In 1980, Science magazine published a dinosaurs-killed-by-a-giant-asteroid theory by Luis Alvarez. Critics asked how creatures outside the impact area were killed. Alvarez replied:
“From darkness. The impact created huge amounts of dust, cutting off the sun’s power by up to 20% for 8 to 13 years.”
Actually, the “dark times” lasted much longer - about 100,000 years, and started a long time before the impact events.
In an article published in Nature in 1989, Meixun Zhao and Jeffrey L. Bada reported that they had found isovaline and aminoisobutyric acid tens of centimeters below and above the Cretaceous-Paleogene (K-PG) boundary. The authors surmised that the collision of a massive extraterrestrial object with Earth may have produced this unique organic chemical signature because certain meteorites contain organic compounds which are either rare or non-existent on Earth. Zhao and Bada suggested that the extraterrestrial amino acids diffused from the boundary clay above and below it. In the boundary clay itself, there are no amino acids.
In 1990, Kevin Zahnle and David Grinspoon of the NASA Ames Research Center suggested that the amino acids had been deposited for 100,000 years by cometary fine dust.
Max Wallis from Cardiff University argues that cometary dust delivered nonterrestrial microfungi or novel genes that were incorporated into existing microfungi on Earth and produced the amino acids.
The asteroid and volcano theories, which are prevalent among scholars, can’t explain the presence of the two amino acids and the iridium spikes before and after the K-PG boundary, and how they were deposited for about 100,000 years.
In short, K-Pg extinction theories that can’t explain the presence of uncommon amino acids above and below the Cretaceous-Paleogene boundary are not viable.
The K Comet
Long-period comets have highly eccentric orbits, extending to the far reaches of the Solar System, and periods ranging from 200 years to thousands or even millions of years.
Sometimes they make close passages by the planets and the Sun, diverting into the inner Solar System and becoming short-period comets.
Dust Clouds Phase
When comets approach the Sun, they begin to sublimate (cometary material transits directly from solid state to gas) and vaporize, creating an envelope of thin gas and fine dust. When a comet is heated to about 2,760 degrees Celsius (5,000 degrees Fahrenheit), it is hot enough to vaporize not just ice and gases, but also rock and metals.
Sunlight pushes the gas and the dust of the comet away to form a tail.
The comet is exhausted when most of the volatile material contained in the nucleus evaporates away by the Sun, and the comet becomes a much smaller, dark, inert lump of rock or rubble that can resemble an asteroid.
The size of the original K comet (K for Cretaceous, or Killer) was more than 100 km in diameter, probably 300 to 400 km. Comets could be much larger than these dimensions, reaching diameters of thousands of kilometers.
If the orbit of the cometary dust intersects the Earth's orbit, our planet and its atmosphere sweep through the dust stream every year, experiencing meteor showers and the deposition of fine dust on the surface of the globe. The cometary dust, containing amino acids, iridium, etc. was exhausted for about 100,000 years.
The amino acids and iridium enrichment before and after the K-PG boundary had several peaks. It was deposited in layers with larger quantities of amino acids and iridium, ergo Earth passed several times through much thicker cometary dust clouds.
Because some of the dust particles are very small, they will be rapidly slowed to a stop in Earth’s upper atmosphere. Instead of burning up in a flash of light like the larger cometary grains, they will drift slowly to the surface of the planet. It will take months or even years for fine cometary dust to settle down from the upper atmosphere.
In such a flyby of a huge comet, Earth would accumulate a large mass of dust in the upper atmosphere, slightly changing the climate and inhibiting the photosynthesis of land and marine organisms. Major food chains would be disturbed. The reduction of the plant mass would lead to starvation of plant-eating animals. The first victims were the large herbivores on land and in the oceans; especially the ones living at the Polar Regions, where the sunlight reduction by the dust cloud was more serious and the temperature drop was substantial, and the loss of plant mass was significant.
Large species at the top of the food chain, such as dinosaurs, are highly vulnerable to ecosystem disruption.
At the end of the Cretaceous, there were much more plant mass and animals per square km than today. Even small disturbances in climate, ecosystem, and food chain caused many animals to die off.
The Dust Clouds Phase lasted for tens of thousands of years before and after the cometary impacts.
The Cretaceous extinction began thousands of years before the K-Pg boundary.
Impacts Phase
Even nowadays, some comets meet a spectacular end - either falling into the Sun or smashing into a planet or other space body.
A recent collision of a comet with a planet occurred in July 1994, when comet Shoemaker–Levy 9 broke up into pieces and collided with Jupiter. Over the next six days, 21 distinct impacts were observed.
The after-effects of the impacts were visible on Jupiter for nearly a year after the event.
The estimates range from 2 to 10 km in diameter for the original comet body and from 1 to 3 km for the largest fragments.
The K comet was much larger, and the consequences for the terrestrial life were tremendous, even before the catastrophic impacts themselves.
A series of impacts of such a disintegrating huge comet could cause colossal earthquakes, giant tsunamis, massive wildfires of plants and fossil fuels all around the globe, and might activate volcanos and basalt floods, changing the chemistry of the oceans. The skies would be covered with thick a dust blanket.
The hitting cometary fragments would cause massive volcanic activity and basalt floods because the previous strikes would weaken the impact sites.
Most of the cometary aminoisobutyric acid and isovaline could not survive the fiery impacts, so in the boundary clay there are almost no amino acids.
About 70 percent of the Earth's surface is water-covered. Probably about 70 percent of the comet fragments struck the oceans.
If the K comet hypothetically broke up into several large pieces and a great number of smaller ones; a few huge chunks, some of them possibly 10 to15 km in diameter, would strike the land in a very short period of time. On Jupiter, the impacts lasted for six days.
Mesozoic Atmosphere and the Mesozoic Metabolism
Earth's primeval atmosphere consisted of mostly carbon dioxide, nitrogen, and water vapor. The atmospheric pressure was very high, probably about 90 bars or even higher, and it gradually reduced to the present 1 bar.
Over millennia, the whole chemistry of the Earth changed, also due to the first organisms, which appeared about 3.8 billion years ago. Oxygen, which is released as a byproduct of photosynthesis, appeared in the Earth's atmosphere; the carbon dioxide was depleted.
The atmospheric pressure during the Mesozoic period was about 3 to 8 bars, and it was declining steadily. The oxygen level was getting higher - it was between 24 to 28 %, some researchers state higher or lower amounts.
In the specific Mesozoic hothouse world, with a much denser atmosphere and high amounts of oxygen and carbon dioxide, animals and plants grow much larger and were more numerous.
The huge reptiles and insects could fly only in a dense atmosphere with higher amounts of oxygen. They needed more fuel (oxygen) for their metabolic engines and thicker air to support their wings.
The amounts of oxygen available to the metabolism of the Mesozoic animals depended not only on the percentage of this gas in the atmosphere, but also on the air pressure. The higher pressure also means more available oxygen.
Even if the percentage of the oxygen is the same, but the air pressure is higher, the amount of oxygen in a given volume is higher. The amount of gas in a given volume is determined by the pressure and the temperature.
During the Mesozoic, there was more oxygen available for metabolism of the animals - a higher percentage, higher pressure, higher temperatures. The higher temperatures and the higher pressure made the utilization of oxygen much easier.
If an animal breathes air under higher pressure, such as inside a hyperbaric chamber (or as it was during the Mesozoic), the amount of oxygen in its blood increases significantly.
About 80 to 90% of the metabolic energy of animals comes from oxygen and only 10 to 20% from food.
The Mesozoic species, especially the dinosaurs, took advantage of the large amounts of oxygen, the abundant food, and the steady, warm climate, with only slight seasonal variations.
The metabolism of the Mesozoic fauna was different from the modern one because the atmosphere they breathed was different.
The large dinosaurs did not need to be truly warm-blooded because they had enough energy (lots of oxygen and food) at their disposal, a steady and warm climate, and almost no rival species outside the dinosauria.
Not being truly warm-blooded was a way for them to resolve the problem of the overheating of their huge bodies in the hot Mesozoic climate. The removal of the body heat is more difficult in a warmer, wetter, and denser atmosphere. The large dinosaurs would be very troubled, if they were truly warm-blooded.
Avian dinosaurs became warm-blooded and smaller in order to fly more efficiently.
Metabolism was not the same by all dinosaurs. Some were more warm-blooded than others. Probably, most of them had a specific dinosaurian metabolism.
The Mesozoic atmosphere, with much higher amounts of carbon dioxide and higher atmospheric pressure, helped plants grow bigger and faster. With lots of plants, herbivorous dinosaurs thrived, providing lots of food for their carnivorous cousins. Both plant-eaters and meat-eaters grew fearsome.
Mammals, the present dominant species, can’t reach the giant size of the Mesozoic dominant species, the dinosaurs, because the modern atmosphere is different - a lower percentage of oxygen, lower air pressure, lower amounts of carbon dioxide.
Dinosaurs were very well adapted to the Mesozoic period. They ruled over a specific world.
Dinosaurs can’t live in the present world for many reasons - different atmosphere, different microbes, etc. Thus, present-day dinosaurs should be genetically modified in order to survive in the contemporary ecosystem. It’s not possible to reconstruct in open habitat the original authentic Mesozoic world as Michael Crichton did in his fiction book Jurassic Park.
Energy Problem
What made dinosaur dominant became their major drawback during the K comet events.
For the Mesozoic plants and animals, the Cretaceous catastrophe was a metabolic disaster.
During the K comet events, the oxygen in the air decreased abruptly. Because comets have more volatile elements (frozen gases and liquids) and very high impact speed, they create tremendous plumes on impact, allowing part of the atmosphere to escape into space. With partially lost atmosphere, the air pressure became lower.
The oxygen in the deflated post-impacts atmosphere was decreasing because a large number of oxygen-producing plants were annihilated by massive wildfires and the impacts; the lower sunlight levels due to massive dust clouds from the impact blast, volcanoes, prolonged fossil-fuel fires, meteoric dust, and wildfires reduced the oxygen produced by the dwindling land and marine plants.
The energy amounts available to the Mesozoic animals during the catastrophic events were tremendously reduced because of the huge loss of the plants mass and the drop of the available oxygen. The ecosystem could no longer sustain such a great number of animals. Especially affected were the huge species, which could not survive the energy deprivation.
The conditions were the worst during the cometary hits, but the reduced sunlight, the lower oxygen levels, and the food reduction lasted for tens of thousands of years after the impacts.
Researchers often ask the question why some species died off while others survived. The most important factor was body size - only small species survived the harsh period of severely reduced energy. Small animals cope much better with low amounts of food and oxygen. Experiments also prove that small animals perform better in a low-oxygen environment.
Initial symptoms of oxygen deficiency may include fatigue, overall weakness, blood circulation problems, poor digestion, muscle aches and pains, dizziness, memory loss, and irrational behavior. When the immune system is compromised by a lack of oxygen, the body is more susceptible to opportunistic bacteria, viral, and parasitic infections, flu and colds.
In the heavily stressed environment during the K-Pg catastrophe, the animals needed even more energy from oxygen and food to survive.
Dinosaurs abruptly lost their metabolic advantages during the catastrophic events because air pressure and the oxygen levels dropped, food became scarce, the temperatures dropped, and seasons appeared.
Cope's Rule, named after the American paleontologist Edward Drinker Cope, postulates that population lineages tend to increase in body size over evolutionary time. Large animals find it easier to avoid or fight off predators, to capture a prey, or to kill competitors, etc. Although this increases each individual's fitness, it leaves the species more susceptible to extinction.
After the K comet impacts the competition was between the small animals. All huge species couldn’t survive.
The average body size of the animals after the K-PG events was between 2 and 5 kg. All species over 25 kg died off.
The average surviving animals were as large as cats, chicken, and rabbits. The largest ones were as “huge” as dogs and goats.
The smallest dinosaurs were mainly from the late Triassic and early Jurassic. Most of them died off before the end of the Cretaceous period. Dinosaurs got largest in the late Jurassic and Cretaceous periods.
Large animals couldn’t squeeze through the K-PG energy filter. The mode of dinosaur body masses was between one and ten metric tonnes.
After the K comet, the Mesozoic world was over.
Championship of Species in Troubled Conditions
Dust, lingering for tens of thousands of years in the upper atmosphere before and after the cometary strikes, changed the climate and reduced the plant mass; multiple impacts of the disintegrating comet, loss of part of the atmosphere, reduced levels of oxygen, reduced air pressure, prolonged fossil fuel wildfires, huge tsunamis, changed chemistry of the oceans, massive volcanic activity and basalt floods, etc., created the specific pattern of the Cretaceous extinction.
The highly stressed post-Cretaceous environment was a very tough playground for the species, fighting to survive and dominate.
Mammals were evolutionary higher animals and they became dominant species on the planet ever since the K-PG extinction.
Their method of breeding gave mammals the ultimate advantage over the egg-laying species.
Because of the extensive fossil record of extinct dinosaur eggs, eggshells, and embryos, it is well established that dinosaurs laid eggs.
The principal disadvantages of dinosaurian reproduction compared to mammalian are:
1. The nutrients inside the egg are very limited compared to the continuous supply that mammals receive inside the womb;
2. The oxygen supply is much lower as well;
3. The temperature of the reptile embryo is dependent upon the environment, while the body heat of the mammalian fetus is constant;
4. Dinosaur newborns don’t get the highly nutritious food that mammals do - milk;
5. Shorter gestation period. This is the time in which the fetus develops, beginning with fertilization and ending with birth.
Eggs hatch between 60 and 105 days after they are laid. The human baby develops inside the mother’s womb for about 270 days. The human brain develops from three to four and a half times longer, and in a much better inner environment, than the dinosaur brain.
The developing sophisticated brain needs more oxygen, more nutrients, a constant temperature, and more time.
The mammalian fetus, developing inside the maternal body, can receive a continuous and generous supply of oxygen and all the nutrients needed to build a complex brain. The milk of mammals contains essential nutrients, important antibodies, and white blood cells. This is a perfect food for infants and for their energy-hungry, developing brains.
The brain of live-birth mammalian animals is evolutionarily higher than the brain of animals that reproduce through egg-hatching, and it is also far more sophisticated.
Even warm-bloodedness does not help much toward intelligence, if one hatches from an egg. Avian dinosaurs (birds) compared to the primates are a typical example.
Mammals were evolutionarily better players and won the world dominance trophy by a single stroke, thanks to the K comet. The non-avian dinosaurs were simply too large and too mesozoic to survive the Great end-Cretaceous Energy Filter.
The dinosaur extinction mechanism is finally revealed.
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My new research book on the Cretaceous-Paleogene mass extinction mechanism, plus about 100 theories on the dinosaur extinction, Dinosaur Killers will be published in early 2014.
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