Sydney's Opera House and Harbor Bridge plunged into darkness Saturday for the Earth Hour environmental campaign, among the first landmarks around the world to dim their lights for the event.

Lights will go out in some 7,000 cities and towns from New York to New Zealand for Earth Hour which this year aims to raise hundreds of thousands of dollars for green projects.

Scientists have created the first man-made chromosome for a complex-celled organism -- a feat hailed Friday as a big step towards acquiring the controversial ability to redesign plants or animals.

A synthetic chromosome was inserted into a brewer's yeast cell, which functioned as normal -- the key test of success, the international team reported in the journal Science.

The spotting of ocean debris by satellites during the search for the lost Malaysian airliner has drawn attention to those orbiting platforms. A primer on what's in orbit, with help from Nicholas Johnson, who retired Thursday as NASA's chief scientist for orbital debris:

HOW MANY SATELLITES ARE UP THERE?

It looks like a giant sandbox — except the sand has a reddish tint and the "toys" on display are very expensive prototypes designed to withstand the rigors of landing on Mars.

The European Mars rover unveiled Thursday at a "Mars Yard" testing ground in Britain is designed to drill beneath the surface of the Red Planet searching for signs of life. It's been dubbed 'Bryan' by its creators — earlier versions were named Bridget (clad in gold material that makes it look like a garish dune buggy) and Bruno.

A Moscow-backed spacecraft carrying two Russians and a U.S. astronaut on Friday docked successfully at the International Space Station after a technical hitch caused an unprecedented two-day delay.

The Soyuz TMA-12M, carrying Russia's Alexander Skvortsov and Oleg Artemyev and NASA's Steve Swanson, docked at 3:53 am Moscow time (1153 GMT Thursday), Russia's mission control said.

Astonished astronomers said Wednesday they had found rings around an asteroid, the smallest object known to have this feature and only the fifth after Jupiter, Saturn, Uranus and Neptune.

The twin rings around a rock called Chariklo were spotted in June last year as it passed in front of a star, scrutinised by seven telescopes dotted over a 1,500-kilometer (930-mile) stretch of South America.

In a blind taste test, eight out of eight pandas agree -- sugar is delicious.

In a new study out Wednesday, scientists put the panda taste receptors to the test, wondering whether the cuddly critters would even notice the difference between plain water and the sweet stuff.

Australia on Thursday rejected a plan to let big-game hunters shoot crocodiles in the country's tropical north, saying such a scheme risked encouraging "cruel" behavior.

Under the proposal about 50 crocodile safaris a year would be allowed in the Northern Territory, where the giant reptiles have become increasingly common since they were declared a protected species in 1971.

Lights will go off in some 7,000 cities around the world for this weekend's Earth Hour event, which will aim to raise hundreds of thousands of dollars for environmental projects worldwide, organizers said Thursday.

Organizers WWF have partnered with payments giant PayPal to allow donors to contribute for specific projects in countries from Russia and India to Canada and Indonesia, using Asian fundraising site Crowdonomic.

Searchers racing to find flight MH370's "black box" face daunting hurdles ranging from undersea volcanoes to mountainous seas as they operate in one of Earth's most remote locations, experts said Wednesday.

They warned there was no guarantee that an unprecedented international search operation involving the militaries of six nations would succeed in retrieving wreckage of the doomed Malaysian Airlines plane which disappeared on March 8 with 239 people on board.