Two scientific papers published Sunday disproved a controversial claim made by NASA-funded scientists in 2010 that a new form of bacterial life had been discovered that could thrive on arsenic.

"Contrary to an original report, the new research clearly shows that the bacterium, GFAJ-1, cannot substitute arsenic for phosphorus to survive," said a statement by the U.S. journal Science, a prestigious, peer-reviewed magazine.

The Defense Department's research arm will seek proposals next month for solutions to technology hurdles in super high-speed flight with a goal of testing a full-scale hypersonic X-plane in four years.

The Defense Advanced Research Projects Agency said Friday it will host a so-called Proposers' Day on Aug. 14 to lay out technical areas for which proposals are being sought.

A solar-powered plane landed in Spain Saturday on its way back home after breaking a record with the first intercontinental flight by an aircraft run on the sun's energy, organizers said.

Swiss adventurer Bertrand Piccard, 54, piloted the experimental plane Solar Impulse on the 17-hour flight from Rabat in Morocco and landed at Madrid's main airport overnight early on Saturday, his team said in a statement.

"Deposits" of gold in electronic waste are around 50 times richer than ore mined from the ground, according to figures put forward by recycling experts on Friday.

The amount of precious metal junked in cellphones, laptop computers, PCs and other electronic goods is rising hugely but very little of it is recovered, they said.

A period of intense, natural changes in climate caused coral reefs in the eastern Pacific to shut down thousands of years ago, and human-induced pollution could worsen the trend in the future, scientists said Thursday.

The study in the U.S. journal Science points to sea temperature fluctuations -- brought on by the same phenomenon that causes El Nino and La Nina events every several years -- as the main cause for the coral die-off near the Panama coast.

Scientists in the United States say they have made the world's most advanced pair of biomechanical legs, bringing the goal of human-friendly household robots a bit closer.

About half the size of their human counterparts, the legs are the first to mimic walking in a biologically accurate, energy-efficient manner, say the researchers.

A scientific body on Thursday urged Mexico and New Zealand to take immediate action to prevent the extinction of small marine mammals that are being killed by gillnets set by the fishing industry.

The International Whaling Commission voiced fears for Maui's dolphins -- some of the world's smallest dolphins found only on New Zealand's North Island -- and the vaquita, a 1.5-meter (five-foot) porpoise in the Gulf of California.

A baby giant panda was born at a Tokyo zoo on Thursday, in a rare success for Japan's captive breeding program, a zoo official said.

The as-yet unnamed infant is Ueno Zoo's first baby panda for 24 years, and its first ever from natural sexual intercourse, she told Agence France Presse.

Physicists said Thursday the potential discovery of the "God particle" was a gateway to a new era that could see humanity unlock some of the universe's great mysteries including dark matter.

The European Organisation for Nuclear Research (CERN) unveiled data from the Large Hadron Collider on Wednesday "consistent with the long-sought Higgs boson", an elusive particle thought to help explain why matter has mass.

Scientists have observed a cross-dressing cuttlefish take sexual trickery to new depths.

On one side of its body, it adopts female markings to deter potential rivals, while on the other, it displays brilliant masculine colors, enabling it to flirt furiously with partners-to-be.