RSSArchive for August, 2010

“Divorced” asteroids go their separate ways

Artist's rendering of an asteroid pair

Artist's rendering of an asteroid pair during its short-lived proto-binary phase, which might last less than 1 million years. Shortly after its splitting, the smaller asteroid will "make a break for it", resulting in two asteroids that share the same orbit around the Sun.

  • If an asteroid rotates fast enough it can split in two
  • The two parts hang around each other as a pair
  • But if one part is small enough, it can drift away on its own

While the common perception of asteroids is that they are giant rocks lumbering in slow orbits around the Sun, a new study shows they actually are constantly changing “little worlds” that can give birth to smaller asteroids that split off to start their own lives.

Astronomers have long known that small asteroids get “spun up” to fast rotation rates by sunlight falling on them, much like propellers in the wind.

The new research shows that when asteroids spin fast enough, they can undergo “rotational fission,” splitting into two pieces which then begin orbiting each other. Such “binary asteroids” are fairly common throughout the Solar System.

The new study, led by Petr Pravec of the Astronomical Institute in the Czech Republic and involving 16 other institutions around the world, shows that many of these binary asteroids do not remain bound to each other but go their separate ways, forming two asteroids in orbit around the Sun when there previously was just one.

The researchers studied 35 so-called “asteroid pairs,” separate asteroids in orbit around the Sun that have come close to each other at some point in the past million years—usually within a few kilometres—at very low relative speeds. They measured the relative brightness of each asteroid pair, which correlates to its size, and determined the spin rates of the asteroid pairs using a technique known as photometry.

“It was clear to us then that just computing orbits of the paired asteroids was not sufficient to understand their origin,” said Pravec. “We had to study the properties of the bodies.”

Time to split

The team showed that all of the asteroid pairs in the study had a specific relationship between the larger and smaller members, with the smallest one always less than 60 percent of the size of its larger companion.

Illustration of an asteroid splitting in two

Over tens of millions of years, a rubble-pile asteroid less than 10 kilometres in diameter can spin up to a speed that will make it split in two. If the smaller one is less than 60 percent the size of the larger asteroid, they will gently separate from each other and eventually become a "divorced" asteroid pair.

The measurement fits precisely with a theory developed in 2007 by study co-author and University of Colorado at Boulder aerospace engineering sciences Professor Daniel Scheeres.

Scheeres’ theory predicts that if an asteroid splits in two by rotational fission, the pair can only escape from each other if the smaller one is less than 60 percent of the size of the larger asteroid.

When one of the asteroids in the pair is small enough, it can “make a break for it” and escape the orbital dance, essentially moving away to start its own “asteroid family,” he said. During rotational fission, the asteroids separate gently from each other at relatively low velocities.

“This is perhaps the clearest observational evidence that asteroids aren’t just large rocks in orbit about the Sun that keep the same shape over time,” said Scheeres. “Instead, they are little worlds that may be constantly changing as they grow older, sometimes giving birth to smaller asteroids that then start their own life in orbit around the Sun.”

Asteroid Gaspra

There are probably 1 million asteroids larger than 1 kilometre in diameter.

From vermin to endangered species

The asteroids that populate the Solar System are primarily concentrated in the main asteroid belt between Mars and Jupiter some 320 million kilometres from the Sun, but extend all the way down into the inner Solar System, where they are known as near-Earth asteroids.

There are probably about a million asteroids larger than 1 kilometre in diameter. Last month, researchers using NASA’s WISE spacecraft announced the discovery of 25,000 never-before-seen asteroids in data collected over just six months.

Astronomers think most asteroids are not solid “mountains”, but rather piles of rock that come in shapes ranging from snowmen and dog bones to potatoes and bananas, with each asteroid essentially glued together by gravitational forces.

“Sunlight striking an asteroid less than 10 kilometres across can change its rotation over millions of years, a slow motion version of how a windmill reacts to the wind,” said Scheeres, who has studied asteroids for the past decade.

“This causes the smaller asteroid to rotate more rapidly until it can undergo rotational fission. It’s not hard for these asteroid pairs to be pushed over the edge.”

CU-Boulder doctoral student Seth Jacobson of CU-Boulder’s astrophysical and planetary sciences department, a co-author on the Nature paper, said the most surprising part of the study was showing that sunlight played the key role in “birthing” asteroids.

“There was a time when most astronomers referred to asteroids as vermin,” said CU-Boulder doctoral student Seth Jacobson. “But the more we learn about them, the more exciting they are. They are not just big chunks of rock, but have the dynamic ability to evolve.”

Adapted from information issued by University of Colorado at Boulder / Pravec, et al. / ESO / M. Kornmesser / L. Calçada.

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Aussie satellite anniversary

Launch of Aussat A1

The Aussat A1 satellite launched from the payload bay of space shuttle Discovery on August 27, 1985, to become the first Australian-owned and -operated communications satellite.

On August 27, 1985, the Aussat A1 satellite silently climbed from the payload bay of the space shuttle Discovery, on it’s way to becoming the first Australian-owned and -operated telecommunications satellite.

Twenty-five years later, and it would be hard to imagine a world without satellite communications. We rely upon them for our day-to-day communications, plus TV, radio, internet, banking services and so on.

The Australian federal government established the government-owned satellite company, Aussat, in 1981. Three A-class satellites were launched during the mid- and late-1980s.

In 1991, the government sold Aussat into private hands, and Optus was born (being a consortium of major domestic companies plus two overseas telecommunications carriers).

Three new satellites were planned; the first, B1, was launched in August 1992. The launch of B2 followed in December 1992, but it was destroyed shortly after launch when the Chinese rocket exploded. The exact cause was never determined. B3 was successfully launched in August 1994.

Artist's impression of an Optus D satellite

Artist's impression of an Optus D satellite in orbit.

One C-class satellite was launched in June 2003, partly funded by, and heavily used by, the Australian Department of Defence.

There are now three D-class Optus satellites on orbit, the most recent being D3, launched in August 2009.

“The geographical size of Australia and the vast distance between some of our remote and regional communities means that satellite has always and will continue to make sense for Australia,” said Paul Sheridan, Director of Optus Satellite.

“Optus is very proud of our Aussat heritage and with 25 years of experience, we continue to be the leading provider of satellite services across Australia and New Zealand.”

Adapted from information issued by Optus.

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The striking Ring Nebula

The Ring Nebula

A colour-composite image of the Ring Nebula, M57, which is 2,300 light-years from Earth. The nebula is a torus, or donut, of gas surrounding a white dwarf star.

The Ring Nebula is often considered the leader of a class of celestial objects known as “planetary nebulae”. The image above was produced by astronomers from the Isaac Newton Group of Telescopes in the Canary Islands.

Despite the term, planetary nebulae have nothing to do with planets. They got their name from observations using early telescopes, through which they looked like small blobs instead of pinprick stars. In this respect, they resembled the discs or faces of planets, and the name has stuck ever since.

In reality, a planetary nebula is a huge cloud of gas that has been “puffed” off by a star in the final stages of its life. Our Sun will eventually go through this phase.

The Ring Nebula, also known as M57 (being the 57th entry in the catalogue compiled by the 18th-19th century French astronomer Charles Messier) is 2,300 light-years from Earth. At its centre is a white dwarf star…the “burned out” remains of a normal type of star.

Some planetary nebula are spherical-shaped clouds that completely surround their central star. The Ring Nebula, though, is thought instead to be a ring (or torus, like a donut) surrounding the white dwarf and fortuitously seen face-on by Earth-bound astronomers.

The image above is a false-colour composite that shows emission from certain specific types of gas in the nebula: hydrogen (shown as red), doubly ionised oxygen (green) and ionised sulphur (blue).

See the full-size, high-resolution version here (new window).

The photos below give two other views. First, a Hubble Space Telescope image that shows the nebula in approximately true colour; and second, an infrared view from the Spitzer Space Telescope.

The Ring Nebula

A Hubble Space Telescope image of the Ring Nebula, showing it in approximately true colours.

The Ring Nebula.

A Spitzer Space Telescope infrared image of the Ring Nebula gives a very different picture, bringing out lots of detail not seen at other wavelengths.

Top image courtesy of the Isaac Newton Group of Telescopes; image obtained and processed by members of the IAC astrophotography group (A. Oscoz, D. López, P. Rodríguez-Gil and L. Chinarro).

Middle image courtesy The Hubble Heritage Team (AURA / STScI / NASA).

Bottom image courtesy NASA / JPL-Caltech / J. Hora (Harvard-Smithsonian CfA).

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Mars rover learns to reach out

NASA’s next Mars rover, Curiosity—also known as the Mars Science Laboratory—is taking shape in advance of its launch next year. The video above recounts the latest milestone…the attachment of the rover’s robotic arm.

About the size of an SUV car, the rover has six wheels with their own electric motors. All up, the wheel mobility system has 10 motors—four for steering the rover and six for driving.

Due to land on the Red Planet in August 2012, Curiosity will be the largest rover ever sent to Mars. It will carry 10 instruments that will help assess an intriguing region of the planet for two things: environments where life might have existed, and the capacity of those environments to preserve evidence of past life.

The video below shows Curiosity taking its first “baby steps” in the laboratory.

Adapted from information issued by NASA.

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Shrinking moon starts to crack up

  • Cliffs or scarps suggest Moon has shrunk in the recent past
  • It could still be slowly shrinking today
  • Observations made by NASA’s Lunar Reconnaissance Orbiter spacecraft

Newly discovered cliffs in the lunar crust indicate the Moon shrank globally in the geologically recent past and might still be shrinking today, according to a team analysing new images from NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft. The results provide important clues to the Moon’s recent geologic and tectonic evolution.

The Moon formed in a chaotic environment of intense bombardment by asteroids and meteors. These collisions, along with the decay of radioactive elements, made the Moon hot. The Moon cooled off as it aged, and scientists have long thought the Moon shrank over time as it cooled, especially in its early history.

Gregory Scarp on the Moon

A prime example of a lunar scarp is this one, called Gregory Scarp. The scale is in metres.

The new research reveals relatively recent tectonic activity connected to the long-lived cooling and associated contraction of the lunar interior.

“We estimate these cliffs, called lobate scarps, formed less than a billion years ago, and they could be as young as a hundred million years,” said Dr. Thomas Watters of the Centre for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum, Washington.

While ancient in human terms, it is less than 25 percent of the Moon’s current age of more than four billion years.

“Based on the size of the scarps, we estimate the distance between the Moon’s centre and its surface shrank by about 300 feet [100 metres],” said Watters, lead author of a paper on this research appearing in the August 20 issue of the journal Science.

The scarps are relatively small; the largest is about 100 metres high and extends for several kilometres or so, but typical lengths are shorter and heights are more in the tens of metres range.

Earth not to blame

The team believes they are among the freshest features on the Moon, in part because they cut across small craters.

Since the Moon is constantly bombarded by meteors, features like small craters (those less than about 400 metres across) are likely to be young because they are quickly destroyed by other impacts and don’t last long.

Diagram of a lunar scarp

Scarps on the Moon could be produced as the rocky world cools and contracts.

So, if a small crater has been disrupted by a scarp, the scarp formed after the crater and is even younger. Even more compelling evidence is that large craters, which are likely to be old, don’t appear on top any of the scarps, and the scarps look crisp and relatively un-degraded.

Because the scarps are so young, the Moon could have been cooling and shrinking very recently, according to the team.

Seismometers emplaced by the Apollo missions have recorded moonquakes. While most can be attributed to things like meteorite strikes, the Earth’s gravitational tides, and day/night temperature changes, it’s remotely possible that some moonquakes might be associated with ongoing scarp formation, according to Watters.

The team plans to compare photographs of scarps by the Apollo Panoramic Cameras to new images from LRO to see if any have changed over the decades, possibly indicating recent activity.

While Earth’s tides are most likely not strong enough to create the scarps, they could contribute to their appearance, perhaps influencing their orientation, according to Watters. During the next few years, the team hopes to use LRO’s high-resolution Narrow Angle Cameras (NACs) to build up a global, highly detailed map of the Moon.

This could identify additional scarps and allow the team to see if some have a preferred orientation or other features that might be associated with Earth’s gravitational pull.

Adapted from information issued by NASA.

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Tuvalu: Islands in Danger

Satellite image of Tuvalu

The world's fourth-smallest nation, Tuvalu, comprises four coral reefs and five atolls, located about 1,000 km north of Fiji in the South Pacific.

Funafuti Atoll in the Tuvalu Islands (formally known as the Ellice Islands), is a coral-reef lagoon 25 km north-to-south, 18 km east-to-west, and surrounded by small islets.

Tuvalu comprises four coral reefs and five atolls, located about 1,000 km north of Fiji in the South Pacific. With an area of 26 square kilometres, it is the fourth smallest country in the world, larger only than Vatican City, Monaco, and Nauru in the Pacific Ocean.

The Ellice Islands became a British protectorate in 1892 together with the Gilbert Islands (a part of the Republic of Kiribati) to the north-northwest, and became a colony in 1915.

The main inhabitants of Tuvalu are Polynesian and those of the Gilbert Islands are Micronesian; therefore, the two islands dissociated in 1975. They achieved independence in 1978 and became members of the Commonwealth of Nations.

The capital, Funafuti, is located at the easternmost bend (right) of the atoll and it possesses the only airport in Tuvalu, the airstrip of which is slightly wider than a road and has no lighting or guidance lights. Air Pacific operates two flights per week between it and Suva, the capital of Fiji.

Satellite image close-up of Funafuti

Close-up of Funafuti, the capital of Tuvalu. The nation's only airstrip can be seen as a thin white line running diagonally. It doubles as a playground and football field.

Since this airstrip is the only open space in the atoll, it is also used as a playground and a football field by the people.

The name Tuvalu consists of Tu, meaning “consist of,” and Valu, meaning “eight.” Thus, it means “a country consisting of eight islands” in the Tuvaluan language.

At the beginning of their independence in 1978, Tuvalu was composed of eight inhabited small islands. Later people moved to an uninhabited islet called Niulakita. Therefore, the new design of the national flag now has nine stars reflecting the number of islands. The name of the nation, however, has not been changed.

The population of the Tuvalu Islands is about 10,000. Rain is the main source of water. Since Tuvalu has almost no natural resources, much of the government revenue depends on overseas remittances from emigrant mariners. The substantial budget deficit is covered by the investment return of the Tuvalu Trust Fund, which was established in 1978 by Australia, the United Kingdom, New Zealand, and Tuvalu. Payment from the US government according to the treaty on fisheries and the sale of Tuvalu’s Internet domain name “.tv” are other sources of income.

As a result of rising sea levels, like the Republic of Kiribati (South Pacific) and Maldives (Indian Ocean), Tuvalu is also in danger of submerging. Water gushes out from the ground, and houses and roads are flooded during high tide. Spring water from dents that were made during construction of the airfield, lowlands where people tend to live, and contaminated wastewater dramatically decreasing foraminifers, which are responsible for forming sands, are suspected as the causes of this phenomenon.

However, in Tuvalu, since the highest point is only 4.5 metres above sea level, it is a land easily affected by rises in the sea level. The nation has already begun evacuating some of its residents to New Zealand. Japan is cooperating in coastal protection, disaster prevention, and developing alternative energy sources.

The image was made by the Japan Aerospace Exploration agency Advanced Land Observing Satellite (ALOS), also known as “Daichi”.

Adapted from information issued by JAXA.

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Galactic super-volcano in action

HST image of M87

This Hubble Space Telescope image shows the central core and accompanying outflowing "jet" of the giant elliptical galaxy M87. In the centre of the galaxy there lurks a supermassive black hole.

A galactic “super-volcano” in the massive galaxy known as M87 is erupting and blasting gas outwards, as witnessed by NASA’s Chandra X-ray Observatory and the US National Science Foundation’s (NSF) Very Large Array (VLA) of radio telescopes.

The cosmic volcano is being driven by a giant black hole in the galaxy’s centre and preventing hundreds of millions of new stars from forming.

At a distance of about 50 million light-years, M87 is relatively close to Earth and lies at the centre of the Virgo cluster, which contains thousands of galaxies.

M87’s location, coupled with long observations over Chandra’s lifetime, has made it an excellent subject for investigations of how a massive black hole impacts its environment.

Core of the galaxy M87

This is the core of the galaxy M87, seen at X-ray and radio wavelengths. A huge black hole, hiding in the middle, is ejecting energetic particles that push gas outwards. That gas would ordinarily form millions of new stars, so the black hole's activity is acting like a brake on star formation.

“Our results show in great detail that supermassive black holes have a surprisingly good control over the evolution of the galaxies in which they live,” said Norbert Werner of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and the SLAC National Accelerator Laboratory, who led one of two papers describing the study.

“And it doesn’t stop there. The black hole’s reach extends ever farther into the entire cluster, similar to how one small volcano can affect practically an entire hemisphere on Earth.”

The space around M87 is filled with hot gas glowing in X-ray light, which has been detected by Chandra. As this gas cools, it should fall in toward the M87’s centre where it could continue to cool even faster and form new stars.

However, radio observations with the Very Large Array suggest that in M87 jets of very energetic particles produced by the black hole interrupt this process. These jets lift up the relatively cool gas near the centre of the galaxy and produce shock waves in the galaxy’s “atmosphere” because of their supersonic speed.

In M87, the plumes of cooler gas being lifted upwards contain as much mass as all of the gas contained within 12,000 light-years of the centre of the galaxy cluster.

This shows the black hole-powered volcano is very efficient at blasting the galaxy free of the gas that would otherwise cool down and form stars.

The eruption in M87 that lifted up the cooler gas must have occurred about 150 million years earlier, but a smaller eruption only about 11 million years earlier produced the shock wave.

Adapted from information issued by Chandra X-ray Centre.

Images courtesy Tod R. Lauer, Sandra M. Faber / NASA / X-ray (NASA / CXC / KIPAC / N. Werner, E. Million et al); radio (NRAO / AUI / NSF / F. Owen)

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Stellar acoustics sound like sunspots

  • CoRoT space telescope sees pressure waves in stars
  • Technique can be used to see “starspots” similar to sunspots
  • Gives clues to stellar magnetism, which can affect planets

In a bid to unlock longstanding mysteries of the Sun, including the influence on Earth of its 11-year cycle, an international team of scientists has successfully studied a distant star.

By monitoring the star’s “sound waves”, the team has revealed a magnetic cycle similar to the Sun’s solar cycle.

The study, conducted by scientists at the National Centre for Atmospheric Research (NCAR) and colleagues in France and Spain, is being published this week as a “Brevia” in the journal Science.

The scientists used a space telescope called CoRoT to study a star known as HD49933, located 100 light-years away. The team examined the star’s acoustic fluctuations, using a technique called “stellar seismology.”

Stars are big, rumbling cauldrons of super-hot gas. Those rumbles—like earthquakes—are actually pressure or “sound” waves, and they can be picked up as tiny Doppler shifts in the stars’ light spectrums.

Careful study of those sound waves can reveal details about activity on the surface of stars. In the case of HD49933, the scientists detected the signature of “starspots,” areas of intense magnetic activity on the surface that are similar to sunspots.

While magnetic cycles have previously been observed in other stars, this is the first time such a cycle has been discovered using the stellar seismology technique.

“Essentially, the star is ringing like a bell,” says NCAR scientist Travis Metcalfe, a co-author of the new study. “As it moves through its starspot cycle, the tone and volume of the ringing changes in a very specific pattern, moving to higher tones with lower volume at the peak of its magnetic cycle.”

“We’ve discovered a magnetic activity cycle in this star, similar to what we see with the Sun,” says co-author and NCAR scientist Savita Mathur. “This technique of listening to the stars will allow us to examine potentially hundreds of stars.”

Artist's impression of the CoRoT space mission

Artist's impression of the CoRoT space mission studying a distant star (not to scale).

Implications for life on distant planets

The team hopes to assess the potential for other stars in our galaxy to host planets, including some perhaps capable of sustaining life.

“Understanding the activity of stars harbouring planets is necessary because magnetic conditions on the star’s surface could influence the habitable zone, where life could develop,” says CEA-Saclay scientist Rafael Garcia, the study’s lead author.

The habitable zone is the orbital distance from a star where temperatures are neither too hot nor too cold for life as we know it to survive.

Studying many stars with stellar seismology could help scientists better understand how magnetic activity cycles can differ from star to star, as well as the processes behind such cycles.

The work could especially shed light on the magnetic processes that go on within the Sun, furthering our understanding of its influence on Earth’s climate. It may also lead to better predictions of the solar cycle and resulting geomagnetic storms that can cause major disruption to power grids and communication networks.

The scientists examined 187 days of data captured by the international Convection Rotation and Planetary Transits (CoRoT) space mission.

Launched on December 27, 2006, CoRoT was developed and is operated by the French National Centre for Space Studies (CNES) with contributions from Austria, Belgium, Brazil, Germany, Spain, and the European Space Agency. CoRoT is equipped with a telescope and a CCD camera sensitive to tiny variations in the light intensity from stars.

The study authors found that HD49933 is much bigger and hotter than the Sun, and its magnetic cycle is much shorter. Whereas past surveys of stars have found cycles similar to the 11-year cycle of the Sun, this star has a cycle of less than a year.

Adapted from information issued by NCAR / UCAR / Institute of Astrophysics of the Canaries.

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More planets found

Artist's impression of two Saturn-like planets orbiting very close to the star Kepler-9b.

Artist's impression of two Saturn-like planets orbiting very close to the star Kepler-9b.

Two planets, similar in size to Saturn, have been spotted by NASA’s Kepler space telescope moving in front of, or transiting, their star.

The transit technique has been used to detect many so-called exoplanets (ones that orbit stars beyond our Solar System), but this is the first confirmed detection via this method of two planets transiting the same star.

The star is known as Kepler-9, and the planets have been dubbed Kepler-9b and Kepler-9c.

Launched in early 2009, Kepler is focusing on over 150,000 candidate stars in the hunt for small, Earth-sized planets. In particular, the aim is to find Earth-sized planets in stars’ habitable zones…orbital slots that are neither too near nor too far from the stars, so that the planets are neither too hot nor too cold.

Kepler can’t see planets—they’re too small and too far away—but its sensitive instruments can see the small dip in starlight as a planet moves in front of its star. From the amount and duration of the dip, the size and orbit of each planet can be derived.

And if there are small deviations in the regularity of the dips, they could indicate the presence of other planets that aren’t on orbits that produce transits.

In June 2010, Kepler scientists published data on 700 potential planets seen in data collected in the first 43 days of the mission. A handful of the stars seemed to have more than one transiting planet.

“Kepler’s high quality data and round-the-clock coverage of transiting objects enable a whole host of unique measurements to be made of the parent stars and their planetary systems,” said Doug Hudgins, the Kepler program scientist at NASA Headquarters in Washington.

Artist's impression of NASA's Kepler space telescope

NASA's Kepler space telescope is dedicated to hunting for planets orbiting distant stars by spotting the dip in starlight as a planet moves in front, or transits, a star.

Scorching orbits

Follow up observations using the giant telescopes of the W.M. Keck Observatory in Hawaii have shown that both planets are slightly less massive than Saturn, and that Kepler-9b is the larger of the two.

The planets orbit very close to their star, which means their years are very short—just 19 Earth days in the case of Kepler-9b, and 38 days for Kepler-9c. Their close proximity to the star means the planets also would be very, very hot.

Seven months of observations have revealed slight variations in the timing of the two planet’s transits, which is exactly what would be expected as each planet gravitationally tugs on the other.

Their observations of the Kepler-9 system also have given the scientists tantalising hints that there could be another, much smaller planet in orbit around the star. The data suggest it could be about 1.5 times the size of Earth and orbiting scorchingly close to the star, taking just 1.6 Earth days to complete one orbit. This would make it a “hot Earth”.

The scientists still have work to do to confirm the presence of the third planet, though, as what can sometimes seem to be a transiting planet can turn out to be an unrelated phenomenon.

Story by Jonathan Nally, editor SpaceInfo.com.au. Images courtesy NASA.

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Greenland’s changing landscape

Petermann Glacier and iceberg

A massive iceberg broke from the Petermann Glacier in Greenland on August 5.

On August 5, 2010, the unassuming Petermann Glacier on Greenland’s northwestern coast hit the world’s headlines when a huge ice island “calved” from it and started drifting down a fjord.

Eleven days later, the island was continuing its slow migration down the fjord. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured a natural-colour image (above) on August 16, 2010.

Although slivers of ice had loosened around its edges, the ice island had largely retained its original shape. The island, which had rotated counterclockwise since the calving, also retained the crevassed structure of the Petermann Glacier; both the glacier and the ice island sport rippled surfaces.

Thin longitudinal cracks appear on the ice island surface, and wider lateral cracks push in from the island’s sides. An uneven line of pools, medium blue in colour, runs down the length of the ice island.

Along the glacier’s new front, some smaller icebergs appear to have broken free, and ice fragments litter the water surface between the ice island and the glacier. Also visible in the image are multiple small glaciers that feed the Petermann, flowing down to the massive glacier from the northeastern side of the fjord.

See the full-size, high-resolution image here (4MB, new window).

Phytoplankton bloom off the east coast of Greenland.

Satellite image of a phytoplankton bloom off the east coast of Greenland.

Meanwhile, on Greenland’s eastern seaboard, the stark black and white landscape of provides a fine palette for the burst of colour created by a large phytoplankton bloom, spotted by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra  satellite on August 7, 2010.

The bloom blends shades of milky blue, turquoise, and green, created by different species of phytoplankton growing in the cold, nutrient-rich waters. Likely shaped by the East Greenland Current, the bloom extends along the southeast coast of Greenland.

The full length of the bloom is visible in the large image (0.7MB, new window), which shows a broader area.

The phytoplankton bloom is not the only source of colour in the scene. The brilliant white of the ice sheet fades to grey in places along the shore where old ice is exposed. Tinted faintly brown like the craggy brown rocks that channel them, glaciers seep from the ice sheet into fjords, rivers of ice draining the great ice sheet. The glaciers give way to green-blue water, milky with the fine sediment created as the ice grinds over rock.

These waters and the deep black-blue waters of the Atlantic Ocean are dotted with icebergs. No more than tiny white specks at this scale, the icebergs resemble tiny grains of salt floating on the water’s surface.

NASA images courtesy Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC; and Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team and the United States Geological Survey. Text adapted from information issued by Michon Scott and Holli Riebeek.

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