The U.S. journal Science published research Thursday on how a mutant bird flu may spread among mammals and possibly humans, following months of controversy over the risks of bioterrorism.

The paper detailed how a Dutch lab engineered an H5N1 bird flu virus that can be transmitted in the air among ferrets, and followed the publication last month of findings by a U.S.-based team that made similar advances.

An international team of scientists said Thursday that the Arctic went through ice-free periods of extreme warmth over the past 2.8 million years, based on a new analysis of deep sediment in Russia.

The team led by Martin Melles of the University of Cologne, Germany, drilled into an iced-over lake formed by a meteorite impact on the Chukchi Peninsula in Siberia for the longest sediment core ever collected in the terrestrial Arctic.

Satellite data has shown that harmful carbon emissions from forest loss around the world may be up to 70 percent less than prior estimates, U.S. researchers said Thursday.

The findings are based on U.S. space agency satellites and not self-reported estimates provided by individual nations, which have formed the basis for most prior data, said the study in the journal Science.

An odd pair of distant worlds -- one rocky like Earth and another gassy like Neptune -- have been found doing the closest dance of any planetary pair ever discovered, U.S. scientists said on Thursday.

The duo are orbiting their star about 1,200 light years from Earth, and were discovered with NASA's Kepler space telescope, which launched in 2009 in search of Earth-like planets orbiting stars similar to our Sun.

The first-ever mission dedicated to looking for dark matter and dark energy, two mysterious entities believed to explain the composition of the universe as we know it, will be launched in 2020, the European Space Agency said Wednesday.

The 800-million-euro ($1-billion) Euclid project was given the final go-ahead by the agency's science program committee, a body composed of ESA member states that decides which missions are flown.

A Singapore mother is suing a clinic for alleged negligence after it mixed up her husband's sperm with that of a stranger during in vitro fertilization, a report said Wednesday.

The ethnic Chinese woman first suspected that something was amiss when her baby, who was born in 2010, had markedly different skin tone and hair color from her Caucasian husband, the Straits Times newspaper reported.

Collections of human biological samples used in medical research should be governed by clear rules that safeguard ethics while advancing knowledge, scientists said Wednesday at a Council of Europe symposium.

The council, a 47-country organization founded to promote democracy and human rights in Europe, plans to release new recommendations on such collections, known as biobanks, after this week's meeting of experts at its headquarters in Strasbourg, France.

Australian scientists Thursday unveiled the biggest-ever graveyard of an ancient rhino-sized mega-wombat called diprotodon, with the site potentially holding valuable clues on the species' extinction.

The remote fossil deposit in outback Queensland state is thought to contain at least 20 diprotodon skeletons including a huge specimen named Kenny, whose jawbone alone is 70 centimeters (28 inches) long.

It takes lots of water and chemicals to make a pair of jeans, and environmentally conscious clothing makers caught on years ago to the need to make more sustainable versions these popular pants.

But a Swiss chemical company said Tuesday its process for making eco-friendly jeans could streamline those efforts, saving enough water to cover the needs of 1.7 million people per year if one quarter of the world's jean-makers started using it.

German paleontologists have dug up the remains of nine turtle pairs that died while mating some 47 million years ago, sinking into poisonous waters while locked in a final embrace, a report said Wednesday.

The find represents the first-ever fossil record of copulating vertebrates (animals with a backbone), said a report in the Royal Society Journal Biology Letters.