NASA's planet-hunting Kepler spacecraft appears to be hobbled by a faulty wheel and may be near the end of its four-year mission, space agency scientists said Wednesday.

Kepler, a $600 million mission, was launched in 2009 on a search for other planets. So far, it has found 2,700 candidates, including a handful that may be habitable worlds, not too hot and not too cold.

A review of thousands of studies published over 21 years found "overwhelming" and growing consensus among scientists that humans are mostly to blame for global warming, its authors said Thursday.

This contradicts a widely held view that scientists are deeply divided on the topic -- a misconception that complicates efforts to win public backing for climate policy, the authors wrote in the journal Environmental Research Letters.

Australia said it was pushing for a ban Thursday of any commercial use of a pioneering technique to reduce the impacts of climate change by "fertilizing" the world's oceans with iron, warning of significant risks.

Environment Minister Tony Burke said Australia had worked with Nigeria and South Korea on an amendment to the London Protocol governing waste dumping at sea which would prohibit commercial fertilization activities.

Ghanaian college students plan Wednesday to launch a model of a satellite the size of a Coke can 200 yards (meters) into the air.

Organizers hope that it will be the start of this West African country's space program.

Scientists said Tuesday they have found a way to extract gold from ore using a seemingly unlikely pantry item -- cornstarch.

Traditional leaching employs poisonous cyanide to dissolve and extract the gold locked up in mineral ore -- but the method is polluting and controversial.

Researchers trying to explain declining elk numbers in the Yellowstone National Park (YNP) placed part of the blame Wednesday on a previously unlinked phenomenon -- a predatory trout invasion.

In a vicious circle of human interference that underscores the delicate balance of nature, the team said the illegal introduction of lake trout more than 20 years ago changed the diet of a key Yellowstone predator -- the grizzly bear.

Indonesia has extended a logging ban aimed at protecting rainforest despite fierce industry pressure, the government said Wednesday, although green groups say the move still does not go far enough.

Vast tracts of the sprawling Indonesian archipelago are covered in trees, including some of the world's most biodiverse tropical rainforest that is home to endangered animals such as orangutans, tigers and elephants.

The sun has fired off a massive flare, the strongest solar eruption this year.

The powerful flare occurred Sunday and erupted on the side of the sun that was not facing Earth. While the planet was not hit with radiation, space weather forecasters say the solar blast briefly disrupted high-frequency radio signals.

The hordes are rising. A cicada invasion is imminent in the U.S., with millions of the large cricket-like insects poised to emerge from the earth after 17 years lying in wait.

The first of the bugs that are expected to blanket the U.S. east coast have already been spotted in North Carolina and New Jersey.

Canadian spaceman Chris Hadfield on Tuesday returned to Earth along with two other astronauts after a half-year mission to the International Space Station that saw him become a global celebrity through his Twitter microblog.

Hadfield landed safely in the Kazakh steppe along with American Tom Marshburn and Russian Roman Romanenko aboard a Russian Soyuz-TMA capsule that had left the space station earlier Tuesday morning, mission control said.