View from space of a gigantic piece of glacier breaks off the Greenland

Enormous chuck of ice breaks off the Petermann Glacier in Greenland. Credit: NASA.

A huge ice island four times the size of Manhattan– and half as thick as the Empire State Building is tall– has broken off from one of Greenland's two main glaciers. On August 5, 2010, an enormous chunk of ice, roughly 97 square miles (251 square kilometers) in size, broke off the Petermann Glacier, along the northwestern coast of Greenland. Satellite images, like this one from NASA’s Aqua satellite show the glacier lost about one-quarter of its 70-kilometer (40-mile) long floating ice shelf. Located a thousand kilometers south of the North Pole, the now-separate ice island contains enough fresh water to keep public tap water in the United States flowing for 120 days, said scientists from the University of Delaware who have been monitoring the break.

While thousands of icebergs detach from Greenland's glaciers every year, the last time one this large formed was in 1962. The flow of sea water beneath Greenland's glaciers is a main cause of ice detaching from them.

This movie made from another satellite — Envisat from the European Space Agency – shows the giant iceberg breaking off.

Time-series animation based on Envisat Advanced Synthetic Aperture Radar (ASAR) data from 31 July, 4 August, and 7 August 2010 showing the breaking of the Petermann glacier and the movement of the new iceberg towards Nares Strait. Credits: ESA

The animation above was created by combining three Advanced Synthetic Aperture Radar (ASAR) acquisitions (31 July, 4 August and 7 August 2010) taken over the same area. The breaking of the glacier tongue and the movement of the iceberg can be clearly seen in this sequence.

The Petermann glacier is one of the largest glaciers connecting the Greenland inland ice sheet with the Arctic Ocean. Upon reaching the sea, a number of these large outlet glaciers extend into the water with a floating 'ice tongue'.
The ice tongue of the Petermann glacier was the largest in Greenland. This tide-water glacier regularly advances towards the ocean at about 1 km per year. During the previous months, satellite images revealed that several cracks had appeared on the glacier surface, suggesting to scientists that a break-up event was imminent.

Scientists say it's hard to tell if global warming caused the event. Records on the glacier and sea water below have only been kept since 2003. The first six months of 2010 have been the hottest globally on record.

Sources: NASA, ESA

Chicxulub crater

The Chicxulub Crater is approximately 180 km in diameter and 10 km deep. The crater was formed about 65 million years ago when a very large celestial body impacted what is now known as the Yucatan Peninsula.

The Chicxulub Crater was formed by an impactor (either an asteroid or a comet) that was roughly 10 km in diameter and it hit with 100 million megatons of force. That is enough to make the bombs dropped during WWII look like bottle rockets. More than 50% of the worlds different species were killed off because of the climate changes caused by the dust that was thrown into the air. Nearly all of the dinosaurs eventually died from all of the changes that this impact event had on the Earth's environment. Acid rain and fires would have finished those that did not die from the initial impact.

The Chicxulub crater was originally discovered by Glen Penfield in the 1970's. He was searching for oil in the vicinity. Initially, Mr. Penfield could not find enough evidence to support his theory that this was an impact crater. It wasn't until he made contact with Alan Hildebrand that he was able to confirm Chicxulub as an impact crater. The evidence that he finally submitted for approval included: shocked quartz, tektites, and a magnetic anomaly in the area. Isotope analysis and the age of the rims rocks show that the crater is around 65 million years old. Another interesting fact about the Chicxulub crater is that it has a ring of sinkholes(cenotes) around its rim.

The importance of the Chicxulub crater can not be ignored. The changes brought about in evolution alone stagger the mind. The number of species that never redeveloped and the number of potentially intelligent creatures that were lost may never be known. That one event could be the reason that humans evolved to be the only self aware species on this planet.

Asteroid extinction theory

The asteroid extinction theory is also known as the K-T asteroid theory and, occasionally, the Alvarez Asteroid Impact Theory. All of these theories vary slightly, but they all center around an impressive event that suddenly destroyed most of the life on Earth around 65 million years ago.

The asteroid extinction theory holds that many of the dinosaurs went extinct long before the catastrophic mass extinction at the end of the Cretaceous period, 65 million years ago. Background extinctions and many minor extinctions accounted for the disappearance of most of the dinosaur species. The latter part of the period saw some heavy tectonic shifting and volcanic activity. The super continents had all separated or were in the process of separating. Many mountain ranges were formed and sea levels rose during the mid-Cretaceous, covering about one-third of the land area. Toward the end of the Cretaceous.there was a drop in sea level, causing land exposure on all continents, more seasonality, and greater extremes between equatorial and polar temperatures. As the Earth aged these climate changes had caused many species to die out and others to emerge.

Another form of the asteroid extinction theory is the K-T (Cretaceous-Tertiary) theory. It is associated with a geological signature known as the K-T boundary, usually a thin band of sedimentation found in various parts of the world. K is the traditional abbreviation for the Cretaceous Period derived from the German name Kreidezeit, and T is the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). Non-avian dinosaur fossils are only found below the K–T boundary, indicating that dinosaurs became extinct immediately before, or during the event. A very small number of dinosaur fossils have been found above the K–T boundary, but they have been explained as reworked, that is, fossils that have been eroded from their original locations then preserved in later sediment layers.

The third form of the asteroid extinction theory is the Alvarez Asteroid Impact Theory. The asteroid-impact theory was first proposed in detail in 1978, by a team led by American geologist Walter Alvarez and physicist Luis Alvarez. The Alvarez team analyzed sediment collected in the 1970s from the K-T layer near the town of Gubbio, Italy. The samples showed a high concentration of the element iridium, a substance rare on Earth but relatively abundant in asteroids. Other samples of K-T boundary strata from around the world were also analyzed; excess iridium was found in these samples as well. Using the average thickness of the sediment as a guide, they calculated that a meteorite about 10 km in diameter would be required to spread that much iridium over the whole Earth.

Although each theory uses a different method to prove its facts they all point to one catastrophe that killed a majority of the dinosaurs around 65 million years ago and they all seem to agree that it happened in the Yucatan Peninsula in Mexico. What is now known as the Chicxulub Crater was the epicenter of the event.

Scientists come to a conclusion:An asteroid killed the dinosaurs

Over the years, scientists have debated the cause of the mass extinction  that wiped out the dinosaurs 65 million years ago. Now, a panel of 41 international experts says it's official: a massive asteroid around 15 kilometers wide slamming into Earth at Chicxulub, Mexico is the culprit. After surveying a wide variety of evidence for the competing theories, the panel said the telling evidence was the structures preserved in the interior of the crater. Computer models predicted how much rock was vaporized or ejected by the impact. "Our work lets us visualize the astonishing events of the few minutes after impact," said Dr. Penny Barton, who led the group. "The front of the asteroid hit the Earth while the far side was still out in the upper atmosphere, punching a hole though the Earth's atmosphere.

The Cretaceous-Paleogene extinction was one of the biggest in earth’s history and geologic evidence of the impact has been discovered in rock layers from this time period, around the world. While the impact is widely accepted as the cause for the mass extinction, some critics disagreed, saying, for example, that the microfossils from the Gulf of Mexico show that the impact occurred well before the extinction and could not have been its primary cause.

The massive volcanism that produced the Deccan traps of India around this time has also been proposed as the main cause of the extinction. But in the panel's review, the computer models synthesized the geologic evidence that support the impact hypothesis. The models showed that such an impact would have instantly caused devastating shock waves, a large heat pulse and tsunamis around the globe.

Moreover, a release of larger amounts of dust, debris and gases would have led to a prolonged cooling of Earth’s surface, low light levels and ocean acidification that would have decimated photosynthesizing plants and the species that relied on them.

The asteroid is believed to have hit Earth with a force one billion times more powerful than the atomic bomb at Hiroshima. It would have blasted material at high velocity into theatmosphere, triggering a chain of events that caused a global winter, wiping out much of life on Earth in a matter of days.

"As the asteroid vaporized explosively," said Barton, from the University of Cambridge in the UK, "it created a crater 30 km deep and 100 km across, with sides as high as the Himalayas. However within only two minutes the sides collapsed inwards and the deepest parts of the crater rebounded upwards to leave a wide, shallow hollow.

"These terrifying events led to darkness and a global winter, resulting in the extinction of more than 70% of known species. The tiny shrew-like mammals which were around at that time proved better adapted to survival than the cumbersome dinosaurs, and the removal of these dominant animals paved the way for the radiation of the mammals and eventual emergence of humans on Earth."

The team's paper was published in the journal Science.

Cosmologists provide the closiest mesures of neutrinos

Cosmologists – and not particle physicists — could be the ones who finally measure the mass of the elusive neutrino particle. A group of cosmologists have made their most accurate measurement yet of the mass of these mysterious so-called "ghost particles." They didn't use a giant particle detector but used data from the largest survey ever of galaxies, the Sloan Digital Sky Survey. While previous experiments had shown that neutrinos have a mass, it is thought to be so small that it was very hard to measure. But looking at the Sloan data on galaxies, PhD student Shawn Thomas and his advisers at University College London put the mass of a neutrino at no greater than 0.28 electron volts, which is less than a billionth of the mass of a single hydrogen atom. This is one of the most accurate measurements of the mass of a neutrino to date.

Their work is based on the principle that the huge abundance of neutrinos (there are trillions passing through you right now) has a large cumulative effect on the matter of the cosmos, which naturally forms into “clumps” of groups and clusters of galaxies. As neutrinos are extremely light they move across the universe at great speeds which has the effect of smoothing this natural “clumpiness” of matter. By analysing the distribution of galaxies across the universe (i.e. the extent of this “smoothing-out” of galaxies) scientists are able to work out the upper limits of neutrino mass.

A neutrino is capable of passing through a light year –about six trillion miles — of lead without hitting a single atom.

Central to this new calculation is the existence of the largest ever 3D map of galaxies, called Mega Z, which covers over 700,000 galaxies recorded by the Sloan Digital Sky Survey and allows measurements over vast stretches of the known universe.

“Of all the hypothetical candidates for the mysterious Dark Matter, so far neutrinos provide the only example of dark matter that actually exists in nature," said Ofer Lahav, Head of UCL’s Astrophysics Group. "It is remarkable that the distribution of galaxies on huge scales can tell us about the mass of the tiny neutrinos."

The Cosmologists at UCL were able to estimate distances to galaxies using a new method that measures the colour of each of the galaxies. By combining this enormous galaxy map with information from the temperature fluctuations in the after-glow of the Big Bang, called the Cosmic Microwave Background radiation, they were able to put one of the smallest upper limits on the size of the neutrino particle to date.

“Although neutrinos make up less than 1% of all matter they form an important part of the cosmological model," said Dr. Shaun Thomas. "It's fascinating that the most elusive and tiny particles can have such an effect on the Universe.”

"This is one of the most effective techniques available for measuring the neutrino masses," said Dr. Filipe Abadlla. "This puts great hopes to finally obtain a measurement of the mass of the neutrino in years to come."

The authors are confident that a larger survey of the Universe, such as the one they are working on called the international Dark Energy Survey, will yield an even more accurate weight for the neutrino, potentially at an upper limit of just 0.1 electron volts.
The results are published in the journal Physical Review Letters.

Source: University College London