Category: Earth Observation

Image credit: NASA

NASA scientists are working on ways to predict earthquakes using an advanced computer simulation. The software is called QuakeSim, and it uses hundreds of thousands of measurements gathered by a variety of land and space-based instruments to calculate how the Earth’s crust deforms through plate tectonics. The technology is already starting to show results – one team has been able to identify regions in California with higher risks of earthquakes and predicted every magnitude 5+ quake since the year 2000 within 11 kilometres.

Advanced computer simulation tools now being developed by NASA and university researchers may soon give scientists new insights into the complex and mysterious physics of earthquakes and enable vastly improved earthquake forecasting.

Scientists at NASA?s Jet Propulsion Laboratory, Pasadena, Calif., together with NASA?s Goddard Space Flight Center, Greenbelt, Md.; Ames Research Center, Mountain View, Calif.; and several universities, are developing an advanced earthquake modeling system called QuakeSim. When completed in late 2004, QuakeSim?s simulation tools will help scientists learn more about what makes earthquakes happen.

The tools are based upon the latest technologies. For example, one uses finite element analysis, which solves complex computer modeling problems by breaking them into small pieces. For QuakeSim, the finite elements are tens to hundreds of thousands of measurements of how Earth?s crust deforms in response to movement of the giant tectonic plates Earth?s landmasses ride upon. The measurements are gathered through both ground and space-based techniques. The latter include global positioning system and interferometric synthetic aperture radar, which measure the ?quiet? (non-earthquake) motions associated with plate tectonics and the quake cycle.

QuakeSim Principal Investigator Dr. Andrea Donnellan of JPL calls QuakeSim a vital step toward eventual earthquake forecasting. ?The deformation of Earth?s crust and the interaction between quake faults is a complex 3-D process happening on timescales of minutes to thousands of years,? she said. ?Studying it requires sophisticated simulation models and high-performance supercomputers. The availability of space-based data and our current limited understanding of quake processes make this an ideal time to develop a system for studying deformation processes such as tectonics, quakes and volcanoes.?

?New quake models developed under QuakeSim are expected to yield future earthquake forecasts that will be used by a variety of federal and state agencies to develop decision support tools that will help mitigate losses from future large earthquakes,” Donnellan added.

QuakeSim?s three major simulation tools are Park, Virtual California and the Geophysical Finite Element Simulation Tool (Geofest).

Park simulates the evolution of a quake on a single, unstable fault over time. It is based upon current knowledge of the rate of movement (or ?slip?) and friction on a well-studied section of the San Andreas Fault in Parkfield, Calif., but is applicable to any fault or collection of faults. Park will be the tool of choice for researchers seeking to determine the nature and detectability of quake warning signals. It will determine how stress is distributed over a fault and how it is redistributed by quakes or ?quiet? seismic motion. It can also be used to compute the history of slip, slip speed and stress on a fault. Up to 1,024 computer processors will be used in parallel to demonstrate Park’s capability.

Virtual California simulates how California?s hundreds of independent fault segments interact and allows scientists to determine correlated patterns of activity that can be used to forecast seismic hazard, especially for quakes of magnitude 6 or greater. Patterns from the simulated data are compared to patterns in real data to strengthen understanding of the quake process. The approach’s potential is already being demonstrated. Under a joint NASA/Department of Energy study lead by Dr. John Rundle, director of the Center for Computational Science and Engineering at the University of California at Davis, Virtual California was used to identify regions of the state with elevated probabilities of quakes over the next decade. Since the study was completed in 2000, all of California’s five largest quakes of magnitude 5 or greater have occurred within 11 kilometers (6.8 miles) of these sites. The probability of this occurring randomly is about one in 100,000. The last three of these quakes occurred after the forecast map was published in the Proceedings of the National Academy of Sciences in February 2002.

Geofest creates 2-D and 3-D models of stress and strain in Earth?s crust and upper mantle in a complex geologic region with many interacting fault systems. It shows how the ground will deform in response to a quake, how deformation changes over time following a quake, and the net effects to the ground from a series of quakes. The entire Southern California system of interacting faults will be analyzed, covering a portion of the crust approximately 1,000 kilometers (621 miles) on a side. The simulation will require millions of equations and hundreds of computer processors.

In addition to JPL, the QuakeSim team includes the Davis and Irvine campuses of the University of California; Brown University, Providence, R.I.; Indiana University; and the University of Southern California. An independent review board provides oversight. Codes will be run on supercomputers at NASA?s Goddard, Ames and JPL facilities and other institutions. The California Institute of Technology in Pasadena manages JPL for NASA.

NASA’s Earth Science Enterprise is dedicated to understanding Earth as an integrated system and applying Earth system science to improve prediction of climate, weather and natural hazards using the unique vantage point of space. A primary goal of NASA’s solid Earth science program is assessment and mitigation of natural hazards. QuakeSim supports the Enterprise’s goal of developing predictive capabilities for quake hazards.

Original Source: NASA News Release

Image credit: NASA

By combining the data from four separate instruments, NASA scientists are able to study the Earth’s volcanoes in tremendous detail. Most recently, Italy’s Mt. Etna was captured mid-eruption using the instruments on board the Terra and Aqua spacecraft, and the data will help the scientists understand the complex behaviour of volcanic plumes and the effects the eruptions have on the environment.

Think of them as the Good Witches of the North, South, East and West, whizzing around the globe daily on their techno “broomsticks” in space. When Europe’s largest, most active volcano, Italy’s Mount Etna, cackled to life and spewed ash and noxious sulfur dioxide gases last October, a quartet of remote sensing instruments from NASA’s Earth Observing System armada flew into action to analyze the smoky, caustic potion.

NASA’s atmospheric science and volcanology wizards can now study the evolution and structure of plumes from Mount Etna and Earth’s 500 or so other active volcanoes in greater detail than ever before. They do this by combining data from the Multi-angle Imaging SpectroRadiometer (Misr), Moderate Resolution Imaging SpectroRadiometer (Modis) and the joint U.S./Japan Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster) sensors on NASA’s Terra spacecraft with the Atmospheric Infrared Sounder (Airs) and Modis sensors on NASA’s Aqua spacecraft.

“The synergies from NASA’s remote sensing capabilities are helping us understand the complex behavior of volcanic plumes and the effects volcanic eruptions have on the environment,” said Dr. Vince Realmuto, a member of the Earth Observing System volcanology team and supervisor of the Visualization and Scientific Animation Group at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “By combining data from Airs, Aster, Misr and Modis, we can study volcanic plumes and clouds from many dimensions at once and observe targets of interest like Mount Etna on a daily basis.”

Mount Etna’s most recent eruption, which has subsided but not ended, has released sulfur dioxide into the atmosphere at rates as high as 20,000 metric tons (44.1 million pounds) a day. A major air pollutant vented by some volcanoes, this gas rapidly converts to sulfate aerosols in Earth’s atmosphere, impacting local, regional and global environments.

“At the local and regional level, sulfate aerosols can affect air quality and visibility and cause acid fog and rain, while their small size allows them to penetrate deep into human lungs, impacting respiratory health,” Realmuto said. “To affect global climate, these aerosols have to make their way into Earth’s upper atmosphere, or stratosphere.

“The eruptions of the Philippines’ Mount Pinatubo in 1991 and Mexico’s El Chichon in 1982 deposited aerosols in the stratosphere and had measurable effects on global climate,” Realmuto continued. “These volcanic aerosol layers can reflect incoming solar radiation, resulting in less radiation reaching the ground and throwing off the radiation balance between the Earth, atmosphere and sun. They can trap greenhouse gasses, such as carbon dioxide and water vapor, rising through the atmosphere. They can also lead to the formation of polar stratospheric clouds, a component of the process that destroys Earth’s protective ozone layer.”

Airs, Aster and Modis all collect measurements in the thermal infrared spectrum. Sulfur dioxide, sulfate aerosols and volcanic ash are all easily detectable in this spectral region.

The high spatial resolution of Aster makes it the only orbiting instrument that can detect the non-explosive venting of sulfur dioxide from small volcanic vents. Aster’s visible and near infrared channels can also be used to determine some properties of aerosols and ash. Aster was built by Japan’s Ministry of Economy, Trade and Industry and has a joint U.S./Japan science team.

Airs’ high spectral resolution will allow scientists to identify the components that make up volcanic plumes and estimate the quantity of these components with greater accuracy. In addition, Airs’ atmospheric temperature and relative humidity data will help scientists develop thermal infrared models that can be used to determine ash and aerosol makeup.

Modis’ spatial resolution falls in between that of Aster and Airs. Thus, Modis data are a bridge between the more localized Aster measurements and the more regional Airs data. Since Aster observations of particular targets must be scheduled in advance, Modis often provides the highest spatial resolution thermal infrared data for a given eruption. Both Modis and Airs transmit data in real time-a key to monitoring volcanoes from space.

Misr’s multi-angle imaging allows scientists to identify thin clouds of airborne volcanic ash and aerosol plumes and estimate the abundance and size of the particles. For thicker plumes, Misr can determine the height of the aerosol plume and the speed at which winds are moving the plume through the atmosphere. Knowing the plume height above the ground is important to thermal infrared modeling because it determines the temperature contrast between clouds and their backgrounds. Wind speed data are essential to accurately estimate the rate at which the material is horizontally dispersed into the atmosphere.

Original Source: NASA News Release

Image credit: NASA

CloudSat, a new satellite mission planned to launch in 2004, will use an advanced radar to study the properties of clouds. It will measure every aspect of the Earth’s clouds, including thickness, height, water and ice content. Using its cloud-penetrating radar, it should be able to increase the accuracy of severe storm, hurricane and flood warnings. It will also fly in orbital formation with several other weather satellites to help form a more complete picture of the Earth’s weather.

“I’ve looked at clouds from both sides now, from up and down and still somehow
It’s clouds’ illusions I recall. I really don’t know clouds at all…”

So laments Joni Mitchell’s classic song “Both Sides Now,” appropriate words as NASA prepares for a mission that should remove much of the mystery from those “rows and flows of angel hair” that so affect Earth’s weather and climate, yet are so misunderstood.

CloudSat, the most advanced radar designed to measure the properties of clouds, will provide the first global measurements of cloud thickness, height, water and ice content, and a wide range of precipitation data linked to cloud development. The Earth System Science Pathfinder Mission is expected to improve weather forecasting and advance our understanding of key climate processes during its two-year design lifetime. CloudSat is planned for launch in 2004 aboard a Boeing Delta rocket from Vandenberg Air Force Base, Calif. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the mission for NASA’s Earth Explorers Program Office at the Goddard Space Flight Center, Greenbelt, Md.

“Despite the fundamental role of clouds in climate and weather, there is much we do not know about them,” said CloudSat Principal Investigator Dr. Graeme Stephens of Colorado State University’s Department of Atmospheric Science, Fort Collins, Colo. “The lack of understanding of cloud feedback is widely acknowledged in the scientific community to be a major obstacle confronting credible prediction of climate change. CloudSat aims to provide observations necessary to greatly advance understanding of climate issues.”

Stephens and Co-Principal Investigator Dr. Deborah Vane of JPL discuss the necessity of CloudSat’s measurements in the current Bulletin of the American Meteorological Society. “The vertical profiles of global cloud properties provided by CloudSat will fill a critical gap in the understanding of how clouds affect climate, uncovering new knowledge about clouds and precipitation, and the connection of clouds to the large-scale motions of Earth’s atmosphere,” Vane said.

CloudSat will help researchers in numerous disciplines. It will provide better understanding of climate processes by supporting new, detailed investigations of how clouds determine Earth’s energy balance and how Earth responds to the incoming solar energy that fuels the climate system. It will improve weather prediction models by measuring cloud properties from the top of the atmosphere to Earth’s surface, filling in a gap in existing and planned space observational systems. CloudSat’s radar can penetrate thick cloud systems, providing information to increase the accuracy of severe storm, hurricane and flood warnings. CloudSat will improve water resource management by linking climate conditions such as El Nino to hydrological processes that affect drought, severe weather and water supply availability. The mission will also develop advanced technologies, including high-power radar sources, methods of radar signal transmission within spacecraft, and integrated geophysical retrieval algorithms.

CloudSat will fly in orbital formation with NASA’s Aqua and Aura satellites, the French Space Agency’s Parasol satellite, and the NASA-French Space Agency Calipso satellite. Its radar measurements will overlap those of the other satellites. It will be the first time five research satellites fly together. The precision of the radar overlap creates a unique multi-satellite observing system, providing unsurpassed information about the role of clouds in weather and climate.

Colorado State’s Stephens conceived CloudSat. JPL, with the Canadian Space Agency, developed the mission’s first-ever space borne millimeter wavelength profiling radar, which measures the altitude and physical properties of clouds. Ball Aerospace, Boulder, Colo., is building the spacecraft. The U.S. Air Force will operate CloudSat on-orbit and deliver raw data to the Cooperative Institute for Research in the Atmosphere at Colorado State, which will process the data for the scientific community, civilian and military weather forecast agencies. The U.S. Department of Energy and an international team of scientists will provide independent verification of the radar performance through its Atmospheric Radiation Measurement Program.

NASA’s Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth system science to improve prediction of climate, weather, and natural hazards using the vantage point of space. This mandate is part of NASA’s overall mission to understand and protect our home planet. The California Institute of Technology in Pasadena manages JPL for NASA.

Original Source: NASA/JPL News Release

Image credit: NASA

An instrument on board NASA’s Quick Scatterometer spacecraft has detected the earliest melting in Antarctica’s Larsen Ice Shelf. This huge plate of glacier-fed ice has been disintegrating since 1995, losing nearly 10-percent of its size (more than two trillion tonnes of ice), and the most recent chunk disappeared due to a cyclone that sent warm weather into the area.

An international research team using data from NASA’s SeaWinds instrument aboard the Quick Scatterometer spacecraft has detected the earliest yet recorded pre-summer melting event in a section of Antarctica’s Larsen Ice Shelf. This huge, nearly 200 meter (656 foot) thick plate of glacier-fed floating ice, which in the late 1980s was about as large as Indiana, experienced dramatic disintegration events beginning in 1995 that have reduced its area by nearly 10 percent, or more than two trillion tons of ice.

Researchers Dr. Mark Drinkwater of the European Space Agency, Dr. David Long of Brigham Young University and Dr. Steve Harangozo of the British Antarctic Survey used near real time Quick Scatterometer (QuikScat) data to document a rapid, extensive melting of the Larsen C Ice Shelf in Antarctica’s Weddell Sea from Oct. 27 to Oct. 29, 2002. The melting, which extended to 68 degrees south, was triggered by a mid-latitude cyclone that delivered warm air to the region. The same storm is believed to have also caused a noticeable recession in the sea-ice margin to the west of the Antarctic Peninsula. The QuikScat images are available at: http://photojournal.jpl.nasa.gov/catalog/PIA03894

Air temperatures in the region typically exceed freezing for a few days on or after November 1 each year-a precursor to sustained summer melting that normally sets in several weeks later at these latitudes. The cumulative duration of these annual summer melting events is likely to have increased substantially over the past 50 years as summer average air temperatures on the eastern side of the Antarctic Peninsula have warmed appreciably (approximately two degrees Celsius, or 3.6 degrees Fahrenheit). Scientists believe these events are responsible for the previous breakups of Larsen and other ice shelves. Therefore, the ability to observe such events in near real time using scatterometers is of great interest to researchers, since they may provide invaluable clues to the fate of other, much larger Antarctic ice shelves.

While scientists used to believe there was no connection between recent Antarctic Peninsula warming and the natural cycle of deglaciation, recent field measurements provide some evidence to suggest the frequency of summer melting, and the resulting quantities of melt water penetrating ice shelves, may be connected with the accelerated disintegration of Larsen and other Antarctic ice shelves.

“The water is believed to penetrate cracks and fissures in the ice and refreeze at depth, where the ice is relatively colder,” said Drinkwater. “As the ice expands, this process effectively drives a wedge into existing cracks to accelerate the natural fracture process.”

Scatterometers operate by transmitting high-frequency microwave pulses to Earth’s surface and measuring the “backscattered,” or echoed, radar pulses bounced back to the satellite. Moshe Pniel, scatterometer projects manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., which developed and manages the instruments, said scatterometers such as SeaWinds on QuikScat and a similar SeaWinds instrument on Japan’s recently launched Advanced Earth Observing Satellite 2 (Adeos 2), are proving to be increasingly important in monitoring land and ice processes.

“Scatterometers can effectively and quickly detect the difference between melting and dry surfaces,” he said. “They provide an important new tool in our capability to monitor climate change impacts on the Antarctic ice cover on a daily basis. These scatterometer data are vital in the southern hemisphere because near real time synthetic aperture radar data is not available there on a frequent, uninterrupted basis. QuikScat measurements being compiled and archived in the Scatterometer Climate Record Pathfinder study by Long and Drinkwater (http://www.scp.byu.edu) enable critical assessments of the links between changes taking place in global ice cover and associated changes in important elements of Earth’s closely-linked ocean-atmosphere climate system.”

QuikScat measurements and image data developed by Long are processed and distributed in near real time by the National Oceanic and Atmospheric Administration, providing scientists at the British Antarctic Survey and elsewhere with rapid access to low-resolution radar data that can be used to report melt events. The British Antarctic Survey compiles and distributes Antarctic Meteorological Station data in near real time.

More information about SeaWinds is available at: http://winds.jpl.nasa.gov/index.html.

NASA’s Earth Science Enterprise is a long-term research effort to understand and protect our home planet. The California Institute of Technology in Pasadena manages JPL for NASA.

Original Source: NASA/JPL News Release

Image credit: NASA

A satellite designed to track the changes in the Earth’s major ice sheets was launched on Sunday after experiencing a month of delays due to technical difficulties. ICESsat (Ice Cloud and Land Elevation
Satellite) was launched aboard a Boeing Delta rocket from the Vandenberg US Air Force Base in California. On board the rocket was another, smaller satellite called CHIPSat, which will help astronomers study the hot gas coming off of stars.

NASA?s Ice, Cloud and Land Elevation satellite (ICESat) and Cosmic Hot Interstellar Spectrometer (CHIPS) satellite lifted off from Vandenberg Air Force Base, Calif., at 4:45 p.m. PST aboard Boeing?s Delta II rocket. Separation of the ICESat spacecraft occurred 64 minutes after launch at 5:49 p.m. PST. Initial contact with ICESat was made 75 minutes after launch at 6 p.m. PST as the spacecraft passed over the Svalbard Ground Station in Norway.

The CHIPS spacecraft separated from the launch vehicle 83 minutes after launch at 6:08 p.m. PST. Initial contact with CHIPS was made 98 minutes after launch at 6:23 p.m. PST as the spacecraft passed over the University of California, Berkeley.

?The Delta vehicle gave us a great ride! The ICESat spacecraft was right where we expected and is performing great. The whole team is thrilled to be having such a wonderful start to our mission? said Jim Watzin, the ICESat Project Manager at NASA?s Goddard Space Flight Center in Greenbelt, Md.

Over the next few days the ICESat spacecraft will gradually be despun and placed into a safe stable attitude. Within two weeks the onboard propulsion system will gradually tune the orbit. Once in its final orbital position, ICESat will be approximately 373 miles (600 kilometers) above the Earth.

ICESat is the latest in a series of Earth Observing System spacecraft, following the Terra satellite launched in December 1999, and the Aqua satellite launched earlier in May of this year. The primary role of ICESat is to quantify ice sheet growth or retreat and to thereby answer questions concerning many related aspects of the Earth?s climate system, including global climate change and changes in sea level.

Ball Aerospace and Technologies Corporation (Ball) in Boulder, Colorado built the ICESat spacecraft. The Earth Science Data and Information System at NASA Goddard will provide space and ground network support and the University of Colorado?s Laboratory for Atmospheric and Space Physics will team with Ball to provide mission operations and flight dynamics support. The GLAS and ICESat data will be initially processed at the ICESat Investigator-led Processing System with support from the University of Texas, Center for Space Research. The mission data will be distributed and archived by the National Snow and Ice Data Center.

Original Source: NASA News Release

The US-German Gravity Recovery and Climate Experiment mission (aka Grace) has taken the last two weeks to produce the most detailed map of the Earth’s gravitational field – lumps and all. Launched in March, the twin spacecraft have been orbiting the planet 16 times a day, 220 km apart from one another. A ground-based microwave ranging system measures the distance between them to see how they speed up and slow down due to changes in gravity. And this is just the low res version; scientists hope to have even more detailed maps by the end of the year.

Image credit: NASA

A new photo released from NASA’s Terra spacecraft shows the huge swath of destruction caused by the enormous fire in Colorado. The fire started on June 8, and has gone on to destroy more than 40,000 hectares. The image was acquired using Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster), one of five Earth imaging instruments on board the spacecraft. This photo was taken on morning of Sunday, June 16.

Thousands of acres of burned vegetation, along with recent hotspots, are visible in a new image of Colorado’s worst forest fire taken by NASA’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster).

Started on June 8, the Hayman forest fire continues to burn in the Pike National Forest, 57 kilometers (35 miles) south-southwest of Denver, Colo. According to the U.S. Forest Service, the fire has consumed more than 100,000 acres.

The image is available at:

http://www.jpl.nasa.gov/images/earth/usa/west.html.

Acquired Sunday morning, June 16, 2002, the Aster image shows active fires in red. The dark blue area is burned vegetation, and the green areas are healthy vegetation. Clouds are white. The blue cloud at the top center is smoke. The image covers an area of 32.2 by 35.2 kilometers (20 by 21.8 miles).

Aster is one of five Earth-observing instruments launched in December 1999 on NASA’s Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), Aster will image Earth for the next six years to map and monitor the planet’s changing surface. Japan’s Ministry of Economy, Trade and Industry built the instrument. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., is responsible for the American portion of the joint U.S./Japan science team that validates and calibrates the instrument and the data products.

Original Source: NASA/JPL News Release

Image credit: NASA

NASA’s Terra Earth Observing Satellite was on hand this week to record some of the worst dust storms to hit China’s Inner Mongolian and Shanxi Provinces in ten years. The photo on the left shows a relatively clear day, while the one on the right is obscured by a yellowish cloud of dust. Each image was captured by the spacecraft’s Multi-angle Imaging SpectroRadiometer, and represents an area of 380 km x 630 km.

Dust covered northern China earlier this week during some of the worst dust storms to hit the region in a decade. The dust obscuring China’s Inner Mongolian and Shanxi Provinces on March 24 is compared with a relatively clear day (October 31, 2001) in these images from the Multi-angle Imaging SpectroRadiometer’s vertical-viewing (nadir) camera aboard NASA’s Terra Earth Observing Spacecraft. Each image represents an area of about 380 by 630 kilometers (236 by 391 miles).

The images are available at:

http://www.jpl.nasa.gov/images/earth/asia.

In the image from late March, shown on the right, wave patterns in the yellowish cloud liken the storm to an airborne ocean of dust. The veil of particulates obscures features on the surface north of the Yellow River (visible in the lower left). The area shown lies near the edge of the Gobi desert, a few hundred kilometers, or miles, west of Beijing. Dust originates from the desert and travels east across northern China toward the Pacific Ocean. For especially severe storms, fine particles can travel as far as North America.

The Multi-angle Imaging SpectroRadiometer, built and managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif., is one of five Earth-observing experiments aboard the Terra satellite, launched in December 1999. The instrument acquires images of Earth at nine angles simultaneously, using nine separate cameras pointed forward, downward and backward along its flight path. The change in reflection at different view angles affords the means to distinguish different types of atmospheric particles, cloud forms and land surface covers. More information is available at:

http://www-misr.jpl.nasa.gov.

NASA’s Earth Science Enterprise is a long-term research and technology program designed to examine Earth’s land, oceans, atmosphere, ice and life as a total integrated system.

JPL is a division of the California Institute of Technology in Pasadena.

Original Source: NASA News Release

The European Space Agency’s recently-launched Envisat began its ten year mission last week to gauge the health of planet Earth. The $2.2 billion, 9 ton satellite successfully turned on all ten of its scientific instruments and took some high-quality images of the break-up of the Larson B ice shelf in Antarctica. Another instrument captured images of photosynthetic plankton near the coast of Mauritania in northwest Africa.

NASA has released a new set of photographs which form the most detailed true-colour image of the entire Earth ever created. The photographs are taken at a resolution of 1km and include the land, seas and even clouds and sea ice. Much of the data for this image was gathered by NASA’s Terra satellite, from an altitude of 700km. An additional image shows actual city lights superimposed over a darkened version of the photograph.