows points at another object which seems to have been squeezed between two of the “eggs”.  The shape of the object arrowed could have been due to physical processes that occurred during fossilisation but it is more likely that these strange structures may be caused by gaseous intrusions into the layers of sedimentary rock as they were being formed.  These would create bubble-like structures and it is probably natural, geological process that has formed the unusual pattern seen in this particular rock strata.  It is unlikely that this is evidence of a giant dinosaur’s nest.

A Fossilised Dinosaur Egg

A fossilised dinosaur egg (Theropoda). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Whilst it remains very likely that these egg-shaped objects are the result of natural , geological processes this has not dampened the enthusiasm or excitement of the locals, who have flocked to the area to take videos and photos of Chechnya’s very own dinosaur discovery.

For dinosaur toys and games including models of prehistoric animals visit: Everything Dinosaur.

Egg-Laying Dinosaurs Doomed Whilst Mammals Live-Birth Reproduction Strategy Triumphed

A team of scientists based in Switzerland have used computer models comparing how dinosaurs grew from a hatchling into an adult with the growth rate of mammals to suggest that the dependence on egg-laying was a factor in the demise of the Dinosauria.  They have added a new twist to the dinosaur extinction theory.

Dinosaur Extinction Theory

Given the physical limitations imposed on the size of hatchlings, dictated by the physical limits of the eggs they hatch from, many dinosaur species had to grow from babies just a few tens of centimetres long into thirty metre and forty tonne giants.  Small, baby dinosaurs having to grow quickly could not compete against mammals that gave birth to much better developed mammalian offspring who could benefit from being suckled by their mothers.

The dinosaurs became extinct approximately sixty-six million years ago, the exact reasons for the extinction of the Dinosauria along with about seventy percent of all terrestrial life at the end of the Cretaceous are still debated, however, within a few million years, life on Earth had recovered and the mammals were rapidly diversifying to fill many of the niches in the ecosystem that were once occupied by dinosaurs.  A team of researchers from the University of Zurich (Switzerland), have used a complex, mathematical model to plot how mammals with their different strategy over reproduction may have gained the ascendancy over those type of dinosaur that survived until the very end of the Mesozoic.

Did the Dinosauria’s Reliance on Eggs Lead to their Demise?

Did a reliance on egg-laying Lead to the extinction of the dinosaurs?

Picture credit: Everything Dinosaur

To view models and figures of extinct non-avian dinosaurs and other prehistoric animals: Safari Ltd Dinosaur Models.

In press releases concerning this new research, detailed in the scientific journal “Biology Letters”, it has been suggested that the mammals won a sort of evolutionary victory over the egg-laying dinosaurs but this does very probably, over simplify the complex environmental factors that were influencing evolution at this crucial time in our own species’s history.  Had the dinosaurs not died out, it is unlikely that there would be the diversity of mammal types around today and it could be argued that the primates, including our own species – Homo sapiens may not have evolved at all.

Ontogenic Studies

The Zurich based scientists looked at how the two sorts of animals (mammals and dinosaurs) grew, they studied the ontogenic properties of typical dinosaurs and mammals that were alive around sixty-six million years ago.  As dinosaurs hatched, they would have had to compete for food with other dinosaurs as well as mammals, whilst the offspring of mammals had their mother’s milk to sustain them.  In addition, dinosaurs had to grow very quickly, for example a baby titanosaur (long-necked dinosaur), may have had to put on more than one kilogramme of body weight a day – a rate of weight gain not seen in the much smaller mammal genera around at the time.

As baby dinosaurs grew, the young animals would have had to compete in several size categories for food, including adults of other animal groups.  This, the scientists claim put the Dinosauria at a distinct advantage and this may help explain why they died out but the majority of mammals did not.

Those niches in the food chain for small and medium-sized animals were already “occupied”, with the intense competition for depleted food reserves after an extraterrestrial impact, volcanism and climate change leaving no room for the dinosaurs.

Being relatively small, as in the case of the Mammalia at the end of the Cretaceous may have been key to their survival, the fossil record suggests that immediately after the extinction event there were very few terrestrial animals larger than a Labrador dog (around 25 kilogrammes).  Some mammals also lived in burrows and bred very rapidly, these factors too could have assisted in the Order’s ultimate survival.

A Fossilised Dinosaur Nest showing Eggs

Two dinosaur eggs. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The Swiss team claim that smaller mammals were able to cope with the post-extinction environment much more effectively than their egg-laying competitors and this led them to evolve and diversify very rapidly in the Cenozoic, rapidly occupying all the niches once held by the dinosaurs.

The team aimed to answer the question using their mathematical model as to why the Dinosauria died out yet the Mammalia survived?  Could adult body mass, and an egg-laying reproduction strategy hold the answer?

Contrary to popular belief, compared to their eventual adult size, many dinosaurs hatched from comparatively small eggs.  The largest dinosaur eggs known in the fossil record are believed to have been laid by titanosaurs (long-necked dinosaurs), these eggs are roughly football-sized and from a hatchling, perhaps less than one metre long and weighing a few kilogrammes, these animals would grow to become a forty metre long, forty thousand kilogramme adult animal.

The discovery of some bizarre, egg-shaped structures by construction workers in Chechyna has recently been featured in a number of media outlets.  The egg-shaped objects, some more than a metre in circumference were believed by some observers and academics to be the fossilised remains of a dinosaur nesting site.  However, palaeontologists have cast doubt over the authenticity of these claims as the structures are simply “too big” to be dinosaur eggs.

To read more about this story: World’s Largest Dinosaur Eggs – The Facts are Scrambled.

The size of an animal that can hatch from an egg is governed by a number of factors.  Firstly, the egg shell has to be thin enough to allow gaseous exchange between the external environment and the embryo inside the egg.  The egg shell has to be thin enough to allow a baby to hatch, to break out of the egg.  If dinosaur eggs were much bigger, then the egg shell surrounding them would have to be much thicker to support the weight of the liquid and the embryo inside.  The egg shell would have to be many times thicker to accommodate this extra weight and therefore, too thick for a baby to break out of.  If the egg shell remained thin as egg size increased then a great many eggs would never hatch as the eggs would crack and split long before the embryo had developed enough to be able to hatch.  Egg size is also limited by the ability of the female to store eggs, to divert enough calcium to permit the formation of egg shell in her body and to allow the passing of eggs via the oviduct so they can be physically laid.

The scientists compared the growth rate of the largest land mammal today, the African elephant (Loxodonta africana) to that of a typical Late Cretaceous titanosaur, the largest type of dinosaur around at the very end of the age of reptiles.  The Swiss team suggested that a titanosaur hatchling was 2,500 times lighter than an adult titanosaur, whilst the African elephant calf was only twenty-two times lighter than its mother.

Cretaceous Mass Extinction Event

Many papers have been written on the Cretaceous mass extinction event.  Egg-laying animals may have been more vulnerable to climate change and this could have been a factor in the demise of the Dinosauria.  However, monotreme mammals (mammals that lay eggs and give birth to very underdeveloped young), did survive the extinction event.  Birds too, survived and they all lay eggs (classified technically as avian dinosaurs).   Body size and the amount of resources needed to sustain a viable breeding population may be a more significant factor in the lottery of life that occurs during an extinction event.  The scientific paper does not help to explain how the pterosaurs or the marine reptiles died out.  Some marine reptiles were viviparous, able to give birth to live young, yet these animals too, went the way of the dinosaurs.

The dinosaurs reliance on an egg-laying reproduction strategy may well have played a role in their eventual demise, but during the Late Cretaceous extinction event all sorts of terrestrial animals became extinct – reptiles, mammals, amphibians and birds.   Thanks to a few types of mammals surviving into the Cenozoic we have the great diversity of mammals seen today.  Within ten million years or so, the main groups of modern mammals had evolved including those prosimians that were to lead eventually to our own species.

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