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Earth from Space: Sideways view of Antarctica

Oblique ISS view of Livingston Island and Deception Island

An astronaut aboard the International Space Station took this photo at a highly oblique angle. It shows a small part of the Antarctic coastline.

THE INCLINED EQUATORIAL ORBIT of the International Space Station (ISS) limits astronauts to nadir views of Earth—looking straight down from the spacecraft—between approximately 52 degrees North latitude and 52 degrees South.

However, when viewing conditions are ideal, the crew can obtain detailed oblique images—looking outwards at an angle—of features at higher latitudes, such as Greenland or, in this image, Antarctica.

While the bulk of the continent of Antarctica sits over the South Pole, the narrow Antarctic Peninsula extends like a finger towards the tip of South America. The northernmost part of the Peninsula is known as Graham Land, a small portion of which (located at approximately 64 degrees South latitude) is visible at the top left in this astronaut photograph.

Off the coast of Graham Land to the north-northwest, two of the South Shetland Islands—Livingston Island and Deception Island—are visible. Both have volcanic origins, and active volcanism at Deception Island has been recorded since 1800. (The last verified eruptive activity occurred in 1970.)

Closer to the coastline of Graham Land, Brabant Island (not part of the South Shetlands) also includes numerous outcrops of volcanic rock, attesting to the complex tectonic history of the region.

The ISS was located over the South Atlantic Ocean, approximately 1,800 kilometres to the northeast when this image was taken. This long viewing distance, combined with the highly oblique angle, accentuates the shadowing of the ground and provides a sense of the topography similar to the view you get from an airplane.

It also causes foreshortening of features in the image, making them appear closer to each other than they actually are. For example, the distance between Livingston and Deception Islands is approximately 20 kilometres.

Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by William L. Stefanov, Jacobs/ESCG at NASA-JSC.

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Earth from Space – Frozen fields of Antarctica

EO-1 image of ice in Antarctica

Satellite image of fields of ice on the Antarctic coast.

THOUGH IT IS ALL COMPOSED of frozen water, ice is hardly uniform. On October 7, 2011, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this image of a variety of ice types off the coast of East Antarctica.

Brilliant white ice fills the right half of this image. It is fast ice, and derives its name from the fact that it holds fast to the shore. This ice is thick enough to completely hide the underlying seawater, hence its brilliant white colour.

Trapped within the fast ice, and stuck along the edge of it, are icebergs. Icebergs form by calving off ice shelves—thick slabs of ice attached to the coast. Ice shelves can range in thickness from tens to hundreds of metres, and the icebergs that calve off of them can tower over nearby sea ice. One iceberg, drenched with meltwater, has toppled and shattered (image upper right). The water-saturated ice leaves a blue tinge.

The icebergs along the edge of the fast ice are likely grounded on the shallow sea floor, and their presence may help hold the fast ice in place.

Farther out to sea is pack ice that drifts with winds and currents. Much thinner than the fast ice, the translucent pack ice appears in shades of blue-grey.

The pack ice includes some newly formed sea ice. As seawater starts to freeze, it forms tiny crystals known as frazil (image centre). Although the individual crystals are only millimetres across, enough of them assembled together are visible from space.

Constantly moved by ocean currents, frazil often appears in delicate swirls. Frazil crystals can coalesce into thin sheets of ice known as nilas (image top). Sheets of nilas often slide over each other, eventually merging into thicker layers of ice.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Michon Scott based on image interpretation by Ted Scambos, National Snow and Ice Data Centre.

Download the full-size (4MB) image here.

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South Pole telescope nears completion

IceCube at the South Pole

An overview of the South Pole, with the US Amundsen-Scott South Pole Station to the left of the runway and the IceCube facility to the right. Photo by Forest Banks

  • IceCube telescope aims to detect neutrinos
  • Network of under-ice detectors, 1 cubic km in volume
  • International effort; due for completion this month

A unique kind of telescope is about to be completed, buried deep beneath the ice under the US Amundsen-Scott South Pole Station.

Called the IceCube Neutrino Observatory, it records the rare collisions of neutrinos, elusive sub-atomic particles, with the atomic nuclei of the water frozen into ice.

Neutrinos come from the Sun, from cosmic rays interacting with the Earth’s atmosphere, and from dramatic astronomical sources such as exploding stars in the Milky Way and other distant galaxies.

Trillions of neutrinos stream through the human body at any given moment, but they rarely interact with regular matter, and researchers want to know more about them and where they come from.

Diagram of IceCube

What IceCube looks like under the ice—strings of special detectors in an array measuring one cubic kilometre in volume. Courtesy IceCube.

IceCube is the world’s largest neutrino detector, measuring a cubic kilometre in volume. The size of the detector is important because it increases the number of potential collisions that can be observed, making neutrino astrophysics a reality. The observatory is slated for completion in December 2010.

Astronomy under the ice

Since 2004, the USA, Belgium, Germany and Sweden have been building the detector in the continental ice sheet that covers Antarctica to a depth of almost three kilometres in places.

A powerful hot-water drill creates holes almost 2.5 kilometres deep into the ice. These holes house strings of digital optical modules that detect the interactions of the neutrinos with the ice.

Seven holes remained to be drilled in December 2010, which will bring the total to 86 strings.

Even now, the IceCube detector records several tens of thousands of neutrino interactions every year. The detector records one terabyte of data (more than 1,000 gigabytes) every day, and over a petabyte of data (quadrillion bytes) per year. Data is meticulously examined for evidence of neutrino events.

International collaboration

While the Observatory is managed by the University of Wisconsin-Madison and primarily funded by the US National Science Foundation, Germany, Belgium and Sweden contributed to its construction.

Jessica Hodges with an IceCube digital optical module

Jessica Hodges, IceCube physics graduate student, pictured with one of the optical detector modules. Photo by Glenn Grant / National Science Foundation.

More than 250 scientists from 36 institutions in the USA, the partner countries, and elsewhere are now analysing the data collected by the observatory.

“The IceCube detector is a superb example of the kind of exciting ‘big science’ at the frontiers of knowledge that is ideally suited for support by the U.S. Antarctic Program, precisely because it could be built nowhere else in the world but in the Antarctic ice sheet,” said Karl A. Erb, director of NSF’s Office of Polar Programs (OPP).

Through OPP, NSF manages the US Antarctic Program, which coordinates all U.S. research on the southernmost continent and surrounding oceans.

“What’s more,” he added, “although the IceCube project is primarily funded by the National Science Foundation, it exemplifies a modern trend in the increasingly complex and multi-disciplinary scientific world; large-scale projects like the IceCube detector are too complex to be effectively mounted by one nation alone, but also require the scientific and logistical expertise of many nations acting together to produce scientifically significant results.”

Adapted from information issued by NSF / University of Wisconsin-Madison.

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Antarctic glacier retreats

Image of Crane Glacier on the Larsen B Ice Shelf on April 6, 2002

This image of Crane Glacier on the Larsen B Ice Shelf on the Antarctic Peninsula was captured on April 6, 2002. Compare with the image below.

In late Southern Hemisphere summer of 2002, the Larsen B Ice Shelf on the Antarctic Peninsula disintegrated into thousands of pieces.

The collapse appears to have been due to a series of warm summers on the Antarctic Peninsula, which culminated with an exceptionally warm summer in 2002. On the surface of the shelf, rows of melt ponds settled into natural crevasses, driving the cracks all the way through the ice shelf.

This pair of images from NASA’s Landsat 7 satellite shows the dramatic impact the collapse had on many of the glaciers that fed the Larsen B Ice Shelf. The loss of the shelf caused the flow of most of the glaciers around the bay to accelerate significantly. More rapid flow and calving of icebergs caused the margins to retreat inland.

The image above was captured on April 6, 2002, about two months after the dramatic collapse. The bay (image right) is filled with slush and icebergs from the collapsed shelf.

Autumn snows have probably already dusted the surface of the mélange of ice; snowfall and seasonal sea ice kept much of the debris frozen in place the first winter after the collapse. The terminus of the Crane Glacier extends into the bay like a fan.

Throughout the summer of 2003, remaining fragments of the shelf broke away, and the mélange of icebergs and smaller ice pieces from the previous summer’s collapse began to drift away.

Without the stabilizing presence of the ice shelf, the Crane Glacier retreated dramatically. Its fan-shaped terminus became C-shaped as the glacier’s centre crumbled more rapidly than the edges pressed against the mountain walls.

By 2003, Crane Glacier had retreated dramatically

By 2003, Crane Glacier had retreated dramatically as fragments of the ice shelf broke away.

The unusually bright blue tinge of the ice debris in the February 20 image (above) is the reflection from the pure ice on the underside of the ice shelf fragments. Many of the icebergs that crumbled from the edge of the shelf were too tall and narrow to float upright, and they toppled over.

The surface of an ice shelf gets covered by snow, but the underside is very pure ice. Pure, thick ice absorbs a small amount of red light. Photo-like satellite images such as these are made by combining the satellite’s observations of red, green, and blue wavelengths of light reflected from the Earth’s surface. When all these visible wavelengths are strongly reflected, the surface looks white; when the reddest light is absorbed, the reflection takes on a bluish tinge.

NASA images by Robert Simmon based on Landsat-7 data. Text adapted from information issued by Rebecca Lindsey.