“NASA and ESA (European Space Agency) spend billions of dollars collecting a few micrograms of comet material and bringing it back to Earth, and now we’ve got a radical new approach of studying this material, without spending billions of dollars collecting it,” said Jan D. Kramers of the University of Johannesburg, South Africa.
The black pebble has been named “Hypatia” in honor of the 4th-century female philosopher and mathematician Hypatia of Alexandria.
In the article “Unique chemistry of a diamond-bearing pebble from the Libyan Desert Glass strewnfield, SW Egypt: Evidence for a shocked comet fragment,” published in 2003 in Earth and Planetary Science Letters, Jan D. Kramers et al. wrote, “We propose that the Hypatia stone is a remnant of a cometary nucleus fragment that impacted after incorporating gases from the atmosphere. Its co-occurrence with Libyan Desert Glass suggests that this fragment could have been part of a bolide that broke up and exploded in the airburst that formed the Glass.”
The Libyan desert glass is triboluminescent.
In their article “The Libyan Desert Silica Glass as a product of meteoritic impact: A new chemical-mechanical characterization,” M. Guzzafame, F. Marino, and N. Pugno reported that the Libyan desert glass is triboluminescent: when scratched, crushed, or rubbed it emits a peculiar faint glow. This property of the materials is called triboluminescence.
Maybe the scarab itself emits a glow if scratched, crushed, or rubbed, looking very much like magic to the ancient Egyptians.
The total mass of the desert glass was estimated of about 1400 tons. Some desert glass also contains iridium and osmium.
The glass fragments found in an area of about 6000 km2 (2,300 square miles) are thought to be remains of a glassy surface layer, resulting from high temperature-melting of sandstone or sand, caused by an airburst of a comet. No corresponding crater has yet been found.
The researchers suggest the stone is result of the large airburst of a mechanically weak bolide that broke up into many smaller fragments before the impact, so that a large portion of their kinetic energy went toward heating of the atmosphere and melting the surface. The velocity of the extraterrestrial object was high enough to create shock diamonds. The probable region of origin is probably the Kuiper Belt.
Mark Boslough, an expert on impact physics based at the Sandia National Laboratories in New Mexico, made computer simulations of the size of the meteorite and estimated that an object about 120 meters (390 feet) in diameter, traveling at 20 km (12.4 miles) per second, and breaking up in the atmosphere would produce enough heat to melt sand and create glass without leaving a crater.
“What I want to emphasize is that it is hugely bigger in energy than the atomic tests,” said Boslough. “Ten thousand times more powerful.”
A comet 120 meters in diameter, travelling at 20 km per second, is as powerful as ten thousand atomic bombs. Can you imagine what would be the devastating power of a comet 10,000 meters in diameter, traveling at 40 km per second?
Above the surface of the desert a column of superheated gas propelled itself into space. The total effect is far more devastating than if it simply hit the ground. Nuclear bombs are more devastating if they are exploded above the surface than on the surface.
Aerial explosions are much more likely if celestial objects breaks up easily, like comets or exhausted comets that became asteroids, because they are more like rubble piles than solid rocks.
In astronomy, a rubble pile is an object that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. It can contain also some amounts of water, dust, and frozen gases.
The impact mechanism of a huge high-velocity cometary fragment disintegrating into several large and many small pieces, hitting the far denser and much more oxygen-saturated Cretaceous atmosphere, and the Earth’s surface, is quite different than of an asteroid the same size hitting the present atmosphere, which is thinner and with much less oxygen. Most computer simulations of the Cretaceous catastrophe are based on a single rock (asteroid) impact hitting the modern atmosphere. And, of course, such simulations can’t re-create the real picture of the K-Pg catastrophe.
To recap, an airburst is the explosion of a bomb, shell, or bolide in the atmosphere.
Naturally occurring airbursts are the Tunguska event, the Curuçá River event (also known as the Brazilian Tunguska event), the Chelyabinsk meteor event, etc.
The airburst of nuclear devices is usually 100 to 1000 meters (several hundred to a few thousand feet) above the hypocenter (the surface position directly beneath the center of a nuclear explosion) to allow the shockwave of the explosion to bounce off of the ground and back into itself, creating a shockwave that is more forceful than one from a detonation at ground level.
The altitude of a nuclear airburst is varied to obtain maximum blast effects, maximum thermal effects, radiation effects, or to balance the combination of these effects.
Numerous small space rocks of a disintegrating comet exploding in the atmosphere can be much more catastrophic that a single asteroid hitting the Earth.
In the case of a high-altitude explosion, the fireball is much larger and can devastate very large areas. Significant loss of atmosphere can occur, depending on the size and the number of the fragments of the high-velocity comet and the altitude of the airburst.
If a space rock is large enough to enter deep into the atmosphere before the explosion, the blast can create a jet of superheated gases that would incinerate everything on the ground; rocks and sand would turn into glass.
Small bolides exploding in the atmosphere could be more devastating than the one hitting Earth.
Numerous small airbursts can destroy almost all vegetation and many animals in huge regions, leaving no craters.
After the shockwave and the heat wave, the acid rain, the reduced sunlight, and the cooling of the climate (but no impact winter except in the polar regions) would destroy most marine and land flora and fauna.
Sandia National Laboratories supercomputer simulations suggest that the stunning amount of forest devastation at Tunguska may have been caused by a bolide only a fraction as large as previously published estimates.
The celestial body or a fragment exploding above the surface is transported downward at speeds faster than sound, forming a fireball, a high-temperature jet of expanding gas.
The material of an incoming space body is compressed by the increasing resistance of the atmosphere, reaching to a moment when the temperatures and the resistance are so high that they cause it to explode as an airburst, sending downward heated gas.
It is possible that at end of the Cretaceous, a swarm of a few large fragments and hundreds smaller ones hit the surface and the oceans, or airburst.
If the comet is very fragmented, the Earth might pass through the train of debris for thousands of years, causing airbursts.
Some scientists have suggested that the multiple layers of impact residue are evidence that there was more than one bolide involved in the mass extinction. But there is “no evidence for multiple impacts.” The fragmented comet may cause airbursts before, during, and after the main impact. Airbursts do not make craters. However, they can enrich Earth’s surface with iridium, alongside the cometary dust.
On Venus there are no craters smaller than about 1.5 to 2 km (1 to 1.2 miles) in diameter because of the planet’s dense atmosphere, which causes intense frictional heating and strong aerodynamic forces as meteorites plunge through it. Only larger meteorites reach the surface intact, but the smaller ones are slowed, fragmented, and airburst in the atmosphere.
The pressure of the atmosphere on Venus is 92 bar, which is about the same as the pressure at a depth of 1 km in Earth’s oceans.
The Cretaceous atmosphere on Earth was not as dense as on Venus, but it was denser than today and more favorable for airbursts and fragmentation of comets and cometary chunks.
The supposed atmospheric pressure during the Mesozoic period was about 3 to 8 bars.
Victor Clube and Bill Napier have written two books on the subject, The Cosmic Serpent, 1982, and Cosmic Winter, 1994,which addressed the origins of the comets, historical impacts, and mythology (seeking evidence of catastrophic events). The authors suggested that the outer planets Jupiter and Saturn occasionally divert huge comets into the inner Solar System into short-period orbits. Debris from the resultant disintegration of these giant comets can adversely affect the environment of the Earth. The cometary dust cloud could significantly cool the climate. Larger fragments, some sort of super-Tunguska, could cause heavy local destruction and sometimes “impact winter.”
The K comet, its orbit, dusting of Earth with cometary particles, and impacts of fragments are not something outlandish. Even now, we can watch events similar to the K comet events—of course, on a much smaller scale.
Ľubor Kresák, a Slovak astronomer, suggested in 1978 that the Tunguska event of June 30, 1908, was a fragment of the periodic comet Encke.
Comet Encke and the annual meteor shower Taurids are remnants of a much larger comet, which has disintegrated over the past 20,000 to 30,000 years, breaking into several pieces and releasing huge amounts of cometary dust and space debris, most of them the size of pebbles and stones, moving across the sky at about 27 km per second (17 miles per second). Now, this stream of matter is the largest in the inner Solar System. Since the meteor stream is rather spread out in space, the Earth takes several weeks to pass through it, causing an extended period of meteor activity. The Taurids are made up of pebbles instead of dust grains. But there are also larger fragments, like the one that hit the Tunguska area in Siberia.
Comet Encke completes an orbit of the Sun once every three years—the shortest period of any known comet. The diameter of the nucleus (the solid central part) of the comet is 4.8 km (2.98 miles). The orbit of Encke is frequently perturbed by the inner planets. Close approaches to Earth usually occur every 33 years. Earth passes periodically through a heavier concentration of material in the stream, causing more intense meteor showers. Every 2,500 to 3,000 years, the core of the stream passes nearer to Earth and produces much more intense meteor showers for a few centuries.
Comet Encke is probably one of the most evolved comets that are active. It may represent a transition between an active comet and a defunct comet.
It only rarely develops a noticeable tail because of its numerous previous visits to the Sun. The comet is partially “worn out”: most of its ices (liquids and gases) have been vaporized by the Sun. Now Encke probably consists of a compact silicate residue thinly mixed with ices.
Comet Encke gives us a pretty good idea about the orbit and the events that were caused by the K comet.
Abbott and Isley reported in Earth and Planetary Science Letters that their statistical analysis shows that 9 of 10 periods of heavy meteor bombardment corresponded to periods of massive volcanism.
The antipodal volcanism theory suggests that a large bolide strike could trigger volcanic activity on the opposite side of the globe.
Astronomers are identifying areas on the Moon, Mercury, and icy satellites where impact craters were antipodal to volcanoes and sites of broken crust.
David A. Williams and Ronald Greeley of Arizona State University reported in the journal Icarus that the largest impact basin on Mars, Hellas Plenitia, is antipodal to Alba Patera, an eruption sprawling for nearly 1600 km (1,000 miles) across the Martian surface. This is the largest volcano in the Solar System. The impact’s reverberations at the antipode were so strong that they tore open fractures more than 160 km (100 miles) deep, triggering a titanic flow of lava.
A theory recently advanced by a team of scientists at Sandia National Laboratories proposes a double engine of destruction: a bolide impact that may have set off massive volcanic eruptions on the opposite side of the Earth from the impact.
“The Earth acts like a lens,” said Mark Boslough. “It focuses the energy. There’s been a lot of speculation about this in relation to asteroid impacts and volcanic eruptions, but we’ve done the first rigorous modeling to show where the energy actually goes.”
Geologists have long known that strong earthquakes send out shockwaves that propagate through the Earth and focus at the quake’s antipode.
In the article “Axial focusing of impact energy in the Earth’s interior: A possible link to flood basalts and hotspots,” M. Boslough, E. Chael, T. Trucano, D. Crawford, and D. Campbell presented the results of shock physics and seismological computational simulations that show how energy from a large impact can be coupled to the interior of the planet.
They wrote, “We suggest that the most likely result of the focusing for a sufficiently large impact, consistent with features observed in the geological record, would be a flood basalt eruption at the antipode followed by hotspot volcanism. A direct prediction of this model would be the existence of undiscovered impact structures whose reconstructed locations would be antipodal to flood basalt provinces. One such structure would be in the Indian Ocean, associated with the Columbia River Basalts and Yellowstone; another would be a second K/T impact structure in the Pacific Ocean, associated with the Deccan Traps and Reunion.”
At the end of Cretaceous, The Deccan Traps were not antipodal to the Chicxulub crater due to tectonic plate movement; however, that does not preclude another, undiscovered impact crater contributing to the Deccan Traps eruption. On the other hand, there is no need of exactly antipodal impact to activate an active volcano, if the impact was of tremendous power.
The enormous lava flows of the Deccan Traps could have produced huge amounts of ash and gases, changing the global climate and ocean chemistry.
Of course, there are researchers like H. J. Melosh that think there is not a single clear instance of volcanism induced by impacts, either in the near vicinity of an impact or at the antipodes of the planet.
I think that impact-induced volcanism is real and that large bolide impacts can cause marine (underwater) and land basalt flows and activate additionally active volcanos. Of course, it is still difficult to discover and research marine basalt flows.
The marine volcanic activity could significantly worsen the situation with the creatures in the oceans during the catastrophic events at the end of the Cretaceous period.
Underwater volcanoes are much larger than the surface volcanoes.
Tamu Massif is an extinct submarine shield volcano located in the northwestern Pacific Ocean. It was built almost entirely of fluid lava flows. Tamu Massif is the largest individual volcano ever documented on Earth, and it is among the largest in the Solar System.
There is enough evidence that the K-Pg extinction was catastrophical, not gradual.
Peter Ward reported in his article “Impact from the Deep,” Scientific American, 2006, that by examining the isotope ratios in samples from before, during, and after a mass extinction, scientists obtain a reliable indicator of the amount of plant life both on land and in the sea.
Ward wrote, “When researchers plot such measurements for the K/T event on a graph, a simple pattern emerges. Virtually simultaneously with the emplacement of the so-called impact layer containing mineralogical evidence of debris, the carbon isotopes shift—13C drops dramatically—for a short time, indicating a sudden die-off of plant life and a quick recovery.”
The sudden die-off of plant life led to severe food shortage and massive starving to death.
According to Peter Ward, this finding is entirely consistent with the fossil record of land plants and the sea’s plankton, which underwent huge losses in the K-Pg catastrophe, and life bounced back rapidly.
Earth’s primeval atmosphere consisted mostly of carbon dioxide, nitrogen, and water vapor. Carbon dioxide degassed from Earth’s mantle during volcanic activity and the processes of plate tectonics. The atmospheric pressure was very high, probably about 90 bars or even higher, close to 120 bars, and it gradually reduced to the present 1 bar.
The atmosphere of Venus, nearly Earth’s twin in terms of size and mass, contains 96.5 percent carbon dioxide; and the air pressure is 92 bars, or 92 times the atmospheric pressure at the Earth’s surface at that moment.
According to model calculations, the Sun becomes 10 percent brighter every billion years; hence it must now be at least 40 percent brighter than at the time of formation of the Earth, but the early oceans did not freeze in spite of the dim Sun, due to the very high pressure and the abundance of atmospheric carbon dioxide, which provided an enhanced greenhouse effect.
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; carbon dioxide was depleted over the ages.
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 percent; some researchers state higher or lower amounts.
Some flying reptiles from the Jurassic and Cretaceous periods weighted about 70 to 130 kg and had wingspans from 10 to 17 m. The largest living bird is the ostrich, which may stand 2.5 meters tall and weigh 140 kilograms, but it can’t fly. Among the modern flying birds, the wandering albatross has the greatest wingspan, up to 3.5 meters, and the trumpeter swan has the greatest weight, up to 17 kilograms.
The laws of aeronautics and physiology would not allow the huge Jurassic and Cretaceous creatures to fly in the present air, but they ruled the ancient skies because the atmosphere was denser and richer with oxygen.
Dinosaur Killers Page 5