With voices hardly louder than an insect's buzz, the tiniest frogs ever discovered are smaller than a coin and hop about the rainforest of the tropical island of Papua New Guinea, U.S. scientists said Wednesday.

Not only are these little peepers with the big names -- Paedophryne amauensis and Paedophryne swiftorum -- the smallest frogs known to man, they are also believed to be the smallest vertebrates on Earth, said the report in the science journal PLoS ONE.

China on Wednesday released six young captive pandas into semi-wild enclosures as part of a project aimed at helping the endangered bears adapt to the wild and eventually go free.

Previous attempts by Chinese authorities to release pandas into the wild have proved unsuccessful. The last bear that was set free in 2006 was found dead after 10 months, apparently killed by wild pandas.

Global uncertainty on how to deal with the threats of nuclear weapons and climate change have forced the "Doomsday clock" one minute closer to midnight, leading international scientists said Tuesday.

"It is now five minutes to midnight," said Allison Macfarlan, chair of the Bulletin of Atomic Scientists, which created the Doomsday clock in 1947 as a barometer of how close the world is to an apocalyptic end.

The ocean's deepest volcanic vents, kilometers below the surface, are teeming with life forms never before seen that thrive near super-hot underwater geysers, according to a new study.

Eyeless shrimps and white-tentacled anemones were photographed bunched around cracks in the ocean floor spewing mineral-rich water that may top 450 degrees Celsius (842 degree Fahrenheit), researchers reported on Tuesday.

An endangered Sumatran tiger found with serious arrow wounds all over its body was rescued from a wire trap in protected Indonesian jungle, officials said Tuesday.

The five-year-old male tiger was found on Monday in Bengkulu province on the lush island of Sumatra with nine arrow wounds estimated to be four days old, Bengkulu's conservation agency chief Supartono told Agence France Presse.

In fall 2009, the theoretical physicist Lawrence M. Krauss gave a talk about recent discoveries in cosmology that he engagingly titled, "A Universe From Nothing: Why There Is Something Rather Than Nothing."

The popularity of the video, viewed nearly a million times on YouTube, prompted Krauss to develop the ideas in the talk into this short, elegant account of the origins of the universe and its likely demise trillions of years from now.

The head of Russia's beleaguered space program hinted on Tuesday that foreign powers may be behind the string of failures that struck his agency in the past year.

Roskosmos chief Vladimir Popovkin told the Izvestia daily he could not understand why several launches went awry at precisely the moment the spacecraft were travelling through areas invisible to Russian radar.

It may be the ultimate paternity test for a reptile believed lost to history.

U.S. scientists said Monday an iconic tortoise that has been presumed extinct in the Galapagos Islands for 150 years may still exist, based on DNA blood samples from the giant creatures' living children.

A rare duck normally only seen in Asia has somehow turned up in California, drawing excited bird watchers from all over the U.S. and Canada to a wildlife refuge in the state's Central Valley.

Wildlife officials say a male falcated duck, a bird common in China, was first spotted at the refuge on Dec. 8.

Iran's nuclear chief says his country is willing to help what he called "friendly" African nations that have uranium reserves to set up facilities to process the ore into nuclear material.

Fereidoun Abbasi says Iran has mastered the entire nuclear fuel cycle from extracting uranium ore to producing fuel for reactors and is ready to share the technology. Abbasi's comment was reported by the semi-official Mehr news agency Saturday.