Japan is once again without atomic energy as its only operating nuclear reactor went offline Sunday for refueling and maintenance, and other plants remain closed for intensified safety checks following the 2011 meltdowns at the tsunami-stricken plant in Fukushima.

Despite signs that the Fukushima crisis is worsening, Japan's commitment to restarting many of its 50 idled reactors appears stronger than ever, a year after a previous government said it would begin to phase out nuclear power completely.

"Hatch," a 10-year-old male Bengal tiger, has lived in a 20-by-16-foot (6-by-5 meter) cage with cement walls and nothing green in sight since he was traded to the Villa Dolores Zoo after spending his first three years in a circus. A similarly dismal cage next door is home to an unnamed female tiger. A poster says tigers "love water" and "bathe on hot days, swimming across rivers and lakes."

But these cats don't even have a paddling pool.

California Gov. Jerry Brown and China's top climate negotiator on Friday signed the first agreement between a U.S. state and China that seeks greater cooperation on clean energy technologies and research meant to reduce greenhouse gas emissions.

The memorandum of understanding signed with China's National Development and Reform Commission was another aggressive move by California to combat climate change. The state has already passed the nation's most ambitious greenhouse gas limits, including a so-called "cap and trade" system that put a price on carbon pollution in the state.

Japan's new solid-fuel rocket blasted off Saturday carrying a telescope for remote observation of planets in a launch coordinated from a laptop computer-based command center.

The Japan Aerospace Exploration Agency (JAXA) launched the Epsilon rocket from the Uchinoura Space Center in Kagoshima, southwestern Japan, at 2:00 pm (0500 GMT), live footage showed.

The three crew of the International Space Station (ISS) who returned to Earth this week endured a hair-raising descent after their height sensors failed, a Russian cosmonaut revealed on Friday.

Pavel Vinogradov said that he and the two other crew of the Soyuz capsule which touched down in Kazakhstan Wednesday had groped their way through the landing after they lost all data about their height from the ground.

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.