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By European Space Agency
Image: This Copernicus Sentinel-2 image shows part of one of the world’s natural wonders – the Great Barrier Reef in the Coral Sea off the east coast of Queensland, Australia.
Zoom in to explore this image at its full resolution or click on the circles to learn more.
The Great Barrier Reef extends for nearly 2300 km and covers an area of more than 344 000 sq km, approximately the size of Italy. It is the largest living organism on Earth and the only living thing the naked eye can see from space.
Despite its name, the Great Barrier Reef is not a single reef, but an interlinked system of about 3000 reefs and 900 coral islands, divided by narrow passages. An area of biodiversity equal in importance to tropical rainforests, the reef hosts more than 1500 species of tropical fish, 400 types of coral, hundreds of species of bird and seaweed and thousands of marine animals, including sharks, barracuda and turtles.
In recognition of its significance the reef was made a UNESCO World Heritage Site in 1981.
The section of reef seen here is the southern part off the coast of the Shire of Livingstone in Central Queensland. Part of the mainland and the islands surrounding the coast are visible in the bottom left corner. The tan-coloured sea along the coasts is due to sediment in the water.
A chain of small coral islands can be seen scattered across the centre of the image. The blue hues of the coral contrast with the dark waters of the Coral Sea.
Part of the reef is covered by clouds dominating the upper part of the image. The clouds form a surprisingly straight line, also visible as a distinct shadow cast over the islands below.
Coral reefs worldwide suffer regular damage due to climate change, pollution, ocean acidification and fishing. Furthermore, they are increasingly under threat from coral bleaching, which occurs when the algae that makes up the coral die, causing it to turn white. This phenomenon is associated with increased water temperatures, low salinity and high sunlight levels.
While these coral reefs are ecologically important, they are difficult to map from survey vessels or aircraft because of their remote and shallow location. From their vantage point in space, Earth-observing satellites such as Copernicus Sentinel-2, offer the means to monitor the health of reefs across the globe.
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By NASA
In northwest Australia, the Great Sandy Desert holds great geological interest as a zone of active sand dune movement. While a variety of dune forms appear across the region, this astronaut photograph features numerous linear dunes (about 25 meters high) separated in a roughly regular fashion (0.5 to 1.5 kilometers apart).NASA On March 25, 2013, an astronaut aboard the International Space Station took this photo of the Great Sandy Desert in northwest Australia, showcasing linear dunes separated in a roughly regular fashion. When you fly over such dune fields—either in an airplane or the space station—the fire scars stand out. Where thin vegetation has been burned, the dunes appear red from the underlying sand; dunes appear darker where the vegetation remains.
Strings of narrow lakes that represent ancient rivers are also present in the region. The white feature down the center of the image is Lake Auld. The color is the result of a cemented combination of fine, clay-like sediment and salts from the evaporation of flood waters that occasionally fill the lake. Linear dunes can be seen entering Lake Auld on the east side. During flooding events, the sand of the dune noses is dispersed, becoming incorporated into the muds and salts of the lake floor sediments. During the long, intervening dry periods, sand can blow across the lake floor to build thinner, smaller dunes, visible as linear accumulations on the west side of the lake.
See more photos taken by astronauts.
Text credit: NASA/M. Justin Wilkinson
Image credit: NASA
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By NASA
4 min read
NASA to Launch Three Rockets from Alaska in Single Aurora Experiment
Three NASA-funded rockets are set to launch from Poker Flat Research Range in Fairbanks, Alaska, in an experiment that seeks to reveal how auroral substorms affect the behavior and composition of Earth’s far upper atmosphere.
The experiment’s outcome could upend a long-held theory about the aurora’s interaction with the thermosphere. It may also improve space weather forecasting, critical as the world becomes increasingly reliant on satellite-based devices such as GPS units in everyday life.
Colorful ribbons of aurora sway with geomagnetic activity above the launch pads of Poker Flat Research Range. NASA/Rachel Lense The University of Alaska Fairbanks (UAF) Geophysical Institute owns Poker Flat, located 20 miles north of Fairbanks, and operates it under a contract with NASA’s Wallops Flight Facility in Virginia, which is part of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The experiment, titled Auroral Waves Excited by Substorm Onset Magnetic Events, or AWESOME, features one four-stage rocket and two two-stage rockets all launching in an approximately three-hour period.
Colorful vapor tracers from the largest of the three rockets should be visible across much of northern Alaska. The launch window is March 24 through April 6.
The mission, led by Mark Conde, a space physics professor at UAF, involves about a dozen UAF graduate student researchers at several ground monitoring sites in Alaska at Utqiagvik, Kaktovik, Toolik Lake, Eagle, and Venetie, as well as Poker Flat. NASA delivers, assembles, tests, and launches the rockets.
“Our experiment asks the question, when the aurora goes berserk and dumps a bunch of heat in the atmosphere, how much of that heat is spent transporting the air upward in a continuous convective plume and how much of that heat results in not only vertical but also horizontal oscillations in the atmosphere?” Conde said.
Confirming which process is dominant will reveal the breadth of the mixing and the related changes in the thin air’s characteristics.
“Change in composition of the atmosphere has consequences,” Conde said. “And we need to know the extent of those consequences.”
Most of the thermosphere, which reaches from about 50 to 350 miles above the surface, is what scientists call “convectively stable.” That means minimal vertical motion of air, because the warmer air is already at the top, due to absorption of solar radiation.
A technician with NASA’s Wallops Flight Facility sounding rocket office works on one of the payload sections of the rocket that will launch for the AWESOME campaign. NASA/Lee Wingfield When auroral substorms inject energy and momentum into the middle and lower thermosphere (roughly 60 to 125 miles up), it upsets that stability. That leads to one prevailing theory — that the substorms’ heat is what causes the vertical-motion churn of the thermosphere.
Conde believes instead that acoustic-buoyancy waves are the dominant mixing force and that vertical convection has a much lesser role. Because acoustic-buoyancy waves travel vertically and horizontally from where the aurora hits, the aurora-caused atmospheric changes could be occurring over a much broader area than currently believed.
Better prediction of impacts from those changes is the AWESOME mission’s practical goal.
“I believe our experiment will lead to a simpler and more accurate method of space weather prediction,” Conde said.
Two two-stage, 42-foot Terrier-Improved Malemute rockets are planned to respectively launch about 15 minutes and an hour after an auroral substorm begins. A four-stage, 70-foot Black Brant XII rocket is planned to launch about five minutes after the second rocket.
The first two rockets will release tracers at altitudes of 50 and 110 miles to detect wind movement and wave oscillations. The third rocket will release tracers at five altitudes from 68 to 155 miles.
Pink, blue, and white vapor traces should be visible from the third rocket for 10 to 20 minutes. Launches must occur in the dawn hours, with sunlight hitting the upper altitudes to activate the vapor tracers from the first rocket but darkness at the surface so ground cameras can photograph the tracers’ response to air movement.
By Rod Boyce
University of Alaska Fairbanks Geophysical Institute
NASA Media Contact: Sarah Frazier
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Last Updated Mar 21, 2025 Related Terms
Sounding Rockets Goddard Space Flight Center Heliophysics Heliophysics Division Heliophysics Research Program Science & Research Science Mission Directorate Sounding Rockets Program Uncategorized Wallops Flight Facility Explore More
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