RSSArchive for March, 2010

North Sentinel Island

North Sentinel Island, seen from space

North Sentinel Island, seen from space

Five years ago this past December 26, a huge earthquake offshore of Sumatra, Indonesia, unzipped a 1,600-kilometre-long stretch of the sea floor, heaved it upward as much as five metres, and unleashed devastating tsunamis that scoured coastlines of countries around the Bay of Bengal and the Andaman Sea. Hundreds of thousands of people died.

From space, the most visible evidence of the event included permanent uplift of islands and coral reefs along the rupture, including remote North Sentinel Island, pictured in this photo-like image from the Advanced Land Imager on NASA’s Earth Observing-1 (EO-1) satellite from November 20, 2009. Surrounding the forested island is a perimeter of uplifted reef.

Compared to their bright white colour in an image acquired in February 2005 (less than two months after the quake), the exposed reefs are duller in this recent image. The darkening may be because the reefs have since been covered with mud, sand, or algae, and because the tide appears to be higher at the time of the recent image.

The undisturbed appearance of the island’s forest might suggest it is uninhabited, but in fact, North Sentinel Island is home to one of the few remaining primitive tribes on Earth—hunter-gatherer tribes which have had little or no contact with modern civilisation. The Indian government, which oversees the Andaman Islands territory, prohibits visitors of any kind, and the islanders themselves violently rebuff any attempts at contact. Following the 2004 tsunami, the Indian Coast Guard flew a reconnaissance mission over the island; according to news reports and photos, men emerged from the forest and fired arrows at the helicopter, which did not attempt to land.

NASA Earth Observatory image created by Jesse Allen, using data provided by the NASA EO-1 team. Caption adapted from information issued by Rebecca Lindsey.

An island of stars in the making

The NGC 1788 nebula

The NGC 1788 nebula, where stars are being born

The delicate nebula NGC 1788, located in a dark and often neglected corner of the constellation Orion, is revealed in a new and finely nuanced image released by the European Space Agency (ESO).

Although this ghostly cloud is rather isolated from Orion’s bright stars, the latter’s powerful winds and light have had a strong impact on the nebula, forging its shape and making it home to a multitude of infant suns.

Stargazers all over the world are familiar with the distinctive profile of the constellation of Orion (the Hunter). Fewer know about the nebula NGC 1788, a subtle, hidden treasure just a few degrees away from the bright stars in Orion’s belt.

NGC 1788 is a reflection nebula, whose gas and dust scatter the light coming from a small cluster of young stars in such a way that the tenuous glow forms a shape reminiscent of a gigantic bat spreading its wings.

Very few of the stars belonging to the nebula are visible in this image, as most of them are obscured by the dusty cocoons surrounding them. The most prominent, named HD 293815, can be distinguished as the bright star in the upper part of the cloud, just above the centre of the image and the pronounced dark lane of dust extending through the nebula.

Birthplace of stars

Although NGC 1788 appears at first glance to be an isolated cloud, observations covering a field beyond the one presented in this image have revealed that bright, massive stars, belonging to the vast stellar groupings in Orion, have played a decisive role in shaping NGC 1788 and stimulating the formation of its stars. They are also responsible for setting the hydrogen gas ablaze in the parts of the nebula facing Orion, leading to the red, almost vertical rim visible in the left half of the image.

Part of the NGC 1788 nebula

The red glow is hydrogen gas being heated by the light of nearby stars.

All the stars in this region are extremely young, with an average age of only a million years, a blink of an eye compared to the Sun’s age of 4.5 billion years.

Analysing them in detail, astronomers have discovered that these “preschool” stars fall naturally into three well separated classes: the slightly older ones, located on the left side of the red rim, the fairly young ones, to its right, making up the small cluster enclosed in the nebula and illuminating it, and eventually the very youngest stars, still deeply embedded in their nascent dusty cocoons, further to the right.

Although none of the youngest stars are visible in this image because of the obscuring dust, dozens of them have been revealed through observations at infrared and millimetre wavelengths of light.

This fine distribution of stars, with the older ones closer to Orion and the younger ones concentrated on the opposite side, suggests that a wave of star formation, generated around the hot and massive stars in Orion, propagated throughout NGC 1788 and beyond.

This image was obtained using the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

Adapted from information issued by ESO.

New images of a Martian moon

Image of Phobos on March 7, 2010

The High Resolution Stereo Camera aboard the Mars Express spacecraft took this image of Phobos on March 7, 2010. It shows details as small as 4.4 metres.

Images have been released following the Mars Express spacecraft’s flyby of Phobos on March 7, 2010, showing Mars’ rocky moon in exquisite detail, with a resolution of just 4.4 metres per pixel. They also show the proposed landing sites for a forthcoming Russian robotic sample-return mission.

The European Space Agency’s (ESA) Mars Express orbits the Red Planet in a highly elliptical, polar orbit that brings it close to Phobos every five months. It is the only spacecraft currently in orbit around Mars whose orbit reaches far enough from the planet to provide a close-up view of Phobos.

Like our Moon, Phobos always keeps the same side facing the planet, so it is only by flying outside the moon’s orbit that it becomes possible to observe the far side. Mars Express did just this on March 7, 10 and 13. The spacecraft also collected data with other instruments.

Phobos is an irregular body measuring some 27 x 22 x 19 kilometres. Its origin is debated. It appears to share many characteristics with the class of ‘carbonaceous C-type’ asteroids, which suggests it might have been captured as it wandered past. However, it is difficult to explain either the capture mechanism or the subsequent evolution of the orbit into the equatorial plane of Mars. An alternative hypothesis is that it formed around Mars, and is therefore a remnant from the planetary formation period.

Mars Express image of Phobos showing the proposed landing sites for the Russian Phobos-Grunt mission

Mars Express image of Phobos showing the proposed landing sites for the Russian Phobos-Grunt mission

This Mars Express image shows the proposed landing sites for the Russian Phobos-Grunt mission, due for launch next year. Phobos-Grunt will scoop up samples of Phobos’ surface and return them to Earth.

In 2011 Russia will send a mission called Phobos-Grunt (meaning Phobos Soil) to land on the Martian moon, collect a sample and return it to Earth for analysis.

For operational and landing safety reasons, the proposed landing sites were selected on the far side of Phobos. This region was imaged by Mars Express’ high-resolution camera (HRSC) during the July-August 2008 flybys of Phobos. But new HRSC images showing the vicinity of the landing area under different conditions, such as better illumination from the Sun, remain highly valuable for mission planners.

It is expected that Earth-based ESA stations will take part in controlling Phobos-Grunt, receiving telemetry and making trajectory measurements.

Mars Express will continue to encounter Phobos until the end of March, when the moon will pass out of range. During the remaining flybys, HRSC and other instruments will continue to collect data.

Adapted from information issued by ESA / DLR / FU Berlin (G. Neukum).

Western Australia’s “Super Pit” gold mine

A NASA satellite image of the huge "Super Pit" gold mine in the middle of the Western Australian desert.

A NASA satellite image of the huge "Super Pit" gold mine in the middle of the Western Australian desert.

Long valued for its ornamental, monetary, and even scientific applications, gold has attracted speculators and miners throughout human history. The greatest quantities of gold mined today occur in ore—rock containing trace amounts of valuable materials. Obtaining even small quantities of gold usually requires extracting huge quantities of ore from open-pit or underground mines.

One of the largest open-pit mines is the “Super Pit” Mine near the city of Kalgoorlie in Western Australia. On February 15, 2010, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this true-colour image of Super Pit and part of the neighbouring town of Kalgoorlie. The pit that gives the mine its name appears in the centre of the image, and some of the steep pit’s walls appear in shadow while others are illuminated by the Sun.

Related mining operations form a rough semicircle on the eastern side of the pit; a cluster of buildings east-northeast of the pit is Fimiston Mill, where ore is processed. Waste dumps and grey-white tailings ponds sprawl over the arid landscape. Tailings are the rocks and chemicals left over after the gold is extracted. Because the chemicals used to separate gold from rock are often caustic, tailings usually pose hazards to human and/or environmental health and must be treated carefully.

The metropolitan area of Kalgoorlie, marked by street grids and manicured green spaces, extends almost to the mine’s central pit. An airport, marked by a long runway, appears along the city’s southern margin. Founded during a late-nineteenth-century gold rush, Kalgoorlie, like the neighbouring mine, occurs near an area nicknamed the “Golden Mile,” which is considered especially rich in gold deposits.

As the beige and reddish colours in the image indicate, vegetation in the area is sparse. Like much of Western Australia, the area around Kalgoorlie and Super Pit is semi-arid, with hot summers and cool winters. January (summer) temperatures in Kalgoorlie frequently reach 40 degrees Celsius (over 100 degrees Fahrenheit).

NASA Earth Observatory image created by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Michon Scott.

Russia’s lost Moon rover found!

Tracks left by Lunokhod 2

An LRO image showing Lunokhod 2 and the tracks it left in the lunar dust.

A Canadian researcher has helped solve a 37-year old space mystery using lunar images released yesterday by NASA and maps from his own atlas of the Moon.

The new images and data come from NASA’s Lunar Reconnaissance Orbiter (LRO). The LRO, scheduled for a one-year exploration mission about 50 kilometres above the lunar surface, is producing a comprehensive lunar map, searching for resources and potential safe landing sites, and measuring lunar temperatures and radiation levels.

Using an lunar atlas he produced in 2007 and the new NASA images, University of Western Ontario professor Phil Stooke has pinpointed the exact location of the Russian rover Lunokhod 2, by finding the tracks left by the lunar robot 37 years ago after it made a 35-kilometre-long trek. The journey was the longest any robotic rover has ever been driven on another celestial body.

As soon as the NASA photos were released, scientists around the world, including Stooke, began work to locate the rover. Stooke set up a searchable image database and located the photograph he needed, among thousands of others.

Lunokhod 2 landed on the Moon in 1973, and drove a record 35 kilometres.

Lunokhod 2 landed on the Moon in 1973, and drove a record 35 kilometres.

As soon as the NASA photos were released, scientists around the world, including Stooke, began work to locate the rover. Stooke set up a searchable image database and located the photograph he needed, among thousands of others.

“The tracks were visible at once,” says Stooke.

“Knowing the history of the mission, it’s possible to trace the rover’s activities in fine detail,” he adds. “We can see where it measured the magnetic field, driving back and forth over the same route to improve the data.”

“And we can also see where it drove into a small crater, and accidentally covered its heat radiator with soil as it struggled to get out again,” says Stooke. “That ultimately caused it to overheat and stop working. And the rover itself shows up as a dark spot right where it stopped.”

The find will mean that older maps published by Russia will now need to be revised.

Adapted from information issued by The University of Western Ontario / NASA / GSFC / ASU.

Jupiter’s giant cyclone revealed

Infrared and visible light images of Jupiter's Great Red Spot

Infrared (left) and visible wavelength images of Jupiter's Great Red Spot, a huge cyclone that has been raging in the planet's atmosphere for at least 400 years.

New thermal images from powerful ground-based telescopes show swirls of warmer air and cooler regions never seen before within Jupiter’s Great Red Spot, giving scientists their first detailed interior weather map of the giant storm system.

The observations reveal that the reddest colour of the Great Red Spot corresponds to a warm core within the otherwise cold storm system, and images show dark lanes at the edge of the storm where gases are descending into the deeper regions of the planet.

These types of data, detailed in a paper appearing in the journal Icarus, give scientists a sense of the circulation patterns within the Solar System’s best-known storm system.

“This is our first detailed look inside the biggest storm of the Solar System,” said Glenn Orton, a senior research scientist at NASA’s Jet Propulsion Laboratory, who was one of the authors of the paper.

“We once thought the Great Red Spot was a plain old oval without much structure, but these new results show that it is, in fact, extremely complicated.”

A multi-telescope effort

Skygazers have been observing the Great Red Spot in one form or another for hundreds of years, with continuous observations of its current shape dating back to the 19th century. The spot, which is a cold region averaging about minus 163 degrees Celsius, is so wide about three Earths could fit inside its boundaries.

Jupiter, showing it's Great Red Spot

Jupiter, showing it's Great Red Spot

The thermal images obtained by giant 8-metre telescopes used for this study—the European Southern Observatory’s Very Large Telescope in Chile, the Gemini Observatory telescope in Chile and the National Astronomical Observatory of Japan’s Subaru telescope in Hawaii—have provided an unprecedented level of resolution and extended the coverage provided by NASA’s Galileo spacecraft in the late 1990s.

Together with observations of the deep cloud structure by the 3-metre NASA Infrared Telescope Facility in Hawaii, the level of thermal detail observed from these giant observatories is comparable to visible-light images from NASA’s Hubble Space Telescope for the first time.

Still a mystery

One of the most intriguing findings shows the most intense orange-red central part of the spot is about 3 to 4 degrees Celsius warmer than the environment around it, said Leigh Fletcher, the lead author of the paper, who completed much of the research as a postdoctoral fellow at JPL and is currently a fellow at the University of Oxford in England.

This temperature differential might not seem like a lot, but it is enough to allow the storm circulation, usually counter-clockwise, to shift to a weak clockwise circulation in the very middle of the storm.

Not only that, but on other parts of Jupiter, the temperature change is enough to alter wind velocities and affect cloud patterns in the belts and zones.

“This is the first time we can say that there’s an intimate link between environmental conditions—temperature, winds, pressure and composition—and the actual colour of the Great Red Spot,” Fletcher said.

“Although we can speculate, we still don’t know for sure which chemicals or processes are causing that deep red colour, but we do know now that it is related to changes in the environmental conditions right in the heart of the storm.”

Unlocking the secrets of Jupiter’s giant storm systems will be one of the targets for infrared spacecraft observations from future missions including NASA’s Juno mission.

Adapted from information issued by NASA / ESO / Gemini Observatory / NAOJ.

The Sun’s stormy surface

An image captured by NASA's SOHO spacecraft shows storms brewing on the Sun.

A flare and a storm brewing on the surface of the Sun.

Magnetic storms from the Sun bombard Earth with charged particles that can interfere with electronics systems and satellites. This image, captured by NASA’s Solar Terrestrial Relations Observatory (STEREO) Ahead spacecraft on February 12, 2010, shows one such storm (albeit a very small one) brewing on the solar surface.

Two active regions glow brightly in this ultraviolet image of the Sun. A small flare rises from the active area on the left. Flares are intense explosions on the Sun that blast radiation into space. This one paints a white line across the left horizon of the Sun.

The active area on the right churns with magnetic loops. Arcs of charged particles rise from the surface and are drawn back down again in the magnetic field. A video showing a sequence of STEREO observations, including this one, reveals that a small coronal mass ejection (CME) burst from this region a short time after this image was taken. Like a flare, a CME sends charged particles and energy into space, but CMEs are larger solar storms that both last longer and carry a larger cloud of particles and magnetic field into space than do flares.

Artist's impression of the twin STEREO Sun-monitoring spacecraft.

Artist's impression of the twin STEREO Sun-monitoring spacecraft.

Both flares and coronal mass ejections can create space weather if aimed at Earth. The charged particles from large storms blast Earth’s magnetic field, which acts as a shield. The charged particles interacting with Earth’s magnetic field generate intense and beautiful aurora, but they can also be destructive. Solar storms in the past have damaged power grids, causing blackouts, and harmed and destroyed satellites.

STEREO is one of several NASA missions studying the Sun. STEREO was launched to help scientists better understand coronal mass ejections. An improved understanding of solar storms will improve space weather forecasts, which will help limit the damage they cause on Earth.

NASA image courtesy the STEREO science team. Text adapted from information issued by the STEREO science team and Holli Riebeek.

The Square Kilometre Array

In recent days we’ve brought you animated videos of Australia’s new radio telescope system, ASKAP, taking shape in the Western Australian desert.

Although ASKAP will be a fully-fledged radio telescope system in its own right — and one of the best in the world — it is also a “pathfinder” facility being built in the hope that Australia will win the rights to host the much larger Square Kilometre Array (SKA), which will be the world’s largest radio telescope system.

The video above, produced by the Swinburne Centre for Astrophysics and Supercomputing, showcases the SKA and the amazing astronomical research it will perform.

Adapted from information issued by the Swinburne Centre for Astrophysics and Supercomputing.

Night-time view of Houston, Texas, from space

Houston, Texas, seen at night from space

Houston, Texas, seen at night from space

Houston, Texas, has been called the “energy capital of the world” due to its role as a major hub of the petroleum and other energy resource industries. The Houston metropolitan area covers almost 2,331,000 hectares (9,000 square miles) along the southeast Texas coastline, with an average elevation of 13 meters (43 feet) above sea level and a population of over 5 million (2006 US Census estimate).

The Houston metropolitan area is also noteworthy as being the largest in the United States without formal zoning restrictions on where and how people can build. This freedom has led to a highly diverse pattern of land use at the neighbourhood scale; nevertheless, more general spatial patterns of land use can be recognized in remotely sensed data. These general patterns are particularly evident in nighttime photography of the urban area taken by astronauts on board the International Space Station.

The image depicts the roughly 100-kilometre (60-mile) east-west extent of the Houston metropolitan area. Houston proper is at image centre, indicated by a “bull’s-eye” of elliptical white- to orange-lighted beltways and brightly lit white freeways radiating outwards from the central downtown area. Suburban and primarily residential urban areas are indicated by both reddish-brown and grey-green lighted regions, which indicate a higher proportion of tree cover and lower light density.

Petroleum refineries along the Houston Ship Channel are identified by densely lit areas of golden yellow light. Rural and undeveloped land rings the metropolitan area, and Galveston Bay to the southeast (image lower right) provides access to the Gulf of Mexico. Both types of non-urban surface appear dark in the image.

Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text by William L. Stefanov, NASA-JSC.

Hubble confirms the universe is expanding faster

A map showing the expected location of dark matter withing a region of deep space

A map showing the expected location of dark matter withing a region of deep space

A new study led by European scientists presents the most comprehensive analysis of data from the most ambitious survey ever undertaken by the NASA/ESA Hubble Space Telescope.

The researchers have, for the first time ever, used Hubble data to probe the effects of the natural gravitational “weak lenses” in space and characterise the expansion of the Universe.

A group of astronomers, led by Tim Schrabback of the Leiden Observatory, conducted an intensive study of over 446,000 galaxies within the COSMOS field, the result of the largest survey ever conducted with Hubble. In making the COSMOS survey, Hubble photographed 575 slightly overlapping views of the same part of the Universe using the Advanced Camera for Surveys (ACS) onboard Hubble. It took nearly 1,000 hours of observations.

In addition to the Hubble data, researchers used redshift data from ground-based telescopes to assign distances to 194,000 of the galaxies surveyed (out to a redshift of 5).

“The sheer number of galaxies included in this type of analysis is unprecedented, but more important is the wealth of information we could obtain about the invisible structures in the Universe from this exceptional dataset,” says Patrick Simon from Edinburgh University.

An illustration showing how Hubble looks back in time to "map" evolving dark matter

Hubble looks back in time to "map" evolving dark matter by splitting the background galaxy population into discrete epochs of time (like cutting through rock strata). By measuring the redshift of the "lensing" galaxies used to map the dark matter distribution, scientists can put them into different time/distance "slices".

In particular, the astronomers could “weigh” the large-scale matter distribution in space over large distances. To do this, they made use of the fact that this information is encoded in the distorted shapes of distant galaxies, a phenomenon referred to as weak gravitational lensing.

Using complex algorithms, the team led by Schrabback has improved the standard method and obtained galaxy shape measurements to an unprecedented precision. The results of the study will be published in an upcoming issue of Astronomy and Astrophysics.

The meticulousness and scale of this study enables an independent confirmation that the expansion of the Universe is accelerated by an additional, mysterious component named dark energy. A handful of other such independent confirmations exist.

Astronomers compared real observations with two predictions – one for a dark matter-dominated universe, the other one dominated by dark energy.

COSMOS Project Astronomers compared real observations with two simulations – one for a dark matter-dominated universe, the other one dominated by dark energy. The dark energy one is the closest match.

Scientists need to know how the formation of clumps of matter evolved in the history of the Universe to determine how the gravitational force, which holds matter together, and dark energy, which pulls it apart by accelerating the expansion of the Universe, have affected them.

“Dark energy affects our measurements for two reasons. First, when it is present, galaxy clusters grow more slowly, and secondly, it changes the way the Universe expands, leading to more distant — and more efficiently lensed — galaxies. Our analysis is sensitive to both effects,” says co-author Benjamin Joachimi from the University of Bonn.

“Our study also provides an additional confirmation for Einstein’s theory of general relativity, which predicts how the lensing signal depends on redshift,” adds co-investigator Martin Kilbinger from the Institut d’Astrophysique de Paris and the Excellence Cluster Universe.

The large number of galaxies included in this study, along with information on their redshifts is leading to a clearer map of how, exactly, part of the Universe is laid out; it helps us see its galactic inhabitants and how they are distributed.

“With more accurate information about the distances to the galaxies, we can measure the distribution of the matter between them and us more accurately,” notes co-investigator Jan Hartlap from the University of Bonn.

“Before, most of the studies were done in 2D, like taking a chest X-ray. Our study is more like a 3D reconstruction of the skeleton from a CT scan. On top of that, we are able to watch the skeleton of dark matter mature from the Universe’s youth to the present,” comments William High from Harvard University, another co-author.

Image credits: NASA, ESA, J. Hartlap (University of Bonn), P. Simon (University of Bonn) and T. Schrabback (Leiden Observatory)