Category: Earth Observation

Image of Antarctica captured by Galileo. Image credit: NASA. Click to enlarge
The asteroid impact that killed the dinosaurs 65 million years ago was big, but geologists have found a new asteroid crater that’s even bigger: in Antarctica. This 482 km (300 mile) crater was discovered using NASA’s GRACE satellites, which can detect the gravity fluctuations beneath Antarctica’s ice sheets. This meteor was probably 48 km (30 miles) across and might have struck 250 million years ago – the time of the Permian-Triassic extinction, when almost all the animals on Earth died out.

Planetary scientists have found evidence of a meteor impact much larger and earlier than the one that killed the dinosaurs — an impact that they believe caused the biggest mass extinction in Earth’s history.

The 300-mile-wide crater lies hidden more than a mile beneath the East Antarctic Ice Sheet. And the gravity measurements that reveal its existence suggest that it could date back about 250 million years — the time of the Permian-Triassic extinction, when almost all animal life on Earth died out.

Its size and location — in the Wilkes Land region of East Antarctica, south of Australia — also suggest that it could have begun the breakup of the Gondwana supercontinent by creating the tectonic rift that pushed Australia northward.

Scientists believe that the Permian-Triassic extinction paved the way for the dinosaurs to rise to prominence. The Wilkes Land crater is more than twice the size of the Chicxulub crater in the Yucatan peninsula, which marks the impact that may have ultimately killed the dinosaurs 65 million years ago. The Chicxulub meteor is thought to have been 6 miles wide, while the Wilkes Land meteor could have been up to 30 miles wide — four or five times wider.

“This Wilkes Land impact is much bigger than the impact that killed the dinosaurs, and probably would have caused catastrophic damage at the time,” said Ralph von Frese, a professor of geological sciences at Ohio State University.

He and Laramie Potts, a postdoctoral researcher in geological sciences, led the team that discovered the crater. They collaborated with other Ohio State and NASA scientists, as well as international partners from Russia and Korea. They reported their preliminary results in a recent poster session at the American Geophysical Union Joint Assembly meeting in Baltimore.

The scientists used gravity fluctuations measured by NASA’s GRACE satellites to peer beneath Antarctica’s icy surface, and found a 200-mile-wide plug of mantle material — a mass concentration, or “mascon” in geological parlance — that had risen up into the Earth’s crust.

Mascons are the planetary equivalent of a bump on the head. They form where large objects slam into a planet’s surface. Upon impact, the denser mantle layer bounces up into the overlying crust, which holds it in place beneath the crater.

When the scientists overlaid their gravity image with airborne radar images of the ground beneath the ice, they found the mascon perfectly centered inside a circular ridge some 300 miles wide — a crater easily large enough to hold the state of Ohio.

Taken alone, the ridge structure wouldn’t prove anything. But to von Frese, the addition of the mascon means “impact.” Years of studying similar impacts on the moon have honed his ability to find them.

“If I saw this same mascon signal on the moon, I’d expect to see a crater around it,” he said. “And when we looked at the ice-probing airborne radar, there it was.”

“There are at least 20 impact craters this size or larger on the moon, so it is not surprising to find one here,” he continued. “The active geology of the Earth likely scrubbed its surface clean of many more.”

He and Potts admitted that such signals are open to interpretation. Even with radar and gravity measurements, scientists are only just beginning to understand what’s happening inside the planet. Still, von Frese said that the circumstances of the radar and mascon signals support their interpretation.

“We compared two completely different data sets taken under different conditions, and they matched up,” he said.

To estimate when the impact took place, the scientists took a clue from the fact that the mascon is still visible.

“On the moon, you can look at craters, and the mascons are still there,” von Frese said. “But on Earth, it’s unusual to find mascons, because the planet is geologically active. The interior eventually recovers and the mascon goes away.” He cited the very large and much older Vredefort crater in South Africa that must have once had a mascon, but no evidence of it can be seen now.

“Based on what we know about the geologic history of the region, this Wilkes Land mascon formed recently by geologic standards — probably about 250 million years ago,” he said. “In another half a billion years, the Wilkes Land mascon will probably disappear, too.”

Approximately 100 million years ago, Australia split from the ancient Gondwana supercontinent and began drifting north, pushed away by the expansion of a rift valley into the eastern Indian Ocean. The rift cuts directly through the crater, so the impact may have helped the rift to form, von Frese said.

But the more immediate effects of the impact would have devastated life on Earth.

“All the environmental changes that would have resulted from the impact would have created a highly caustic environment that was really hard to endure. So it makes sense that a lot of life went extinct at that time,” he said.

He and Potts would like to go to Antarctica to confirm the finding. The best evidence would come from the rocks within the crater. Since the cost of drilling through more than a mile of ice to reach these rocks directly is prohibitive, they want to hunt for them at the base of the ice along the coast where the ice streams are pushing scoured rock into the sea. Airborne gravity and magnetic surveys would also be very useful for testing their interpretation of the satellite data, they said.

NSF and NASA funded this work. Collaborators included Stuart Wells and Orlando Hernandez, graduate students in geological sciences at Ohio State; Luis Gaya-Piqu??bf? and Hyung Rae Kim, both of NASA’s Goddard Space Flight Center; Alexander Golynsky of the All-Russia Research Institute for Geology and Mineral Resources of the World Ocean; and Jeong Woo Kim and Jong Sun Hwang, both of Sejong University in Korea.

Original Source: Ohio State University

The Antarctic ozone hole. Image credit: NASA.
Over the last few decades, scientists have been tracking the depletion of the ozone layer in the Earth’s atmosphere. A large hole still opens up over Antarctica, but ozone levels worldwide have stopped declining. The question is why. The relatively recent reduction of ozone-destroying gasses shouldn’t make an improvement so quickly. NASA scientists think that atmospheric wind patterns could be transferring ozone around the planet, helping with the recovery. At this rate, we’ll return to 1980 levels between 2030 and 2070.

Think of the ozone layer as Earth’s sunglasses, protecting life on the surface from the harmful glare of the sun’s strongest ultraviolet rays, which can cause skin cancer and other maladies.

People were understandably alarmed, then, in the 1980s when scientists noticed that manmade chemicals in the atmosphere were destroying this layer. Governments quickly enacted an international treaty, called the Montreal Protocol, to ban ozone-destroying gases such as CFCs then found in aerosol cans and air conditioners.

Today, almost 20 years later, reports continue of large ozone holes opening over Antarctica, allowing dangerous UV rays through to Earth’s surface. Indeed, the 2005 ozone hole was one of the biggest ever, spanning 24 million sq km in area, nearly the size of North America.

Listening to this news, you might suppose that little progress has been made. You’d be wrong.

While the ozone hole over Antarctica continues to open wide, the ozone layer around the rest of the planet seems to be on the mend. For the last 9 years, worldwide ozone has remained roughly constant, halting the decline first noticed in the 1980s.

The question is why? Is the Montreal Protocol responsible? Or is some other process at work?

It’s a complicated question. CFCs are not the only things that can influence the ozone layer; sunspots, volcanoes and weather also play a role. Ultraviolet rays from sunspots boost the ozone layer, while sulfurous gases emitted by some volcanoes can weaken it. Cold air in the stratosphere can either weaken or boost the ozone layer, depending on altitude and latitude. These processes and others are laid out in a review just published in the May 4th issue of Nature: “The search for signs of recovery of the ozone layer” by Elizabeth Westhead and Signe Andersen.

Sorting out cause and effect is difficult, but a group of NASA and university researchers may have made some headway. Their new study, entitled “Attribution of recovery in lower-stratospheric ozone,” was just accepted for publication in the Journal of Geophysical Research. It concludes that about half of the recent trend is due to CFC reductions.

Lead author Eun-Su Yang of the Georgia Institute of Technology explains: “We measured ozone concentrations at different altitudes using satellites, balloons and instruments on the ground. Then we compared our measurements with computer predictions of ozone recovery, [calculated from real, measured reductions in CFCs].” Their calculations took into account the known behavior of the sunspot cycle (which peaked in 2001), seasonal changes in the ozone layer, and Quasi-Biennial Oscillations, a type of stratospheric wind pattern known to affect ozone.

What they found is both good news and a puzzle.

The good news: In the upper stratosphere (above roughly 18 km), ozone recovery can be explained almost entirely by CFC reductions. “Up there, the Montreal Protocol seems to be working,” says co-author Mike Newchurch of the Global Hydrology and Climate Center in Huntsville, Alabama.

The puzzle: In the lower stratosphere (between 10 and 18 km) ozone has recovered even better than changes in CFCs alone would predict. Something else must be affecting the trend at these lower altitudes.

The “something else” could be atmospheric wind patterns. “Winds carry ozone from the equator where it is made to higher latitudes where it is destroyed. Changing wind patterns affect the balance of ozone and could be boosting the recovery below 18 km,” says Newchurch. This explanation seems to offer the best fit to the computer model of Yang et al. The jury is still out, however; other sources of natural or manmade variability may yet prove to be the cause of the lower-stratosphere’s bonus ozone.

Whatever the explanation, if the trend continues, the global ozone layer should be restored to 1980 levels sometime between 2030 and 2070. By then even the Antarctic ozone hole might close–for good.

Original Source: NASA News Release

Magnesiowustite crystals lose the ability of infrared transmission when squashed. Image credit: JHU/NASA. Click to enlarge
Researchers from the Carnegie Institution’s Geophysical Laboratory have discovered that certain minerals stop conducting infrared light as they near the Earth’s core. Even though they transmit infrared light perfectly well on the surface, they actually absorb it when crushed by the intense pressures near the Earth’s core. This discovery will help scientists better understand the flow of heat in the Earth’s interior, as well as helping to develop new models of planetary formation and evolution.

Minerals crunched by intense pressure near the Earth’s core lose much of their ability to conduct infrared light, according to a new study from the Carnegie Institution’s Geophysical Laboratory. Since infrared light contributes to the flow of heat, the result challenges some long-held notions about heat transfer in the lower mantle, the layer of molten rock that surrounds the Earth’s solid core. The work could aid the study of mantle plumes-large columns of hot upwelling magma believed to produce features such as the Hawaiian Islands and Iceland.

Crystals of magnesiowustite, a common mineral within the deep Earth, can transmit infrared light at normal atmospheric pressures. But when squashed to over half a million times the pressure at sea level, these crystals instead absorb infrared light, which hinders the flow of heat. The research will appear in the May 26, 2006 issue of the journal Science.

Carnegie staff members Alexander Goncharov and Viktor Struzhkin, with postdoctoral fellow Steven Jacobsen, pressed crystals of magnesiowustite using a diamond anvil cell-a chamber bound by two superhard diamonds capable of generating incredible pressure. They then shone intense light through the crystals and measured the wavelengths of light that made it through. To their surprise, the compressed crystals absorbed much of the light in the infrared range, suggesting that magnesiowustite is a poor conductor of heat at high pressures.

“The flow of heat in Earth’s deep interior plays an important role in the dynamics, structure, and evolution of the planet,” Goncharov said. There are three primary mechanisms by which heat is likely to circulate in the deep Earth: conduction, the transfer of heat from one material or area to another; radiation, the flow of energy via infrared light; and convection, the movement of hot material. “The relative amount of heat flow from these three mechanisms is currently under intense debate,” Goncharov added.

Magnesiowustite is the second most common mineral in the lower mantle. Since it does not transmit heat well at high pressures, the mineral could actually form insulating patches around much of the Earth’s core. If that is the case, radiation might not contribute to overall heat flow in these areas, and conduction and convection might play a bigger role in venting heat from the core.

“It’s still too early to tell exactly how this discovery will affect deep-Earth geophysics,” Goncharov said. “But so much of what we assume about the deep Earth relies on our models of heat transfer, and this study calls a lot of that into question.”

Original Source: Carnegie Institution

Global map of forest fires. Image credit: ESA. Click to enlarge
ESA satellites have been keeping track of global forest fires for more than 10 years, and now this data is available online through ESA’s ATSR World Fire Atlas. More than 50 million hectares (123 million acres) of forests burn every year, and these fires make a signficant contribution to global pollution. By monitoring these fires, researchers can improve computer models to predict which regions are at greatest risk based on weather patterns.

For a decade now, ESA satellites have been continuously surveying fires burning across the Earth’s surface. Worldwide fire maps based on this data are now available to users online in near-real time through ESA’s ATSR World Fire Atlas.

The ATSR World Fire Atlas (WFA) – the first multi-year global fire atlas ever developed – provides data approximately six hours after acquisition and represents an important scientific resource because fire is a major agent of environmental change.

“The atlas is an excellent resource that provides a glimpse of the world that was not previously possible, and which is certain to allow ecologists to address both new and old questions regarding the role of fire in structuring the natural world,” Matt Fitzpatrick of the University of Tennessee’s Department of Ecology & Evolutionary Biology said.

More than 50 million hectares of forest are burnt annually, and these fires have a significant impact on global atmospheric pollution, with biomass burning contributing to the global budgets of greenhouse gases, like carbon dioxide. In the past decade researchers have realised the importance of monitoring this cycle. In fact, WFA data are currently being accessed mostly for atmospheric studies.

Quantifying fire is important for the ongoing study of climate change. The 1998 El Niño, for example, helped encourage fires across Borneo which emitted up to 2.5 billion tonnes of carbon into the atmosphere, equivalent to Europe’s entire carbon emissions that year.

There are over 200 registered users accessing the WFA. The data are being used in Europe, Asia, North America, South America, Africa and Australia for research in atmospheric chemistry, land use change, global change ecology, fire prevention and management and meteorology.

Harvard University, University of Toronto, National Centre for Atmosphere and NASA, among others, have used the data in research publications. To date, there are more than 100 scientific publications based on WFA data.

In addition to maps, the time, date, longitude and latitude of the hot spots are provided. The database covers 1995 to present, but complete yearly coverage begins from 1997.

The WFA data are based on results from the Along Track Scanning Radiometer (ATSR) on ESA’s ERS-2 satellite, launched in 1995, and the Advanced Along Track Scanning Radiometer (AATSR) on ESA’s Envisat satellite, launched in 2002.

These twin radiometer sensors work like thermometers in the sky, measuring thermal infrared radiation to take the temperature of Earth’s land surfaces. Fires are detected best during local night, when the surrounding land is cooler.

Temperatures exceeding 312º K (38.85 ºC) are classed as burning fires by ATSR/AATSR, which are capable of detecting fires as small as gas flares from industrial sites because of their high temperature.

The WFA is an internal and Data User Programme (DUP) project.

Original Source: ESA News Release

Artist illustration of the GOCE mission. Image credit: ESA. Click to enlarge
The European Space Agency has decided on the shortlist of spacecraft that could launch in less than a decade and contribute to the scientific exploration of our planet. The missions include Biomass, which will measure the Earth’s forests; TRAQ, which will monitor air quality; PREMIER, to watch how gasses change in the atmosphere; FLEX, to observe global photosynthesis; A-SCOPE, to track the global carbon cycle; and CoReH20, which will measure the ice/water/snow cycle. ESA requested proposals more than a year ago, and received 24 from different research groups.

ESA has announced the shortlist of new Earth Explorer mission proposals within its Living Planet Programme. This is part of the selection procedure that will eventually lead to the launch of the fourth Earth Explorer Core mission during the first half of the next decade.

The six missions cover a range of environmental issues with the aim of furthering our understanding of the Earth system and changing climate:

* BIOMASS – to take global measurements of forest biomass.

* TRAQ (TRopospheric composition and Air Quality) – to monitor air quality and long-range transport of air pollutants.

* PREMIER (PRocess Exploration through Measurements of Infrared and millimetre-wave Emitted Radiation) – to understand processes that link trace gases, radiation, chemistry and climate in the atmosphere.

* FLEX (FLuorescence EXplorer) – to observe global photosynthesis through the measurement of fluorescence.

* A-SCOPE (Advanced Space Carbon and Climate Observation of Planet Earth) – to improve our understanding of the global carbon cycle and regional carbon dioxide fluxes.

* CoReH2O (Cold Regions Hydrology High-resolution Observatory – to make detailed observations of key snow, ice and water cycle characteristics.

The selection of these six mission proposals follows the release of the Call for Earth Explorer Core mission ideas in March 2005. ESA received 24 responses, which covered a broad range of Earth science disciplines, and in particular responded well to the priorities set by the Agency’s Earth Science Advisory Committee (ESAC). These priorities focused on the global carbon and water cycles, atmospheric chemistry and climate, as well as the human element as a cross cutting issue.

The proposals were peer reviewed by scientific teams, and also appraised technically and programmatically. Based on these reviews, the ESAC evaluated the proposals and recommended the list of six mission ideas in order of priority. Following these recommendations, ESA’s Programme Board for Earth Observation on 18-19 May approved the proposal of the Director of Earth Observation Programmes to initiate assessment studies for these six mission candidates.

Earth Explorer Core missions are ESA-led research missions and the budget limit for the current set is 300 M€. The first Earth Explorer Core Missions were selected in 1999: the Earth Gravity field and Ocean Circulation (GOCE) mission and the Atmospheric Dynamics Mission (ADM-Aeolus) to be launched in 2007 and 2008 respectively. The third Core mission, Earth Clouds Aerosols and Radiation Explorer (EarthCARE), was selected in 2004 and will be launched in 2012.

In addition to the Earth Explorer Core missions, three Earth Explorer Opportunity missions are currently under implementation: SMOS for soil moisture and ocean salinity, CryoSat-2 for the study of ice sheets and sea ice, and Swarm, which is a constellation of small satellites to study the dynamics of the Earth’s magnetic field and its interactions with the Earth system, due for launch in 2007, 2009 and 2010, respectively.

The six mission candidates recently selected will significantly extend the scientific disciplines covered by ESA’s Living Planet Programme. When the assessment studies have been completed, a subset of the six candidates will be selected for feasibility study, and the mission finally selected for implementation will be launched during the first half of the next decade.

BIOMASS – the mission aims at global measurements of forest biomass. The measurement is accomplished by a space borne P-band synthetic aperture polarimetric radar. The technique is mainly based on the measurement of the cross-polar backscattering coefficient, from which forest biomass is directly retrieved. Use of multi-polarization measurements and of interferometry is also proposed to enhance the estimates. In line with the ESAC recommendations, the analysis for this mission will include comparative studies to measure terrestrial biomass using P- or L-band and consideration of alternative implementations using L-band.

TRAQ – the mission focuses on monitoring air quality and long-range transport of air pollutants. A new synergistic sensor concept allows for process studies, particularly with respect to aerosol-cloud interactions. The main issues are the rate of air quality change on regional and global scales, the strength and distribution of sources and sinks of tropospheric trace gases and aerosols influencing air quality, and the role of tropospheric composition in global change. The instrumentation consists of imaging spectrometers in the range from ultraviolet to short-wave infrared.

PREMIER – Many of the most important processes for prediction of climate change occur in the upper troposphere and lower stratosphere (UTLS). The objective is to understand the many processes that link trace gases, radiation, chemistry and climate in the atmosphere – concentrating on the processes in the UTLS region. By linking with MetOp/ National Polar-orbiting Operational Environmental Satellite System (NPOESS) data, the mission also aims to provide useful insights into processes occurring in the lower troposphere. The instrumentation consists of an infrared and a microwave radiometer.

FLEX – The main aim of the mission is global remote sensing of photosynthesis through the measurement of fluorescence. Photosynthesis by land vegetation is an important component of the global carbon cycle, and is closely linked to the hydrological cycle through transpiration. Currently there are no direct measurements available from satellites of this parameter. The main specification is for instruments to measure high spectral resolution reflectance and temperature, and to provide a multi-angular capability.

A-SCOPE – The mission aims to observe total column carbon dioxide with a nadir-looking pulsed carbon dioxide DIfferential Absorption Lidar (DIAL) for a better understanding of the global carbon cycle and regional carbon dioxide fluxes, as well as for the validation of greenhouse gas emission inventories. It will provide a spatially resolved global carbon budget combined with diagnostic model analysis through global and frequent observation of carbon dioxide. Spin-off products like aerosols, clouds and surface reflectivity are important parameters of the radiation balance of the Earth. A contribution to Numerical Weather Prediction is foreseen in connection with accurate temperature profiles. Investigations on plant stress and vitality will be supported by a fluorescence imaging spectrometer.

CoReH2O – The mission focuses on spatially detailed observations of key snow, ice, and water cycle characteristics necessary for understanding land surface, atmosphere and ocean processes and interactions by using two synthetic aperture radars at 9.6 and 17.2 GHz. It aims at closing the gaps in detailed information on snow glaciers, and surface water, with the objectives of improving modelling and prediction of water balance and streamflow for snow covered and glacierised basins, understanding and modelling the water and energy cycles in high latitudes, assessing and forecasting water supply from snow cover and glaciers, including the relation to climate change variability

Original Source: ESA News Release

Gamma ray burst host galaxies. Image credit: NASA/ESA/STScI. Click to enlarge
If a gamma ray burst happened near the Earth, it would make for a very bad day: our ozone layer would be stripped away, worldwide climate would change dramatically, and life would struggle to survive. Fortunately, it looks like they don’t happen in galaxies like our Milky Way. Researchers have found that bursts tend to occur in small irregular galaxies that lack heavier chemical elements.

A gamma-ray burst (GRB) occurring in our own galaxy could decimate life on Earth, destroying the ozone layer, triggering climate change and drastically altering life’s evolution. However, the good news is that results published online in the journal Nature show that the likelihood of a natural disaster due to a GRB is much lower than previously thought.

Long-duration GRBs are powerful flashes of high-energy radiation that arise from some of the biggest explosions of extremely massive stars. Astronomers have analysed a total of 42 long duration GRBs ??bf? those lasting more than two seconds ??bf? in several Hubble Space Telescope (HST) surveys.

They have found that the galaxies from which they originate are typically small, faint and misshapen (irregular) galaxies, while only one was spotted from a large spiral galaxy similar to the Milky Way. In contrast, supernovae (also the result of collapsing massive stars) were found to lie in spiral galaxies roughly half of the time.

These results, published in the May 10 online edition of the journal Nature, indicate that GRBs form only in very specific environments, which are different from those found in the Milky Way.

Andrew Fruchter, at the Space Telescope Science Institute, the lead author of the paper said, “Their occurrence in small irregulars implies that only stars that lack heavy chemical elements (elements heavier than hydrogen and helium) tend to produce long-duration GRBs.”

This means that long bursts happened more often in the past when galaxies did not have a large supply of heavy elements. Galaxies build up a stockpile of heavier chemical elements through the ongoing evolution of successive generations of stars. Early generation stars formed before heavier elements were abundant in the universe.

The authors also found that the locations of GRBs differed from the locations of supernovae (which are a much more common variety of exploding star). GRBs were far more concentrated on the brightest regions of their host galaxies, where the most massive stars reside. Supernovae, on the other hand, occur throughout their host galaxies.

“The discovery that long-duration GRBs lie in the brightest regions of their host galaxies suggests that they come from the most massive stars ??bf? perhaps 20 or more times as massive as our Sun,” said Andrew Levan of the University of Hertfordshire, a co-author of the study.

However, massive stars abundant in heavy elements are unlikely to trigger GRBs because they may lose too much material through stellar “winds” off their surfaces before they collapse and explode. When this happens, the stars don’t have enough mass left to produce a black hole, a necessary condition to trigger GRBs. The energy from the collapse escapes along a narrow jet, like a stream of water from a hose. The formation of directed jets, that concentrate energy along a narrow beam, would explain why GRBs are so powerful.

If a star loses too much mass, it may only leave behind a neutron star that cannot trigger a GRB. On the other hand, if the star loses too little mass, the jet cannot burn its way through the star. This means that extremely high-mass stars that puff away too much material may not be candidates for long bursts. Likewise, neither are the stars that give up too little material.

“It’s a Goldilocks scenario,” said Fruchter. “Only supernovae whose progenitor stars have lost some, but not too much mass, appear to be candidates for the formation of GRBs??bf?.

“People have, in the past, suggested that it might be possible to use GRBs to follow the locations of star formation. This obviously doesn’t work in the universe as we see it now, but, when the universe was young, GRBs may well have been more common, and we may yet be able to use them to see the very first stars to form after the Big Bang,” added Levan.

Original Source: RAS News Release

Double Star TC-2 spacecraft. Image credit: ESA. Click to enlarge
Like many comets when they get close to the Sun, the Earth has a tail. But instead of a shower of icy particles, it’s the Earth’s magnetic field that gets pushed into a long trail directed away from the Sun. Five spacecraft from ESA – the 4 Cluster spacecraft and DoubleStar – recently observed how this magnetotail can experience strange turbulence through its interaction with the Sun’s solar wind and coronal mass ejections. How and why this phenomenon happens is still a mystery.

Five spacecraft from two ESA missions unexpectedly found themselves engulfed by waves of electrical and magnetic energy as they travelled through Earth’s night-time shadow on 5 August 2004.

The data collected by the spacecraft are giving scientists an important clue to the effects of ‘space weather’ on Earth’s magnetic field.

Shortly after 15:34 CEST, something set the tail of Earth’s natural cloak of magnetism oscillating. “It was like the waves created by a boat travelling across a lake,” says Dr Tielong Zhang of the Austrian Academy of Sciences, Graz.

Only in this case, the identity of the ‘boat’ is unknown. It might be the fast flow of particles often observed in the central part of the magnetotail. Whatever it was produced waves that travelled from the centre of the tail to its outer edges.

The five spacecraft caught in this event were the four units of ESA’s Cluster mission and the first unit of the joint CNSA/ESA mission Double Star. The Cluster quartet fly in formation, passing through Earth’s magnetotail at distances of between 16 and 19 times Earth’s radius.

One of the two spacecraft of Double Star, the TC-1 spacecraft, orbits at between 10 and 13 Earth radii. All five spacecraft are designed to collect data on the magnetic bubble surrounding our planet, called the ‘magnetosphere’.

Earth’s magnetic field is generated deep inside the planet and rises into space where it constantly interacts with the solar wind, a perpetual stream of electrically charged particles released by the Sun.

The stream pulls Earth’s magnetic field into a tail that stretches behind the planet for tens of thousands of kilometres. Gusts and storms in the solar wind are known as ‘space weather’ and can make Earth’s magnetic field quake.

On 5 August 2004, Cluster and Double Star satellites found themselves in the right place at the right time. The readings showed that the oscillations took place simultaneously across an area over 30 000 km in length. This is the first time that the true extent of the oscillations has been revealed.

Previous Cluster measurements, before the launch of Double Star, could only reveal the movement across a restricted location surrounded by the four satellites.

Understanding the way Earth’s magnetic field interacts with the solar wind is the space-age equivalent of a meteorologist investigating the way a mountain range disturbs airflow, creating weather systems.

In the case of space weather, storms consist of fluctuating magnetic and electrical fields that can damage satellites and pose health risks to astronauts. If we are to fully exploit the potential of space, we have to understand the effects of space weather and be able to predict them. That’s where missions like Cluster and Double Star come in.

“By studying the August oscillations, we may be able to develop a unifying theory for all the various motions of the magnetotail,” says Zhang, who is heading the investigation into what happened that day.

Original Source: ESA Portal

Dust storms are being mapped for the ESA-led Epidemio project. Image credit: ESA Click to enlarge
All those eyes in the sky are coming in handy for purposes scientists never imagined. Now researchers from ESA are using Envisat data to track places on Earth where disease epidemics could get started. The team was able to link the outbreak of diseases in Africa with dryness and drought. So far they’ve been able to track regions which are dry, which contribute to the spread of meningitis. Aid workers can then target these regions to give vaccinations and provide early warnings.

The amount of data acquired by satellites is increasing at an exponential rate, and researchers are learning about the value of this data in fighting epidemic outbreaks as a result of the ESA’s Epidemio project.

“I was negative about the role satellites could play in addressing epidemics, but now I am positive,” Penelope Vernatsou of the Swiss Tropical Institute in Switzerland said.

The ESA-funded Epidemio project was developed in January 2004 to illustrate the benefits of remote-sensing data for studying, monitoring and predicting epidemic outbreaks.

By using data which focuses on a region’s landscape ? rainfall, vegetation, water bodies, elevation, dust mapping and temperature ? researchers are able to pinpoint climatic conditions which are favourable for harbouring various epidemic hosts, indicating where people are at greatest risk.

As the project draws to completion, epidemiologists and data users gathered in Frascati, Italy, at the ‘Earth Observation in Epidemiology Workshop’, on 8-10 March 2006, to report on how Earth observation (EO) has benefited the field of epidemiology.

Ghislain Moussavou of the Gabon-based International Centre for Medical Research (CIRMF) began studying Ebola haemorrhagic fever, which can cause runaway internal and external bleeding in humans and apes, in Congo and Gabon in the hope of spotting particular environmental characteristics associated with infected sites.

Combining ESA Envisat satellite data, under the Epidemio project, on water bodies, forest cover and digital elevation models (DEMs) with field results, Moussavou and his team were able to link the epidemic with dryness and drought.

Moussavou said determining these factors will allow officials to tell the villagers in the area that current conditions for transmission are high, and that they need to take extra precautions. “Because there are no medicines to prevent or cure Ebola, predictions and prevention are necessary.”

Dry conditions are also favourable for the spread of meningitis, an inflammation of the brain and spinal cord lining. Epidemics nearly always start in the early part of the dry season when it is hot and dusty. For this reason, ESA has been providing dust maps for high-risk areas to aid in implementing early warning systems.

Christelle Barbey of Silogic, in France, is currently involved in an Epidemio project to provide wind blown dust maps for Africa. Although her final results are still coming in, she was able to detect 100 percent of known dust events, using MeteoSat data, and determine that dust maps do correspond to a user need to contribute to meningitis prevention.

The Epidemio project – funded by the Data User Element of the ESA Earth Observation Envelope Programme – concludes its two-year mission in April 2006, but the groundwork it has laid will aid users in the continuance of their research and allow new projects to be undertaken.

Giuseppe Ottavianelli and Aude de Clercq of the HISTAR Solutions in the Netherlands are currently working on a project, backed by ESA business incubator financing, to confirm the onset of malaria epidemics in Africa, as predicted by remote sensing data.

They have designed a prototype of a sensor located in a box that detects mosquitoes as they fly overhead. The data collected by the sensor is then processed by a program inside the box, which will be placed in hat hutches in high-risk African villages, and indicates the species and numbers of the mosquitoes detected.

Malaria is transferred by the female mosquito of the species Anopheles, so if the sensor detects her presence in high numbers, public officials will be alerted so that preventive measures can be put into place.

Original Source: ESA Portal

Earth factors may be the most probable scenario for past mass extinctions. Image credit: NASA Click to enlarge
Most scientists agree that a large meteor probably wiped out the dinosaurs 65 million years ago, but two geologists from the University of Leicester think that some homegrown cataclysms might have done the trick for previous extinctions. There just isn’t enough evidence that an impact caused the mass extinction that happened 250 million years ago. But one of the largest flood basalt eruptions did occur at that time, and released enough greenhouse gasses to dramatically change the Earth’s climate – killing the dinosaurs off in the process.

Earth history has been punctuated by several mass extinctions rapidly wiping out nearly all life forms on our planet. What causes these catastrophic events? Are they really due to meteorite impacts? Current research suggests that the cause may come from within our own planet – the eruption of vast amounts of lava that brings a cocktail of gases from deep inside the Earth and vents them into the atmosphere.

University of Leicester geologists, Professor Andy Saunders and Dr Marc Reichow, are taking a fresh look at what may actually have wiped out the dinosaurs 65 million years ago and caused other similarly cataclysmic events, aware they may end up exploding a few popular myths.

The idea that meteorite impacts caused mass extinctions has been in vogue over the last 25 years, since Louis Alverez’s research team in Berkeley, California published their work about an extraterrestrial iridium anomaly found in 65-million-year-old layers at the Cretaceous-Tertiary boundary. This anomaly only could be explained by an extraterrestrial source, a large meteorite, hitting the Earth and ultimately wiping the dinosaurs – and many other organisms – off the Earth’s surface.

Professor Saunders commented: “Impacts are suitably apocalyptic. They are the stuff of Hollywood. It seems that every kid’s dinosaur book ends with a bang. But are they the real killers and are they solely responsible for every mass extinction on earth? There is scant evidence of impacts at the time of other major extinctions e.g., at the end of the Permian, 250 million years ago, and at the end of the Triassic, 200 million years ago. The evidence that has been found does not seem large enough to have triggered an extinction at these times.”

Flood basalt eruptions are – he says – an alternative kill mechanism. These do correspond with all main mass extinctions, within error of the techniques used to determine the age of the volcanism. Furthermore, they may have released enough greenhouse gases (SO2 and CO2) to dramatically change the climate. The largest flood basalts on Earth (Siberian Traps and Deccan Traps) coincide with the largest extinctions (end-Permian, and end-Cretaceous). “Pure coincidence?”, ask Saunders and Reichow.

While this is unlikely to be pure chance, the Leicester researchers are interested in precisely what the kill mechanism may be. One possibility is that the gases released by volcanic activity lead to a prolonged volcanic winter induced by sulphur-rich aerosols, followed by a period of CO2-induced warming.

Professor Andy Saunders and Dr. Marc Reichow at Leicester, in collaboration with Anthony Cohen, Steve Self, and Mike Widdowson at the Open University, have recently been awarded a NERC (Natural Environment Research Council) grant to study the Siberian Traps and their environmental impact.

The Siberian Traps are the largest known continental flood basalt province. Erupted about 250 million years ago at high latitude in the northern hemisphere, they are one of many known flood basalts provinces – vast outpourings of lava that covered large areas of the Earth’s surface. A major debate is underway concerning the origin of these provinces -including the Siberian Traps- and their environmental impact.

Using radiometric dating techniques, they hope to constrain the age and, combined with geochemical analysis, the extent, of the Siberian Traps. Measuring how much gas was released during these eruptions 250 million years ago is a considerable challenge. The researchers will study microscopic inclusions trapped in minerals of the Siberian Traps rocks to estimate the original gas contents. Using these data they hope to be able to assess the amount of SO2 and CO2 released into the atmosphere 250 million years ago, and whether or not this caused climatic havoc, wiping out nearly all life on earth. By studying the composition of sedimentary rocks laid down at the time of the mass extinction, they also hope to detect changes to seawater chemistry that resulted from major changes in climate.

From these data Professor Saunders and his team hope to link the volcanism to the extinction event. He explained: “If we can show, for example, that the full extent of the Siberian Traps was erupted at the same time, we can be confident that their environmental effects were powerful. Understanding the actual kill mechanism is the next stage. watch this space.”

Original Source: University of Leicester

A RADARSAT map of Antarctica. Image credit: AMM/SVS/NASA/CSA Click to enlarge
NASA has completed the most comprehensive survey ever made of the Earth’s polar ice caps, and confirmed that they’re disappearing at increasing rates. These rates match computer climate models precisely, giving climate scientists greater confidence in their predictions about global warming. The survey combined data from airborne maps and measurements from two ESA satellites. NASA’s ICESat satellite is taking an even more comprehensive survey of ice levels, which should be available next year.

In the most comprehensive survey ever undertaken of the massive ice sheets covering both Greenland and Antarctica, NASA scientists confirm climate warming is changing how much water remains locked in Earth’s largest storehouse of ice and snow.

Other recent studies have shown increasing losses of ice in parts of these sheets. This new survey is the first to inventory the losses of ice and the addition of new snow on both in a consistent and comprehensive way throughout an entire decade.

The survey shows that there was a net loss of ice from the combined polar ice sheets between 1992 and 2002 and a corresponding rise in sea level. The survey documents for the first time extensive thinning of the West Antarctic ice shelves and an increase in snowfall in the interior of Greenland, as well as thinning at the edges. All are signs of a warming climate predicted by computer models.

The survey, published in the Journal of Glaciology, combines new satellite mapping of the height of the ice sheets from two European Space Agency satellites. It also used previous NASA airborne mapping of the edges of the Greenland ice sheets to determine how fast the thickness is changing.

In Greenland, the survey saw large ice losses along the southeastern coast and a large increase in ice thickness at higher elevations in the interior due to relatively high rates of snowfall. This study suggests there was a slight gain in the total mass of frozen water in the ice sheet over the decade studied, contrary to previous assessments.

This situation may have changed in just the past few years, according to lead author Jay Zwally of NASA’s Goddard Space Flight Center, Greenbelt, Md. Last month NASA scientists at the Jet Propulsion Laboratory, Pasadena, Calif., reported a speed up of ice flow into the sea from several Greenland glaciers. That study included observations through 2005; Zwally’s survey concluded with 2002 data.

When the scientists added up the overall gains and losses of ice from the Greenland and Antarctic ice sheets, there was a net loss of ice to the sea. The amount of water added to the oceans (20 billion tons) is equivalent to the total amount of freshwater used in homes, businesses and farming in New York, New Jersey and Virginia each year.

“The study indicates that the contribution of the ice sheets to recent sea-level rise during the decade studied was much smaller than expected, just two percent of the recent increase of nearly three millimeters a year,” says Zwally. “Continuing research using NASA satellites and other data will narrow the uncertainties in this important issue.”

NASA is continuing to monitor the polar ice sheets with the Ice, Cloud and land Elevation Satellite (ICESat), launched in January 2003. ICESat uses a laser beam to measure the elevation of ice sheets with unprecedented accuracy three times a year. The first comprehensive ice sheet survey conducted by ICESat is expected early next year, said Zwally, who is the mission’s project scientist.

Original Source: NASA News Release