Voyager 1 has crossed a new frontier, becoming the first spacecraft ever to leave the solar system, NASA said.

Thirty-six years after it was launched from Earth on a tour of the outer planets, the plutonium-powered probe is more than 11 1/2 billion miles (18.51 billion kilometers) from the sun, cruising through interstellar space — the vast, cold emptiness between the stars, the space agency said Thursday.

As one of the world's most densely populated cities, Hong Kong is searching for more space to house thousands priced out of its sky-high property market -- raising fears for its cherished nature reserves.

A government minister's suggestion this week that developing the city's green spaces should no longer be off limits drew scorn from environmentalists, adding to concerns that Hong Kong's natural habitats are slowly being eroded by developers.

The Kenyan government and UNESCO on Wednesday announced the discovery of a huge supply of underground water in the impoverished, drought-stricken extreme north of the country.

The find, made using advanced satellite exploration technology and backed up by UNESCO drilling, was hailed as a scientific breakthrough that could radically change the lives of the half-million people living in one of the world's most arid regions.

Scientists in the United States said on Tuesday they had coated spider silk with carbon nanotubes, creating a fibre that is not only super-strong but also conducts electricity.

The new thread is three times stronger than untreated spider silk, which weight-for-weight is already one of the strongest substances in Nature, they reported.

The European Parliament on Wednesday backed plans to cap the use of traditional biofuels to address concern over greenhouse gas emissions.

Parliament voted in favour of a text to reduce greenhouse gas emissions resulting from the increasing use of agricultural land for biofuel production.

The U.S. space agency has narrowed its hunt for an asteroid to capture to three, NASA said Wednesday.

The asteroids fit the requirements of being between seven to 10 meters (yards) in size, and further study should be able to narrow the choice even more, scientists said at a conference in San Diego, California.

A wide-ranging probe into woolly mammoths has added to evidence that the towering tusker was wiped out by climate change, scientists said on Wednesday.

British and Swedish researchers sequenced DNA from 88 samples of mammoth bone, tooth and tusk, looking for a signature in the genetic code that is handed down on the maternal line.

NASA officials say brilliant lights and loud booms reported across the southern U.S. came from a meteor.

Officials at the Marshall Space Flight Center say a fragment of a comet entered Earth's atmosphere Monday night.

Three astronauts returned to Earth Wednesday on board a Russian Soyuz capsule after a half-year mission on the International Space Station (ISS), landing in Kazakhstan, mission control in Moscow announced.

Russians Pavel Vinogradov and Alexander Misurkin landed on schedule at 8:58 am Kazakh time (0258 GMT) in the Kazakh steppe, along with American Chris Cassidy.

A new study of the Monarch butterflies' winter nesting grounds in central Mexico says small-scale logging is worse than previously thought and may be contributing to threats facing the Monarch's singular migration pattern.

The reserve's 33,482-acre (13,550-hectare) core zone lost 41 acres (16.6 hectares) of pine and fir trees so far in 2013, about half of that because of illegal logging, said the study by Omar Vidal, head of Mexico's chapter of the World Wildlife Fund, the WWF, and other authors. The rest of the loss was due to drought or disease-control removal of trees.