Six men who spent 520 days in isolation in Moscow to simulate a flight to Mars on Tuesday spoke of their pride at becoming "spacemen" but complained of the monotony and cravings for crusty baguettes.

Wearing blue jumpsuits and badges with the project name Mars 500, the international team of one Chinese, one Italian, one Frenchman and three Russians said they were proud of their "flight" in a Moscow car park.

An asteroid bigger than an aircraft carrier will dart between the Earth and moon on Tuesday — the closest encounter by such a huge rock in 35 years.

But scientists say not to worry. It won't hit.

Harmful carbon emissions from burning fossil fuels made their biggest ever annual jump in 2010, according to the U.S. Department of Energy's latest world data released this week.

China led the way with a spike of 212 million metric tons of carbon in 2010 over 2009, compared to 59 million metric tons more from the United States and 48 million metric tons more from India in the same period.

Six volunteers from a multi-national crew on Friday stepped out of an isolation module in Moscow after almost one-and-a-half years locked away from the outside world to simulate the effects of a return voyage to Mars.

A researcher broke the seal and then opened the door of the capsule and all six crew members, dressed in blue overalls, walked out one-by-one in good health to cheers from scientists and family who had gathered.

After years of quiet, the sun is coming alive with solar storms in a big way.

The sun shot off a flare Thursday afternoon from a region that scientists are calling a "benevolent monster."

They may not be Sonny and Cher, but certain South American birds sing duets, taking turns as the tune goes along.

"Calling it a love song is probably too strong a word," says researcher Eric S. Fortune of Johns Hopkins University in Baltimore. But, he adds, the little wrens shift their heads around and move closer together as they sing.

The global output of heat-trapping carbon dioxide jumped by the biggest amount on record, the U.S. Department of Energy calculated a sign of how feeble the world's efforts are at slowing man-made global warming.

The new figures for 2010 mean that levels of greenhouse gases are higher than the worst case scenario outlined by climate experts just four years ago.

A Japanese utility operator has denied any problematic nuclear reactions at a tsunami-hit power plant, saying a radioactive gas in one of the damaged reactors came from spontaneous fission that occurs in any idle reactor.

The operator this week found radioactive xenon, initially hinting unexpected nuclear fission and injected boric acid as a precaution against further nuclear reactions.

Leading scientists from around the world are meeting in Britain from Thursday to consider a proposal that could eventually see Greenwich Mean Time relegated to a footnote in history.

For more than 120 years GMT has been the international standard for timekeeping, but it is now under threat from a new definition of time itself based not on the rotation of the Earth, but on atomic clocks.

A fresh look at fossilized remains has turned up a surprise: the earliest modern people in Europe.

From stone tools and other artifacts, scientists have long suspected that the earliest populations of Homo sapiens, or modern humans, settled the continent between 42,000 and 44,000 years ago.