Dinosaur Killers

by Popoff, Alexander

  The unexpected breakup of comets, some at considerable distances from the Sun, has long puzzled researchers.

  When in 1976, Comet West, which never approached closer than 30 million kilometers from the Sun, split into four fragments, astronomers were baffled.

  In the year 2000, Comet Linearin broke up explosively over a hundred million kilometers from the Sun.

  Eighty percent of comets that split do so when they are far from the Sun, according to Carl Sagan and Nancy Druyan, authors of the book Comet.

  Sagan and Druyan wrote, “The gravitational tides of the Sun or unequal heating cannot be sole causes of the splitting of comets. We still do not know why comets split.”

  Usually, all fragments follow the original orbit of the parent body, including the dust released by disintegration.

  In 2006, comet 73P/Schwassmann-Wachmann 3 broke up and formed a chain of over 33 separate fragments. The same comet in 1995 was seen to break into four large pieces. It is now known to have split into at least 66 separate objects. In 1930, when it passed close to the Earth, there were meteor showers with as many as 100 meteors per minute.

  The cometary fragments that slammed into the Earth 66 million years ago were partially exhausted. They were losing volatiles for about 30,000 to 50,000 years, nearly the half the life of a comet that entered the inner Solar System.

  Cometary fragments are usually named. The one that hit Earth and killed most of the Cretaceous species with the help of the rest of its cometary brethren, we could name the Big One, B1. The rest: B2, B3, etc. The B1 caused the impact crater and the K-Pg boundary layer.

  Dust Clouds Phase

  If the orbit of the cometary dust intersects 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 fragments tend to fall apart into dust, sand, and pebbles, and spread out along the orbit of the comet to form a dense meteoroid stream, which subsequently evolves into Earth’s path.

  The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a “dust trail.” Not to be confused with the “dust tail” of the comet.

  The amino acids and iridium enrichment before and after the K-Pg boundary has several peaks: 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 somewhat inhibiting the photosynthesis of land and marine plants. There wouldn’t be an inky darkness at noon or nuclear winter. Just prolonged periods that would look like dark, cloudy days.

  But what would be the effect on the plants and animals of the lower light intensity and a slightly cooler climate?

  What would be the effect of a mere 1°C (2°F) decrease of global temperatures for a few years only?

  In the last 2,000 years, we have historical records of similar events after volcano eruptions. Compared to a prolonged global saturation of the entire atmosphere with cometary dust from space, these are minor local events, but we could get a real picture of the consequences, not just computer simulations.

  After major volcanic eruptions, ash and the droplets of sulfuric acid in the atmosphere obscure the Sun and increase the reflection of the solar radiation, reducing global temperatures. Because of the reduced light and the somewhat cooler weather, the crops fail, and animals and people begin to starve, sometimes to death.

  “The sun was dark and its darkness lasted for eighteen months; each day it shone for about four hours; and still this light was only a feeble shadow; the fruits did not ripen and the wine tasted like sour grapes,” wrote Michael the Syrian regarding the weather in the year 536 CE.

  The extreme weather of 535 and 536 CE was the most severe short-term cooling in the last 2,000 years. It had been caused by an extensive atmospheric dust veil, possibly resulting from a large volcanic eruption in the tropics or debris from a bolide impact. Its effects were widespread, causing globally unseasonal weather, crop failures, and famines. The temperatures were low; there was even snow during the summer. Snow fell in August in China. A dense, dry fog was reportedin Europe, the Middle East, and China.

  John the Lydian, a Roman official, reported that “the sun became dim for nearly the whole year.”

  Many documents from the time of King Arthur speak of the terrible “dry fog” or cloud of dust that obscured the Sun, causing crop failures, summer frosts, drought, and famine. This caused the death of a vast percentage of the population through starvation and disease. Tree-ring studies in many parts of the worldconfirm several years of very poor growth. Climactic extremes continued for about 30 years after the event.

  1816 is known as The Year Without Summer. The average global temperatures decreased by 0.4 to 0.7 °C (0.7 to 1.3°F), caused by the eruption of the Tambora volcano and lower solar activity.

  In the spring and summer of 1816, a steady “dry fog” was reported in the northeastern USA. The peculiar fog reddened and dimmed sunlight. Neither rainfall nor wind could disperse the “fog,” because it was high in the stratosphere. Frost killed off most crops, especially at higher elevations. In June snow fell.

  In large parts of Europe the harvest failed. It was the worst famine of the 19th century. European fatalities totaled about 200,000 deaths.

  In China, the cold weather killed trees, rice crops, and water buffalo.

  Long-term cooling effects are primarily dependent upon the dust particles in the stratosphere, where little or no precipitation occurs, thus requiring a long time to wash the aerosols and dust out of a region.

  Sixty-six million years ago, the cometary particles from space dust could have stayed in the stratosphere for very long time, reducing the sunlight. There was a constant supply of fresh cometary dust, which sometimes was much thicker.

  Major food chains were disturbed. The reduction of the plant mass led to the 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, 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 kilometer than today. Even small disturbances in climate, ecosystem, and food chain caused many animals to die off.

  Brian K. McNab wrote in “Resources and energetics determined dinosaur maximal size,” “For example, the highest mammalian biomass on the African plains varies between 17,500 and 20,000 kg/km2. If herbivorous dinosaurs had FEEs (field energy expenditure) that were only 22% of their mammalian equivalents and if Mesozoic plant communities were about as productive as East African communities today, the maximal dinosaur biomasses would be expected to fall between 80,000 and 90,000 kg/km2.”

  The Dust Clouds Phase lasted for tens of thousands of years before and after the cometary impact; thus, the Cretaceous extinction began thousands of years before the catastrophic events.

  Paul R. Renne et al. reported, “We suggest that the brief cold snaps in the latest Cretaceous, though not necessarily of extraordinary magnitude, were particularly stressful to a global ecosystem that was well adapted to the long-lived preceding Cretaceous hot-house climate.”

  The pre-Cretaceous cooling of the climate is confirmed by many researchers.

  To sum up, we have geological records that the catastrophe began tens of thousands years before the K-P
g boundary.

  Impact Phase

  Jason Moore and Mukul Sharma from Dartmouth College in New Hampshire compiled all the published data on iridium and osmium from the K-Pg boundary. They described their findings in a paper presented to the 44th Lunar and Planetary Conference in 2013. In the final analysis, the overall trace element levels were much lower than those that scientists had been using for decades. They claim that the iridium and osmium levels across the K-Pg boundary indicate a small impactor, about 5.7 km in diameter.

  “But an asteroid that size would not make a 200-km diameter crater,” wrote Moore. “So we said: how do we get something that has enough energy to generate that size of crater, but has much less rocky material? That brings us to comets.”

  Luis Alvarez and his team wrote, in their article “Extraterrestrial Cause for the Cretaceous-Tertiary Extinction,” about the size of the bolide: “We conclude that the data are consistent with an impacting asteroid with a diameter of about 10 ± 4 km.” They calculated the size of the asteroid in four independent ways. According to their calculations based on the iridium levels at Gubbio, Italy, the size of the asteroid would be 6.6 km.

  Asteroids are traveling too slowly for a small rock to generate enough energy to create the Chicxulub crater. Comets travel a lot faster than asteroids and a comet of about 7 kilometers across, traveling at typical comet velocities, could release enough impact energy to create the Yucatan crater, think Moore and Sharma.

  “Comets have a lower percentage of iridium and osmium than asteroids, relative to their mass, yet a high-velocity comet would have sufficient energy to create a 110-mile-wide crater.”

  Sharma said that, “In synthesizing the data generated by two very disparate fields of research—geochemistry and geophysics—we are now 99.9 percent sure that what we are dealing with is a 66-million-year-old comet impact—not an asteroid.”

  The average velocity of space bodies entering the atmosphere of our planet is 10 to 70 km per second.

  Smaller meteorites are quickly slowed by atmospheric friction. For large meteorites, atmospheric friction has little effect on their speed and they hit our planet with the enormous velocity of their entry into Earth’s atmosphere.

  Comets are much more dangerous than asteroids because they travel a lot faster. The average velocity of an asteroid is about 25 km per second.

  Comets travel in elongated or nearly parabolic orbits around the Sun that allow them to move very fast. They move at speeds of 40 to 70 km per second.

  The kinetic energy of an incoming object from space follows the equation:

  Ek = ½ mv2

  Ek = kinetic energy, m = mass of object, v = velocity or speed of object.

  An object moving with twice the velocity of another object with the same mass has four times the kinetic energy.Yes, four times more impact energy! Ergo, comets have four times more destructive power than asteroids with similar mass.

  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.

  It was the first comet observed to be orbiting a planet, and had probably been captured by Jupiter around 20 to 30 years earlier.

  The after-effects of the impacts were visible on Jupiter for nearly a year after the event.

  The estimates range from 2 to 10 kmin diameter for the original comet body ofShoemaker–Levy 9 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. But even before the catastrophic impacts themselves, it started to kill off the terrestrial biota because of the cometary dust cloud.

  Large space bodies strike the ground with a significant fraction of their cosmic velocity. The kind of crater and degree of destruction depend on the size, velocity, composition, degree of fragmentation, and incoming angle of the impactor.

  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 tremendous hurricanes, and might activate volcanoes and basalt floods, changing the chemistry of the oceans. The skies would be covered with a thick dust blanket.

  A disintegrating huge comet can create a heat wave in the atmosphere with a devastating effect on the biota that cannot be created by an a stony or iron asteroid.

  The heat impulse lasted at least several days and destroyed a large proportion of the plants of many regions without burning them. The vegetation was destroyed by the thermal impulse, acid rains, numerous local wildfires, and the lack of enough sunlight.

  Belcher et al. noted that significant quantities of uncharred organic remains are present in the K-T boundary layers. The heat wave can destroy vegetation without burning it.

  The hitting cometary fragments could activate 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 (especially taking into account that cometary material partially consisted of burning stuff), so in the boundary clay researchers didn’t find amino acids.

  Now, about 70 percent of the Earth’s surface is water-covered. Sea level was high throughout much of the Cretaceous Period. At its maximum height, only about 18 percent of the Earth remained land.

  If there were multiple impacts, probably about 70 to 80 percent of the comet fragments struck the oceans.

  Ocean impact might be less hazardous to the biota than a land impact because no debris is thrown high into the atmosphere (only water); there were no wildfires, etc.; and the direct and indirect effects are not so devastating. Nevertheless, ocean impacts could punch the atmosphere and part of it could be ejected into space.

  Researchers claim that if an asteroid or comet with a diameter of about 5 km (3.1 miles) or more hits in the ocean or explodes above the surface of the waters, there would still be an enormous amount of debris ejected into the atmosphere, contributing to the cooling of the climate.

  In their article “Records of post–Cretaceous-Tertiary boundary millennial-scale cooling from the western Tethys: A smoking gun for the impact-winter hypothesis?” published in Geology in 2004, S. Galeotti, H. Brinkhuis, and M. Huber reported evidence that the post-catastrophic cooling of climate really happened.

  Matthew Huber said that for the first time someone has found a fossil record indicating the Earth cooled significantly at that time. The evidence was in the form of small, cold-loving ocean organisms called dinoflagellates and benthic formanifera that appeared suddenly in the waters that had previously been very warm.

  Huber said that life on the surface was probably recovering about 30 years after the impact events. It took much longer for the oceans to get back to normal, about 2,000 years.

  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 to 15 km in diameter, would strike the land and the waters in a very short period of time, probably a few minutes or hours only.

  Some of the fragments hit the surface of the Earth, but it is also possible that many smaller or larger chunks were airbursts, i.e., exploded in the atmosphere.

  Macroscopic—large enough to be examined by the unaided eye—cometary matter has never been found on Earth, until recently.

  The first-ever hard evidence of a comet impact on Earth was discovered in 1922 in Tutankhamun’s tomb.

  Among the precious artifacts there was a splendid piece of jewelry, a brooch, with an intriguing yellow-greenish winged scarab set in its center.

  In 1996, the Italian mineralogist Vincenzo de Michele spotted in the Egyptian Museum in Cairo the unusual glowing yellow-greenish gem in the middle of Tutankhamun’s brooch. Howard Carter, the archaeologist who discovered the tomb, suggested that the scarab was made of chalcedony, a semiprecious stone. But de Michele was not so sure.
It looked to him like some sort of glass.

  De Michele, working with the Egyptian geologist Aly Barakat, asked for permission to analyze Tutankhamun’s brooch.

  De Michele and Barakat, surrounded by armed guards and officials, were allowed to examine and test the jewel.

  The tests confirmed that the scarab was not a semiprecious stone. It was made of glass, but not a glass like any other produced by ancient Egyptian craftsman.

  Glass was a common material in the ancient world, but this glass was very different. Its silica content is about 98 to 99 percent, with an extremely high melting point. An ancient craftsman could not produce such pure glass and at such a high temperature.

  Several hypotheses have been suggested about the origin of the glass: a volcanic eruption, a shower of solid material originating in space, the impact of a bolide, airburst of a celestial body, etc.

  Barakat had an idea where such glass could come from. He knew of a 10th-century Arabic book with a map inside, which showed the location of greenish-yellow minerals in the Sahara Desert. Barakat suggested that the Arabs had discovered the source of the glass in Tutankhamun’s brooch. In the geology museum where Barakat worked, there were samples of glass brought back from Sahara by the English explorer Patrick Clayton in 1932.

  Clayton reported that, far in the desert, he had discovered a large number of glass pieces scattered over thousands of square kilometers. He had no idea how it had got there.

  The glass in Tutankhamun’s brooch and the mineral samples from the Sahara Desert looked very much alike.

  Studies showed that the glass was formed 28.5 million years ago.

  Something hitting Earth heated the sands to 2,000°C (3,600°F) and turned them into glass. But what crashed into our planet 28.5 million years ago?

  Evidence of the origin of the strange glass was found in a small, black, microdiamonds-bearing pebble found in 1996 by Aly Barakat in the desert amongst the numerous pieces of glass.