Search for Traces of Ancient Supernova in Antarctica

Japanese scientists journeyed to Antarctica to recover evidence of alterations to Earth’s atmosphere caused in medieval times by supernovae recorded by scholars – including obscure Irish monasteries where monks later interpreted them signs of the Antichrist . No, this isn’t the plot of the next Dan Brown novel (or a Dan Brow fanfiction written by an X-Files addict): this is real science.

Supernovae release terrific amounts of energy, as in “If one happened too close, the planet would be sterilized” truly terror-inducing terrific.  Some of this energy is fired off as gamma rays, which can travel thousands of light-years and still pack enough of a punch after to alter the atmosphere – which is exactly what happened in 1006 and again in 1054, when gamma rays blasted the upper atmosphere and created spikes in NO3 levels.  There was also quite a lot of visible light, creating a star visible even during the day which was noted by various Chinese, Egyptian and even monastic records.

To access past records of the atmosphere, a team of Japanese scientists carefully extracted 122 meters of ice core from Antarctica.  Even better, to locate events on such a stretch of frozen time you use known volcanic atmosphere-altering events as reference points – in other words, these guys use exploding mountains as a ruler. 

The team found NO3 spikes at times corresponding to 1006 and 1054, as well as a mysterious unknown third event – and we remind you that this is not a movie, even though that sounds so much like a second act reveal leading to a lost city or something, we can practically see Nicolas Cage’s shocked expression.

Unlike any movie adventurer of the unknown, who has a tendency to steal/detonate every single relic they find, the Japanese team have also made things easier for anyone who follows them.  The unprecedented detail of their observations reveals a standard 11-year cycle in ice-core records, corresponding to the sunspot cycle. This will help future ice-core observers track the time of events.

These people look at timescales so huge that the pulsing of the sun itself is just the ticking of a clock.

Ever Heard of: The Fermi Paradox

The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations.

The extreme age of the universe and its vast number of stars suggest that if the Earth is typical, extraterrestrial life should be common. In an informal discussion in 1950, the physicist Enrico Fermi questioned why, if a multitude of advanced extraterrestrial civilizations exist in the Milky Way galaxy, evidence such as spacecraft or probes are not seen. A more detailed examination of the implications of the topic began with a paper by Michael H. Hart in 1975, and it is sometimes referred to as the Fermi-Hart paradox. Another closely related question is the Great Silence—even if travel is hard, if life is common, why don’t we detect their radio transmissions?

There have been attempts to resolve the Fermi Paradox by locating evidence of extraterrestrial civilizations, along with proposals that such life could exist without human knowledge. Counterarguments suggest that intelligent extraterrestrial life does not exist or occurs so rarely that humans will never make contact with it.

Starting with Hart, a great deal of effort has gone into developing scientific theories about, and possible models of, extraterrestrial life, and the Fermi paradox has become a theoretical reference point in much of this work. The problem has spawned numerous scholarly works addressing it directly, while various questions that relate to it have been addressed in fields as diverse as astronomy, biology, ecology, and philosophy. The emerging field of astrobiology has brought an interdisciplinary approach to the Fermi paradox and the question of extraterrestrial life.

Should alien artifacts be discovered, even here on Earth, they may not be recognizable as such. The products of an alien mind and an advanced alien technology might not be perceptible or recognizable as artificial constructs. Exploratory devices in the form of bio-engineered life forms created through synthetic biology would presumably disintegrate after a point, leaving no evidence; an alien information gathering system based on molecular nanotechnology could be all around us at this very moment, completely undetected. Clarke’s third law suggests that an alien civilization well in advance of humanity’s might have means of investigation that are not yet conceivable to human beings.

Certain theoreticians accept that the apparent absence of evidence proves the absence of extraterrestrials and attempt to explain why. Others offer possible frameworks in which the silence may be explained without ruling out the possibility of such life, including assumptions about extraterrestrial behaviour and technology. Each of these hypothesized explanations is essentially an argument for decreasing the value of one or more of the terms in the Drake equation. The arguments are not, in general, mutually exclusive. For example, it could be that both life is rare, and technical civilizations tend to destroy themselves, or many other combinations of the explanations below. 

One explanation is that the human civilization is alone in the galaxy. Several theories along these lines have been proposed, explaining why intelligent life might be either very rare, or very short lived. Implications of these hypotheses are examined as The Great Filter.

Further reading:

The Fermi Paradox

Why Isn’t the Universe Crawling with Intelligent Life?

In his famous lecture on Life in the Universe, Stephen Hawking asks: “What are the chances that we will encounter some alien form of life, as we explore the galaxy?”

If the argument about the time scale for the appearance of life on Earth is correct, Hawking says “there ought to be many other stars, whose planets have life on them. Some of these stellar systems could have formed 5 billion years before the Earth. So why is the galaxy not crawling with self-designing mechanical or biological life forms?” 

Why hasn’t the Earth been visited, and even colonized? Hawking asks. “I discount suggestions that UFO’s contain beings from outer space. I think any visits by aliens, would be much more obvious, and probably also, much more unpleasant.”

Hawking continues: “What is the explanation of why we have not been visited? \One possibility is that the argument, about the appearance of life on Earth, is wrong. Maybe the probability of life spontaneously appearing is so low, that Earth is the only planet in the galaxy, or in the observable universe, in which it happened. Another possibility is that there was a reasonable probability of forming self reproducing systems, like cells, but that most of these forms of life did not evolve intelligence.”

We are used to thinking of intelligent life, as an inevitable consequence of evolution, Hawking emphasized,  but it is more likely that evolution is a random process, with intelligence as only one of a large number of possible outcomes.

Intelligence, Hawking believes contrary to our human-centric existece, may not have any long-term survival value. In comparison the microbial world, will live on, even if all other life on Earth is wiped out by our actions. Hawking’s main insight is that intelligence was an unlikely development for life on Earth, from the chronology of evolution:  “It took a very long time, two and a half billion years, to go from single cells to multi-cell beings, which are a necessary precursor to intelligence. This is a good fraction of the total time available, before the Sun blows up. So it would be consistent with the hypothesis, that the probability for life to develop intelligence, is low. In this case, we might expect to find many other life forms in the galaxy, but we are unlikely to find intelligent life.”

Another possibility is that there is a reasonable probability for life to form, and to evolve to intelligent beings, but at some point in their technological  development “the system becomes unstable, and the intelligent life destroys itself. This would be a very pessimistic conclusion. I very much hope it isn’t true.”

Hawkling prefers another possibility: that there are other forms of intelligent life out there, but that we have been overlooked. If we should pick up signals from alien civilizations, Hawking warns,”we should have be wary of answering back, until we have evolved” a bit further. Meeting a more advanced civilization, at our present stage,’ Hawking says “might be a bit like the original inhabitants of America meeting Columbus. I don’t think they were better off for it.”

Source: Daily Galaxy

Global Dimming and Death of Our Sun

by Brian Cox

The Sun is Dying

Sol, our sun, will not live forever. It has enough fuel left, if our current understanding is correct, for another 5 billion years, at which point it will die. But could it be possible for the Sun to die much sooner, within the next 100 years even? From a scientific perspective, it should be said that this is very unlikely. But, it is also true that there is a lot about the universe that we do not understand.

Over the last few years astronomers have observed that there is extra “stuff” in the universe that we can see only by its gravitational influence on stars and galaxies. This stuff goes by the name of Dark Matter, and there is five times as much Dark Matter in the universe as there is normal matter, the stuff that makes up you, me, and the stars and planets we can see with our telescopes. What is this mysterious stuff? It’s possible, some scientists would say likely even, that this stuff is made of particles known as supersymmetric particles, a new and exotic form of matter that is high on the list of potential discoveries at CERN’s giant Large Hadron Collider, a 27km in circumference machine which begins operations this year after almost a decade of construction.

Theoretical physicists have spent many years calculating the properties of these supersymmetric particles, and we have a reasonable theoretical understanding of how they might behave. One possibility is that they could clump together into giant balls known as Q-balls. If this is true, then these heavy and exotic objects could have been made billionths of a second after our Universe began, and still be roaming the Universe today. It is speculated that, if a Q-ball drifts into the heart of a super-dense object such as a neutron star, it could begin to eat away at it’s core like a cancer, until the star is no longer massive enough to maintain itself and explodes in a violent explosion. Such explosions, known as gamma ray bursts, are seen in the Universe, although their cause is as yet unknown.

Could such a dangerous, exotic object drift into the Sun’s core and cause it to stop shining? It is likely that the Sun is many times too diffuse to stop a Q-ball – it would power right through. But maybe, just maybe, some strange exotic form of matter from the earliest times in the universe could settle deep within the Sun’s core, and disrupt its function enough to cause the catastrophic scenario seen in Sunshine. It’s far-fetched, but we have a saying in physics that anything that isn’t explicitly ruled out is therefore possible, so in the final analysis, you never quite know.

Global Dimming 

It is now suspected that pollution in the Earth’s atmosphere, caused by industrialization and natural phenomena such as volcanic eruptions, may have significantly reduced that amount of sunlight reaching the Earth’s surface. It is estimated that this could have led to a cooling effect of over 1 degree overt he last 40 years, which would go some way to offsetting the effect of global warming. Global warming is caused primarily by increasing carbon dioxide levels in the atmosphere that prevent heat being radiated back out into space from the Earth’s surface.

The phenomenon of global dimming may therefore have saved us, so far, from the worst affects of climate change, although it has been noticed that as pollution levels have been reduced, particularly in Western Europe, the affects of global dimming seem to be reducing, leading to an accelerating temperature rise once again. We may therefore be in the paradoxical situation that reducing pollution might INCREASE the effects of global warming, leading us ever more quickly towards catastrophe.

This discovery isn’t all bad, however, because it may suggest a short term solution to climate change. Why not intentionally put pollutants, which may be designed to be benign in other respects, into the atmosphere to accelerate global dimming, and therefore slow the climate change caused by carbon dioxide emissions. Several suggestions along these lines have been made, including adding small particles to airplane fuel, and therefore using one of the main contributors to climate change, aircraft, to slow its effects. It’s an intriguing possibility, and one that is the focus of significant research, although it should be said that we cannot at present predict the effects of such fine-tuning of the climate, so global dimming shouldn’t be seen as a means to allow us to continue to increase carbon dioxide emissions.

Was the Universe Destroyed by Dark Matter?

Did dark matter destroy the universe?  You might be looking around at the way things “exist” and thinking “No”, but we’re talking about ancient history.  Three hundred million years after the start of the universe, things had finally cooled down enough to form hydrogen atoms out of all the protons and electrons that were zipping around – only to have them all ripped up again around the one billion year mark.  Why?

Most believe that the first quasars, active galaxies whose central black holes are the cosmic-ray equivalent of a firehose, provided the breakup energy, but some Fermilab scientists have another idea.  Dan Hooper and Alexander Belikov posit that invisible, self-destructing dark matter may have blown up every atom in the universe.  At least it’s plausible in that if we wanted to ionize an entire universe, we’d want something that sounded that awesome.

Dark matter is a candidate for providing ionizing radiation because, if it exists at all, it’s its own antiparticle: if two dark matter particles hit each other they can blow up.  Insane as it sounds, the theory predicts that despite making up most of everything the particles themselves are so tiny, and so terribly fussy about colliding, that they can form huge structures without destroying themselves.  Positron emissions which may be an indication of exactly this kind of self-destruction have been observed by the European PAMELA satellite currently orbiting the Earth.

As theories go, this one is more awesome than accepted.  The quasar hypothesis has wide support, and crediting something we’ve never even seen with reshaping the universe may be going a little far.  Then again, that’s what modern cosmology is doing with dark matter anyway, so maybe this idea will fit right in.

Ever Heard of: Auroras

Auroras, sometimes called the northern and southern (polar) lights or aurorae (singular: aurora), are natural light displays in the sky, usually observed at night, particularly in the polar regions. They typically occur in the ionosphere. They are also referred to as polar auroras. In northern latitudes, the effect is known as the aurora borealis, named after the Roman goddess of dawn, Aurora, and the Greek name for north wind, Boreas by Pierre Gassendi in 1621. The aurora borealis is also called the northern polar lights, as it is only visible in the sky from the Northern Hemisphere, the chance of visibility increasing with proximity to the North Magnetic Pole, which is currently in the arctic islands of northern Canada. Auroras seen near the magnetic pole may be high overhead, but from further away, they illuminate the northern horizon as a greenish glow or sometimes a faint red, as if the sun was rising from an unusual direction. The aurora borealis most often occurs from September to October and from March to April. The northern lights have had a number of names throughout history. The Cree people call this phenomenon the “Dance of the Spirits.” Auroras can be spotted throughout the world. It is most visible closer to the poles due to the longer periods of darkness and the magnetic field.

Its southern counterpart, the aurora australis or the southern polar lights, has similar properties, but is only visible from high southern latitudes in Antarctica, South America, or Australasia. Australis is the Latin word for “of the South.”

Benjamin Franklin first brought attention to the “mystery of the Northern Lights.” He theorized the shifting lights to a concentration of electrical charges in the polar regions intensified by the snow and other moisture.

The phenomenon of aurora is an interaction between the Earth’s magnetic field and solar wind.

Auroras are produced by the collision of charged particles from Earth’s magnetosphere, mostly electrons but also protons and heavier particles, with atoms and molecules of Earth’s upper atmosphere (at altitudes above 80 km (50 miles)). The particles have energies of 1 to 100 keV. They originate from the Sun and arrive at the vicinity of Earth in the relatively low-energy solar wind. When the trapped magnetic field of the solar wind is favorably oriented (principally southwards) it connects with Earth’s magnetic field, and solar particles enter the magnetosphere and are swept to the magnetotail. Further magnetic reconnection accelerates the particles towards Earth.

The collisions in the atmosphere electrically excite electrons to take quantum leaps (a mechanism in which the electron’s kinetic energy is converted to visible light); and molecules in the upper atmosphere. The excitation energy can be lost by light emission or collisions. Most auroras are green and red emissions from atomic oxygen. Molecular nitrogen and nitrogen ions produce some low level red (pink) and very high blue/violet auroras. The light blue and green colors are produced by ionic nitrogen and the neutral helium gives off the purple colour whereas neon is responsible for the rare orange flares with the rippled edges. Different gasses interacting with the upper atmosphere will produce different colors, caused by the different compounds of oxygen and nitrogen. The level of solar wind activity from the Sun can also influence the color and intensity of the auroras.

The Earth is constantly immersed in the solar wind, a rarefied flow of hot plasma (gas of free electrons and positive ions) emitted by the Sun in all directions, a result of the million-degree heat of the Sun’s outermost layer, the corona.

The IMF originates on the Sun, related to the field of sunspots, and its field lines (lines of force) are dragged out by the solar wind. That alone would tend to line them up in the Sun-Earth direction, but the rotation of the Sun skews them (at Earth) by about 45 degrees, so that field lines passing Earth may actually start near the western edge (“limb”) of the visible sun.^[9]

Earth’s magnetosphere is the space region dominated by its magnetic field. It forms an obstacle in the path of the solar wind, causing it to be diverted around it, at a distance of about 70,000 km (before it reaches that boundary, typically 12,000–15,000 km upstream, a bow shock forms). The width of the magnetospheric obstacle, abreast of Earth, is typically 190,000 km, and on the night side a long “magnetotail” of stretched field lines extends to great distances.

When the solar wind is perturbed, it easily transfers energy and material into the magnetosphere. The electrons and ions in the magnetosphere that are thus energized move along the magnetic field lines to the polar regions of the atmosphere.

The aurora is a common occurrence in the Poles. It is occasionally seen in temperate latitudes, when a strong magnetic storm temporarily expands the auroral oval. Large magnetic storms are most common during the peak of the eleven-year sunspot cycle or during the three years after that peak. ^{Geomagnetic storms that ignite auroras actually happen more often during the months around the equinoxes. It is not well understood why geomagnetic storms are tied to Earth’s seasons while polar activity is not.}

Global Warming Shrinking Sheep

Changing winter conditions are causing Scotland’s wild Soay sheep to get smaller, according to a study that suggests climate change can trump natural selection.

The authors of the study published in “Science” believe that it highlights how wide-ranging the effects of global climate change can be, adding further complexity to the changes we might expect to see in animal populations in future.

“It’s only in the last few years that we’ve realized that evolution can influence species’ physical traits as quickly as ecological changes can. This study addresses one of the major goals of population biology, namely to untangle the ways in which evolutionary and environmental changes influence a species’ traits,” said Andrew Sugden, deputy and international managing editor at Science.

The researchers analyzed body-weight measurements and life-history data for the female members of a population of Soay sheep. The sheep live on the island of Hirta in the St. Kilda archipelago of Scotland and have been studied closely since 1985.

They selected body size because it is a heritable trait, and because the sheep have, on average, been decreasing in size for the last 25 years.

According to the findings lambs are not growing as quickly as they once did as winters have become shorter so do not need to put on as much as weight in the first months of life to survive.

The results suggest that the decrease is primarily an ecological response to environmental variation over the last 25 years. Evolutionary change, the report says, has contributed relatively little.

“Sheep are getting smaller. Well, at least the wild Soay sheep living on a remote Scottish island are. But according to classic evolutionary theory, they should have been getting bigger, because larger sheep tend to be more likely to survive and reproduce than smaller ones, and offspring tend to resemble their parents,” said study author Tim Coulson of Imperial College London.

“Our findings have solved a paradox that has tormented biologists for years — why predictions did not match observation. Biologists have realized that ecological and evolutionary processes are intricately intertwined, and they now have a way of dissecting out the contribution of each. Unfortunately it is too early to tell whether a warming world will lead to pocket-sized sheep,” said Coulson.

What Temperature is the Earth Supposed to Be?

If we don’t get our act together and slash greenhouse gas emissions, the UN climate change panel tells us, average global temperatures could rise by as much as 10 degrees F. by the end of the century.

But would that really be so bad? Sure, much of the South would be unbearable during the summer months (as would many of those tropical countries), but think of all that beautiful real estate in Alaska that we’d open up! And many of us here in Boston would willingly trade a dozen or more 100-degree F. days each year to wear shorts and flip-flops through October. Less snow shoveling, more Frisbee tossing. What’s not to like?

Who decreed that average global surface temperatures have to stay at the 58 degrees F. or so that modern humans are used to? After all, we’ve experienced temperatures much higher than that in the past (by “we,” I mean multicellular organisms living a half-billion years ago), and we’ve also had our share of ice ages. What is the “right” temperature for the planet?

Climate-change deniers love posing this question (economist Mark W. Hendrickson asked it earlier this week in a Monitor op-ed), because it makes those who try to answer it sound sentimental and unscientific. There is no “supposed to be” in nature. It is what it is.

But the question also misses the point: The alarming thing about global warming is not how high the average temperature will be, but how fast it’s rising.

And it’s rising really fast, compared to historical temperature shifts. The planet’s surface has warmed about 1.4 degrees F. since 1880, most of it in the past 30 years. And it’s accelerating. According to Britain’s Met Office, which has been recording temperature data since 1850, the next 10 hottest years after 1998 were, in order, 2005, 2003, 2002, 2004, 2006, 2007, 2001, 1997, 2008, and 1995.

When the temperature shifts this rapidly, living things may not be able to keep up. For instance, many insects, birds, and mammals time their breeding and migration based on temperature, while the many species of plants that they eat time their growth according to the sunlight. When this synchronicity gets thrown off, animals arrive on the scene before their meal is ready, the plants don’t get their seeds propagated, and species start going extinct. Whether we like to admit it or not, humans are part of this ecosystem.

This has happened before. About 250 million years ago, 9 of 10 marine species and 7 out of 10 of terrestrial species suddenly went extinct in what paleontologists call “The Great Dying.” They don’t know exactly what caused this mass extinction, but in all major proposed scenarios – an asteroid impact, a giant volcanic eruption, and changes in the composition of ocean gases – it was the resulting shift in the earth’s climate that, by throwing ecosystems out of whack, ultimately did in these creatures. Indeed, climate changes played a major role in all of the mass extinctions in the planet’s history.

None of this is to suggest that global warming will wipe out humanity. Homo sapiens, while perhaps not always living up to its name, has proven itself to be a highly adaptable species so far. But if we continue to allow our atmosphere to rapidly destabilize, will we be able to provide enough food and water, much less a measure of prosperity, for most of the 8 or 9 billion people predicted to be living here by midcentury? Do we really want to find out?

Earth Will Become Planet Without Ice Caps

Rising sea levels will not extinguish humanity, but they will transform life on planet Earth as we know it according to Peter Ward professor of biology and earth sciences at the University of Washington. Here are his predictions in a new book, The Flooded Earth, which will be published this July.

By 2050: Sea levels will rise 0.5 to 1 meter. Well established coastal cities will battle the rising waters with dikes and levees; other cities will see their underground infrastructure impaired and face building collapse.

By 2300: The seas will rise 20 meters reshaping the world’s geography, forming new rivers and lakes as Antarctica’s ice melts. Massive icebergs will form in the southern hemisphere interrupting historic shipping lanes.

2500-3000: the sea will reach its maximum levels completely wiping out coastal cities and forcing massive human and animal migration. Greenland and Antarctica will be transformed into prime farmlands. Southern regions will face the spread of tropical diseases and the possibility of mass extinctions.

Image above: Red represents areas where temperatures have increased the most during the last 50 years, particularly in West Antarctica, while dark blue represents areas with a lesser degree of warming. Temperature changes are measured in degrees Celsius. Credit: NASA/GSFC Scientific Visualization Studio.

Further reading:

Is Global Warming Part of Earth’s Natural Cycle: MIT Team Says “Yes” -A Galaxy Insight

Global-Warming Tipping Point: 9 Degrees Temperature Increase Would Devastate Earth’s Population

Source: http://www.nasa.gov/topics/earth/features/warming_antarctica.html

Hawking Says Asteroids Biggest Threats to Intelligent Life

Stephen Hawking believes that one of the major factors in the possible scarcity of intelligent life in our galaxy is the high probability of an asteroid or comet colliding with inhabited planets. We have observed, Hawking points out in Life in the Universe, the collision of a comet, Schumacher-Levi, with Jupiter (below), which produced a series of enormous fireballs, plumes many thousands of kilometers high, hot “bubbles” of gas in the atmosphere, and large dark “scars” on the atmosphere which had lifetimes on the order of weeks. 

 

It is thought the collision of a rather smaller body with the Earth, about 70 million years ago, was responsible for the extinction of the dinosaurs. A few small early mammals survived, but anything as large as a human, would have almost certainly been wiped out.

Through Earth’s history such collisions occur, on the average every one million year. If this figure is correct, it would mean that intelligent life on Earth has developed only because of the lucky chance that there have been no major collisions in the last 70 million years. Other planets in the galaxy, Hawking believes, on which life has developed, may not have had a long enough collision free period to evolve intelligent beings.

“The threat of the Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity,” according to Nick Bailey of the University of Southampton’s School of Engineering Sciences team, who has developed a threat identifying program.[ Image: Comet Shoemaker-Levy 9 collision with Jupiter]

The team used raw data from multiple impact simulations to rank each country based on the number of times and how severely they would be affected by each impact. The software, called NEOimpactor (from NASA’s “NEO” or Near Earth Object program), has been specifically developed for measuring the impact of ‘small’ asteroids under one kilometer in diameter.

Early results indicate that in terms of population lost, China, Indonesia, India, Japan and the United States face the greatest overall threat; while the United States, China, Sweden, Canada and Japan face the most severe economic effects due to the infrastructure destroyed.

The top ten countries most at risk are China, Indonesia, India, Japan, the United States, the Philippines, Italy, the United Kingdom, Brazil and Nigeria.

“The consequences for human populations and infrastructure as a result of an impact are enormous,” says Bailey. “Nearly one hundred years ago a remote region near the Tunguska River witnessed the largest asteroid impact event in living memory when a relatively small object (approximately 50 meters in diameter) exploded in mid-air. While it only flattened unpopulated forest, had it exploded over London it could have devastated everything within the M25. Our results highlight those countries that face the greatest risk from this most global of natural hazards and thus indicate which nations need to be involved in mitigating the threat.”

What would happen to the human species and life on Earth in general if an asteroid the size of the one that created the famous K/T Event of 65 million years ago at the end of the Mesozoic Era that resulted in the extinction of the dinosaurs impacted our planet.

As Stephen Hawking says, the general consensus is that any comet or asteroid greater than 20 kilometers in diameter that strikes the Earth will result in the complete annihilation of complex life – animals and higher plants. (The asteroid Vesta, for example, one of the destinations of the Dawn Mission, is the size of Arizona).

How many times in our galaxy alone has life finally evolved to the equivalent of our planets and animals on some far distant planet, only to be utterly destroyed by an impact? Galactic history suggests it might be a common occurrence.

The first this to understand about the KT event is that is was absolutely enormous: an asteroid (or comet) six to 10 miles in diameter streaked through the Earth’s atmosphere at 25,000 miles an hour and struck the Yucatan region of Mexico with the force of 100 megatons -the equivalent of one Hiroshima bomb for every person alive on Earth today. Not a pretty scenario!

Recent calculations show that our planet would go into another “Snowball Earth” event like the one that occurred 600 million years ago, when it is believed the oceans froze over (although some scientists dispute this hypothesis -see link below).

While microbial bacteria might readily survive such calamitous impacts, our new understanding from the record of the Earth’s mass extinctions clearly shows that plants and animals are very susceptible to extinction in the wake of an impact.

Impact rates depend on how many comets and asteroids exist in a particular planetary system. In general there is one major impact every million years -a mere blink of the eye in geological time. It also depends on how often those objects are perturbed from safe orbits that parallel the Earth’s orbit to new, Earth-crossing orbits that might, sooner or later, result in a catastrophic K/T or Permian-type mass extinction.

The asteroid that hit Vredefort located in the Free State Province of South Africa is one of the largest to ever impact Earth, estimated at over 10 km (6 miles) wide, although it is believed by many that the original size of the impact structure could have been 250 km in diameter, or possibly larger(though the Wilkes Land crater in Antarctica, if confirmed to have been the result of an impact event, is even larger at 500 kilometers across). The town of Vredefort is situated in the crater (image).

Dating back 2,023 million years, it is the oldest astrobleme found on earth so far, with a radius of 190km, it is also the most deeply eroded. Vredefort Dome Vredefort bears witness to the world’s greatest known single energy release event, which caused devastating global change, including, according to many scientists, major evolutionary changes.

What has kept the Earth “safe” at least the past 65 million years, other than blind luck is the massive gravitational field of Jupiter, our cosmic guardian, with its stable circular orbit far from the sun, which assures a low number of impacts resulting in mass extinctions by sweeping up and scatters away most of the dangerous Earth-orbit-crossing comets and asteroids

Posted by Casey Kazan with Rebecca Sato

Note: This post was adapted from a news release issued by University of Southampton.

Source: http://www.rationalvedanta.net/node/131

Source: http://www.dailygalaxy.com