In this aerial photo taken Wednesday, April 21, 2010 in the Gulf of Mexico, more than 50 miles southeast of Venice on Louisiana's tip, rising smoke and an oil slick are seen as the firefighting boats attend to the burning Deepwater Horizon oil rig. (AP Photo/Gerald Herbert) #

A poison dart frog of the dendrobates genus clings to a leaf at the Botanic Gardens in Medellin April 22, 2010. (REUTERS/Fredy Builes) #

An explosion, part of mining technology, takes place at Olimpiadinskoye gold mine, 660 km (410 mi) northeast of Russia's Siberian city of Krasnoyarsk, April 13, 2010. (REUTERS/Ilya Naymushin) #

Windmills turn in the breeze at Horns Rev 2, the world's largest wind farm, 30 km (19 mi) off the west coast of Denmark near Esbjerg September 15, 2009. (REUTERS/Bob Strong) #

A visitor takes photographs of cherry blossoms at the Royal Botanic Gardens in Kew, west London April 15, 2009. (REUTERS/Eddie Keogh) #

The eye and skin of a circus elephant, seen in the sun in Berlin, Germany on Wednesday, April 7, 2010. (AP Photo/Markus Schreiber) #

An armored vehicle from the Centurion Company, 2-1 Infantry Battalion, 5/2 Stryker Brigade Combat Team is framed by a bolt of lightning during a storm at Combat Outpost Terminator in Maiwand District, Kandahar Province, Afghanistan on April 19, 2010. (REUTERS/Tim Wimborne) #

Skeletal remains of cattle lie on the shore of the Grijalva river in Villahermosa April 20, 2010. According to Mexico's National Committee for Protected Areas (CONANP), 12 tons of garbage are illegally dumped daily at the Canyon del Sumidero where the river runs through. (REUTERS/Luis Lopez) #

A general view shows a "solucar" solar park in Sanlucar La Mayor, near Seville, Spain. (REUTERS/Marcelo del Pozo) #

A worker unloads coal at a storage site along a railway station in Shenyang, Liaoning province April 13, 2010. (REUTERS/Sheng Li) #

A gray whale surfaces near the mouth of the Duwamish River late Saturday March 27, 2010 in Seattle, Washington. The nearly 40 foot-long animal was watched by excited spectators as it hugged the shore around the West Seattle peninsula earlier in the day. Gray whales are not as common in Puget Sound as orca whales; gray whales are rarely seen in Elliott Bay near downtown Seattle. Maritime officials with the Port of Seattle were concerned the whale would attempt to travel up the Duwamish River, a major industrial area and Superfund site. (AP Photo/Seattle Post Intelligencer, Joshua Trujillo) #

A worker walks past a wall made of recycled plastic bottles at the Flora Expo construction site in Taipei, taiwan on April 13, 2010. The world's first green building made of plastic bottles will be used as one of the 14 exhibition halls at the 2010 Taipei International Flora Expo, starting from November 6. (SAM YEH/AFP/Getty Images) #

Hoover Dam, on the on the Colorado River, on the border of Arizona and Nevada, seen from a DigitalGlobe satellite on February 28, 2010. The energy generated by Hoover Dam annually is about 4.2 billion kilowatt-hours. (DigitalGlobe) #

Swans stretch and swim after being released from their winter quarters on Hamburg's city lake Alster April 12, 2010. Every year the swans are collected from waterways around Hamburg and taken to winter quarters where they are fed and cared for until the spring. (REUTERS/Christian Charisius) #

A Union Pacific freight train passes between windmills on January 17, 2010 near of Palm Springs, California. (David McNew/Getty Images) #

The underside of space shuttle Discovery is visible in this image photographed by an Expedition 23 crew member on the International Space Station soon after the shuttle and station began their post-undocking relative separation on April 17th, 2010. The recognizable feature on Earth below is the south end of Isla de Providencia, about 150 miles off the coast of Nicaragua. (NSAA) #

A mature bald eagle calls out to its mate Monday, April 12, 2010, near the the confluence of the Tanana and Chena Rivers outside of Fairbanks, Alaska. (AP Photo/The Fairbanks Daily News-Miner, John Wagner) #

Young Indian ragpickers search for valuables and recyclable materials at the city's largest legal municipal waste landfill in Mavallipura village on the outskirts of Bangalore on April 20, 2010. (DIBYANGSHU SARKAR/AFP/Getty Images) #

A woman herds horses along a snow covered road in a valley below Iceland's Eyjafjallajokull volcano, near Evindarholar April 22, 2010. (REUTERS/Lucas Jackson) #

Cape Cod, Massachusetts, as seen from the International Space Station on April 14th, 2010. The image spans just over 80 km (50 mi). (NASA) #

Mike Cianchette, operations manager of the Stetson Mountain wind project, checks his safety line before making inspections on top of a 300-foot tall windmill, in Range 8, Township 3, Maine on July 14, 2009. (AP Photo/Robert F. Bukaty) #

A larval tube-anemone fishes for food with the tentacles it will use as an adult as seen in an undated handout photo released April 18, 2010. (REUTERS/Cheryl Clarke-Hopcroft/UAF/CMarZ) #

The Northern Lights appear above the ash plume of Iceland's Eyjafjallajokull volcano in the evening April 22, 2010. (REUTERS/Lucas Jackson) #

A young male giraffe named Carlo takes his first walk around an outdoor enclosure with his parents at the zoo in the southern German city of Nuremberg on April 20, 2010. (Timm Schamberger/AFP/Getty Images) #

A worker looks through a solar concentrator panel at the Gadhia solar energy systems manufacturing unit at Gundlav village, about 400 km (250 mi) south of the Ahmedabad, India on December 16, 2009. (REUTERS/Amit Dave) #

Health officials on a truck spray chemicals to disinfect animal farms around the village where outbreaks of foot-and-mouth disease were reported in Gimpo, about 30 km (18 miles) northwest of Seoul, South Korea on April 20, 2010. (REUTERS/Ha Sa-Hun/Yonhap) #

High above the African continent, tall, dense cumulonimbus clouds loom on April 22, 2010. The clouds can form alone, in clusters, or along a cold front in a squall line. The high energy of these storms is associated with heavy precipitation, lightning, high wind speeds and tornadoes. (AFP/Getty Images/NASA) #

Kurniah collects rust from a beach at a ship demolition site, near Tanjung Priok port in Jakarta, Indonesia on April 16, 2010. Kurniah said she can earn approximately $2 after collecting about 100 kg (220 lbs) of rust a day. The rust is sold to a middleman who will sell it to a factory that will recycle it. (REUTERS/Enny Nuraheni) #

A plastic bottle rests on cracked earth at Las Canoas Lake, 59 km (37 mi) north of the capital Managua, Nicaragua on April 20, 2010. The water level of the lake has fallen to dangerously low levels due to a severe drought. (REUTERS/Oswaldo Rivas) #

The Sun appears slightly squished in this image of the Earth eclipsing the Sun seen from NASA's recently-launched Solar Dynamics Observatory in high orbit. An instrument on board, the Helioseismic and Magnetic Imager, was undergoing a series of adjustments when its view was partially blocked by the Earth. At the edges of the shadow, the Sun's shape bends, due to the light's refraction by the Earth's atmosphere. (NASA) #

A crowd watch as a baby hawksbill turtle swims into the deep after a symbolic release ceremony on Pramuka Island located north of Jakarta, Indonesia on April 20, 2010. Twenty baby hawksbill turtles and four four months old hawksbill turtles were released from the turtle conservation area. (ROMEO GACAD/AFP/Getty Images) #

A late afternoon rainbow appears briefly above Port Susan near Stanwood, Washington on April 5, 2010. (AP Photo/Skagit Valley Herald, Frank Varga) #

A interior view of several large turbines at the construction site of the Three Gorges Dam in Yichang, Hubei province, China on September 10, 2009. (REUTERS/China Daily) #

Palestinian beekeepers inspect hives at an apiary near the central Gaza Strip refugee camp of Bureij on April 19, 2010. (MOHAMMED ABED/AFP/Getty Images) #

In this Friday night April 2, 2010 picture, people watch the sunset from the edge of the frozen mudflats near Elderberry Park in Anchorage, Alaska. The Mt. Spurr volcano is at right. (AP Photo/Anchorage Daily News, Anne Raup) #

A man rows a boat down a flooded street in the village of Radul, north of Kiev, Ukraine on April 19, 2010. (REUTERS/Konstantin Chernichkin) #

An aircraft passes the moon over Frankfurt, Germany on Thursday, April 22, 2010, as German air traffic went back to normality following the airspace closure due to the volcanic ash cloud that came from Iceland. (AP Photo/Michael Probst) #

A man takes a break on a sunny day on the grass of LaFayette Park near the White House in Washington, D.C. on April 22, 2010. (REUTERS/Jonathan Ernst) #