Imagens de rara beleza divulgadas pelo Earth Observatory, da NASA

NASA, Earth Observatory. Posted 03 january 2011.

Tidal Flats and Channels, Long Island, Bahamas
The islands of the Bahamas are situated on large depositional platforms—the Great and Little Bahama Banks—composed mainly of carbonate sediments ringed by reefs. The islands are the only parts of the platform currently exposed above sea level. The sediments were formed mostly from the skeletal remains of organisms settling to the sea floor; over geologic time, these sediments consolidated to form carbonate sedimentary rocks such as limestone.

This astronaut photograph provides a view of tidal flats and channels near Sandy Cay, on the western side of Long Island and along the eastern margin of the Great Bahama Bank. The continuously exposed parts of the island are brown, a result of soil formation and vegetation growth. To the north of Sandy Cay, an off-white tidal flat composed of carbonate sediments is visible; light blue-green regions indicate shallow water on the tidal flat. The tidal flow of seawater is concentrated through gaps in the land surface, leading to the formation of relatively deep channels that cut into the sediments. The channels and areas to the south of the island have a vivid blue color that indicates deeper water.

Astronaut photograph ISS026-E-5121 was acquired on November 27, 2010, with a Nikon D2Xs digital camera using an 800 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 26 crew. The image has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by William L. Stefanov, NASA-JSC.

NASA, Earth Observatory. Posted 1 january 2011.

Stirring Up a Bloom off Patagonia

The most interesting art often arises from the convergence of different ideas and influences. And so it is with nature sometimes. Off the coast of Argentina, two strong ocean currents recently stirred up a colorful brew of floating nutrients and microscopic plant life just in time for the summer solstice.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this image of a massive phytoplankton bloom off of the Atlantic coast of Patagonia on December 21, 2010. Scientists used seven separate different spectral bands to highlight the differences in the plankton communities across this swath of ocean.

The milky green and blue bloom developed in an area known as the Brazil-Falklands Confluence. It's where the warm salty waters of the subtropical Brazil Current flow south and meet the colder, fresher waters brought north from the Southern Ocean by the Falklands (Malvinas) Current. Where these currents collide along the continental shelf—known to oceanographers as a shelf-break front—turbulent eddies form and pull nutrients up from the deep ocean. Also, the Rio de la Plata runs off the land and deposits nitrogen and iron-laden sediment into the ocean just north of the area shown in the image.

Add in some strong summer sun, and you have a bountiful feast for the microscopic, floating plants—phytoplankton—that form the center of the ocean food web. Those plants become food for everything from microscopic animals (zooplankton) to fish to whales.

Though it is impossible to say for sure without direct sampling of the water, most of the phytoplankton blooming in this photo are likely coccolithophores, single-celled plants that form calcite scales. (Calcite is a carbonate mineral often found in limestone chalk.) Blooms of coccolithophores are common in those waters in southern hemisphere's spring and summer. Diatoms might also be in the mix.

NASA, Earth Observatory. Posted 30 december 2010.

Semisopochnoi Island, Alaska

It is the “Island of the Seven Mountains, ” or more precisely in Russian: “having seven hills.” This uninhabited volcanic island is also an important nesting area for maritime birds of the North Pacific.

Situated on the far end of the Aleutians, Semisopochnoi Island is simultaneously the most easterly and westerly point of the United States of America. Roughly 1,275 miles (2,050 kilometers) west-southwest of Anchorage, Alaska, Semisopochnoi lies near the 180-degree line of longitude, in the Rat Islands group in the western Aleutian Islands.

This pseudo-true color image was acquired on June 22, 2000, by the Enhanced Thematic Mapper Plus (ETM+) on Landsat 7. Colors are what you would expect: snow is white, bare ground is tan, water is blue, clouds are grey, and vegetation is green.

The seven hills of the island are volcanic peaks, each with a summit crater, including Cerberus, Sugarloaf Peak, Lakeshore Cone, Anvil Peak, Pochnoi, Ragged Top, and Three-quarter Cone. The high point of the island is Anvil Peak at 1,221 meters, a double-peaked cone. The three-peaked Mount Cerberus volcano (774 meters high) grew up within the caldera as the volcanic hot spot rose up from the sea floor. Most documented eruptions have come from Cerberus, with the most recent major eruption recorded in 1873. The most recent eruption on the island, though minor, came from Sugarloaf in 1987.

Semisopochnoi has no native land mammals, so it is a natural nesting area for sea birds. But bird populations were decimated after Arctic foxes were introduced to the island for fur farming in the 19th century. In 1997, the last fox was removed from the island to allow the birds a safe refuge again. Part of the Alaska Maritime National Wildlife Refuge (AMNWR), the island now supports more than a million seabirds, particularly auklets, according to the National Audubon Society.

Fonte: http://earthobservatory.nasa.gov/